It's always been political, both in terms of the relative "scariness" of nuclear technology after Hiroshima and Nagasaki, as well as the costs of space programs.
Most of the space flight technologies using nuclear power were devised for manned flights beyond Earth's gravitational influence, and were on the drawing boards as early as the fifties. Once America successfully landed on the moon and the Soviets gave up, there was immense political pressure to scale back the US space program. With the Space Race won, it was harder to justify the costs of manned interplanetary spaceflight, so a lot of more exotic (read: expensive) plans were shelved. This included more than a couple nuclear propulsion ideas for spacecraft, including one for a nuclear thermal rocket that had been successfully prototyped in the lab and was ready for an actual launch.
Lots of stuff we could have done and could be doing in space if there was money for it.
Most of the space flight technologies using nuclear power were devised for manned flights beyond Earth's gravitational influence, and were on the drawing boards as early as the fifties. Once America successfully landed on the moon and the Soviets gave up, there was immense political pressure to scale back the US space program. With the Space Race won, it was harder to justify the costs of manned interplanetary spaceflight, so a lot of more exotic (read: expensive) plans were shelved. This included more than a couple nuclear propulsion ideas for spacecraft, including one for a nuclear thermal rocket that had been successfully prototyped in the lab and was ready for an actual launch.
Lots of stuff we could have done and could be doing in space if there was money for it.