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this post was submitted on 26 Jul 2023
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Hmm it seems like we are still relying on a propellant of some kind.
I mean, you will always need a propellant, E=MC^2 after all, even if you’re Pushing with light, you’re still losing mass as you expel that out the back, no matter how you cut it.
The real question is how much work you’re getting out of each unit of mass you toss out they back, and that depends on how fast you toss it. These kinds of engines (nuclear thermal engines) get about expel their reaction mass at about 8000 meters per second, the most efficient conventional engine pushes exhaust out at about 4500 meters per second. So, you’re getting a. It less than twice as much change in the crafts speed per unit of mass used for these kinds of engines.
That may not seem like a game changer, but a 50% increase in efficiency rapidly compounds since most of the mass you’re trying to move with propellant is… well other propellant.
I imagine the engine has to weigh a lot more though? So only really suited to huge or deep space missions where also having a nuclear reactor is incredibly useful
Oh yah, much heavier, and lower max thrust to, but the whole package is still much lighter considering the huge fuel savings which are most of the mass of the vehicle anyways.
Generally they are mainly intended for longer range missions or where a lot of big maneuvers need to be made. So something that needs to ferry cargo to the moon and back would be an excellent use case.