>>12187196REBCO superconducting tapes will let us build Q>5 reactors and put fusion-powered electrical generation capacity into the grid, probably before ITER gets tot he point of first fusion plasma experiments. I have no doubt about this. As for the space implications though, fusion as a power source in space falls apart in the face of fission, because both fusion and fission work to generate power simply by acting as a nuclear powered heat source which drives a heat engine which spins an electromagnetic field which pushes electrons through wires. Since the mass of hardware required to get a kilowatt of fission heat is WAY smaller than the mass of hardware required to get a kilowatt of fusion heat, fission is the way to go if you're making electricity, no question. Fusion reactors are simply way to heavy.
Of course, if we can get some other kind of fusion reactor working which can also be easily modified to serve as a means of direct propulsion, then that would be very attractive even if each fusion engine weighed a hundred tons. Some fusion designs which are based on using magnetic 'mirrors' to bounce plasma back and forth along a linear chamber may be suited for this niche; if we ever get one with Q>5 we could design it such that the fore 'mirror' is twice as strong as the 'aft' mirror, and behind the aft mirror there is a magnetic nozzle. To run the engine, we squeeze and heat the plasma to initiate fusion with Q>5, creating a burning plasma, and as this burning plasma exerts pressure on both of the magnetic mirrors some is able to escape by being pushed through the aft mirror and into the magnetic nozzle, which keeps it from touching anything solid as it expands and is hurled away at >500 km/s. Boom, you have a fusion plasma rocket with an Isp of ~51,000. TWR is not great but who cares, muh Isp
