Al wrote:
Can't let this thread pass without mention that Bussard was, at one
time, one of the world's most important experts in nuclear rocketry
during the 1950's and 1960's(*,**). An important figure in the
development and implementation of the USA's only nuclear rocket motors
at Los Alamos.

We still aren't using them you'll note, which may say something...coming
up on fifty years afterwards.
NERVA was heavy; Dumbo was iffy, and both were dirty for surface liftoff.
Even the far later Timberwind project went nowhere fast.
A lot of the isp advantage disappeared in shielding weight and the
weight of the reactor itself.

Pat