NASA has released a study claiming there is a need for continued use of plutonium-energized power systems for future space flights. It also says the use of actual nuclear reactors in space "has promise" but "currently" there is no need for them. http://solarsystem.nasa.gov/rps/docs/NPAS.pdf
The space plutonium systems--called radioisotope thermoelectric generators (RTGS)--use the heat from the decay of plutonium to generate electricity in contrast to nuclear reactors, usually using uranium, in which fission or atom-splitting takes place.
The "Nuclear Power Assessment Study" describes itself as being done as a "collaboration" involving "NASA centers," among them Johnson Space Center, Kennedy Space Center and the Jet Propulsion Laboratory, "the Department of Energy and its laboratories including Los Alamos National Laboratory, Idaho National Laboratory, Sandia National Laboratories," and the Johns Hopkins University Applied Physics Laboratory.
The study, released this month, comes as major breakthroughs have been happening in the use of solar and other benign sources of power in space. The situation parallels that on Earth as solar and wind power and other clean, safe technologies compete with nuclear, oil, coal and other problematic energy sources and the interests behind them.
Examples of the use of benign power in space include the successful flight in May of a solar-powered spacecraft named LightSail in a mission funded by members of the Planetary Society. Astronomer Carl Sagan, a founder of the society, was among those who have postulating having a spacecraft with a sail propelled through the vacuum of space by the pressure of photons emitted by the sun. LightSail demonstrates his vision.
Yet, meanwhile, NASA cancelled its own solar sail mission scheduled for this year. It was to involve the largest solar sail ever flown. In 2010, the Japan Aerospace Exploration Agency made the first solar sail flight with a spacecraft it named Ikaros. Before the NASA solar flight cancellation, NASA last year declared on its website: "The concept of a huge, ultra-thin sail unfurling in space, using the pressure of sunlight to provide propellant-free transport, hovering and exploration capabilities, may seem like the stuff of science fiction. Now a NASA team developing the 'In-Space Demonstration of a Mission-Capable Solar Sail'--or Solar Sail Demonstrator for short--intend[s] to prove the viability and value of the technology in the years to come." http://www.nasa.gov/mission_pages/tdm/solarsail/solarsail_overview.html NASA said the mission, also called Sunjammer, was cancelled by NASA because of problems " with the project's contractor, L'Garde of California.
And also, meanwhile, demonstrating that solar power can be harvested far out in space, the Rosetta space probe of the European Space Agency (ESA), energized with solar power, successfully rendezvoused last year with a comet 375 million miles from the sun. ESA at the start of this mission explained that it did not have the plutonium power systems that NASA had, so instead it developed high-efficiency solar photovoltaic panels for use in space. And they worked enabling Rosetta to meet up with Comet 67P/Churyumov-Gerasimenko and send a lander to its surface. Rosetta continues flying alongside the comet.
NASA, too, has a space probe energized with high-efficiency solar photovoltaic panels it developed now on its way to Jupiter in a mission it has named Juno. For decades, NASA insisted that solar power could not be harvested beyond the orbit of Mars and thus plutonium power systems were necessary. This was NASA's central argument in federal court in 1989 to rebut opponents of its plutonium-energized Galileo mission to Jupiter. Now it has shown it was mistaken. Juno using solar power instead of plutonium RTGs is to reach Jupiter next year.
NASA Administrator Charles Bolden, a former astronaut and Marine Corps major general, remains a big booster of using nuclear-propelled rockets to get to Mars. Work on such a rocket has been going on at NASA's Marshall Space Flight Center. NASA on its website says that a nuclear-powered rocket "could propel human explorers to Mars more efficiently than conventional spacecraft." http://www.nasa.gov/topics/technology/features/ntrees_prt.htm l
Through the years, NASA has worked closely with the U.S. Atomic Energy Commission and after the commission was disbanded its successor, the Department of Energy, on space nuclear programs. And there's a program at DOE's Los Alamos National Laboratory to develop a "robust fission reactor prototype that could be used as a power system for space travel," according to Technews World. http://www.technewsworld.com/story/76699.html
This is occurring despite Russia now abandoning its development of nuclear-propelled rockets for missions to Mars, a project it had earlier much-heralded. Reported TASS in April:
"Russia's space agency Roscosmos is planning to shut down works on developing a megawatt-class nuclear propulsion system for long-range manned spacecraft." http://russia-insider.com/en/russia-drops-plans-create-nuclear-space-engine-source/6031
But the DOE has resumed production for NASA of the isotope of plutonium--Plutonium-238--used in RTGs. It is a form of plutonium 280 times more radioactive than the plutonium used as a fuel in atomic bombs, Plutonium-239. Reported the journal Nature:
"NASA will be relieved to get this 238 Pu [Plutonium] because it is increasingly anxious about running out. The isotosope is not found in nature, so it has to be made in nuclear reactors"NASA now has just 35 kilograms of plutonium product--a small supply that may not match the demands to send missions to Mars, the moons of Jupiter and beyond." The restart of Plutonium-238 production involves the DOE's Idaho National Laboratory, Oak Ridge National Laboratory and Los Alamos National Laboratory. http://www.nature.com/news/nuclear-power-desperately-seeking-plutonium-1.16411
"We've known for years that the nuclear industry has taken control of the seats at the NASA and DOE planning committees that decide whether solar or nuclear power should be used on space missions," said Bruce Gagnon, coordinator of the Global Network Against Weapons and Nuclear Power in Space (www.space4peace.org). "The nuclear industry views space as a new market for their deadly product. Nuclear generators on space missions, nuclear powered mining colonies on Mars and other planetary bodies and even nuclear reactors on rockets to Mars are being sought. Thus there are many opportunities for things to go wrong."