Nice, at least this doesn't seem like one of those horrible 60s designs that spewed radiation everywhere by basically detonating a small nuclear bomb against a pusher plate.
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.
NERVA in the 1960s operated under a similar principal to the one just announced. Orion (what you're describing) was not the only proposal in the 1960s.
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.
So I've been working on a sci-fi book that involves interplanetary governance, and one of the things I've realized is that if one wanted to have a civilization that worked on an interplanetary scale nuclear is probably the only way to go for meaningful power production.
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.
Naively I'd expect that you would need fusion specifically. Uranium isn't plentiful unless you're on a rocky planet, and isn't very high energy density compared to hydrogen.
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).
Isaac Arthur on YouTube has some interesting commentary on antimatter, and other advanced proposed propulsion systems. It seems that for the moment, at least, antimatter is strictly in the realm of science fiction, until some very difficult problems are solved.
Probably easier to generate chemical fuel on the moon/mars too then to refine nuclear fuel, although if you could carry enough nuclear fuel in the first place maybe that would be moot.
Nuclear rockets are a bit funny: they have a separate fuel (something that produces heat, like U-235, Thorium, etc) and propellant (something that gets heated and pushed out the back, like Hydrogen, Nitrogen, 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.
It sounds like you’re referring to nuclear pulse propulsion, a proposed method of reaching Mars from the Earth’s surface in 2 weeks.[1]
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.
In the 60s we were much too cavalier about nuclear pollution. Barfing out nuclear isotopes everywhere is just not feasible. The whole spacecraft would get polluted with it.
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.
Apparently a nuclear drive could half the transit time to Mars for astronauts, which has the additional benefit of less hard radiation exposure (assuming the nuclear reactor doesn't have any issues in transit).
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.
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.
Given the increased speeds, how does arrival at the destination work? I assume the rocket is rotated 180° and fired. Is the plume the rocket flies through radioactive?
There are some other options like aerobraking in the thin Martian atmosphere, and the gravity of Mars helps capture the vehicle at the other end, so not that much braking thrust is needed, and it's going to be fired at some complex angle:
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.
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.