I have heard of nuclear propulsion, however I wonder that is it possible for it to launch into space, and if so, how much fuel would it need?
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1$\begingroup$ Is "to space" a verb? As in, "to launch into"? Well, I like it, anyway. NERVA produced 75,000 pounds of force. SpaceX's Merlin engine produces 94,000 pounds at sea level, which is a bit higher, but comparable. So maybe, depending on the size of the rocket. But they used liquid hydrogen and were meant for upper stages and space tugs, not first stages. $\endgroup$– GregMay 26, 2019 at 0:07
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1$\begingroup$ @Greg the NERVA weighs about 15 times more than the Merlin. $\endgroup$– Starfish PrimeMay 26, 2019 at 9:32
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The NERVA was a fairly heavy engine, with a thrust to weight ratio of about 3:1 in flight configuration (as compared to ratios of better than 100 for liquid-fueled engines). Between that and the fact that its exhaust included radioactive material, it wouldn't have been a good choice for a lower-stage engine, but it would have been possible. Improved nuclear-thermal engine designs like Project Timberwind could have achieved 30:1 TWR, but the cost and environmental issues would still make it a poor choice for a first stage.
Fuel efficiency of a nuclear-thermal engine is about twice as good as a hydrogen-oxygen combustion rocket, so you'd need only half as much fuel mass as your hydrogen-oxygen-fueled competition as a rule of thumb, but the fines from the EPA would easily wipe out any cost savings.
answered May 26, 2019 at 1:57
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$\begingroup$ Any idea about Alan Bond's Scorpion design? using a lithium loop to avoid contaminating the propellant (and generate copious amounts of electricity) removes the radioactive exhaust issue. $\endgroup$– user20636May 26, 2019 at 5:35