Comment Re: Lol (Score 2) 22
The first fission reactor in space, the American SNAP-10A had an experimental ion thruster.
The Soviets launched dozens of nuclear powered satellites, but again, thrusters were only used experimentally.
So while not actually "the first nuclear powered interplanetary spacecraft" (RTGs win that) it is the first nuclear-powered rocket in space, aside from small experiments.
With only 2N thrust, it is no use below LEO, and solar power is plenty good enough for ion-drives in earthly satellites. So nuclear-powered rockets are only useful for interplanetary missions, for now.