Russia planning nuclear-powered manned spaceship
Reactor cruiser aimed at Moon, Mars missions
Russian space chiefs are considering plans for a manned spacecraft with a nuclear powerplant aboard, according to reports. Indications are that the nuclear kit would provide electrical power rather than being used directly for propulsion.
RIA Novosti reports that Anatoly Perminov, chief of the Russian space agency Roscosmos, revealed the scheme at a meeting yesterday. Reportedly Perminov specifically mentioned Megawatt-class nuclear space power systems (MCNSPS), which would normally refer to "an appropriate nuclear reactor heat source" generating electrical power aboard a spacecraft by one of several conversion methods (massive old NASA pdf here ).
The report says that the Roscosmos boss mentioned MCNSPS specifically in the context of "implementing large-scale space exploration programs". His fellow Russian space bigwig Anatoly Koroteyev had earlier stated that the key issue with manned missions to the Moon and Mars was "development of new propulsion systems and energy supplies with a high degree of energy-mass efficiency".
Spacecraft today are typically propelled by chemically-fuelled rockets and powered by solar panels (or sometimes fuel cells for short-duration missions). Chemical rockets in particular tend to require so much fuel to accomplish anything that very little actual payload can be carried, especially in the case of return trips beyond Earth orbit.
Any chemically-powered manned mission to Mars would have to coast almost all the way there and back, taking six months each way. Aboard a typical lightweight spacecraft - the only sort that feeble chemical rockets can propel - this would be quite likely to mean astronauts dying of cosmic radiation sickness. Magnetic shielding  is a possibility, but this would probably be a serious power drain.
Feeble chemical fuels and solar cells can never achieve serious travel beyond LEO
Solar cells can deliver useful amounts of power for ships in space or planetary landings, but almost all of the Moon suffers from two-week-long nights - and the possible iceberg rocket-fuel mines of the polar craters , a likely spot for Moon bases, are in permanent darkness. On Mars, further from the Sun than the Earth-Moon system, solar cells deliver less power and they are the main limiting factor on current rovers and landers there. Thus NASA's plans for the next Mars rover  to be nuclear powered.
For all these reasons there are many in the space community who argue that travel beyond low Earth orbit will never become a serious activity without more powerful technologies than chemical fuels and solar cells. Nuclear power has already been used in space, mostly aboard radar spy satellites needing more juice than solar could supply (famously, some Russian ones  with actual reactors aboard - not just radioisotope batteries - have cracked up on launch or ploughed uncontrolled back into the atmosphere).
Some have argued for actual nuclear rockets , where thermal energy is used to squirt reaction mass rather than generate 'leccy. Others contend that a better and more efficient method is to use electric power to run a plasma rocket . This might allow for heavier radiation shielding for astronauts or alternatively provide power for the possible magnetic shields of the future - and nuclear generators could power bases or probes on planets far from the sun, too.
Judging by the RIA Novosti report , Russia is leaning more toward the nuclear-electric options. Perminov's planned megawatt nuke spaceship will cost 17 billion rubles ($580m) by his estimates, and he says the design will be finalised in 2012.
That's not much money in the context of a NASA budget, but it's big bucks for Russia even in the gas-revenue era. There has to be a lot of doubt whether Roscosmos will get the funds. ®