Earlier quoted context omitted.
>Nuclear fusion is a more likely answer to spaceflight and Earth's clean energy problem. Considering we don't even have fission rockets or airplanes in normal use, making a fusion powerplant that is light enough to get off the ground seems very far fetched. Even if we eventually use fusion for travel beyond earth orbit, I'd bet chemical rockets would still be in use. Don't we already have thrusters that are useful in…
For those interested: As absurd as it sounds nuclear powered aircraft engines are a thing.[1] They have also been proposed for spacecraft, Scott Manley does a great video talking about nuclear rocket engines[2]. [1] https://en.wikipedia.org/wiki/Project_Pluto [2] https://www.youtube.com/watch?v=cvZjhWE-3zM
Safety is a very valid concern for any supersized airborne vehicle but especially a nuclear powered one! However, this is one department where scale in itself brings it's own benefits. The volume increases faster than the surface area so you could have a hull far thicker than that of many naval ships while still having a truly vast interior volume. Not needing to ever land also reduces avenues for sabatoge and presumably the craft's interior itself would be heavily compartmentalized. You can also optimise your hull to deal with a narrow air pressure range which you cannot do with normal craft which need to be able to handle a wide range from ground level to the stratospheric.