xkcd #2929: Good and Bad Ideas
xkcd #2929: Good and Bad Ideas
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While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.
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All chemical propulsion is just controlled explosions that we use to push a thing forward. It's not that different, as long as you don't use it in the atmosphere or near humans.
Yeah I know, it's the same principle behind modern fuel engines. Still, using nukes for propelling something forward is a bit of a stretch.
Not just nukes, but nuclear shaped charges, at a rate of maybe one per second for a manned vehicle or even more for a faster cargo only mission.
If you can trust the human monkeys with the "shaping" of a rock that got us here, how you gonna distrust the widdle trivial matter of taking little bits of something and splitting them.
It's shaped charges, it's totally fine and sane. I'd happily get on the 1,000th Orion flight*.
*Only if that's a fresh hull
Ah the 50s, when everything atomic was rad.
::Fallout theme starts playing::
"I don't want to set the world on fire...."
It's not uncommon in scifi. Netflix's Three Body Problem also explores such a solution in quite some depth.
I love The Three Body Problem, both the books and the show. But it bothered me to no end to read Netflix's Three Body Problem.
I'm not familiar with the books, and the plot summary of their Wikipedia article does not mention nuclear propulsion whereas the article for the series does, so I went with that.
Unless what bothers you is the x followed by the apostrophe and the s, which I never know when to omit the s, so it is what it is.
Ah gotcha. Yeah you should check out the books if you're liking the show! The books go into a ton more detail and the Staircase Project is pretty cool. Seeing it on the screen is cool too, but if you really wanna nerd out I highly recommend the books.
It would probably work just fine, but it needs a huge ship. It could get up to a few percent of the speed of light.
FWIW, nuclear test ban treaties are considered to outlaw it. I think we're more likely to solve the technical difficulties of antimatter propulsion than we are to get over the political difficulties of nuclear bomb propulsion.
It could get up to a few percent of the speed of light.
So could a person sticking their head out and blowing, but it's still a terrible idea.
Just as an observation, there was a time when everyone on the Internet was gaga over the idea of Project Orion, and you didn't dare speak out against it lest you get a hail of downvotes.
It'd work fine in deep space. It's not a good idea to launch from Earth this way. But again, we'll probably find something better once we're at the stage of needing it.
But then how would you launch nukes on orbit without the risk of accudental nuclear explosion?
Implosion-type nukes are all but impossible to make go off that way. They need a whole bunch of small explosives to go off very precisely to squeeze the core in just the right way. A short circuit or a crash won't have the necessary precision. This isn't entirely safe, either--it can still cause a small explosion with a flash of fallout and radiation--but it's a manageable problem.
Gun-types (Little Boy was one) are easier to go off on accident, but the US retired its last gun-type design decades ago. I don't think Russia used them much, either. They're only good for smaller bombs, and their safety issues make them questionable for any use. Smaller nuclear powers aren't bothering with them.
Read "Footfall" for a hard scifi story featuring such a ship.
I like Footfall, but it's also a little over the top for me.
Co-written by the guy who tried to sell the US military the concept of "rods from god" (orbital kinetic weapon). I wouldn't expect anything less.
Will do! Thanks
Not worse than a fusion torch. Or open-cycle nuclear propulsion. Or an antimatter drive.
You know, the Kzinti lesson😉
Never heard of those, but if they are on par with project Orion I have some nice readings to do today.
If you're into hard sci-fi and you're looking for a good read, they actually dropped a pretty good recommendation with that reference at the end - Larry Niven does a great job of blending real-world theories like Dyson spheres and advanced propulsion drives, with some of the more far-flung standards of the genre like an intra-planetary teleportation grid.
Aren't there plans again?
Considering that you need huge shields and dampening and you only have the mass of the bomb itself as propelant, is it still as effective as controlled propulsion?
I think you may be mixing up Project Orion (let's chuck bombs out of the back to make us go zoom) with NERVA (a nuclear thermal rocket engine where the heat from chemical reactions is replaced with heat from a nuclear reactor to generate gas expansion out of a nozzle). Something like NERVA is actually a great idea. Let me tell you why!
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It's completely clean (unlike Orion and fission-fragment rockets)
- the reactor and fuel never touch, the fuel goes through a heat exchanger and is not radioactive
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it provides extremely high efficiency
- chemical rockets top out at ~400-500 isp in vacuum
- NERVA tests in 1978 gave a vacuum isp of 841
- ion thrusters like NEXT has an isp of 4170
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it provides lots of thrust
- NERVA had 246kN of thrust
- NEXT (which was used on the DART mission) is 237 millinewtons
- That's 6 orders of magnitude more thrust!
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No oxidizer is needed
- All you need is reaction mass, just like ion thrusters
For automated probes, the extreme efficiency and low thrust of ion thrusters makes perfect sense. If we ever want to send squishy humans further afield, we need something with more thrust so we can have shorter transit times (radiation is a bastard). Musk is supposedly going to Mars with Starship, and the Raptor engine is a marvel of engineering. I don't like the man and I'm not confident that he'll actually follow through with his plan, but the engineers at SpaceX are doing some crazy shit that might make it happen.
Just think though, if the engine was literally twice as efficient and they didn't need to lug around a tank of oxidizer, how much time could they shave off their transit? How much more could they send to Mars? Plus, they could potentially reduce the number of big-ass rockets they have to launch from Earth to refuel. If you can ISRU methane, then I imagine you could probably get hydrogen.
There are problems that still need to be resolved (the first that comes to mind is how to deal with cryogenic hydrogen boiling off), but like, the US had a nuclear thermal engine in the 70s. It was approved for use in space, but congress cut funding after the space race concluded so it never flew.
I'm happy to see that NASA is once again researching nuclear thermal rockets. Maybe we'll get somewhere this time.
I'm more with VASIMIR though, maybe with a nuclear reactor for power, since it's variable.
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Don't forget the mass of whatever ablates from your shield!