Part One of Three Parts:
I have mentioned thermionic power generators that use plutonium-238 to provide power for space probes in past posts. Recently there have been some problems with obtaining sufficient Pu-238 for NASA deep space missions. Nuclear propulsion systems for large spacecraft have also been proposed for decades. With the recent expansion of private space industry, interest in nuclear propulsion has increased.
I have posted before about the problem with all the space junk in orbit around the Earth. It is estimated that there are over a hundred million pieces of space junk including old satellites, rocket boosters, fragments of rockets, and fragments of metal and paint. About twenty thousand pieces are more than four inches in diameter.
Last year, I blogged about Moon Express, the first private space company to be licensed for travel beyond Earth orbit by the U.S. government. Moon Express plans a lunar mission in late 2017. Recent developments have certainly been positive for ME.