Nuke Propulsion / VASIMR

http://www.wired.com/wiredscience/2009/11/nuclear-propulsion-in-space/

Between 1955 and 1972, the United States spent more than $1.4 billion in then-year dollars on developing nuclear rockets and related technologies. At the end of that period, when the Nixon administration cut NASA’s budget generally and NERVA’s specifically, the United States was well on its way to developing nuclear power for spacefaring and space purposes.

One major reason is that NASA picks its propulsion systems based on its targets — and true exploration of the solar system and beyond hasn’t really been a serious goal, the Constellation plans for a return to the moon aside.
McDaniel agreed that the targets drive things, citing the general decline of pure technology development research at NASA.
“Until we commit to going back to Mars, we’re not going to have a nuclear rocket,” McDaniel said.
Or perhaps a new nuclear-powered Russian spacecraft could get anxious minds at the Pentagon and NASA worrying about the need to keep pace with the Ivanovs.


http://news.discovery.com/space/mars-rocket-vasimr-nasa.html

"In the early days... NASA support for the project was rather minimal because the agency did not emphasize advanced technologies as much as it's doing now," Chang-Diaz told AFP.