>>12029495>How many Gs will a fusion engine create? Can we survive the Gs inside a fusion spaceship?Fusion is efficient, not powerful. Chemical rockets are powerful by default, unless you make them very tiny.
Fusion rockets can in theory be powerful as well as efficient, but it's an extremely hard problem to crack, and also by "powerful" I really mean "approaches a thrust to weight ratio of 1 in Earth gravity".
Also, while the thrust to weight ratio of your engine is something that you generally want to be as high as possible, the thrust to weight ratio of your entire vehicle is something that you almost never want to be able to go above 5 or so. This is for two basic reasons; first off, it's hard to design something that has a decently light structural mass ratio that can also take high accelerations, and, if your final acceleration at burnout with a highly efficient engine is getting very high, that usually means that you're wasting a lot of energy to accelerate a very small payload.
With highly efficient engines, say of around 50,000 Isp (compared to chemicals which practically top out at around 480 Isp), you can easily design single-stage vehicles that have a delta V budget of about 340,000 m/s with a propellant mass fraction of just 50%. To put that into perspective, the first stage of a Falcon 9 is approximately 90% propellant by mass, and it can do all kinds of flips and shit and land back on a barge in rough seas. Achieving a 50% mass fraction would be trivial, even if fusion engines turned out to be very heavy (they certainly will, at least to start). That dV budget is enough to go from low Earth orbit to a low Lunar orbit and back 86 times in a row, without ever refueling.
Delta V has nothing to do with TWR, though. That fusion rocket with 340 km/s in the tanks may only accelerate at 0.5 m/s^2, and take a long time to execute burns of thousands of meters per second of velocity. That would matter less the further away the destination was.
