Nuclear Powered Space Missions - Past and Future
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STOP CASSINI EARTH FLYBY Nuclear Powered Space Missions - Past and Future |
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Introduction2.1 The U.S. - RTG, Nuclear Reactor, And RHU
2.1.1 Radioisotope Thermoelectric Generators (RTGs)
2.1.2 Nuclear Reactors
2.1.3 Radioisotope Heater Units (RHUs)
2.2 The USSR/Russia - RORSAT, Topaz, And RTG
2.2.1 RORSAT Nuclear Reactors
2.2.2 TOPAZ
2.2.3 Radioisotope Thermoelectric Generators (RTGs)
2.2.4 Radioisotope Heater Units (RHUs)
2.3 Other Nations - RTG Technology Is Not Available"
3 Past Missions a Chronology
4.1 Upcoming Plutonium Launches" (pre-1997)
4.2 Potential Future Nasa Space Missions With RTGs" (1997)
4.3 NASA FACTS: Future NASA Spacecraft" (1998)
4.4 Future RTG Development
4.5 Advanced Solar Arrays And Solar Reflectors"
4.6 Details About Future Missions
4.6.1 Comet Nucleus
4.6.2 Europa Lander (Europa Lander Network)
4.6.3 Europa Orbiter (Europa Ocean Observer)
4.6.4 Interstellar Probe
4.6.5 Io Volcanic Observer
4.6.6 Mars Missions (5 Launches)
4.6.7 Moon Missions (4 Launches)
4.6.8 Neptune Orbiter
4.6.9 Pluto/Kuiper-Express (2 Launches)
4.6.10 Solar Probe
4.6.11 Titan Organic Explorer
4.6.12 Venus Lander
4.7 Future Missions Summary
6 Acronyms
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"On January 16, 1959, a dramatic photograph appeared in a Washington, D.C., newspaper. The headline proclaimed »President Shows Atom Generator«. The photograph pictured President Eisenhower and a group of U.S. Atomic Energy Commission (AEC) officials in the Oval Office at the White House. They were gathered around the president's desk, staring at a strange grapefruit-shaped object. Dubbed the world's first atomic battery, it was actually one of the earliest models of a radioisotope thermoelectric generator (RTG), a nuclear generator specifically developed by the AEC to provide electric power during space missions." [USDOE/d, page 4](1)
This text from the DoE brochure "Nuclear Power in Space" describes the early steps of what continues until today: the use of nuclear power to produce electrical energy for spacecraft instruments and experiments. Since the 1980s, when concerned U.S. citizens, scientists, and journalists protested against the NASA (National Aeronautics and Space Administration) Galileo and Ulysses missions, public interest in nuclear powered space missions has increased. Just one year ago, citizens' groups in the U.S. and in Europe attempted to prevent the launch of the joint NASA/ESA (European Space Agency) mission Cassini with its payload of 72 pounds of plutonium dioxide. (Cassini was launched in October 1997.) Most articles and reports about Cassini mentioned 63 previous nuclear powered space missions, nine of which resulted in problems and/or accidents. It proved difficult, however, to find details beyond the two or three most spectacular accidents.
Therefore, this article attempts to give basic information about the nuclear technology used for space missions, followed by a comprehensive chronology of all nuclear powered space missions launched by the U.S. and by the USSR/Russia.(2) An overview of future NASA plans (which involve eight nuclear powered deep space missions, four of which can be done solar according to several NASA documents), a conclusion, a list of acronyms, and a literature list complete the text.
Currently, the chronology in this article lists 71 nuclear powered space missions, ten of which encountered problems or accidents, respectively. A few more space missions leave open questions. Fully aware that some information might be missing, mis-interpreted, or even wrong, it is hoped that this article helps to come to a better understanding of past and future nuclear powered space missions. Rather than talk about speculative data, it might then be possible to discuss facts. Corrections and comments on the information presented below are expected and welcomed by the author.
Apart from several hardcopy documents, Internet search provided vast amounts of information. Huge numbers of documents from U.S. government organizations, mostly NASA and the U.S. Department of Energy, were found on various homepages. Consequently, it was decided to base this article mainly on official information from government agencies and the space industry rather than to rely on books, magazines, and newspapers.(3) Not surprisingly, the data basis is much smaller when it comes to the Soviet/Russian missions - which is reflected by the lack of details about many Soviet space missions in Chapter 3, Past Missions a Chronology.
For the purpose of this article, it was decided to quote (sometimes in length) the original
statements from the official organizations instead of summarizing their contents in the author's
own words. This leaves room for the reader's interpretation of the data given (although,
admittedly the choice of quotes is a matter of interpretation by itself.)
============================================== 2. Technology
2.1 The U.S. - RTG, Nuclear Reactor, And RHU
2.1.1 Radioisotope Thermoelectric Generators (RTGs)
All but one of the nuclear powered space missions launched by the U.S. used RTGs. In a document about the Ulysses mission, ESA/ESTEC (European Space Agency/European Space Research and Technology Center) explains the RTG technology as follows:
"What Are RTGs?
RTGs are lightweight, compact spacecraft power systems that are highly reliable. RTGs are not nuclear reactors and have no moving parts. They use neither fission nor fusion processes to produce energy. Instead, they provide power through the natural radioactive decay of plutonium (mostly Pu-238, a non-weaponsgrade isotope). The heat generated by this natural process is changed into electricity by solid-state thermoelectric converters. RTGs enable spacecraft to operate at significant distances from the Sun or in other areas where solar power systems would not be feasible. In this context, they remain unmatched for power output, reliability and durability.
Safety Design
More than 30 years have been invested in the engineering, safety analysis and testing of RTGs. Safety features are incorporated into the RTG's design, and extensive testing has demonstrated that they can withstand physical conditions more severe than those expected from most accidents.
First, the fuel is in the heat-resistant, ceramic form of plutonium dioxide, which reduces its chance of vaporizing in fire or reentry environments. This ceramic-form fuel is also highly insoluble, has a low chemical reactivity, and primarily fractures into large, non-respirable particles and chunks. These characteristics help to mitigate the potential health effects from accidents involving the release of this fuel.
Second, the fuel is divided among 18 small, independent modular units, each with its own heat shield and impact shell. This design reduces the chances of fuel release in an accident because all modules would not be equally impacted in an accident.
Third, multiple layers of protective materials, including iridium capsules and high-strength graphite blocks, are used to protect the fuel and prevent its accidental release. Iridium is a metal that has a very high melting point and is strong, corrosion resistant and chemically compatible with plutonium dioxide. These characteristics make iridium useful for protecting and containing each fuel pellet. Graphite is used because it is lightweight and highly heat-resistant." [ESTEC/b](4)
On its web page "Cassini RTG Information", NASA's Jet Propulsion Laboratory gives additional technical information:
"Each RTG NASA uses on recent planetary spacecraft contains approximately 10.9 kg (24 lb.) of plutonium dioxide fuel. On Galileo's two RTGs, that amounted to a total of about 48 lb. On Cassini, which has three RTGs, it's about 72 lb. ...
RTGs have been used on 23 U.S. space missions including Voyager, Pioneer, Viking, Apollo, and more recently the Galileo and Ulysses missions(5). As in the past, Cassini's RTGs are to be provided by the U.S. Department of Energy (DoE). Heat source technology pursued by DoE has resulted in several models of an RTG power system, evolving from the Systems for Nuclear Auxiliary Power (SNAP)-RTG to the Multi-Hundred Watt (MHW)-RTG, to the currently used General Purpose Heat Source (GPHS)-RTG used on Galileo, Ulysses and Cassini spacecraft. The GPHS technology is the culmination of almost 25 years of design evolution.
A GPHS-RTG assembly weighs 56 kg (123.5 lb), is approximately 113 cm (44.5 in) long and 43 cm (16.8 in) in diameter and contains 10.9 kg (24 lb) of plutonium dioxide fuel. At launch, the three RTGs will provide a total of 888 watts of electrical power from 13,182 watts of heat. By the end of the mission the power output will be 628 watts." [JPL/c]
A specific aspect of RTG usage is pointed out by Canadian journalist Michael Bein: "Although the
American planners have obviously been concerned enough about safety to draft general criteria
and institute a three-step, multi-agency review process that must be completed before each
launch, there are a number of weaknesses in the U.S. regulatory system vis a vis NPS [Nuclear
Powered Satellites]. First of all, there is no licensing by an independent authority like the Nuclear
Regulatory Commission, the watchdog of America's commercial nuclear power industry. All the
nuclear missions flown to date have been classed as research devices and have therefore been
exempted from licensing under a provision of the Atomic Energy Act. DoE, meanwhile, reserves
the right to approve deviations from the published safety criteria. And, perhaps most importantly,
there is no provision for public participation in the safety review process." [BEIN]
2.1.2 Nuclear Reactors
Although the U.S. has also worked on nuclear reactors for space missions, they launched but one
spacecraft equipped with a reactor: the SNAPSHOT mission of 1965 (see Section 3, Past
Missions a Chronology for details.) The funding to build or test space nuclear reactor systems
was stopped in 1972. After the end of the Cold War, U.S. nuclear laboratories purchased Russian
Topaz II reactors and tested them thoroughly (British, French, and Russian scientists were part of
the research team.) However, plans for a test space mission were not pursued for various reasons.
2.1.3 Radioisotope Heater Units (RHUs)
Many of NASA's scientific space missions are not (only) equipped with RTGs but also with nuclear heaters, the RHUs. "The Cassini spacecraft and the Huygens Probe will use approximately 117 lightweight radioisotope heater units (RHUs) to regulate temperatures on the spacecraft and on the probe. Each RHU provides about one watt of heat, derived from the radioactive decay of 2.7 gm (0.1 oz) of non-weapons grade radioisotope, plutonium 238-dioxide, contained in a platinum-30 rhodium alloy clad. The exterior dimensions of an RHU are 2.6 cm (1 in) by 3.2 cm (1.3 in) long, weighing about 40 gm (0.09 lb.)" [USDOE/a]
RHUs are used to keep instruments warm during cold Moon and Mars nights as well as during
deep space missions. RHUs were for example used for the Apollo 11-17 missions, for Galileo, as
well as for Cassini. This article focuses on RTGs and reactors, therefore the use of RHUs is not
listed in the chronology of past missions.
2.2 The USSR/Russia - RORSAT, Topaz, And RTG 2.2.1 RORSAT Nuclear Reactors
Generally, little information was found about the RORSAT missions. A few pages in the book "Der rote Orbit" (The Red Orbit) by journalist Harro Zimmer (published in 1996) deal with Soviet nuclear powered space missions. Some additional information was found at the Federation of American Scientists' Internet homepage [FAS].
Harro Zimmer describes the RORSAT missions as follows [ZIMMER, pages 110- 112](6):
"Additional details became known about a 'dirty' side of Moscow's military spaceflight program. From December 1967 to March 1988, the USSR orbited 33 radar satellites with nuclear reactors. They functioned at orbits of appr. 255 km altitude with an average lifetime of two to three months. Usually, the RORSATs - the acronym for RADAR OCEAN RECONNAISSANCE SATELLITE - were launched to coincide with major naval maneuvers of NATO and US Navy.
The characteristic feature were their large radar antennae the signals of which were sent to the surface of the ocean in order to locate the ships. Ideal objects were aircraft carriers with their large and flat surfaces which made particularly good reflectors. When planning these satellites, the Soviets had to compromise between various requirements. On the one hand, the orbit of a reconnaissance satellite must be low enough to receive the weakly reflected signal. On the other hand, the orbit must be high enough to cover a maximum area. Considerable electronic deficiencies enforced simple but power-consuming solutions, as a result of which only a small nuclear reactor could be used.
A RORSAT consists of three major components: the payload and propulsion section, the nuclear reactor, and the disposal stage, which is used to maneuver the reactor to an orbit of 900 to 1,000 km of altitude at the end of the mission. The satellite is 1.3 m in diameter and 10 m in length. A RORSAT weighs 3,800 kg, of which 1,250 kg are made up by the reactor and the disposal stage. These two components are 5.3 m long. The reactor core consists of 37 cylindrical fuel elements with 31.1 kg of highly enriched (90%) uranium-235(7) embedded in a beryllium casing.
The cooling liquid for the reactor is liquid sodium-potassium. The thermo-ionic converter uses the dissipated heat to create electrical energy with an efficiency as low as 2 to 4%.
For the radar equipment, a RORSAT requires appr. 2 kilowatt electrical power. The technical structure of the system was extremely simple. Shielding was omitted unless absolutely required. Therefore, these satellites were a flying source of radiation which severely impacted the operation e.g. of science satellites equipped with gamma ray detectors.
As mentioned before, the active RORSAT lifetime was fairly short. The 'record' was 134 days. How should the radioactive payload - which was not limited to the reactor alone - be dealt with? From the relatively low orbit, the satellites would have entered the denser spheres of Earth's atmosphere after one year at the latest, and they would have burned up only partially. The purpose of the disposal stage was to avoid this happening by injecting the reactor into a higher orbit between 900 and 1,000 km of altitude.
The lifetime of a fairly massive object at this altitude should be appr. 600 years, while uranium-235 and uranium-238 have a half-life of more than one billion years."
After describing the two major accidents (Kosmos 954 and Kosmos 1402, see Chapter 3, Past Missions a Chronology), Harry Zimmer continues with the following conclusion [ZIMMER, page 113]:
"The heritage of this program: at appr. 900 to 1,000 km of altitude about 940 kg highly enriched
uranium as well as more than 15 metric tons of radioactive material orbit with an inclination of
65o. In addition, recent radar observation indicates that several ten thousand 'drops' 0.6 to 2 cm in
diameter circle on this orbit. The drops consist of liquid sodium-potassium, the reactor coolant."(8)
2.2.2 TOPAZ
About the Topaz program, Harro Zimmer writes as follows: "These [RORSAT] missions were not discontinued because the risks of using nuclear power in the orbit might be too high as compared to the advantages. Rather, ocean surveillance should have been continued by means of satellites at a higher altitude, equipped with larger and more powerful reactors. As soon as February 1, 1987, Kosmos 1818 was launched into an orbit at 800 km altitude. On board the large satellite was a reactor of the Type Topaz, weighing appr. 1,000 kg, which produced electrical power of about 5 to 6 kilowatt with an improved efficiency between 5 and 10% for six months. ... On July 10, 1987, Kosmos 1867 followed, equipped identically. This reactor operated about one year. At their altitude, these satellites might be safely stored at least for the next three hundred years." [ZIMMER, page 114](9)
The Russian Institute of Physics & Power Engineering describes the development process and results as follows: "In 1958 comprehensive research was started to develop a reactor-converter with the advanced thermionic principle of direct energy conversion. As compared to thermoelectric conversion, thermionic conversion makes it possible to increase efficiency, to prolong the life-time, and to improve the overall dimensions of the power system and the spacecraft as a whole.
The investigations performed at the IPPE in the field of small-sized reactors and shadow radiation shielding, the solution of the problems concerning collector and emitter materials selection and elaboration, investigations of the processes of electron emission and diffusion in cesium plasma, heat and mass exchange and liquid metal coolant technology (Na, K-alloy) provided creation of the first in the world intermediate neutrons thermionic reactor-converter which was called 'TOPAZ'.
Between 1970-1984 seven power systems with reactors of this type were tested on the ground at the special IPPE test site. 'TOPAZ'-units were tested twice in space as an electric power source for the 'COSMOS' satellites. Thermionic fuel elements (TFE's) for 'TOPAZ' reactors were designed, fabricated, and in-pile tested in the IPPE." [IPPE]
Whereas funding for space nuclear reactors was stopped in 1972 in the U.S. [USAF], research continued in the USSR and led to the development of a follow-up version of Topaz I.
"TOPAZ-2 small-sized nuclear power system with a thermionic converter represents a power source developed around a nuclear reactor and a thermionic heat-to-electricity converter.
Advantages: high power and reliability; long lifetime; small overall dimensions; complete radiation safety; the possibility to fully discharge the fuel and to store/ship it separately from the system; the possibility of final fuel loading directly during the system pre-flight preparation.
Application: space power systems. ... Characteristics of the reactor core: height, mm 375; diameter, mm 260; uranium charge, kg up to 27; guaranteed lifetime, yr over 3." [KURCHATOV]
In the mid-90s, a "program managed by the Ballistic Missile Defense Organization" resulted in the
purchase of six Topaz II reactors from Russia by the U.S. A joint team of U.S., British, French,
and Russian engineers tested the space reactors "to evaluate the Russian technology and to find
peaceful civilian applications". [USAF] None of the Topaz II reactors have actually been used for
space missions, however.
2.2.3 Radioisotope Thermoelectric Generators (RTGs)
Extremely little information could be found about the use of RTGs in the Soviet and Russian
space program. Information that RTGs are used at all was made public by the media in their
reports about the accident of the Russian Mars-96 probe in November 1996. This mission got out
of control soon after launch and decayed over South America (see Chapter 3, Past Missions a
Chronology for further details.)
2.2.4 Radioisotope Heater Units (RHUs)
RHUs are also used in the Soviet/Russian space program. For example, the Moon missions Luna
17 (1970) and Luna 21 (1973) used polonium-210 isotopic heat sources to keep the Lunokhod
rovers warm during the lunar nights. No further details are known.
2.3 Other Nations - "RTG Technology Is Not Available"
Up to date, no other nations launched nuclear powered space missions and little information is available about corresponding research programs. The American Institute of Aeronautics and Astronautics (AIAA) sums the status up as follows:
"During the 1960s and early 1970s several other nations, including France, Germany, and the United Kingdom (U.K.) examined space nuclear reactor power systems. In the 1980s some studies were done by Japan and the U.K. The French government assembled a design team that worked on a reactor concept employing a Brayton cycle to convert reactor heat into electrical power. The French, Japanese, and Chinese now have small programs to explore the use of space nuclear technologies.
Currently the U.S. is not producing plutonium-238 for space use, so DoE has been buying some plutonium-238 from Russia to supplement the existing inventory." [AIAA]
The non-availability of RTG technology has quite an impact on space mission planning outside the U.S. and Russia. The most striking examples are ESA's Rosetta mission to comet Wirtanen and ESA plans for the EuroMoon 2000 mission.
Wirtanen is a comet at approximately the same distance from the Sun as planet Jupiter. This means that the brightness of the Sun at Jupiter reaches about 5% of the brightness at Earth. According to NASA, current solar energy technology is not yet advanced enough to provide enough power for the spacecraft instruments at that distance. ESA, on the other side, had to look for an alternative for their Rosetta mission.
"ESA's next cometary mission takes its name from the Rosetta Stone. Just as the Rosetta Stone deciphered the hieroglyphics of ancient Egypt, so the Rosetta spacecraft will help to decode the messages of atoms and molecules that help us to make sense of our cosmic origins.
The Rosetta spacecraft will rendezvous with comet 46 P/Wirtanen as it makes one of its periodic visits to the Sun. The spacecraft will map the comet's surface in fine detail and land a package of instruments (the Rosetta Lander) on it. Waltzing around the comet for many months, Rosetta will be able to watch its surface erupting in the warmth of the Sun. On-board instruments will analyse the effusions of dust and gas.
Scheduled for launch by Ariane-5 in January 2003, Rosetta will take eight years to reach its target. On the way it will inspect two asteroids (planned targets currently Mimistrobell and Rodari) at close quarters." [ESTEC/c]
In a Press Release from 1994, ESA explains why RTG technology could not be used:
"New solar cells with record efficiency
Under contract with ESA, European industry has recently developed high efficiency solar cells for use in future demanding deep-space missions such as the recently approved ROSETTA mission. The new solar cells reach a 25% efficiency under deep space conditions. ...
Until now, deep space probes had to use thermonuclear power generators, like the so called RTGs (Radioisotope Thermoelectric Generators). As RTG's technology is not available in Europe, ESA therefore attempted to develop a power source based on very high-efficiency solar cells. ...
ESA expects that the new high performance Silicon solar cells could profitably be used in deep space missions for Europe and that this technology could also be of interest for near-Earth orbit space applications as well as for Earth based ones." [ESA/a](10)
Similarly, ESA had to be inventive for EuroMoon 2000 to be launched in autumn 2000.
"What is EuroMoon 2000?
The EuroMoon 2000 mission consists of a Lander and an Orbiter with a total mass in lunar transfer orbit of at least 2900 kg. The composite spacecraft would be placed into a circular polar orbit of 200 km altitude with a dedicated Ariane-4 launch. After about one month of observations, mainly for establishing preliminary gravitational data, the composite's altitude would be lowered to 100 km, where the Orbiter (weighing about 300 kg) would be separated from the Lander.
The Orbiter's task would be to make a detailed topographic map using a stereoscopic camera and to establish the lunar gravitational potential more accurately with the help of a small subsatellite, in order to assist the subsequent landing operation. The Orbiter's payload (approx. 50 kg) would also address a large proportion of the MORO mission's objectives, including geochemical science.
The Lander would set down (to within ±100 m) on the highest point of the rim of the South Pole crater, in order to take advantage of the permanent sunlight there. The landed mass of 1000 kg would include more than 250 kg of payload, the primary objective of which would be to study the soil composition, heat flow and possibly seismic activity in the neighbourhood of the intended landing site, which lies inside the largest lunar crater, the Aitken Basin.
In addition to the ESA element, more than half of the Lander's payload capacity would be allocated to three or four 'Millennium Challenge' experiments. These would be the winners of a contest involving Universities and European Industry. Their 'challenge' would be to devise various robotic devices to investigate the inside of the South Pole crater (20 km in diameter and approximately 3000 m deep, with temperatures on the order of 200 deg C), hopefully reaching the South Pole itself." [ESTEC/a]
This design has two advantages: ESA's lander can use solar panels as it will not descend into the deep crater where no sunlight is available but remain on the rim of the South Pole crater. "This location enjoys almost continuous sunlight thus missions can rely on solar power instead of bulky batteries or costly and potentially hazardous nuclear power generation." [ESA/b] And ESA leaves it to the participating universities and industry enterprises to find a solution for robotic devices' power supply - knowing they can not use nuclear power.
In addition to having found alternatives to nuclear power for board instruments, ESA was also successful in solving another problem. As described above, Radioisotope Heater Units (RHUs) are used to keep the sensitive instruments warm during the cold space nights. ESA managed to develop "a thermal control system securing operation without the use of radioactive heaters" [JPL/q] for the Rosetta Lander. "The design of the thermal control subsystem is challenging, because the lander has to operate on a comet nucleus with unknown rotation period, in distances between 3 and 1 AU from the sun with temperatures of the environment in the range between 120 K and 350 K. Special effort has to be taken for thermal insulation and heat storage to keep the temperature inside the lander in a range between -55oC and +70oC throughout the mission." [JPL/q]
==============================================
3. Past Missions a Chronology
The following pages list those missions launched by the U.S. and the USSR/Russia which use(d) nuclear power to provide electrical energy for the on-board instruments.
For each mission, some basic data are given:
Mission name mostly from the TRW Space Log 1996 [TRW]; other information sources
Launch date mostly from the TRW Space Log 1996 [TRW]; other information sources
Country mostly from the TRW Space Log 1996 [TRW]; other information sources
Mission Type various information sources
Launch Site TRW Space Log 1996 [TRW], other information sources
Power Source DoE, NASA, and other information sources
Number NASA's Cassini FEIS [NASA/c] and other information sources
Source Term NASA's Cassini FEIS [NASA/c] and other information sources for the US RTGs;
Harro Zimmer, "Der rote Orbit" [ZIMMER] for the Soviet RORSAT nuclear reactors
Status DoE information [USDOE/d], TRW Space Log 1996 [TRW]; NASA's Cassini FEIS, others.
The Estimated Life Duration given for the Soviet RORSAT missions is stated in the Missions database of the Institut für Luft- und Raumfahrt, Technische Universität Berlin (Institute of Aeronautics and Astronautics at the Technical University of Berlin). [ILR]
This is followed by additional information about the mission, the power source, the current mission status, and specific mission-related events where appropriate. Accidents and problems are marked by bold print. In order to avoid redundant information, details are not repeated for similar missions (e.g. many of the Kosmos missions.)
Where contradictory information was found in official sources, this is specifically pointed out.
Name: Transit 4A Power Source: SNAP-3B7
Launch Date: June 29, 1961 Number: 1
Country: U.S. Source Term: 1,500 - 1,600 Curies
Mission Type: Navigational (US Navy)
Launch Site: Cape Canaveral, Florida Status: in orbit
"In 1961, the first RTG used in a space mission was launched aboard a U.S. Navy transit navigation satellite. The electrical power output of this RTG, which was called Space Nuclear Auxiliary Power (SNAP-3), was a mere 2.7 watts. But the important story was that it continued to perform for 15 years after launch.
Since that initial SNAP-3 mission, RTGs have been an indispensable part of America's space program. They have been involved in more than 25 missions, orbiting Earth and traveling to planets and their moons both nearby and in deep space. (Astronauts on five Apollo missions left RTG units on the lunar surface to power the Apollo Lunar Surface Experiment Packages.)" [USDOE/d, page 6]
The RTG used for the Transit 4A and the Transit 4B missions worked on polonium-210, which has a half-life of 138.4 days. Therefore, it seems rather unlikely that it actually operated for 15 years. This would mean that at the end of its lifetime, 2% of the original heat dissipation would have been sufficient to provide the power for the satellite. See also Transit 4B mission.
The stage used to launch this satellite exploded after the launch. It broke up into 298 pieces, of which appr. 200 were still tracked in orbit according to a 1995 report of NASA's Johnson Space Center [KESSLER].
Name: Transit 4B Power Source: SNAP-3B8
Launch Date: Nov. 15, 1961 Number: 1
Country: U.S. Source Term: 1,500 - 1,600 Curies
Mission Type: Navigational (US Navy)
Launch Site: Cape Canaveral, Florida Status: in orbit
Contradictory information exists about the operating time of this SNAP. The DoE states "RTG operated for 9 years. Satellite operated periodically after 1962 high altitude test. Last reported signal in 1971." [USDOE/d, pages 15/16] The TRW Space Log 1996 states "In orbit; transmitted until 7/62, SNAP-3 operated 8 months." [TRW, page 71]
Name: Transit 5-BN-1 Power Source: SNAP-9A
Launch Date: Sept. 28, 1963 Number: 1
Country: U.S. Source Term: 17,000 Curies
Mission Type: Navigational (US Air Force & Navy)
Launch Site: Vandenberg AFB, California Status: decayed??? in orbit?
This was the first U.S. satellite which used an RTG based on plutonium-238.(11)
On the use of plutonium RTGs, the DoE says the following: "Although other radioactive fuels have been considered for RTGs, plutonium-238 (Pu-238) has been used most widely. Pu-238 is a radioactive isotope - a form of plutonium that gives off energy as rays and particles. It continues to be the radioactive fuel of choice today and in planned future missions. ... Longer space missions require a radioisotope with a longer half-life. Pu-238, with its half-life of 87.7 years, fills the need. For example, after five years, approximately 96 percent of the original heat output of Pu-238 is still available. ... Because the nuclear fuel in RTGs is radioactive, safety is a critical issue. ... Only lightweight shielding is necessary because alpha particles cannot penetrate a sheet of paper." [USDOE/d, pages 18-19]
Accident?: Contradictory information exists about the status of this satellite. DoE states: "RTG operated as planned. Non-RTG electrical problems on satellite caused satellite to fall after 9 months." [USDOE/d, pages 15/16] No further information about this incident could be found. The TRW Space Log 1996 [TRW, page 80] as well as the NASA Cassini FEIS [NASA/c] state that the satellite is currently in orbit.
Name: Transit 5-BN-2 Power Source: SNAP-9A
Launch Date: Dec. 5, 1963 Number: 1
Country: U.S. Source Term: 17,000 Curies
Mission Type: Navigational (US Air Force & Navy)
Launch Site: Vandenberg AFB, California Status: in orbit
"RTG operated for over 6 years. Satellite lost ability to navigate after 1.5 years." [USDOE/d, pages 15/16, emphasis added]
Name: Transit 5-BN-3 Power Source: SNAP-9A
Launch Date: April 21, 1964 Number: 1
Country: U.S. Source Term: 17,000 Curies
Mission Type: Navigational (US Air Force & Navy)
Launch Site: Vandenberg AFB, California Status: burned up during re-entry
Accident: "Mission was aborted because of launch vehicle failure. RTG burned up on re-entry as designed." [USDOE/d, pages 15/16] This is the short version of the events on April 21, 1964.
A more detailed account is given by another DoE document: "In 1964, a U.S. Navy Transit navigation satellite failed to reach orbit and disintegrated in the atmosphere. The satellite received its electrical power from a 4.5 pound, grapefruit-sized radiothermal generator that produced energy from the heat of its decaying radioisotopes. The device, known as a SNAP or System for Nuclear Auxiliary Power, disintegrated, scattering plutonium particles in the atmosphere over the southern hemisphere." [USDOE/b] According to a U.S. General Accounting Office report, the Transit 5-BN-3 RTG contained 2.2 pounds of plutonium fuel. [USGOA], page 18]
In the Cassini FEIS, NASA describes the results of this accident: "Since 1964, essentially all of the SNAP-9A release has been deposited on the Earth's surface. About 25 percent ... of that release was deposited in the northern latitudes, with the remaining 75 percent settling in the southern hemisphere. ...The Pu-238 in the atmosphere from weapons tests (about 3.3 x 1014 Bq [9,000 Ci]) was increased by the 1964 reentry and burnup of a Systems for Nuclear Auxiliary Power (SNAP)-9A RTG, which released 6.3 x 1014 Bq (17,000 Ci). ... The release into the atmosphere was consistent with the RTG design philosophy of the time. (Subsequent RTGs, including the RTGs on the Cassini spacecraft, have been designed to contain the Pu-238 fuel to the maximum extent possible, recognizing that there are mass and configuration requirements relative to the spacecraft and its mission that must be considered with the design and configuration of the power source and its related safety requirements.) ... Since 1964, essentially all of the SNAP-9A release has been deposited on the Earth's surface." [NASA/c, page 3-44]
The following table from NASA's Cassini FEIS [NASA/c, page 3-44] lists the effect of this SNAP-9A burn-up on the worldwide plutonium-238 distribution.
Table 1: Plutonium-238 Distribution from SNAP-9A Burn-Up
| Sources | Amount (Bequerels [Curies]) |
| Atmospheric Testing 1945-74 Deposited near testing sites and worldwide | 3.3 x 1014 (9,000) |
| Space Nuclear - SNAP-9A, 1964 | 6.3 x 1014 (17,000) |
| Overseas Nuclear Reprocessing Plants, 1967-1987 | 1.1 x 1014 (3,000) (estimated) |
| Chernobyl Nuclear Power Station, 1986 | 3.0 x 1013 (810) |
| Total | 1.1 x 1015 (29,810) |
Name: SNAPSHOT Power Source: SNAP-10A (reactor)
Launch Date: April 3, 1965 Number: 1
Country: U.S. Source Term: ?(12)
Mission Type: Experimental (US Air Force & Army)
Launch Site: Vandenberg AFB, California Status: in orbit
The satellite successfully achieved orbit. According to NASA's Cassini FEIS, the reactor was shut down after 43 days in orbit.
Journalist Michael Bein commented this test flight of a space mission powered by a nuclear reactor as follows: "The only U.S. satellite thus far to carry a nuclear fission reactor failed in 1965 after 43 days aloft and was subsequently boosted into a 4000-year orbit in order that its radioactivity might have time to decay to safer levels before it descends to earth. Injection into higher orbit is the method of reactor 'disposal' preferred by both the American and Soviet programs."(13) [BEIN]
Some additional information is given in the TRW Space Log 1996: "SNAP-10A operated at more than 500 W for 43 days. Since 1979, many objects separating. The only U.S. space reactor flown, a test flight in 1964, used uranium-235 as the fuel." [TRW, page 90, emphasis added]
Technical information about the SNAP-10A, the amount of U-238 used, or the effect of the continuing disintegration of the satellite mentioned in the TRW Space Log 1996 was not given in the sources available at the time of writing.
Name: Kosmos 84(14) Power Source: Polonium-RTG
Launch Date: Sept. 3, 1965 Number: 1
Country: USSR Source Term: ?
Mission Type: Military communication
Launch Site: Tyuratam(15) Status: in orbit
Kosmos 84 is generally regarded as the first mission of the USSR which used nuclear power to provide energy for the on-board instruments. Like the U.S., the USSR used polonium-210 to power their first RTGs. "Due to the short half life (138 days), this RTG model had a lifetime of only 3000 hours." [NILSEN] The USSR used RTGs only for the first two nuclear powered missions. All other Kosmos missions which relied on nuclear power used nuclear reactors instead.
Name: Kosmos 90 Power Source: Polonium-RTG
Launch Date: Sept. 18, 1965 Number: 1
Country: USSR Source Term: ?
Mission Type: Military communication
Launch Site: Tyuratam Status: in orbit
See Kosmos 84.
Name: Kosmos 198 Power Source: reactor
Launch Date: Dec. 27, 1967 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235(16)
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 500a yrs
This was the first of the 33 so-called RORSAT missions usually listed as nuclear powered space missions launched by the USSR. RORSAT is the acronym for 'Radar Ocean Reconnaissance Satellite'. According to the Federation of American Scientists (FAS), Kosmos 198 was a "1-day flight test of spacecraft support systems" [FAS]. For more details about the RORSAT reactors, see Section 2.2, The USSR/Russia - RORSAT, Topaz, And RTG.
Name: Kosmos 209 Power Source: reactor
Launch Date: March 22, 1968 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 500a yrs
See Kosmos 198. According to the Federation of American Scientists, this was the second 1-day flight test of spacecraft support systems [FAS].
Name: Nimbus-B-1 Power Source: SNAP 19B2
Launch Date: May 18, 1968 Number: 2
Country: U.S. Source Term: 34,400 Curies
Mission Type: Meteorological (NASA & US Air Force)
Launch Site: Vandenberg AFB, California Status: failed to orbit; RTG recovered
According to information from the DoE, this was the first RTG usage on a non-military, i.e. on a NASA mission. [USDOE/a]
Accident: "Mission was aborted because of range safety destruct. RTG heat sources recovered and recycled." [USDOE/d, pages 15/16] A 'range safety destruct' is a deliberate destruction of a mission by the Range Safety Officer of the mission launch pad when a launch vehicle gets out of control.
A report of the U.S. General Accounting Office describes the event as follows: "In 1968, a NIMBUS-B-1 weather satellite was destroyed after its launch vehicle malfunctioned. The plutonium fuel cells from the spacecraft's two RTGs were recovered intact from the bottom of the Santa Barbara Channel near the California coast." [USGOA, page 18] The plutonium from the RTGs was recycled and re-used for another RTG.
Name: Nimbus III Power Source: SNAP 19B2
Launch Date: April 14, 1969 Number: 2
Country: U.S. Source Term: 37,000 Curies
Mission Type: Meteorological (NASA)
Launch Site: Vandenberg AFB, California Status: in orbit
"RTGs operated for over 2.5 years." [USDOE/d, page 15/16] A fact sheet published by the Florida State University, Department of Meteorology states: "The craft was powered by 10,500 solar cells and two SNAP-19 nuclear powered generators." [FSU/b]
Name: Kosmos 305 Power Source: reactor
Launch Date: Oct. 22, 1969 Number: 2 ?
Country: USSR Source Term: 2 x 31.1 kg highly enr. U-235 ?
Mission Type: RORSAT
Launch Site: Tyuratam Status: decayed
See Kosmos 198.
Accident: The TRW Space Log 1996 states, "Decayed Oct. 24, 1969; possible lunar mission test; two modules." [TRW] Proposition One suggests that "radiation was detected as craft burns up in atmosphere." [PROP1](17)
This mission is frequently listed in newspaper articles about accidents which occurred with nuclear powered spacecrafts. However, no details are given. This mission is not contained in the otherwise comprehensive Berlin database [ILR].
Name: Apollo 12 Power Source: SNAP-27
Launch Date: Nov. 14, 1969 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Moon
"RTG operated for about 8 years until station was shut down." [USDOE/d, page 15/16)(18)
It is a little known fact that the seismic stations left on the Moon in the course of the Apollo 12 and Apollo 14 to Apollo 17 missions(19) contain one RTG each. The plutonium heat source was loaded into the SNAP RTGs by the astronauts on the moon. [USDOE/d, page 5]
Name: Nimbus IV Power Source: SNAP-19
Launch Date: April 8, 1970 Number: 2
Country: U.S. Source Term: 37,000 Curies ?
Mission Type: Meteorological (NASA)
Launch Site: Vandenberg AFB, California Status: in orbit
Other than the Nimbus III mission, Nimbus IV to Nimbus VII are not contained in any of the official NASA and DoE mission lists. However, fact sheets about these missions were published by the Florida State University, Department of Meteorology. For all four missions, this organization states: "The craft was powered by 10,500 solar cells and two SNAP-19 nuclear powered generators." [FSU/b to FSU/f] The launch and mission data is confirmed by the TRW Space Log 1996 [TRW] which does not mention the RTGs (neither does it for any of the Apollo missions). Therefore, information about the four additional Nimbus missions was included in this list.
"Stage exploded Oct. 17; 300 pieces." [TRW, emphasis added]
Name: Apollo 13 Power Source: SNAP-27
Launch Date: April 11, 1970 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: returned to Earth
RTG recovered
Accident: "The Apollo 13 mission was aborted and the spacecraft returned to Earth. The RTG was attached to the lunar module, which broke up on reentry. The RTG heat source reentered the Earth atmosphere intact, with no release of plutonium, and currently is located deep in the Tonga trench in the Pacific Ocean. Extensive testing of RTGs in sea water has been conducted, and there will be no release of plutonium over time from this unit." [USDOE/a]
Name: Kosmos 367 Power Source: reactor
Launch Date: Oct. 3, 1970 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Apollo 14 Power Source: SNAP-27
Launch Date: Jan. 31, 1971 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on moon
See Apollo 12. "RTG operated for over 6.5 years until station was shut down." [USDOE/d, page 15/16]
Name: Kosmos 402 Power Source: reactor
Launch Date: April 1, 1971 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Apollo 15 Power Source: SNAP-27
Launch Date: July 26, 1971 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Moon
See Apollo 12. "RTG operated for over 6 years until station was shut down." [USDOE/d, page 15/16]
Name: Kosmos 469 Power Source: reactor
Launch Date: Dec. 25, 1971 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Pioneer 10 Power Source: SNAP-19
Launch Date: March 2, 1972 (?) Number: 4
Country: U.S. Source Term: 80,000 Curies
Mission Type: Planetary/solar system escape (NASA)
Launch Site: Cape Canaveral, Florida Status: departed solar system
"RTGs still operating. Spacecraft successfully operated to Jupiter and is now beyond orbit of Pluto." [USDOE/d, page 15/16]
Other information sources [NSSDC/c and TRW] give March 3, 1972, as the launch date.
Name: Apollo 16 Power Source: SNAP-27
Launch Date: April 16, 1972 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Moon
See Apollo 12. "RTG operated for about 5.5 years until station was shut down." [USDOE/d, page 15/16]
Name: Kosmos 516 Power Source: reactor
Launch Date: Aug. 21, 1972 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: "Transit" (Triad-01-1X) Power Source: Transit-RTG
Launch Date: Sept. 2, 1972 Number: 1
Country: U.S. Source Term: 24,000 Curies
Mission Type: Navigational (US Air Force)
Launch Site: Vandenberg AFB, California Status: in orbit
"RTG still operating." [USDOE/d, pages 15/16]
Name: Apollo 17 Power Source: SNAP-27
Launch Date: Dec. 7, 1972 Number: 1
Country: U.S. Source Term: 44,500 Curies
Mission Type: Lunar surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Moon
See Apollo 12. "RTG operated for almost 5 years until station was shut down." [USDOE/d, page 15/16]
Name: Nimbus V Power Source: SNAP-19
Launch Date: Dec. 11, 1972 Number: 2
Country: U.S. Source Term: 37,000 Curies ?
Mission Type: Meteorological (NASA)
Launch Site: Vandenberg AFB, California Status: in orbit
See Nimbus IV. The satellite was deactivated on March 29, 1983 [FSU/d].
Name: Pioneer 11 Power Source: SNAP-19
Launch Date: April 5, 1973 (?) Number: 4
Country: U.S. Source Term: 80,000 Curies
Mission Type: Planetary/trans-solar trajectory (NASA)
Launch Site: Cape Canaveral, Florida Status: departed solar system
There is contradictory information about the RTG operation: "RTGs still operating. Spacecraft successfully operated to Jupiter, Saturn, and beyond." [USDOE/d, pages 15/16] But: "The Mission of Pioneer 11 has ended. Its RTG power source is exhausted." [NASA/h] The latter is confirmed by another source: "Instrument power sharing began in February 1985 due to declining RTG power output. Science operations and daily telemetry ceased on September 30, 1995, when the RTG power level was insufficient to operate any experiments." [NSSDC/d] DoE states: "The spacecraft contained two [sic?] nuclear electric-power generators, which generated 144 W at Jupiter, but decreased to 100 W at Saturn." [USDOE/a]
As for Pioneer 10, contradictory information is given about the launch date. Other information sources (NSSDC/d and TRW, page 151] give April 6, 1973, as the launch date.
Name: Kosmos Power Source: reactor
Launch Date: April 25, 1973 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: failed to orbit
See Kosmos 198.
Accident: The TRW Space Log 1996 lists this mission as "Failed to orbit. Rorsat." [TRW, page 152] Proposition One adds "Location: Pacific Ocean, north of Japan. Radiation released from the reactor was detected." [PROP1] No further details about this accident could be found.
Name: Kosmos 626 Power Source: reactor
Launch Date: Dec. 27, 1973 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 651 Power Source: reactor
Launch Date: May 15, 1974 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 654 Power Source: reactor
Launch Date: May 17, 1974 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 723 Power Source: reactor
Launch Date: April 2, 1975 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 724 Power Source: reactor
Launch Date: April 7, 1975 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit
Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Nimbus VI Power Source: SNAP-19
Launch Date: June 12, 1975 Number: 2
Country: U.S. Source Term: 37,000 Curies ?
Mission Type: Meteorological (NASA)
Launch Site: Vandenberg AFB, California Status: in orbit; broke up?
See Nimbus IV.
Accident?: Broke up into 236 parts; currently tracked are 190; date of event: May 01, 1991. This is NASA information [JSC/a]. No further information is given, therefore it is not clear whether it is the satellite which broke up and what happened to the RTGs.
Name: Viking 1 Power Source: SNAP-19
Launch Date: Aug. 20, 1975 Number: 2
Country: U.S. Source Term: 40,980 Curies
Mission Type: Mars surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Mars
"RTGs operated for over 6 years until lander was shut down." [USDOE/d, page 15/16] The RTGs are contained in the Viking Lander, not in the orbiter. Another NASA documents adds the following information: "Power was provided by two radioisotope thermal generator (RTG) units affixed to opposite sides of the lander base, each containing plutonium 238, providing 70 W continuous power." [NSSDC/e]
Name: Viking 2 Power Source: SNAP-19
Launch Date: Sept. 9, 1975 Number: 2
Country: U.S. Source Term: 40,980 Curies
Mission Type: Mars surface (NASA)
Launch Site: Cape Canaveral, Florida Status: on Mars
See Viking 1. "RTGs operated for over 4 years until relay link was lost." [USDOE/d, page 15/16] According to the TRW Space Log 1996, the lander operated less: "Lander died April 12, 1978." [TRW, page 167]
Name: Kosmos 785 Power Source: reactor
Launch Date: Dec. 12, 1975 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: LES 8 Power Source: MHW-RTG
Launch Date: March 14, 1976 Number: 2
Country: U.S. Source Term: 159,000 Curies
Mission Type: Communications (US Air Force)
Launch Site: Cape Canaveral, Florida Status: in orbit
"RTGs still operating." [USDOE/d, page 15/16]
Name: LES 9 Power Source: MHW-RTG
Launch Date: March 14, 1976 Number: 2
Country: U.S. Source Term: 159,000 Curies
Mission Type: Communications (US Air Force)
Launch Site: Cape Canaveral, Florida Status: in orbit
"RTGs still operating." [USDOE/d, page 15/16]
Name: Kosmos 860 Power Source: reactor
Launch Date: Oct. 17, 1976 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 861 Power Source: reactor
Launch Date: Oct. 21, 1976 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Voyager 2 Power Source: MHW-RTG
Launch Date: Aug. 20, 1977 Number: 3
Country: U.S. Source Term: 240,000 Curies
Mission Type: Planetary/trans-solar trajectory (NASA)
Launch Site: Cape Canaveral, Florida Status: departed solar system
"RTGs still operating. Spacecraft successfully operated to Jupiter, Saturn, Uranus, Neptune, and beyond." [USDOE/d, pages 15/16]
Name: Voyager 1 Power Source: MHW-RTG
Launch Date: Sept. 5, 1977 Number: 3
Country: U.S. Source Term: 240,000 Curies
Mission Type: Planetary/trans-solar trajectory (NASA)
Launch Site: Cape Canaveral, Florida Status: departed solar system
"RTGs still operating. Spacecraft successfully operated to Jupiter, Saturn, and beyond." [USDOE/d, pages 15/16] Another DoE document points to the fact that "...the Voyager spacecraft ...[has been] providing data over the last 20 years. The Voyager spacecraft are expected to provide data for another 25 years." A NASA Voyager Project Information specifies: "Power System: Radioisotope Thermal Generators (RTGs) of 420 W. ... Data collection continues as the recently renamed Voyager Interstellar Mission searches for the edge of the solar wind's influence (the heliopause) and exits the solar system." [NASA/k]
Name: Kosmos 952 Power Source: reactor
Launch Date: Sept. 16, 1977 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 198.
Name: Kosmos 954 Power Source: reactor
Launch Date: Sept. 18, 1977 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: decayed
See Kosmos 198.
Accident: The re-entry of Kosmos 954 is one of the best covered and most serious accidents of a nuclear powered space mission. DoE states: "Decayed Jan. 24, 1978; spread radioactive debris over western Canada at re-entry." [USDOE/d, pages 15/16] RADNET details the amount of radioactive material which was spread: "Reentry inventories: 3TBq strontium-90; 131-I: 0.2 Bq; 137-Cs: 3TBq (81 Curies.)" [CENTER, quoting Health Physics, No. 47, pages 225-233]
In an article almost ten years after the accident, journalist Michael Bein describes the Canadian efforts to recover part of the radioactive material: "Operation Morning Light continued into October and eventually resulted, according to Canada's Atomic Energy Control Board (AECB), in the estimated recovery of 0.1 percent of Cosmos 954's nuclear core. Tens of millions of pepper-flake sized radioactive particles, comprising a fifth to a quarter of the core, remained scattered over a 124,000 square kilometer 'footprint', stretching southward from Great Slave Lake into northern Saskatchewan and Alberta. The clean-up of these populated and frequented areas and the recovery of a number of large satellite fragments from the more remote bush cost Canada nearly $14,000,000, of which only $3,000,000 was later recovered from the USSR." [BEIN]
He continues: "Within a week after the Cosmos crash, U.S. President Carter called for »an agreement with the Soviets to prohibit earth-orbiting satellites with atomic radiation material in them.«" [BEIN] Although this request was not enforced afterwards, the incident resulted in broad discussions of the issue. "At the end of the year, in November 1978, the General Assembly of the United Nations authorized its Committee on the Peaceful Uses of Outer Space (UNCOPUOS) to establish a technical working group. The assembly also passed a resolution requesting that a country whose NPS [Nuclear Powered Satellite] is about to fall notify others of the impending danger." [BEIN]
Many years later, in 1992, discussions in the UNCOPUOS resulted in the "Principles Relevant to the Use of Nuclear Power Sources in Outer Space" (resolution 47/68). This document "recognizes that nuclear power sources are essential for some missions, but that such systems should be designed so as to minimize public exposure to radiation in the case of accident." [UN]
In the U.S., the accident provoked discussions not only on a political but also on a technical level: "Regarding the best form of dispersal upon re-entry, a 1979 DoE-commissioned safety study found that »break-up of the reactor into non-respirable particles ... is preferable to uncontrolled intact re-entry or to high altitude vaporization.« In other words, break-up into pepper-flake sized particles like those produced by Cosmos 954 is the best (as well as the most likely) form of reentry." [BEIN]
In the USSR, the opposite conclusion was drawn from the Cosmos 954 accident. It led to a re-design of the future nuclear powered Kosmos missions as described by the Federation of American Scientists: "Following the reentry of Kosmos 954 over Canada in 1978, the RORSAT reactor underwent several modifications, including the ability to eject the fuel assembly at the end of life, hopefully in the disposal orbit but prior to reentry in the event of accident, e.g. Kosmos 1402 in 1983. Between 1980 and 1988, at least 14 RORSATs did perform fuel assembly ejection in the higher altitude storage orbits. However, not until 1994 did terrestrial-based space surveillance sensors detect what may be large numbers of very small particles of NaK reactor coolant released when the fuel assembly was ejected." [FAS] (For more details see Kosmos 1176.)
Name: Nimbus VII Power Source: SNAP-19
Launch Date: Oct. 24, 1978 Number: 2
Country: U.S. Source Term: 37,000 Curies ?
Mission Type: Meteorological /environmental research (NASA)
Launch Site: Vandenberg AFB, California Status: in orbit
See Nimbus IV.
Name: Kosmos 1176 Power Source: reactor
Launch Date: April 29, 1980 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
This is the first mission where in addition to lifting the reactor to the higher storage orbit, 'core separation' was introduced, i.e. in a case of a re-entry the 'naked' core would completely burn up in the atmosphere rather than come back to Earth (see description of the FAS quoted for Kosmos 954 above.) This method was demonstrated a few years later, when Kosmos 1402 entered the Earth atmosphere and burned up.
Core separation had an unexpected side aspect which was described by NASA. In its April-June, 1997 edition of the Orbital Debris Quarterly News, NASA gives details about "a large number of small-debris objects injected into orbit with very low velocities relative to one another. ... Times of increased flux at 600 km altitudes were found to be associated with overhead passing of COSMOS 1900, A Radar Ocean Reconnaissance Satellite (RORSAT) orbiting around 720 km - providing a clue about, but not explaining the higher-altitude debris. Specially-configured measurements using the Haystack radar determined the orbital inclination of the debris source between 850 km and 1000 km to be between 63 and 67 degrees, matching that of the remaining orbiting RORSATs. The RORSAT design was examined to determine a possible cause of this debris and was found to contain a significant amount of coolant consisting of the liquid-metal alloy Sodium-Potassium (NaK). The leakage of this coolant from COSMOS 1900 and a number of other RORSATs, producing a large number of orbiting liquid metal spheres, was consistent with all observations." [KESSLER]
Name: Kosmos 1249 Power Source: reactor
Launch Date: March 5, 1981 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 1172.
Name: Kosmos 1266 Power Source: reactor
Launch Date: April 21, 1981 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 1172.
Name: Kosmos 1299 Power Source: reactor
Launch Date: August 24, 1981 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 1172. "Raised Sept. 6, 1981." [TRW, page 208]
Name: Kosmos 1365 Power Source: reactor
Launch Date: May 14, 1982 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 1172. "Raised Sept. 27, 1982." [TRW, page 214]
Name: Kosmos 1372 Power Source: reactor
Launch Date: June 1, 1982 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a yrs
See Kosmos 1172. "Raised Aug. 11, 1982." [TRW, page 215]
Name: Kosmos 1402 Power Source: reactor
Launch Date: August 30, 1982 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: decayed
See Kosmos 1172.
Accident: The mission Kosmos 1402 is another one of the often mentioned accidents which occurred with nuclear powered space missions. It "decayed January 23, 1983; reactor core separated; completely burned-up." [ILR] Proposition One adds the following information: "Location: South Atlantic; 68 lbs uranium-238; it is unknown whether any debris reached the ground." [PROP1] According to Harro Zimmer, the reactor casing burned up on January 24, 1983 above the Indian Atlantic, the reactor core burned up on February 7, 1983, above the South Atlantic [ZIMMER, page 113].
Name: Kosmos 1412 Power Source: reactor
Launch Date: Oct. 2, 1982 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172.
Name: Kosmos 1461 Power Source: reactor
Launch Date: May 7, 1983 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit; exploded?
See Kosmos 1172.
Accident: The TRW Space Log 1996 mentions the following status: "In orbit: Rorsat. Exploded March 11, 1985." [TRW] A NASA report also mentions "Catalogued upon breakup: 158 parts; Currently tracked in orbit: 3 parts." [JSC/a] No information is given about the nuclear reactor. Therefore, it might be assumed that the spacecraft exploded after the reactor had been injected into the higher orbit. This mission is not listed in the Berlin database [ILR].
Name: Kosmos 1579 Power Source: reactor
Launch Date: June 29, 1984 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172. "Placed in storage orbit Sept. 27, 1984." [TRW, page 233]
Name: Kosmos 1607 Power Source: reactor
Launch Date: Oct. 31, 1984 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172.
Name: Kosmos 1670 Power Source: reactor
Launch Date: August 1, 1985 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172.
Name: Kosmos 1677 Power Source: reactor
Launch Date: August 23, 1985 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172.
Name: Kosmos 1736 Power Source: reactor
Launch Date: March 21, 1986 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated life duration: 600 years
See Kosmos 1172.
Name: Kosmos 1771 Power Source: reactor
Launch Date: August 20, 1986 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years
See Kosmos 1172.
Name: Kosmos 1818 Power Source: Topaz I reactor
Launch Date: Feb. 1, 1987 Number: 1
Country: USSR Source Term:
Mission Type: Test mission
Launch Site: Tyuratam Status: in orbit?(20)
This was the first development test of a Topaz I reactor in space. For more details about the Topaz reactors, see Section 2.2, The USSR/Russia - RORSAT, Topaz, And RTG.
Name: Kosmos 1860 Power Source: reactor
Launch Date: June 18, 1987 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: reactor in orbit
See Kosmos 1172. "Craft split up July 20; RTG boosted to high orbit on July 28, 1987." [ILR, emphasis added]
Name: Kosmos 1867 Power Source: Topaz I reactor
Launch Date: July 10, 1987 Number: 1
Country: USSR Source Term:
Mission Type: Test mission
Launch Site: Tyuratam Status: in orbit?
See Kosmos 1818. This was the second development test of a Topaz I reactor in space.
Name: Kosmos 1900 Power Source: reactor
Launch Date: Dec. 12, 1987 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in storage orbit, but too low Estimated Life Duration: ?
Accident: The reactor was injected into a storage orbit but reached only an altitude of 720 km. This means the reactor will take considerably less than 600 years to decay.
Name: Kosmos 1932 Power Source: reactor
Launch Date: March 14, 1988 Number: 1
Country: USSR Source Term: 31.1 kg HEU-235
Mission Type: RORSAT
Launch Site: Tyuratam Status: in orbit Estimated Life Duration: 600a years(21)
See Kosmos 1172. This was the last of the Soviet RORSAT missions. The missions were not continued by Russia. See also text for Kosmos 1818.
Name: Galileo Power Source: GPHS-RTG
Launch Date: Oct. 18, 1989 Number: 2
Country: U.S. Source Term: 264,000 Curies
Mission Type: Planetary
Launch Site: Cape Canaveral, Florida Status: on interplanetary trajectory
"[Galileo] will involve the first-time use of the shuttle to transport a RTG power source to low Earth orbit." [NASA/b] This sentence is from the Draft Environmental Impact Statement for Project Galileo from 1985. Galileo actually became the first RTG powered mission to be launched by a shuttle. Before, however, the shuttle Challenger exploded during its January 28, 1986 launch. Seven astronauts died. The shuttle failure was eventually traced back to an O-ring seal. [TRW]
Therefore, two RTG missions, Galileo and Ulysses (see below) were delayed by several years. Finally, Galileo with its 49 pounds of plutonium was "lifted into space in October 1989 aboard the space shuttle Atlantis. Its mission involves a scheduled eight-year, deep-space voyage to the solar system's largest planet, Jupiter, and its four major moons. ... Galileo used a technique called gravity-assist to make the journey to Jupiter, which is nearly 500 million miles from Earth. ... The craft flew by Venus first, then made two passes by Earth. ...
The effectiveness of Galileo's instruments depends not only on RTG power, but also on heat from radioisotope heater units (RHU). Because the journey is far from the sun, these compact, light, and long-lasting RTG and RHU units are the only effective power and heat sources for the Galileo mission.(22)
Two RTGs provide electrical power to drive the Galileo spacecraft and its instruments. Each RTG produces about 285 watts of electricity at the beginning of the mission. One hundred and twenty small RHUs protect the craft's sensitive instruments from damage in the cold vacuum of outer space, which can reach -400 degrees Fahrenheit. ... Each heater unit produces about 1 watt of heat - about as much as a miniature Christmas tree bulb. But, it is enough to protect the instruments from the cold. ... None [of the Pioneer, Voyager, Ulysses, and Galileo] missions could have been accomplished without RTGs, which have played a key role in helping the U.S. establish its position as the world leader in outer planetary and space science exploration." [USDOE/d, page 14]
"If you think about it, we run our entire spacecraft on less than half the power of an average hair dryer!" [NASA/d] Without knowing this argument, the protest movement against the Cassini mission of 1997 used the same comparison to oppose the RTG usage: it was thought that 72,3 pounds of plutonium is too much to produce no more than 750 watts - less than an ordinary hair dryer would consume. The argument is valid for Galileo too: "Galileo carried 49 pounds of Pu-238 on board to meet its electricity needs." [ANDERSON]
Name: Ulysses Power Source: GPHS-RTG
Launch Date: Oct. 6, 1990 Number: 1
Country: U.S. and ESA Source Term: 132,500 Curies
Mission Type: Planetary/Solar
Launch Site: Cape Canaveral, Florida Status: on interplanetary trajectory
"The Ulysses mission is a joint enterprise of the European Space Agency and NASA, with the Jet Propulsion Laboratory in California providing major support. The craft was launched in October 1990 aboard the space shuttle Discovery. Its mission is to study the sun, the magnetic fields and streams of particles the sun generates, and the interstellar space below and above it. ... A single RTG provides all the power for instruments and other equipment aboard Ulysses. It is the only available power source capable of meeting the mission's power requirements. Furthermore, the RTG will provide power for many years, enabling mission scientists and program managers to extend the life of the spacecraft by several years and reap more scientific benefits." [USDOE/d, pages 12 - 14]
Name: Mars-96 Power Source: Pu generator
Launch Date: Nov. 16, 1996 Number: 4
Country: Russia Source Term: 200 g Pu-238
Mission Type: Mars
Launch Site: Tyuratam Status: decayed
This is the most recent and also a broadly covered accident of a nuclear powered space mission. Mars-96 was meant to send two penetrators and two launchers to Mars. The spacecraft, however, went out of control and re-entered the Earth atmosphere on November 17, 1996. The US Space Command, which followed the route of the craft, claims that it fell intact into the sea off the coast of Chile. Eye-witnesses, however, report they saw the craft falling down in the Chile/Bolivia border area - disintegrating and burning. So far, no proof for either version has been presented.
"No news stories have appeared that RADNET is aware of since this date. Presumably, if the plutonium had been recovered intact, some type of public relations effort would result to emphasize the safety of the upcoming Cassini mission. In lieu of a public relations news byte on this topic, one may assume the plutonium vaporized upon re-entry." [CENTER, written before the Cassini launch]
Name: Cassini Power Source: GPHS-RTG
Launch Date: Oct. 15, 1997 Number: 3
Country: U.S. and ESA Source Term: 398,760 Curies
Mission Type: Planetary
Launch Site: Cape Canaveral, Florida Status: on interplanetary trajectory
This is a joint mission by NASA and the European Space Agency (ESA). After a Venus Venus Earth Jupiter gravity assist (VVEJGA), Cassini will be flung to Saturn, its moons, and its rings. The Earth flyby is scheduled for August 1999. The European probe Huygens shall be released over the Saturn moon Titan and collect information about Titan's atmosphere and surface while parachuting down. Cassini carries three RTGs with a total of 72 pounds of plutonium to produce 750 W of electrical energy for the on-board instruments.(23)
==============================================
4. NASA Plans
Russian information policy with respect to space missions differs considerably from U.S. policy. Therefore, this Chapter deals exclusively with NASA plans to launch nuclear powered space missions. It should, however, be pointed out that the Russian government and space organization also continue to push development of nuclear power systems for space missions. In February 1998, an ITAR-TASS press release announced that the "Russian government approved the concept of space nuclear power development in Russia".(24) According to this press information, the Russian government considers nuclear power in space as a key aspect for space and military technology.
4.1 "Upcoming Plutonium Launches" (pre-1997)
During the Cassini protest campaign, one of the web pages from the Florida Coalition for Peace and Justice provoked particular discussions. It is titled "Upcoming Plutonium Launches" and lists twelve planned NASA missions with a total of 132.5 kg plutonium [FCPJ]. NASA as well as DoE kept repeating that the list was wrong and that they did not know how the Florida Coalition came to post this information. However, the data given by the Florida Coalition are a perfect match of a spreadsheet with no indication as to its origin or creation date which is titled "Plutonium-238 Requirements (kg)" [USDOE/c](25). The spreadsheet lists twelve mission names with additional information about the launch year, the number and watts of RTGs, the plutonium requirements for the years 1992 to 2001, and the total plutonium-238 requirements in kg. The following table repeats the information from the spreadsheet with the exception of the individual plutonium amounts for the years 1992-2001.
Table 2: Plutonium-238 Requirements (kg)
| Year of Launch | Level RTG (WE) | Number of RTG's | Total | |
| Outer Solar System | ||||
| Cassini | 1997 | 300 | 3 | 24.0 |
| Comet Nucleus Mission | 2002 | 300 | 3 | 25.5 |
| Pluto Flyby | 2003 | 300 | 3 | 25.5 |
| Mars | ||||
| MESUR | 1999 | 15 | 4 | 3.5 |
| 2001 | 15 | 4 | 2.5 | |
| 2003 | 15 | 8 | 4.5 | |
| Mars SR | 2007 | 30 | 2 | 4.0 |
| 2009 | 30 | 2 | 2.5 | |
| Moon | ||||
| Site Rover | 1998 | 100 | 3 | 13.5 |
| Telescope | 1999 | 400 | 4 | 18.0 |
| Network (2) [sic?] | 2001 | 100 | 2 | 4.5 |
| Network (2) | 2002 | 100 | 2 | 4.5 |
| Total | 132.5 |
4.2 "Potential Future Nasa Space Missions With RTGs" (1997)
Although NASA insisted on the invalidity of the "Upcoming Plutonium Launches" list, the organization was rather reluctant to provide up-to-date information about nuclear power usage for their planned deep space missions. In August 1997, a few weeks before the Cassini start, NASA headquarters issued a Fact Sheet with the title "Information on potential future NASA space science missions which may be powered with Radioisotope Power Sources (RTGs or RHUs)". As the Fact Sheet lists the conditions for RTG and RHU use as well as potential missions, it is quoted in full length here:
"Information on potential future NASA space science missions which may be powered with Radioisotope Power Sources (RTGs or RHUs).
Radioisotope Power Sources (RPSs) and/or RHUs are generally considered for potential use on missions constrained by one or more of the following conditions:
the mission occurs too far from the sun to make feasible use of solar power,
the mission occurs in a space radiation environment too harsh to allow sustained use of solar cells,
the mission occurs near a planet's poles where solar illumination is insufficient for solar arrays,
the mission occurs on a dust- or cloud-enshrouded world, or in a subsurface application, where the use
of solar power is impractical or impossible,
the mission must operate in night environments with time frames beyond practical battery capacity,
and/or
the mission occurs where the solar intensity is so high as to be damaging (i.e., very near sun
environment).
Examples of potential space science missions that are under study [and] fall into one or more of these categories include:
Europa (Jupiter's Moon) Ocean Explorer (Orbiter) - this mission would occur far from the Sun (5 times the Earth-Sun distance), in an intense radiation environment, and with the possibility of lengthy eclipses.
Europa Lander - this mission would not only occur far from the Sun in an intense radiation environment, with frequent day-night cycles and Jupiter solar eclipses, but might also involve submersible exploration of a Europa ocean.
Pluto Express (Flyby) - this mission would occur very far from the Sun (30 times the Earth-Sun distance).
Titan (Saturn's Moon) Biologic Explorer - this mission would involve the use of an aerobot within Titan's atmosphere and a data relay orbiter; both would be far from the Sun (9 times the Earth-Sun distance), and the aerobot would be operating in Titan's cloud enshrouded atmosphere.
Interstellar Probe - this mission would occur at 150 to 200 times the Earth-Sun distance.
Mars landers, rovers, or penetrators involving extended operations (2 to 19 years) in very dusty conditions, at extremely low temperatures, or in subsurface applications (generally, RHUs are required).
Venus lander - would involve operation beneath dense clouds; carbon dioxide and sulfuric acid atmosphere.
The amount of plutonium-238 dioxide potentially required for each of these missions generally ranges between roughly 3 grams (one RHU) to 2 kg (for a 150 watt-electric class RPS).
Such missions are currently being studied, but are not yet approved. Other missions that potentially could require RPSs or RHUs are in the conceptual phase - the foregoing being examples that establish power requirements for technology planning purposes.
4.3 "NASA FACTS: Future NASA Spacecraft" (1998)
In response to a Freedom of Information Act inquiry of journalistic professor Karl Grossman, NASA's JPL finally issued another Fact Sheet in April 1998: "NASA FACTS: Future Spacecraft: Solar Arrays, Batteries, and Radioisotope Power and Heating Systems." When he returned from the international annual meeting of the Global Network Against Weapons and Nuclear Power in Space which took place in the first week of April 1998 in Colorado Springs/Colorado, he found the long-asked-for information in his mail. At the same time, NASA made the fact sheet available in the Internet [JPL/f]. Shortly afterwards, the same text was re-posted on the Internet by NASA under a different web address. The title has been changed to "NASA Facts: Future Missions", the layout has been improved, and all pictures have been included [JPL/e]. As this Fact Sheet states the current NASA policy with respect to nuclear powered space missions and future plans, it is re-printed in full length in this Working Paper.
In summary, the 1998 Fact Sheets says that no nuclear powered missions are planned for the next five years (RHU usage is mentioned in the Fact Sheet but not further considered in this section of the article). Three missions are "under advanced study", i.e. "NASA generally accepts the concept, however, detailed spacecraft and mission design (and sometimes specific funding approval) are needed before development can begin". Another five missions are "conceptual studies" which "means the mission is an idea that might be proposed by or to NASA but has not been selected for advanced study" [all quotes JPL/e].
In the 1998 Fact Sheet, the conditions given for RTG usage are the same as in the 1997 Fact Sheet. This is not quite the case for the planned missions. As an attempt is made to give more details about the planned missions below, the mission list according to the 1998 Fact Sheet is quoted here:
"Examples of future missions, which may require the use of radioisotope power systems are:
Pluto/Kuiper Express (Adv. Study): Map the surface and characterize the atmosphere of Pluto and its moon Charon.
Europa Orbiter(26) (Adv. Study): Study Europa (a moon of Jupiter) in search of possible liquid water oceans beneath the surface ice.
Solar Probe (Adv. Study): Study the origin of the solar wind.
Interstellar Probe (Conceptual Study): Characterize interstellar dust and gas at 900 million miles from the sun and beyond.
Europa Lander (Conceptual Study): Study the seismology and possibly penetrate the ice crust to reach a liquid water ocean.
Io Volcanic Observer (Conceptual Study): Extensive study of Io's (a moon of Jupiter) surface and volcanic activity.
Titan Organic Explorer(27) (Conceptual Study): Use landers or aerobots to investigate the surface and chemistry or Titan's (a moon of Saturn) atmosphere.
Neptune Orbiter (Conceptual Study): Extensive study of Neptune's system." [JPL/e]
4.4 Future RTG Development
In addition to the conditions and future missions, the 1998 NASA Fact Sheet gives some basic information about RTGs and RHUs. In this context, NASA basically repeats the information from the previous Fact Sheet: "NASA is working with the Department of Energy to identify power requirements of future spacecraft, and to design smaller and more efficient power systems. These power systems may only need to carry about 2-3 kg (about 4-7 lb) of nuclear material for power generation." [JPL/b]
The need to develop new RTGs is mentioned by several U.S. government organizations. DoE says: "NASA has identified a number of potential missions that can best or only be undertaken using radioisotope power and/or heat sources. These future missions depend upon two important conditions.
First, there must be a reliable and continuing supply of Pu-238 fuel from the U.S. Department of Energy. U.S. facilities that could supply Pu-238 are being considered, as are foreign sources such as Russia, England, and France.
Second, smaller and more efficient power systems will have to be developed consistent with NASA's needs." [USDOE/d, pages 26/27]
In another document, DoE becomes more explicit about the infrastructure required to build RTGs and about the importance of RTG development for 'national security': "In all, the Department has provided a total of 41 power sources for 24 missions since 1961. DoE continues to maintain the capability to provide power and heater systems to NASA for further missions.
The space and defense radioisotope thermoelectric generator program provides support for radioisotope power source development, demonstration, testing, and delivery. Radioisotope power sources are the enabling technology for space and terrestrial applications requiring proven, reliable and maintenance-free power supplies capable of producing up to several kilowatts of power and operating under severe environmental conditions for many years.
The program will develop new, state-of-the-art power supplies required to support both the National Aeronautics and Space Administration (NASA) space missions as well as the national security applications. The outyear planning for these missions reflects arrangements with the national security users, NASA, and the U.S. Department of Energy (DoE) to ensure the capabilities of the facility infrastructure to produce RTGs. This infrastructure represents the sole national capability to produce radioisotope power systems. Without these systems, critical national security activities and NASA missions to explore deep space and the surfaces of neighboring planets would not occur." [USDOE/a]
DoE also describes technological solutions for nuclear spacecraft power supply other than the traditional RTGs: "One option is the dynamic isotope power systems (DIPS), which are much more efficient in converting heat into electricity than the RTGs used on recent missions. ... The range of technologies under investigation is wide. For instance, a process called Alkaline Metal Thermal to Electric Conversion (AMTEC) converts infrared radiation into electricity using liquid metal ions, which are charged atoms. By contrast, the thermo-photovoltaic (TPV) converter changes infrared radiation emitted by a hot surface into electricity. Design goals for AMTEC and TPV technology call for even more efficient conversion of heat into electricity of about 20-30%, or a three-fold increase over RTGs. The higher efficiencies of these new technologies mean that future spacecraft may require less Pu-238 than RTGs typically use. ...
Because of its many advantages, it seems likely that nuclear energy will continue to provide power on space missions into the next century, whether in RTGs, other advanced generators, or nuclear reactors." [USDOE/d, page 27]
In May 1998, the U.S. General Accounting Office (GAO) published a report to U.S. Senator Barbara Boxer, "Space Exploration. Power Sources for Deep Space Probes". The report has its focus on the Cassini mission and gives an outlook to future NASA plans. It is one of two official government documents known to the author of this article which deals with financial details of RTG development:(28)
"During the past 30 years, NASA , DoE, and DoD have invested over $180 million in solar array technology, the primary non-nuclear power source. In fiscal year 1998, NASA and DoD will invest $10 million to improve solar array systems, and NASA will invest $10 million to improve nuclear-fueled systems. (29) ... There are no currently practical alternatives to using nuclear fueled power generation systems for most missions beyond the orbit of Mars. ...
NASA is studying eight future deep space missions between 2000 and 2015 that will likely require nuclear-fueled power systems to generate electricity for the spacecraft. None of these missions have been approved or funded, but typically about one-half of such missions are eventually funded and launched." [USGOA, page 3, emphasis added]
"NASA and DoE are working on new nuclear-fueled generators for use on future space missions. NASA and DoE's Advanced Radioisotope Power Source Program is intended to replace RTGs with an advanced nuclear-fueled generator that will more efficiently convert heat into electricity and require less plutonium dioxide fuel than existing RTGs. NASA and DoE plan to flight test a key component of the new generator on a space shuttle mission. The test system will use electrical power to provide heat during the test. If development of this new generator is successful, it will be used on future missions." [USGOA, page 13, emphasis added]
In a statement explaining the DoE budget 1999, Director Terry R. Lash summarizes the requested budget as follows:
|
"Budget Authority ($ in Millions) |
||
| Program Element Request | FY 1999 | |
| Nuclear Energy R&D | $116.9 | |
| Advanced Radioisotope Power Systems | 40.5 | |
| Test Reactor Area Landlord | 7.4 | |
| University Nuclear Science and Reactor Support | 10.0 | |
| Nuclear Energy Research Initiative | 24.0 | |
| Nuclear Energy Plant Optimization | 10.0 | |
| Nuclear Technology R&D | 25.0 | |
| Program Direction | 23.6 | |
| Facilities | *96.2 | |
| International Nuclear Safety | 35.0 | |
| Uranium Programs | 66.7 | |
| Isotope Support | 22.4 | |
| TOTAL NUCLEAR ENERGY, SCIENCE AND TECHNOLOGY REQUEST | $360.8 |
*Includes $31.2 million in activities transferred from the Environmental Management budget associated with the Fast Flux Test Facility." [USDOE/e]
Terry Lash continues to give details about the individual items, among them Radioisotope Power Systems.
"ADVANCED RADIOISOTOPE POWER SYSTEMS
The Department of Energy and its predecessor agencies have provided radioisotope power systems for use in space and terrestrial applications for over 35 years. These systems are safe, proven, reliable, maintenance free, and capable of producing either heat or electricity for many years under the conditions required for deep space and unattended terrestrial missions. The unique characteristics of these systems make them especially suited to applications where large arrays of solar cells or batteries are not practical, e.g., at large distances from the sun where there is little sunlight or in harsh environments. To date, the Department has provided over 40 radioisotope power systems for use on a total of 25 spacecraft; in addition, two spacecraft were launched with radioisotope heaters on board. In FY 1998, NASA launched the Cassini spacecraft to Saturn. Cassini is entirely electrically powered by three radioisotope thermoelectric generators provided by the Department. Many isotope power systems have also been provided for terrestrial applications. Critical national security activities and NASA missions to explore deep space and the surfaces of planets would not occur without these systems.
In FY 1999, the program will continue developing new power supplies required to support both future NASA space exploration such as a mission to Pluto and national security applications. The national security users will require upgraded versions of existing terrestrial power systems. Future missions by NASA will require both new radioisotope power systems as well as the continued use of radioisotope heater units. The emphasis will be on lighter weight, lower power systems. The R&D will include more efficient energy conversion technology and new materials. There will be an emphasis on developing a relatively standardized family of systems that could meet a range of power requirements based on mission needs at reasonable cost.
The outyear planning for future space missions reflects arrangements with the national security users, NASA, and the Department to ensure maintenance of the facility infrastructure to produce radioisotope power systems. This infrastructure represents the sole national capability to produce radioisotope systems. The Department of Energy recognized the need to keep these facilities operational, and maintenance level operations will continue at each facility with limited amounts of hardware being fabricated. Maintenance of this capability will allow for a quick transition into a production mode without having to requalify facilities and personnel as new missions become finalized. In accordance with arrangements with our customer agencies, NASA, or other users, will provide funds to the Department to pay for mission specific costs including development, hardware fabrication, and other support costs.
A key factor in the ability to provide radioisotope systems for future missions is to have an adequate supply of plutonium-238 (Pu-238) that is used in all of these systems. It is very important to note that Pu-238 is not weapons-grade material and is not useable as the explosive in nuclear weapons. The current inventory of this isotope, with the exception of approximately nine kilograms that were purchased from Russia, was produced in Savannah Rivers K-reactor and processing facilities that have been, or are in the process of being, shut down. In the near term, the inventory will be augmented by purchasing additional Pu-238 from Russia, while development of a domestic production source is investigated further. The Department is discussing with NASA a new funding approach that would have NASA provide the Department with funding prior to making purchases of Pu-238. This new approach could be implemented beginning in FY 1999.
The Advanced Radioisotope Power Systems Program is an important part of the R&D efforts of the Department. In conjunction with the user agencies, the Department will maintain the capability to supply these systems for future missions that are important to the exploration of space and vital to U.S. security interests." [USDOE/e]
With respect to the development of a new RTG type, Pluto Express seems to play a key role:
"NASA has asked DoE to sponsor design studies on a lower-power RTG that could be used on
the proposed Pluto Express mission, which is under very restrictive mass and cost constraints. In
order to reduce both mass and the amount of plutonium-238 a number of advanced
thermal-to-electric conversion options are being considered, including small Stirling engines,
thermophotovoltaics (essentially solar cells tuned to the infrared radiation of the radioisotope heat
source), and alkali metal thermal-to-electric conversion (AMTEC). Maintenance of these
technology options is essential to meet the power requirements of the new, smaller, cheaper space
missions such as the Pluto Express mission." [AIAA]
4.5 "Advanced Solar Arrays And Solar Reflectors"
NASA information about the future mission Io Volcanic Observer (see Section 4.6.5, Io Volcanic Observer) contains a link to another page titled "Advanced Solar Arrays and Solar Reflectors"(30). This page shows two pictures subtitled "Linear Concentrator Array" and "Inflatable Antenna Experiment". The text of this Internet page describes development work for deep space solar technology (spelling changed by author of this article):
"Improved solar array technology will enable solar-electric propulsion and inexpensive missions to the Jupiter System.
50-100 W required at Jupiter
Up to 15 kW at 1 AU for SEP(31)
Efficiency exceeding 100 W/kg
Radiation and thermal tolerance
Current solar array technology at 40 W/kg is too heavy for many future missions
New millenium Scarlet'
Inflatable demo completed May 1996
Solar concentrators can focus sunlight on collection surface/converter
Inflatables or rigid surfaces
Inflatable technology also required to deploy large panels of advances solar arrays." [JPL/a]
4.6 Details About Future Missions
The missions mentioned by the Florida Coalition [FCPJ] and by NASA [NASA/d and JPL/e] amount to a total of 20 launches for which RTG usage has been considered in recent years. The following sections provide some basic information about the objectives of the individual missions. Where available, additional information about the missions' power supply or other features is also given. As will be shown in the quotations below, official NASA documents point to the feasibility of solar power alternatives for several of the RTG missions listed in the 1998 NASA Fact Sheet!
4.6.1 Comet Nucleus
"NASA has selected the 5th and 6th missions to be conducted on behalf of its DISCOVERY program for low-cost interplanetary probes. The US$216-million GENESIS spacecraft will be launched in January 2001 to collect solar wind particles and return them to Earth in August 2003. The US$154-million COMET NUCLEUS TOUR (CONTOUR) mission will be launched in July 2002 to flyby comets P/Encke in November 2003, P/Schwassmann-Wachmann-3 in June 2006 and P/d'Arrest in August 2008." [ORBITAL]
"Science Objectives
CONTOUR's goals are to dramatically improve our knowledge of key characteristics of comet nuclei and to assess their diversity. The targets span the range from a very evolved comet (Encke) to a future 'new' comet such as Hale-Bopp. CONTOUR builds on the exploratory results from the Halley flybys, and will extend the applicability of data obtained by NASA's Stardust and ESA's Rosetta to broaden our understanding of comets. Key measurements include
Imaging nuclei at resolutions of 4 m (25 times better than Giotto).
Spectral mapping of nuclei at resolutions of 100-200 m.
Detailed compositional data on both gas and dust in the near-nucleus environment at precisions comparable to those of Giotto or better. ...
The CONTOUR Comets
Encke: A unique object. Comet Encke has been observed at more apparitions than any other comet including Halley. It is one of the most evolved comets that still remains active. In its present orbit, Encke returns to perihelion (dist. ~ 0.34 AU) every 3.3 years. Because Encke has been in this orbit for thousands of years, its continued high level of activity is rather puzzling.
SW3: First discovered in 1930, the activity pattern of SW3 is usually very predictable. However, in late 1995, this comet displayed dramatic variability, and split into at least three pieces. When CONTOUR arrives in 2006, it is likely that relatively unmantled materials will be visible in the cleaved areas, and that evidence of internal structures will remain exposed.
d'Arrest: Since this comet's discovery in 1851, the repeatability of its visual light curve from apparition to apparition suggests that the rotation state is stable, and that its surface outgassing vents change very little with time. ...
CONTOUR Spacecraft
... Body-mounted solar array
... Designed for 0.75 to 1.5 AU solar distance" [JHUAPL]
Comet Nucleus is part of NASA's Discovery program. Discovery missions are not permitted to use RTGs.(32) Therefore, Comet Nucleus will not use RTGs to produce electricity but solar arrays. This mission is no longer listed in the 1998 NASA Fact Sheet.
4.6.2 Europa Lander (Europa Lander Network)
"Europa stands out among outer solar system objects in that it may possess subsurface liquid water in global shells, regional zones, or in isolated pockets. As such the top science objective for such a mission is to detect and characterize these zones." [NASA/i]
Not much information about this mission is provided in the NASA web. However, the information available clearly points to the feasibility of solar power for the mission.
"Science Objectives:
Measure ice thickness
Tomography of layers
Chemical analysis of surface
Mission Description:
Minimum of 3 landers though precursor mission could use just 1 for seismicity measurements
Semi-hard landing with caging
Some penetration of ice surface (for rad protection and seismic improvement)
Precursor mission
Tech[nology]:
... Efficient, lightweight solar power generation at Jupiter distance ..." [JPL/g]
This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.3 Europa Orbiter (Europa Ocean Observer)
Europa Orbiter, which is also named Europa Ocean Explorer, is planned to be launched in 2002 or 2004. This mission is part of NASA's Outer Planets Program.(33) NASA's Solar System Exploration Subcommittee identified several criteria which should be addressed before deciding about the Europa Orbiter mission (radar sounder development, radiation tolerance of electronics, propulsion technology, and interpretation of additional Galileo science data, [NASA/i]) development of non-nuclear power systems for the Europa mission is not one of them.
As for the Europa Lander mission, little information is available about the Europa Orbiter/Europa Ocean Observer mission. But the little information mentions feasibility of solar power for this mission:
"Science Objectives:
Verify presence of liquid layer
Measure ice thickness and interior properties
Image surface features
Tech[nology]:
... Efficient, lightweight solar power generation at Jupiter distance." [JPL/h]
This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.4 Interstellar Probe
"In our present view of the large scale structure of the heliosphere, the solar wind flows radially outward to a 'termination shock' surrounded at somewhat greater distance by a contact surface called the heliopause, which is the boundary between solar wind and interstellar plasma. A bubble of solar wind therefore shields the inner heliosphere from the plasma, energetic particles, and fields of the interstellar medium; to observe these directly, one must get outside the heliopause. Although the size of the heliosphere is not certain, several recent estimates place the distance to the termination shock at ~80 to 90 AU(34), with the heliopause somewhat further beyond.
The Interstellar Probe Mission would be designed to cross the solar wind termination shock and heliopause and make a significant penetration into nearby interstellar space. The principal scientific objectives of this mission would be to (1) explore the structure of the heliosphere and its interaction with the interstellar medium; (2) explore the nature of the interstellar medium, and its implications for the origin and evolution of matter in the galaxy, and (3) investigate fundamental astrophysical processes occurring in the heliosphere and interstellar medium. ...
To accomplish its objectives an Interstellar Probe should acquire data out to a heliocentric distance of ~200 AU [which] requires spacecraft velocities of ~10 AU/year to achieve this within ~25 years or less." [NASA/g]
"Technology Requirements: Advanced propulsion and non-solar power source (if not RTGs) ...
Mission Description: ... Potential methods: close Jupiter/Sun flybys; nuclear or RTG electric propulsion." (35) [NASA/f]
This mission would operate at a distance from the sun where currently only RTGs can provide the
required electricity. It is listed as one of eight nuclear powered space missions in the 1998 NASA
Fact Sheet.
4.6.5 Io Volcanic Observer
Information provided about the Io Volcanic Observer mission explicitly points at the feasibility of solar power.
"Io's extraordinary rates of volcanism and heat flow make it a prime target for the study of planetary evolution. Understanding how Io's volcanism is generated and sustained is key to understanding how planets generate and loose heat. The Earth, while contrasting the styles of volcanism on Io with those of Moon, Mars and Venus, provides a window through which we can view mantle composition and differentiation on these different planets. Galileo's recent results have shown that high temperature volcanism is abundant on Io, and that the active volcanic centers are more numerous than previously thought. ...
To understand this very active planet [sic! Io is a moon of Jupiter], a mission is needed which can unequivocally determine the total heat flow and the mechanism which sustains it, the degree of differentiation of the mantle and the composition of the lavas which rise from it, and the mechanism which feeds clouds surrounding Io. ...
Tours which orbit Jupiter require a delta V of about 1.2 km/sec, which is achievable within Discovery resources. A flyby requires significantly less delta V, permitting a larger spacecraft (or larger solar panels). Solar Electric Propulsion (SEP) is practical and is a good match with the large solar arrays needed at 5.2 AU. Inflatable and concentrator arrays both appear useable at Jupiter, though the radiation effects can be serious for missions of long duration." [JPL/o]
This evaluation is repeated in another NASA document: "Tech[nology]: ... Efficient, radiation-tolerant solar arrays." [JPL/i] (See also Section 4.5"Advanced Solar Arrays And Solar Reflectors".)
This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.6 Mars Missions (5 Launches)
The Florida Coalition web page [FCPJ] lists a total of five upcoming Mars missions: 3 MESUR launches in 1999, 2001, and 2003, and two Mars SR launches in 2007 and 2009.
Mars landers, rovers, or penetrators are listed as RTG missions in the 1997 but not in the 1998 NASA Fact Sheet. Quite on the contrary: a picture subtitle in the 1998 Fact Sheet explicitly explains: "The Mars Surveyor Program would embark on a mission to bring back soil samples from Mars. These samples would help us understand whether life ever existed on Mars. The Lander and Rover can use solar arrays and batteries for power, but may need RHUs to keep electrical components warm enough to survive the cold Martian nights." [JPL/e]
In all, NASA plans a total of ten Mars launches within the next years:
Mars Surveyor '98 consisting of Mars Climate Orbiter (planned launch Dec. 10, 1998) and Mars Polar Lander (planned launch Jan. 3, 1999)
Mars Surveyor 2001 consisting of the 2001 Orbiter (planned launch Jan. 27, 2001), the 2001 Rover (planned launch on April 3, 2001) and 2001 Lander (planned launch April 3, 2001)
Mars Surveyor 2003 with an Orbiter, a Lander, and a Rover (planned launch May/June 2003)
Mars Surveyor 2005 with an Orbiter and a Lander for sample acquisition and return of the samples to Earth (planned launch July/August 2005).(36)
4.6.7 Moon Missions (4 Launches)
The Florida Coalition web page [FCPJ] lists four Moon missions as Upcoming Plutonium Launches: Site Rover (1998), Telescope (1999), and two Network launches (2001 and 2002).
One Moon mission, the Lunar Prospector, was launched by NASA on Jan. 6, 1998. The NASA
web pages contain no information which points to any future planned Moon missions.
4.6.8
Neptune Orbiter
"The results from the highly successful Voyager Neptune encounter pose many profound questions that only follow-on missions will be able to answer. Recent investigations of other star systems have resulted in fundamental questions that may be approached through probing our solar system's gas giants as astrophysical analogs and solar system laboratories. The Neptune Orbiter mission is a high priority part ... for the future NASA Solar System Exploration program. The potential science returned from a Neptune Orbiter mission is in the break through category and enabled by advanced technologies." [JPL/p]
"Science Objectives
Atmospheric structure and circulation at Neptune and Triton
Ring particle physical properties, dynamics, and distribution
Magnetosphere structure and dynamics
Map the gravity field (Neptune)
Composition, structure, and activity of Triton surface
Mission Description
Delta-class launch vehicle
Flight time: 6-7 years using advanced SEP
Autonomous operation and navigation
Aerocapture for orbit insertion
Daily flybys of Triton possible" [JPL/b]
In addition to investigating Neptune, the mission is also planned to explore Triton, Neptune's largest moon. Although NASA plans to use high-power solar electric propulsion for this mission, the use of solar panels is not feasible at Neptune. Neptune is too far away from the Sun, consequently there is not sufficient light available.
This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.9 Pluto/Kuiper-Express (2 Launches)
"Pluto is the largest of a class of primordial bodies at the edge of our Solar System which have comet-like properties and remain relatively unmodified by warming from the Sun. Pluto is thought to be compositionally similar to Triton, the largest moon of Neptune, which was reconnoitered by Voyager 2. These two bodies may also be similar to Charon at 10 to 20 AU(37) and the recently discovered Kuiper belt objects out at 40 AU and beyond. All of these objects probably hold important clues to the origin of comets and the evolution of the solar system. Pluto has a large moon, Charon, which has properties very different from Pluto, and this bizarre double body system may have resulted from a catastrophic planetary collision.
At the present time, Pluto has just passed perihelion at 30 AU and is now moving farther away from the Sun on its way out to 50 AU. Stellar occultation observations have shown that Pluto currently has a temporary atmosphere now that it has been warmed by the Sun during this very brief 'summer' in its 248 year orbit. It is anticipated that these gases will freeze out onto the planet's surface sometime over the next 2-3 decades. It is highly desirable to observe this atmosphere with UV and radio occultation experiments before it disappears, and to observe surface features and chemical makeup that may be obscured if and when the atmosphere collapses." [JPL/CIT]
"Planned launch date: 2001
Launch vehicle: Delta or Russian Proton
Planned on-orbit mass: <100 kg
Power System: Radioisotope Thermal Generators (RTGs) of 65 W
Originally designated the Pluto Fast Flyby (PFF), the Pluto Express mission is planned to be a two spacecraft mission designed to make studies of the planet Pluto and its satellite Charon. Its major science objectives are to: (1) characterize the global geology and geomorphology of Pluto and Charon; (2) map the composition of Pluto's surface; and (3) determine the composition and structure of Pluto's atmosphere. Intended to reach Pluto as quickly as possible (before the tenuous Plutonian atmosphere can refreeze onto the surface as the planet recedes from the Sun), the two Pluto Express spacecraft will arrive one year apart after 6-9 years of travel, depending on the ultimate mass of the spacecraft. Studies of the double-planet system will begin 12-18 months prior to closest approach. The overall structure of the spacecraft is an aluminum hexagonal bus with no deployable structures. Power will be provided by radioisotope thermal generators (RTGs) similar in design to those used on earlier missions (e.g. Galileo). ... A potential cooperative effort with Russia may lead to the inclusion of Zone probes, to study the Plutonian atmosphere." [UNKNOWN]
The information about two launches for the Pluto-Kuiper Express mission is repeated in an official document: "The current plan is to have two launches to Pluto, each carrying one flight system and possibly attached probes." [JPL/CIT](38)
"In order to reduce the launch costs the Pluto Express sciencecraft will loop around Venus three times, building momentum with each passing before getting a final tug at Jupiter to fling them on through the outer Solar System.
This trajectory path is one of several options(39) being considered providing an opportunity to arrive at the distant double-planet system in 2013." [JPL/k]
The optimum trajectory is a major issue for NASA. The direct trajectory to Pluto would be preferred but is considered too expensive as a large rocket with an additional stage would be required for the launch. "Today's funding environment" does not allow for this option. Therefore, a flyby trajectory must be chosen.
"In order to allow for lower cost missions on Delta or Molniya class launchers without the expense of an upper stage, there are other mission design options. Earth/Jupiter gravity assist trajectories can achieve flight times of around ten years, but require the spacecraft to be capable of surviving significantly higher radiation levels(40), and require a much larger onboard propulsion system. Another drawback with these trajectories is the amount of effort needed to ensure that the probability of an Earth impact during the Earth flyby is acceptably low. A straight Jupiter Gravity Assist (JGA) trajectory is available for Delta and Molniya class launchers in 2003 and 2004. ... There is an attractive option for a Venus/Venus/Venus/Jupiter Gravity Assist (VVVJGA) trajectory which avoids an Earth flyby and can be launched on a Delta or Molniya class vehicle without an upper stage, with a flight time of about 11.8 years, launching in March 2001. There is a backup Venus/Venus/Jupiter Gravity Assist (VVJGA) trajectory available in July 2002." [JPL/CIT]
Pluto is the last planet in our solar system. Its distance from the sun is so large that virtually no light is available which could be used to produce solar electricity. This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.10 Solar Probe
As for several of the other missions, NASA documents show the feasibility of solar power for the Solar Probe mission:
"The solar corona is one of the last unexplored regions of the solar system and one of the most important to understand in terms of Sun-Earth connection. SOHO and Ulysses results have focused understanding of regions to the point when the in situ measurements are necessary for further progress.
This report describes a robust, scientifically important space mission to explore the source of the solar wind from inside the solar corona at 2 to 110 solar radii from the Sun.
Our primary science objective is to understand the processes that heat the solar corona and produce the solar wind. ...
The mission and spacecraft designs are partly derived from concepts developed for earlier missions but with important differences which result in cost saving and enhanced science return:
A science payload mass of under 16 kilograms, requiring less than 16 watts and a data return of up to 100 kilobits per second meets the focused science objectives." [JPL/l]
""The present design uses non-nuclear power systems, ..." [JPL/n] "As shown above [in a picture], low illumination solar panels will provide power for the spacecraft from 5 AU to 0.7 AU, where the panels will be discarded. In the baseline mission, high temperature arrays will be used from 0.7 to 0.2 AU, where this second set will be jettisoned. Power will be supplied by batteries from 0.2 AU to perihelion plus 14 hours. In a mission option, high temperature arrays which are currently under technological development will be used from 0.7 to 0.1 AU and will then be tucked into the spacecraft umbra inside 0.1 AU. They will be redeployed at 0.1 AU on the outbound leg and the mission will continue until perihelion plus 17 days." [JPL/m]
This mission is listed as one of eight nuclear powered space missions in the 1998 NASA Fact Sheet.
4.6.11 Titan Organic Explorer
(= Titan Biologic Explorer)
"Titan has an atmosphere with a higher surface pressure than Earth's that is filled with organic compounds produced by the action of sunlight. A Titan organic explorer would determine the composition of organic compounds in Titan's atmosphere and on its surface, and whether these organics display pre-biological characteristics." [OSS]
Although this mission is mentioned in several NASA documents, no further details are provided. Titan is a moon of planet Jupiter. The ESA probe Huygens of the joint ESA/NASA mission Cassini/Huygens (see Section 3, Past Missions a Chronology for more details) is planned to descend to Titan and explore the moon's atmosphere.
Although not explicitly mentioned, it seems that Titan's atmosphere is so dense that not enough
sunlight might pass through to power solar panels. This mission is listed as one of eight nuclear
powered space missions in the 1998 NASA Fact Sheet.
4.6.12 Venus Lander
The full mission name is Venus Geophysical Network Pathfinder (VGNP) and includes a Venus surface lander. In addition to some mission details, Malin Space Science Systems, Inc. (MSSS) specifies the power supply of the mission as follows: "On top of the lander, beneath the boom, is the cylindrical housing of the radioisotope thermoelectric generator, which generates 6500 thermal watts to supply 260 electrical watts needed to power a three-stage refrigeration system. The system is capable of cooling the electronics, housed in a dewer, to about 80 deg. C. The VGNP is designed to survive in the 460 deg C, 93 bar ambient Venusian environment for at least one Earth year." [MALIN/b]
According to MSSS, Venus Lander is planned to be launched in early June 1999 and due to arrive at Venus appr. 120 days later.
The MSSS document informs about the VGNP power generation in some detail:
"Although the science instruments and their support electronics require only a small amount of power (~12 W, only 5.5 W within the refrigerated dewar), the refrigeration subsystem itself will require a significant amount of uninterruptable electric power for the duration of the mission. Several options were examined in terms of meeting the following criteria:
1. The power system must operate in the ambient Venusian atmosphere for a period of at least one year.
2. The power system must utilize technology of a developed and proven nature. Modifications were allowed within the overall paradigm.
3. The power system must meet cost and schedule constraints consistent with a Discovery-class mission.
There are few power sources available at the surface of Venus. Batteries would not meet the mission duration requirements, and would have difficulty in the ambient environment. Sunlight reaching the Venusian surface is roughly 2% at its cloud tops, mostly long wavelength and very diffuse that, along with the high operating temperature, precludes the use of solar cells. Although wind energy may be a potential source of power, it is probably unreliable for continuous operations on the timescale of a year. Brayton, high condenser temperature Rankine, and Sterling technologies are not reasonable power systems for reasons noted earlier. After careful consideration, Radioisotope Thermal Generators (RTGs) utilizing silicon-germanium thermo-electric elements were chosen as the most appropriate technology for this mission. Based primarily on a design utilized by Cassini and planned for MESUR(41), General Electric/AstroSpace Space Power division have outlined a system which could operate on the Venusian surface." [MALIN/a]
It should be pointed out that MSSS mentions the involvement of General Electric (GE) in RTG development and production. After some explanations about required RTG modifications for the Venusian environment, the MSSS document continues to talk about financial matters:
"Future availability of RTGs is presently(42) a topic of considerable discussion within the Federal government. The Department of Energy's (DoE) Special Projects office provides RTGs to NASA more or less at cost. NASA has not, in the past, been required to pay a fee towards maintaining DoE's ability to provide these devices. However, with the decrease in demand for weapons-grade Pu and other issues leading to the shutdown of DoE facilities, there is concern that RTGs may not be available in the future. This proposal assumes that NASA must maintain access to radioisotope power generation, both for large unmanned missions and for initial power systems for large space endeavors. Discussions with GE and DoE indicate their willingness and ability to meet the VGNP requirements, and the cost estimate given assumes a worst case wherein VGNP would be responsible for the entire production cost." [MALIN/a]
Venus Lander is part of the Discovery program, therefore RTG usage is not permitted.
Consequently, this mission is no longer listed in the 1998 NASA Fact Sheet.
4.7 Future Missions Summary
Of the 20 missions which have been mentioned as nuclear powered missions during recent years, the 1998 Fact Sheet lists still eight (Pluto/Kuiper Express is listed as one mission although it will involve two launches.)
Of the eight missions listed, four are technically feasible only when RTGs are used (based on today's technology and under the assumption that Titan Organic Explorer can not be powered by solar arrays.)
For four of the eight missions listed in the latest Fact Sheet, however, other NASA information
clearly shows that the missions can be done with solar power - and that corresponding planning is
under way!
==============================================
5. Conclusion
Currently, hundreds of kilograms plutonium and almost a metric ton of uranium circle the Earth on board of U.S. and Soviet spacecrafts - many of them on orbits which are all but safe. It is hoped, that the list in Chapter 3, Past Missions a Chronology creates an awareness of just how huge these amounts are and how many accidents occurred. On an average, there is one accident for each seven space missions - this is also true for nuclear powered space missions.
Another obviously ignored problem might yet seem ahead. In the Orbital Debris Quarterly News, Volume 2, Issue 4 (1997), NASA's Johnson Space Center pointed to a 'mystery': the slow disintegration of spacecrafts many years after launch. The author of this article can not evaluate the implications this might have for the nuclear powered U.S. satellites orbiting Earth. It should, however, not be excluded that disintegration could happen for such satellites also with a sharp increase in the likelihood of RTGs decaying into the Earth atmosphere almost any time.
As degradation seems to be a serious and 'mysterious' spacecraft behavior, the beginning of the article is quoted here:
Naval Space Operations Center Finds New Evidence of Debris Separations from Three Spacecraft
by Nicholas Johnson
During July and August personnel of the Naval Space Operations Center, which serves as the alternate Space Control Center for the US Space Surveillance Network, detected five new debris from three spacecraft, each more than 15 years old. The causes of these 'anomalous events', which involve very low separation velocities, remain a mystery, although material degradation or small particle impacts are probable agents.
At least six polar-orbiting Transit satellites have generated debris more than 20 years after launch. Sometime between 20 and 23 July, a single object was released from Transit 17 (1967-92A, Satellite Number 2965), marking at least the fourth such event for this spacecraft since 1981. The last previous debris release was in December 1996 (see Orbital Debris Quarterly News, January 1997). The five debris previously cataloged with this source all exhibited high area-to-mass ratios and have decayed from orbit.
Another newly discovered debris has been traced to Transit 10 (1965-109A, Satellite Number 1864) which was also involved in a late 1996 release. The debris was found in early August, but orbital analysis could not determine when it had been created. The two debris pieces remain in orbits very similar to that of the parent.
In late August the NOAA 7 spacecraft (1981-59A, Satellite Number 12553) spawned at least three new debris, one of which was cataloged as Satellite Number 24935. The debris appear to have been released, perhaps at the same time, during 23-24 August. The spacecraft had previously released two debris on 26 July 1993, three years after spacecraft deactivation, but both decayed the following year.
The mechanism behind the generation of anomalous event debris large enough to be tracked by ground-based sensors remains poorly understood. Some space objects, e.g., U.S. Transit spacecraft and Soviet Vostok upper stages, seem predisposed to such incidents and, therefore, are probably related to the design or materials selection of the vehicles. Transit spacecraft are likely to exhibit multiple events, whereas the Vostok upper stages appear limited to a single event. However, only a small percentage of vehicles in these families are involved in anomalous events." [JSC/b]
For information about nuclear powered Transit missions, see Chapter 3, Past Missions a Chronology.
In addition to the past accidents and the recently observed 'anomalous events', the burden left to future generations has so far been completely neglected. Orbits of 900 km altitude for the Soviet RORSAT satellites are safe a few hundred years but eventually they will fall back to Earth. Responsibility demands to think about methods to prevent re-entry and burn-up of these generators and reactors today, rather than leave the problem to our descendants. And of course, alternatives to nuclear powered space missions should be found. The innovative approach of the European Space Agency described in Section 2.3, Other Nations - RTG Technology Is Not Available" gives an example for future-oriented solutions. In addition, NASA documents clearly show that for four of the eight suggested nuclear powered space missions the solar alternative is feasible.
==============================================
6. Acronyms
The following acronyms were used in this article:
ACE Atomic Energy Commission (U.S.)
AECB Atomic Energy Control Board (Canada)
AFB Air Force Base
AMTEC Alkaline Metal Thermal to Electric Conversion
AO Announcement of Opportunity
AU Astronomical Unit (1 AU = distance between Sun and Earth)
Bq Becquerel
C Celsius
Ci Curie
DIPS Dynamic Isotope Power Systems
DoD Department of Defense (U.S.)
DoE Department of Energy (U.S.)
ESA European Space Agency
ESTEC European Space Research and Technology Centre
FEIS Final Environmental Impact Statement
GAO General Accounting Office (U.S.)
GE General Electric
GPHS General Purpose Heat Source
HEU Highly Enriched Uranium
JGA Jupiter Gravity Assist
JSC Johnson Space Center (part of NASA)
K Kelvin
lbs pound; 1 lbs = 453,59 g
MSSS Malin Space Science Systems, Inc.
NASA National Aeronautics and Space Administration (U.S.)
NPS Nuclear Powered Satellite
PFF Pluto Fast Flyby
Pu-238 plutonium-238
Radar Radio detecting and ranging
RHU Radioisotope Heater Unit
RORSAT Radar Ocean Reconnaissance Satellite
RPS Radioisotope Power Source
RTG Radioisotope Thermoelectric Generator
SEP Solar Electric Propulsion
SNAP Space Nuclear Auxiliary Power
TFE Thermionic Fuel Element
TPV Thermo-Photovoltaic
U-235 uranium-235
U.S. United States (of America)
UNCOPUOS United Nations Committee on the Peaceful Uses of Outer Space
USSR Union of Socialist Soviet Republics
VGNP Venus Geophysical Network Pathfinder
W, w Watt
WE Watts electric
VVEJGA Venus Venus Earth Jupiter Gravity Assist
VVJGA Venus Venus Jupiter Gravity Assist
VVVJGA Venus Venus Venus Jupiter Gravity Assist
==============================================
7. Literature List
The URLs listed below were all verified to function correctly on August 10, 1998. The dates are either stated in the corresponding document or reflect the "last updated/reviewed" comment on the web page.
| Aerospace Power Systems Technical Committee of the American Institute of
Aeronautics and Astronautics
"Space Nuclear Power: Key to Outer Solar System Exploration" March 1995; http://www.aiaa.org/policy/papers/space-nuclear.html |
[AIAA] |
| Analytical Graphics
"The MARS96 Incident. An AGI News Brief" no date; http://stk.com/mars96/mars96.html |
[ANALYTICAL] |
| Anderson,Mark/Springfield Advocate
"Rocket's Dread Glare" Sept. or Oct. 1997; http://www.springfieldadvocate.com/articles/rocket.html |
[ANDERSON] |
| Bein, Michael
"Star Wars & Reactors in Space: A Canadian View" 1986; http://www.afn.org/~fcpj/space/art/canadapl.htm |
[BEIN] |
| Center for Biological Monitoring
"RADNET: Information about source points of anthropogenic radioactivity - A Freedom of Nuclear Information Resource" 1997; http://p3.acadia.net/cbm/Rad.html esp. Chapter 11. Anthropogenic Radioactivity: Major Plume Source Points Section 11.10 Nuclear Powered Satellite Accidents |
[CENTER] |
| European Space Agency, Public Relations Division
"New solar cells with record efficiency" Press Information Note No. 07-94, April 19, 1994 (hardcopy)(43) |
[ESA/a] |
| European Space Agency
"Taking Europe To The Moon" Press Release Nr. 09-98, March 5, 1998; http://www.esa.int/Press/98/press09.html |
[ESA/b] |
| European Space Research and Technology Centre/European Space Agency
"EuroMoon2000 - A Plan for a European Lunar South Pole Expedition" no date; http://www.estec.esa.nl/euromoon/public/brochure/pag4a.htm |
[ESTEC/a] |
|
European Space Research and Technology Centre/European Space Agency "Spacecraft Power for Ulysses" no date, http://helio.estec.esa.nl/ulysses/RTG.HTML |
[ESTEC/b] |
| European Space Research and Technology Centre/European Space Agency
"The International Rosetta Mission" 31 March 1998; http://www.estec.esa.nl/spdwww/rosetta/html/main.html |
[ESTEC/c] |
| Federation of American Scientists
"RORSAT" 1997; http://www.fas.org/spp/guide/russia/military/sigint/rorsat.htm |
[FAS] |
| Florida Coalition for Peace and Justice
"Upcoming Plutonium Launches" no date; http://www.afn.org/~fcpj/space/upcoming.htm |
[FCPJ] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS B" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbusB.html |
[FSU/a] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS III" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbus3.html |
[FSU/b] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS IV" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbus4.html |
[FSU/c] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS V" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbus5.html |
[FSU/d] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS VI" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbus6.html |
[FSU/e] |
| Florida State University, Department of Meteorology
"Weather Satellites: NIMBUS VII" no date; http://www.met.fsu.edu/explores/Guide/Nimbus_Html/nimbus7.html |
[FSU/f] |
| Institut für Luft- und Raumfahrt, Technische Universität Berlin
(Institute of Aeronautics and Astronautics at the Technical University of Berlin) "Object class: Mission Category: Rorsat" no date;http://vulcain.fb12.tu-berlin.de/AIM/FileCache/Mission_Ro.html |
[ILR] |
| Institute of Physics & Power Engineering (Russia)
"High-Temperature Nuclear Reactors for Space Applications" 1997; http://www.ippe.rssi.ru/activity/space.html |
[IPPE] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Advanced Solar Arrays and Solar Reflectors" no date; http://eis.jpl.nasa.gov/roadmap/site/tech/a/solar_arrays.html |
[JPL/a] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Astrophysical Analogs in the Solar System Mission: Neptune Orbiter With Triton Flybys" Sept. 27, 1996; http://eis.jpl.nasa.gov/roadmap/site/nasa/astroanalogs/astro09.html |
[JPL/b] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Cassini RTG Information" Dec. 1997; http://www.jpl.nasa.gov/cassini/rtg/rtginfo.htm |
[JPL/c] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"JPL Solar Probe Breckenridge Report" no date; http://solarprobe2.jpl.nasa.gov/solarprobe/SPBR.html |
[JPL/d] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"NASA Facts: Future Missions" (May 1998); http://www-b.jpl.nasa.gov/facts/future |
[JPL/e] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"NASA FACTS: Future NASA Spacecraft: Solar Arrays, Batteries, and Radioisotope Power and Heating Systems" April 1998; http://www.jpl.nasa.gov/cassini/rtg.future/index.html |
[JPL/f] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"NASA Roadmap Missions: Europa Lander Network" [sic! the title of this page says "Europa Ocean Observer" but talks about the Lander] no date; http://eis.jpl.nasa.gov/roadmap/site/missions/B/europa_lander_network.html |
[JPL/g] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"NASA Roadmap Missions: Europa Ocean Observer" no date; http://eis.jpl.nasa.gov/roadmap/site/missions/B/europa_ocean_observer.html |
[JPL/h] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"NASA Roadmap Missions: Io Volcanic Observer" no date; http://eis.jpl.nasa.gov/roadmap/site/missions/C/io_volcanic_observer.html |
[JPL/i] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Pluto-Kuiper Express Trajectories" Nov, 6, 1997; http://www.jpl.nasa.gov/pluto/trajectory.htm |
[JPL/k] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Solar Probe Executive Summary" no date; http://solarprobe2.jpl.nasa.gov/solarprobe/SPBR_Page3.html |
[JPL/l] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Solar Probe Mission Profile" no date; http://solarprobe2.jpl.nasa.gov/solarprobe/SPBR_Page12.html |
[JPL/m] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"The JPL/NASA Solar Probe Mission" October 30, 1997; http://www.jpl.nasa.gov/ice_fire/sppaper1.htm |
[JPL/n] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Third IAAA International Conference on Low-Cost Planetary Missions: Abstracts Getting Back To Io" no date; http://techinfo.jpl.nasa.gov/www/iaa98con/085.html |
[JPL/o] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration | [JPL/p] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Third IAAA International Conference on Low-Cost Planetary Missions: Abstracts Rosetta Lander In Situ Characterization of Comet Nucleus" no date; http://techinfo.jpl.nasa.gov/www/iaa98con/062.html |
[JPL/q] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration
"Third IAAA International Conference on Low-Cost Planetary Missions: Abstracts Technology Needs of Future Planetary Missions" no date; http://techinfo.jpl.nasa.gov/www/iaa98con/017.html |
[JPL/r] |
| Jet Propulsion Laboratory/National Aeronautics and Space Administration;
California Institute of Technology
"Pluto Express Sciencecraft Sytem Design" no date, http://www.jpl.nasa.gov/ice_fire/iaal0603.pdf |
[JPL/CIT] |
| John Hopkins University, Applied Physics Laboratory/Space Department
"CONTOUR - COmet Nucleus TOUR: A Mission to Study the Diversity of Comet Nuclei" April 1997;http://sd-www.jhuapl.edu/Contour/ |
[JHUAPL] |
| Johnson Space Center/National Aeronautics and Space Administration
"Interagency Report on Orbital Debris 1995 Appendix: History of On-Orbit Fragmentations" 1995; http://www-sn.jsc.nasa.gov/Debris/appendix.html |
[JSC/a] |
| Johnson Space Center/National Aeronautics and Space Administration
"Orbital Debris Quarterly News. Naval Space Operations Center Finds New Evidence of Debris Separations from Three Spacecraft" October - December, 1997; Volume 2, Issue 4; http://sn-callisto.jsc.nasa.gov/newsletter/v2i4/v2i4.html |
[JSC/b] |
| Kessler, Don
Johnson Space Center/National Aeronautics and Space Administration Orbital Debris Quarterly News Volume 2, Issue 2/April - June 1997 "The Search for a Previously Unknown Source of Orbital Debris: The Possibility of a Coolant Leak in Radar Ocean Reconnaissance Satellites (JSC-27727) 1997; http://sn-callisto.jsc.nasa.gov/newsletter/v2i2/v2i2.html |
[KESSLER] |
| Kurchatov Institute (Russia)
"Small-Sized Space Nuclear Power System" no date; http://kiae.polyn.kiae.su/eng/t6.html |
[KURCHATOV] |
| Malin Space Science Systems, Inc.
"Venus Geophysical Lander Discovery Concepts" 1996; http://barsoom.msss.com/http/new_directories/venus/vgnp/vgnp.txt.html This page was accessible on July 8, in August 1998 it said "Access forbidden" |
[MALIN/a] |
| Malin Space Science Systems, Inc.
"VGNP Cover Photo Caption" no date; http://barsoom.msss.com/venus/vgnp/covcap.html This page was accessible on July 8, in August 1998 it said "Access forbidden" |
[MALIN/b] |
| Mark Wade
"ENCYCLOPEDIA ASTRONAUTICA" May 2, 1998; http://solar.rtd.utk.edu/~mwade/project/quiacsat.htm |
[MARKWADE] |
| National Aeronautics and Space Administration
"Announcement of Opportunity Discovery Program" (AO-96-OSS-02) Sept. 20, 1996; http://www.hq.nasa.gov/office/oss/solar_system/Solar/discover.asc |
[NASA/a] |
| National Aeronautics and Space Administration
"Draft Environmental Impact Statement for Project Galileo" 1985; hardcopy) |
[NASA/b] |
| National Aeronatuics and Space Administration/Solar System Exploration
Division, Office of Space Science
"Final Environmental Impact Statement for the Cassini Mission" June 1995; hardcopy; in PDF format also available at http://www.jpl.nasa.gov/cassini/rtg/rtgrhu.htm |
[NASA/c] |
| National Aeronautics and Space Administration
"Galileo Frequently Asked Questions" no date; http://galileo.ivv.nasa.gov/newfaq.html |
[NASA/d] |
| National Aeronautics and Space Administration
"Information on potential future NASA space science missions which may be powered with Radioisotope Power Sources (RTGs or RHUs)" Fact Sheet dated August 1997 in e-mail from Don Savage (NASA headquarters) from September 11, 1997 |
[NASA/e] |
| National Aeronautics and Space Administration
"Interstellar Probe" no date; http://umbra.nascom.nasa.gov/SEC/secr/missions/ISP.html |
[NASA/f] |
| National Aeronautics and Space Administration
"Interstellar Probe" no date; http://umbra.nascom.nasa.gov/SEC/secr/missions/ISP2.html |
[NASA/g] |
| National Aeronautics and Space Administration
"Pioneer 10" Dec. 1, 1997; http://nssdc.gsfc.nasa.gov/planetary/text/pioneer_10-11_status_971201.txt |
[NASA/h] |
| National Aeronautics and Space Administration
"Solar System Exploration Subcommittee: Findings of the Strategic Planning Workshop" May 5, 1997; http://eis.jpl.nasa.gov/ssematerial/sses_strategies/index.html |
[NASA/i] |
| National Aeronautics and Space Administration
"Voyager Project Information" no date; http://ndadsb.gsfc.nasa.gov/anon_dir/coho/voyager_1/voyager_1.nmc |
[NASA/k] |
| National Aeronautics and Space Administration
"Voyager Project Information" March 11, 1998; http://nssdc.gsfc.nasa.gov/planetary/voyager.html |
[NASA/l] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display: Spacecraft - Luna 17" March 20, 1998; http://nssdc.gsfc.nasa.gov/nmc/tmp/70-095A.html |
[NSSDC/a] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display Spacecraft - Luna 21" April 16, 1998; http://nssdc.gsfc.nasa.gov/nmc/tmp/73-001A.html |
[NSSDC/b] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display Spacecraft - Pioneer 10" NSSDC ID: 72-012A March 4, 1998: http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?72-012A |
[NSSDC/c] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display Spacecraft - Pioneer 11" NSSDC ID: 73-019A Jan. 29, 1998; http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?73-019A |
[NSSDC/d] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display Spacecraft - Viking 1 Lander" NSSDC ID: 75-075C July 22, 1998; http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?75-075C |
[NSSDC/e] |
| National Space Science Data Center and Goddard Space Flight Center/National
Aeronautics and Space Administration
"NSSDC Master Catalog Display Spacecraft - Viking 2 Lander" NSSDC ID: 75-083C July 22, 1998; http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?75-083C |
[NSSDC/f] |
| Nilsen, Thomas and Bøhmer, Nils
"Bellona Report no. 1:1994" Chapter 8.6: Rocket launching-range Plesetsk" 1994; http://www.bellona.no/e/russia/murmark/murmark8.htm |
[NILSEN] |
| "THE ORBITAL REPORT ON-LINE"
Space Executive's Weekly News Digest Vol. 1 - No. 16, October 23, 1997; http://www.orbireport.com/OReOL1.16.html |
[ORBITAL] |
|
Office of Space Science/National Aeronautics and Space Administration "Charting the Universe. Strategy. The Program: 2005 and Beyond" 1997; http://www.hq.nasa.gov/office/oss/strategy/1997/2b3.htm |
[OSS] |
| Proposition One
"Reckless Endagerment" 1997; http://www.prop1.org/2000/accident/reckless.htm |
[PROP1] |
| Rossi, A.; Pardini, C.; Anselmo, L.; Cordelli, A.; Farinella, P.
CNUCE/CNR, Consorzio Pisa Ricerche, and Dipartimento di Matematica/Università di Pisa; Pisa, Italia "Effects of the RORSAT NaK Drops on the Long Term Evolution of the Space Debris Population" 1997; http://apollo.cnuce.cnr.it/rossi/publications/iaf97/iaf97_html.html |
[ROSSI] |
| TRW Space & Electronics Group
"TRW Space Log 1996, Volume 32" July 1997; Hardcopy One Space Park, Mail Station E2/3014; Redondo Beach, CA 90278, USA Ordering on company or organization letterhead required. |
[TRW] |
| U.S. Air Force
"Air Force News Service: Topaz II for peace" June 30, 1995; http://www.af.mil/news/features/features95/f_950630-087_95jun30.html |
[USAF] |
| U.S. Department of Energy
"Nuclear Energy: Space Nuclear Power Systems" no date (1997); http://www.ne.doe.gov/programs/space/rtgs.stm and http://www.ne.doe.gov/programs/space/space1.stm |
[USDOE/a] |
| U.S. Department of Energy
"Oral Histories: Biochemist John Randolph Totter, Ph.D.: Footnotes" no date; http://www.ohre.doe.gov/roadmap/histories/0481/footnote.html |
[USDOE/b] |
| U.S. Department of Energy ???
"Plutonium-238 Requirements (kg)" no date (probably 1992 or earlier); hardcopy |
[USDOE/c] |
| U.S. Department of Energy/Office of Nuclear Energy, Science and Technology
"Nuclear Power in Space" no date (1996 or 1997); http://www.ne.doe.gov/programs/space/npspace.pdf |
[USDOE/d] |
| U.S. Department of Energy
"Statement of Terry R. Lash, Director, Office of Nuclear Energy, Science and Technology, U.S. Department of Energy, Before the House Appropriations Subcommittee on Energy and Water Development" March 11, 1998; http://www.ne.doe.gov/org/testimony/fy1999.htm |
[USDOE/e] |
| U.S. General Accounting Office
Report to the Honorable Barbara Boxer, U.S. Senate "Space Exploration. Power Sources for Deep Space Probes" May 1998 (Hardcopy) |
[USGAO] |
| United Nations
"General Assembly Resolutions and International Treaties Pertaining to the Peaceful Uses of Outer Space" http://www.un.or.at/OOSA_Kiosk/treat/treat.html |
[UN] |
| unknown
"Pluto Express Information" no date; http://ispec.scibernet.com/student-pages/oort/pluto_express.html |
[UNKNOWN] |
| Zimmer, Harro
"Der rote Orbit. Glanz und Elend der russischen Raumfahrt" 1996; Franckh-Kosmos Verlag, Stuttgart |
[ZIMMER] |
A choice of Karl Grossman's publications on space issues:
"The Wrong Stuff. The Space Program's Nuclear Threat to Our Planet"
1997, Common Courage Press, ISBN 1-56751-125-2
"Nukes in Space. The Nuclearization and Weaponization of the Heavens"
Video
"Nuclear Space Missions Break Down Political Barriers"
Just Peace, Fall, 1993 (Issue #28)
"Risking the World. Nuclear Proliferation in Space"
CovertAction Quarterly, Summer 1996, Number 57"
Nuclear menace in outer space"
The Baltimore Sun, August 12, 1996
"Space Probe Explodes, Plutonium Missing"
CovertAction Quarterly, Spring 1997, Number 60
1.
1 See Chapter 7, Literature List for references. Page numbers are given for formatted and
page-oriented documents. DoE develops and produces all RTGs used by DoD and NASA.
2.
2 So far, no nuclear powered space missions seem to have been launched by other countries.
However, the European Space Agency as well as individual universities and research institutes
from other countries used U.S. and Russian space missions to send their own
experiments/instruments/probes into space.
3.
3 Invaluable information about the use of nuclear power in space by NASA as well as by the U.S.
military can be found in many articles as well as in a book and a video by journalistic professor
Karl Grossman. For the purpose of this article, however, it seemed to make sense to not quote
him but official sources. Some of Karl Grossman's publications are listed at the end of Chapter 7,
Literature List.
4.
4 Different information about RTG safety features can be found in the articles of Karl Grossman
and Michio Kaku in this Working Paper.
5.
5 Various DoE and NASA documents give different numbers of previous nuclear powered space
missions, namely between 21 and 25. Chapter 3, Past Missions a Chronology lists 30
corresponding missions.
6.
6 Translation of the quotation by the author of this article.
7.
7 The amount and enrichment of the U-238 in the Soviet RORSAT nuclear reactors stated by
Harro Zimmer is confirmed by the Bellona Report, see [NILSEN].
8.
8 For more details about the coolant debris, see the information for Kosmos 1176.
9.
9 Translation of the quotation by the author of this article.
10.
10 For further information about solar cells development for deep space missions, see Gerhard
Strobl's article in this "orking Paper.
11.
11 Plutonium-238 is not identical to the weapons-grade plutonium-239 used for nuclear weapons.
For details about the effects and toxicity of Pu-238 see the articles of Karl Grossman, Michio
Kaku, and Roland Wolff in this Working Paper.
12.
12 NASA's Cassini FEIS states the source term of all other missions it lists, but not for this
reactor.
13.
13 For more details about the injection of reactors into higher orbit see the information given for
Kosmos 198.
14.
14 The Kosmos missions are sometimes spelled Cosmos.
15.
15 Tyuratam is a launch site in Kazachstan. The Bellona Report [NILSEN] mentions that the
Kosmos missions were launched from Plesetsk. The TRW Space Log 1996 [TRW], however,
names Tyuratam for all Soviet nuclear powered space missions.
16.
16 HEU-235 = highly enriched uranium-235
17.
17 In his book "The Wrong Stuff" (Common Courage Press, 1997), Karl Grossman mentions
Kosmos 305 as one possible lunar mission which fell back to earth in 1969. As a second one he
lists Kosmos 300, launched on Sept. 23, 1996. As this information was not confirmed by the
information sources used for this article, Kosmos 300 is not listed here. It should be pointed out,
however, that the TRW Space Log 1996 explicitly mentions two modules for Kosmos 305.
Therefore, it may be concluded that this mission carried two reactors.
18.
18 One DoE list [USDOE/d, pages 15/16] also mentions Apollo 11 which was launched on July
16, 1969. It states 'ALRH' as the power source. The text continues to say that Apollo 11 was
equipped with RHUs (Radioisotope Heater Units) for the seismic experimental package.
Therefore it may be assumed that no RTG was on board for this mission.
19.
19 Apollo 13 did not reach the moon; see below.
20.
20 Although the TRW Space Log 1996 [TRW] often gives information about the mission status,
this is not the case for the two Topaz test missions Kosmos 1818 and Kosmos 1867.
21.
21 The Berlin database [ILR] does not include this information. However, there is no reason to
believe life duration should be any different from the other Kosmos missions.
22.
22 Radioactive Heater Units (RHUs) were used on all Apollo and interplanetary missions. One
recent example of RHU usage is the otherwise solar powered mission Sojourner/Pathfinder which
landed on Mars on July 4, 1997.
23.
23 For further details about Cassini, see the articles by Karl Grossman and Michio Kaku in this
Working Paper.
24.
24 Private communication with a Russian space engineer; he quoted an ITAR-TASS press release
of February 10, 1998.
25.
25 Although no origin is stated on the hardcopy available to the author of this article, it is safe to
assume that the spreadsheet was created by DoE and lists the plutonium-238 inventory required
to build the RTGs for the planned NASA missions. As the lists refers to requirements from
1992-2001, the spreadsheet has probably been created in 1992. Earlier compilation of the list is
unlikely, as according to [JPL/CIT] a Pluto Flyby mission was first considered in 1992.
26.
26 Identical to the Europa Ocean Explorer mission.
27.
27 Identical to the Titan Biologic Explorer mission.
28.
28 A document by Malin Space Science Systems, Inc., also deals with financial issues. See Section
4.6.12, Venus Lander.
29.
29 In a DoE statement from March 1998 [USDOE/e] the figure given for R&D (research and
development) alone, i.e. without actually building any RTGs, is $40.5 million. See table below.
30.
30 Additional information about Solar Concentrator Arrays can be found at NASA's home page
for the Deep Space 1 mission, see http://nmp.jpl.nasa.gov/ds1/tech/scarlet.html. In addition to
using exclusively solar concentrators, Deep Space 1 will also use Solar Electric Propulsion (Ion
Propulsion). For details see http://nmp.jpl.nasa.gov/ds1/tech/sep.html.
31.
31 SEP = Solar Electric Propulsion
32.
32 "Radioisotope Thermal Generators (RTGs) are not permitted on Discovery missions proposed
to this AO. Other, smaller radioactive sources (such as radioactive heating units or instrument
calibration sources) are permitted." [NASA/a]
33.
33 About the Outer Solar System Program, the Solar System Exploration Subcommittee writes:
"Technology development progress should govern mission selection, with the goals of conducting
the overall program at the lowest possible cost and maximizing science return from the individual
missions. A set of decision gates will be laid out to indicate when mission targets must be selected
and what criteria will be used. Generally the final selection will be made about 3 years prior to
launch." [NASA/i] Although technology development is analyzed by the Subcommittee,
non-nuclear power supply is not an issue. Instead, one of the technology criteria are that "all
top-priority needs can be met by existing programs" [NASA/i]. Other technology issues are
leightweight, low-cost, high-performance chemical propulsion, sensor/detector and instrument
development, and avionics development.
34.
34 That equals 80 to 90 times the distance between Sun and Earth.
35.
35 "Nuclear or RTG electric propulsion" is very imprecise. Nuclear propulsion has been under
consideration for many years, is not identical with the RTG technology used to provide electrical
energy for instruments, however.
36.
36 For detailed information about the Mars missions, see http://mars.jpl.nasa.gov/
37.
37 That equals 10-20 times the distance between Sun and Earth.
38.
38 This document also gives information about NASA's effort to use state-of the art and
miniaturized technology to keep the mission small (and therefore cheaper as a smaller launch
vehicle can be used.) The article explains that many of the "enabling technologies result from
breakthroughs by the Ballistic Missile Defense Organization (BMDO)." [JPL/CIT]
39.
39 Cassini uses a Venus-Venus-Earth-Jupiter Gravity Assist (VVEJGA) trajectory.
40.
40 High natural background radiation is a mission problem in the Jupiter environment.
41.
41 These are the Mars missions; see above.
42.
42 The MSSS document was written in 1996.
43.
43 Although ESA press releases back to 1993 are available in the Internet, this one is not provided online. Another press information numbered "07/94" is listed instead.