How does one convert nuclear heat energy into directional energy for propulsion purposes?
Take a look at this: https://en.wikipedia.org/wiki/Nuclear_lightbulb
NASA Wants to Send Nuclear Rockets to the Moon and Mars
51–60 of 89 posts
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#52I’m disappointed. I expected a project-Orion-type interstellar solution. Not a measly ”twice as fast as conventional“ water kettle. Also, no word about what they will acually use. Because classic uranium is a quite limited resource actually. It has been said to run out even before fossil fuels. Also, why not a fusion rocket? Given that we know how to make fusion bombs. Because until we find a massive amount of anti-m…
> Because until we find a massive amount of anti-matter
I honestly hope this never occurs, or we never are able to contain/store such a mass for any real length of time.
Because if we can do it, it will be used for a weapon.
Seriously - I can't even imagine what - for instance - one kilogram of anti-matter coming in contact with regular matter - the amount of energy that would be released...it staggers the imagination. Today's fusion weapons release only a fraction of their potential energy; anti-matter conversion would be 100% (roughly):
https://en.wikipedia.org/wiki/Antimatter_weapon
"Using the convention that 1 kiloton TNT equivalent = 4.184×1012 joules (or one trillion calories of energy), one gram of antimatter reacting with one gram of ordinary matter results in 42.96 kilotons-equivalent of energy (though there is considerable "loss" by production of neutrinos)."
So...one kilo of anti-matter would be equivalent to 42 megatons - which is close to yield of the Tsar Bomba:
https://en.wikipedia.org/wiki/Tsar_Bomba
...but in a much more compact package. 50 kg of antimatter - which would be feasible for current launch systems, and comparable in size to current warheads:
https://en.wikipedia.org/wiki/W80_(nuclear_warhead)
Well - that's a 2 GT weapon...while I'm sure such a thing has been considered as to it's effects...I honestly don't know what that would be. Best guess might be that one such warhead could easily take out a good portion of say, the west coast (of the United States)?
Ultimately - we are not ready in any manner - socially, morally, politically - as a species to wield that kind of power responsibly. Honestly, even nuclear weapons fall into that assessment, despite recent history - I'm honestly not sure how we have gotten this far without a major nuclear war occurring.
Sadly, though, I know that my conjecture (in which I am not alone, I hope) will not do anything to stop the research - right now, though, the cost to produce anti-matter (let alone contain it) is so high as to make even a small mass cost an exorbitant amount of money. I sincerely hope there isn't any breakthrough on that front.
I honestly think we, as a species, are not ready for it (that isn't to say none of us are - but those who would be responsible with such "stuff" are likely very few - I know I am not one of them).
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#53Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#54Anyone else just get a JSON 404 page from this link? { statusCode: 404, error: "Not Found", message: "Not Found" }
I got that error from another article linked to Wired from HN the other day. After a short time, I clicked again and all was fine.
Something wonky is going on there, since it probably shouldn't even be 404 unless they keep deleting their articles and then resurrecting them shortly thereafter (which would be just a little weird).
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#55I’m disappointed. I expected a project-Orion-type interstellar solution. Not a measly ”twice as fast as conventional“ water kettle. Also, no word about what they will acually use. Because classic uranium is a quite limited resource actually. It has been said to run out even before fossil fuels. Also, why not a fusion rocket? Given that we know how to make fusion bombs. Because until we find a massive amount of anti-m…
> Because until we find a massive amount of anti-matter I honestly hope this never occurs, or we never are able to contain/store such a mass for any real length of time. Because if we can do it, it will be used for a weapon. Seriously - I can't even imagine what - for instance - one kilogram of anti-matter coming in contact with regular matter - the amount of energy that would be released...it staggers the imaginatio…
Who cares about weapon power? We already have _ridiculously_ and _maximally_ powerful weapons now. Our urge to kill one another is no longer constrained by the limits of our tools. It doesn't matter whether we're able to make even more powerful weapons.
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#56Earlier quoted context omitted.
The risk is that in a catastrophic launch failure (read: exploded rocket), the radioactive materials could be dispersed downrange. The solution--if that's really a problem--is to use the same escape systems used for crewed launches to eject the nuclear fuel with a parachute and emergency beacon, and keep it all inside a durable shielded container until the craft needs to start up the nuclear engine.
Effectively, they already do that. Although the United States doesn't launch reactors, we do on occasion launch radioisotope thermoelectric generators (RTGs). These use a core of sub-critical plutonium surrounded by thermocouples, which turn the heat into electricity. These are used for probes going to the outer solar system, where solar panels aren't effective enough. Anyway - there is certainly a concern with the p…
IIRC long ago a US RTG ended up in the ocean due to launch failure, only to be recovered and sussessfully re-launched on a new satellite.
These things are tough! And also expensive, so you might as well reuse them once they shrug off the rocket exploding under them.
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#57UFO's are real, the government just admitted it (someday they may even admit recovered ET craft), and yet the media is failing so hard at diving in deeper. Until the headline is "NASA now has working vehicles than that can warp spacetime" I just can't be bothered to get excited.
They admitted to encountering the literal definition of UFO -- "Unidentified Flying Object", which in no way at all proves or even suggests alien activity. If you want to get annoyed with the media, direct it at them convincing people that "UFO" = aliens
By unidentified they probably meant unidentified to anyone without a clearance.
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#58How big is the added risk of toxic waste? I'm not sure how much waste is produced in relation to propulsion energy given but it must be quite small? And I imagine that during travel in space you could just dump that waste out into space considering the vastness of it all.
The risk is that in a catastrophic launch failure (read: exploded rocket), the radioactive materials could be dispersed downrange. The solution--if that's really a problem--is to use the same escape systems used for crewed launches to eject the nuclear fuel with a parachute and emergency beacon, and keep it all inside a durable shielded container until the craft needs to start up the nuclear engine.
Except that's not a big problem. A non-activated reactor just contains enriched uranium. Uranium is dug out of the ground and you can buy it on amazon and chemically concentrate it yourself. It's safe to hold and handle (wash your hands afterwards so you don't eat particles) and store in your house even. (In the US this is all legal.)
Reactors only become dangerous after you activate them and short lived isotopes are created that also happen to be types that are bioavailable, like cesium-137 and strontium-90 which the body will take up and store inside the body.
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#59Earlier quoted context omitted.
You do what you would on a terrestrial reactor, and shut down the reactor e.g. by using control rods, or pulling out fuel rods to shut down the chain reaction. These wouldn't be simple radiothermal devices, but proper actively managed reactor cores. Having said that you absolutely would need active cooling even in a 'shut down' state, probably by circulating a cooling fluid to radiator fins. You might use the same fl…
your option of coolant without loss implies radiative cooling, how large a surface would be needed for how large a rocket for radiative cooling in the off shut down state? would the sunny side need to be reflective while the dark side needs to be emissive?
Nuclear reactors can stand quite high temperatures, so it will be much easier than you would assume if you looked at other rocket projects. Remember that radiating power increases with the 4rth power of the temperature.
Also, a shut down reactor quickly gets to ~1% of the energy of an active one, so, again, it's easier than it seems. Generated energy goes down exponentially with time.
Of all the problems of creating a nuclear rocket, I don't think cooling stands up.
Re: NASA Wants to Send Nuclear Rockets to the Moon and Mars
#60> which will almost certainly be used on any crewed mission to Mars.
This is interesting. I hadn't seen anything about NASA plans to get humans to Mars requiring nuclear-thermal propulsion. Does NASA even currently have a serious plan for Mars missions with the whole Artemis thing going on?