> Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground?

> Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground? Yes. For example ion thrusters have specific impulse that is like an order of magnitude or two (or three?) better than chemical rockets, but they can't lift anything out of the atmosphere. > I feel like I've read something that said fusion power would fall in the same category. Sorry I have no idea about that.