Nuclear Space Propulsion

A nuclear rocket still needs propellant, doesn't it?

If you're already bringing a nuclear reactor into space, you could use it to heat up the hydrogen and use it as propellant directly, for more efficient travel. (In situations where you need bursts of high thrust and are willing to sacrifice efficiency, you can also go with a hybrid system that uses both nuclear heat and combustion.)Oh, and fun safety fact: a nuclear reactor isn't actually particularly radioactive until it's turned on. If you launch it out of Earth's orbit before turning it on

Why not have a nuclear battery/generator powering an array of ion thrusters?

I'd settle for fission power, a known rocket technology:https://www.youtube.com/watch?v=cqov9MJwM_A

NASA uses plutonium for radioisotope thermoelectric generators whereas the OP is talking about nuclear pulse propulsion, which uses the shockwave from nuclear warhead detonations to propel a spacecraft. These are two fundamentally different things. The latter is illegal in most countries because of the aforementioned Partial Nuclear Test Ban Treaty, which bans any atmospheric or outer space detonations.

Reactors? The article doesn't mention any reactors.If you're talking about radioisotope thermoelectric generators (RTGs) used on spacecraft, they are limited to deep space (Voyager, Cassini, etc) and long duration planetary missions (Curiosity rover) only. Only a handful of 1960's military satellites used RTGs on Earth orbit [0].RTGs also tend to be rather small, the environmental impact of the small amount of Pu-238 shouldn't be very large (compared to nuclear testing

Could it just be an RTG to power the rocket's systems in flight, instead of an actual nuclear propulsion system?

Maybe RTGs [1] that are used on some spacecraft will reappoint you.[1]: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

I'm not sure how nuclear engines would help?A nuclear reactor is a bit like an ion drive: great for long distance space travel, but not great for getting off a planet.Unless you mean the kind of nuclear engine that consists of detonating atomic bombs behind you? See https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

Is it true this is also why nuclear pulse propulsion from Earth surface to orbit is impractical?