I think nuclear propulsion is there only way forward for interplanetary colonisation because we've long reached the limits of chemical. And ion is too slow.
As for nuclear propulsion being the only way forward, I doubt that, I suspect that chemical will be more cost efficient for a lot of the trips, especially for unmanned cargo trips.
Chemical means, based on carbon products that we've used up till now, would be very rare on remote planets, solar wouldn't work because planets could be various distances from a star they orbit, or could have different atmospheric, or magnetospheric conditions that would make that impractical, wind suffers a similar issue.
The only power source that could be guaranteed to work at the large scale, both in terms of space and time, reliably, and is likely to be available is nuclear power. With your other options being the quantum vacuum energy or anti-matter, but both fall more into the fiction part of sci-fi right now than the science part.
it was just a fun interesting little thought exercise. I'd love to hear if anyone has a criticism of the reading though.
Hydrogen is everywhere by comparison.
The other reasonable option might be solar power near stars, and forwarding the power on to your ships/distant planets using some form of directed energy (lasers, lenses, etc).
I think the idea is to carry a lifetime supply of nuclear fuel. Nuclear rockets aren't necessarily super particular about what propellant they use in conjunction with that fuel, so you can probably easily either directly scoop or otherwise easily refine/distill usable propellants anywhere you can find gas or something that is liquefiable.
I’m not sure what’s “horrible” about it. Research was halted because of the Test Ban Treaty, but if a safe way could be found to get the nuclear material into orbit, why not try it?
2 weeks is far better than 45 days which is what Nasa estimates nuclear thermal propulsion would achieve.
Zero gravity and space radiation are deadly to humans, and the more exposure we can cut, the better.
The same attitude also gave us the Russian RORSATs, many nuclear reactor cores are still in a parking orbit and will come down at some point in the future.
I don't think the launch issue is the main problem: after all the nuclear thermal system also requires nuclear materials in orbit.
/s
There were projects to develop nuclear thermal designs at the Nevada Test Site (Area 25, 'Jackass Flats') run by Los Alamos, 1955-1973. They had three designs (Kiwi, Phoebee, Pewee), all using highly-enriched uranium (bomb grade, as with nuclear engine reactors). I think these have longer lifetimes and are more efficient, but the new NASA report makes a point of using low-enriched designs this time around.
https://en.wikipedia.org/wiki/Project_Rover
I can't imagine it would be plausible to launch something like that without first testing it at a DOE/NNSA facility of some kind however, which might be a little problematic, as blowing up a nuclear reactor during a rocket test would be bad optics.
Decelerating into orbit is no problem.
https://marspedia.org/Earth-Mars_Transfer_Trajectory
https://en.wikipedia.org/wiki/Hohmann_transfer_orbit
These types of rockets ideally shouldn't produce much radiation, as the working fluid (propellant) is just heated up by passage through the reactor, although I don't know if there's a primary coolant loop and a heat exchange or if it's just basically the primary coolant being blown out to space, in which case maybe there'd be some 3H-tritium formed? Probably not much of a concern, though it might be for a Earth-based test firing.