No spacecraft has yet reached Mars using nuclear propulsion. The US ground-tested nuclear thermal rockets under Rover and NERVA from 1959 to 1972, then cancell…
The US set out to see whether a reactor could heat hydrogen to rocket temperatures without falling apart.
Kiwi-A, named after a bird that never flies, ran in the Nevada desert. Kiwi tests continued to 1964.
Yes, for power. SNAP-10A ran 43 days in 1965 and even carried a small experimental ion thruster.
On the ground, yes. XE-Prime was fired downward in a stand simulating space, with repeated restarts.
Apollo wound down, Mars plans were dropped and budgets cut. The engine lost its mission.
A NASA plan for a nuclear-electric probe to Jupiter's moons, cancelled in 2005 as priorities shifted.
A test of a 1-kilowatt-class space reactor, including a full-power run of about 28 hours.
The DARPA and NASA plan to fly a nuclear thermal engine in orbit got no funding and was ended.
Gas pushed through a flight-like reactor core showed it resists damaging vibration. No fission involved.
A robotic craft with a ~20 kW HALEU reactor driving Hall thrusters, carrying three SkyFall Mars helicopters.
JPL's lithium-fed thruster reached 120 kW, over 25 times Psyche's. The goal is up to 1 MW.
NASA set 2036 as a planning goal and ordered a study of nuclear thermal, nuclear electric and chemical options.
End-to-end cooperation from fuel and testing to launch and operations, for SR-1 and a 2030 Moon reactor.
Thermal heats hydrogen for high thrust at ~2x chemical efficiency. Electric makes power for thrusters: tiny thrust, huge efficiency.
Chemical plans often take ~3 years round trip. NASA nuclear studies aim near 2 years. SR-1 takes ~1 year one way.
Hot fuel, shielding, giant radiators, keeping hydrogen cold, testing rules and funding that outlasts politics.
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