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Project Orion is a really bad idea. I guess it could be a good idea in specific situation where have to get a lot of mass off the planet and don't care about th

Project Orion is a really bad idea. I guess it could be a good idea in specific situation where have to get a lot of mass off the planet and don't care about the effects. Problem one is that detonating a series of nuclear bombs in the atmosphere. The first couple are close to the ground and produce local fallout, the higher ones produce global fallout. Problem two is that detonating nuclear bombs in space causes EMP. That doesn't destroy electronics on ground as thought but will knock out the electrical grid. The extra radiation will knock out satellites in space. There is interstellar Orion, Project Daedalus, but that is quite different with inertial confinement fusion and magnetic fields directing the exhaust.

nwah1 4y ago
Launching from lunar orbit would obviate EMP and terrestrial radiation concerns. But those are the least of the concerns.
- ianburrell 4y ago
  The problem with that is Orion is that it is heavy. It only makes sense when launching the whole thing from the ground. Orion has been proposed for interplanetary propulsion since it is pretty efficient. But would need to be convertible from ground-launch to space propulsion. Nuclear rockets are pretty good and safer to launch. The other problem is that nuclear weapons are expensive. Something like Davy Crockett is 2kg of plutonium, and mid-sized Orion would use 800 to get to orbit. Plutonium is $4000/g which means $6.4 billion to launch Orion. Orion that puts 1600t in orbit. Or 10 Starships which is less as disposable rockets and way less if reuasable.
  - philipkglass 4y ago
    In 1965 the Atomic Energy Commission put the cost of plutonium 239 at $10/gram, which by simple consumer price indexing (only a rough guide, admittedly) would make it $96/gram today. See Table I in this publication "Values In Spent Fuel From Power Reactors": https://www.osti.gov/servlets/purl/4618921 https://www.osti.gov/servlets/purl/4618921 At $96 per gram instead of $4000, that's a much more attractive $154 million to put 1600 tons in orbit. Uranium enrichment costs have fallen greatly since the 1960s as centrifuges have replaced gaseous diffusion, so uranium-fueled units would probably cost less (despite the greater mass of uranium required). I'd say that the main modern problems of a terrestrially launched Orion are treaty violations and giving a plausible cover for nations to again pursue developing "peaceful" nuclear explosives.
tomatotomato37 4y ago
Not as "spicy" an idea as the Nuclear saltwater rocket however, which instead of discrete bombs involves dissolving a load of bomb-grade fissiles into water and then ejecting them out a conventional rocket engine, with the idea the solution goes critical somewhere in the vincinity of the exhaust nozzle. Now if you're thinking "Does that replace singular discrete nuclear explosions with a continual nuclear explosion shrouded in an expanding cloud of radioactive superheated steam?", the answer is yes, yes it does. Weirdest thing is the design doesn't actually have as much potential ISP as a pulsed detonation system like an Orion, despite being a bonafide torchship. Go figure https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket
hermitcrab 4y ago
IIRC the estimate was that the extra radiation from a launch would kills tens of people per launch, not thousands. Still not great (especially if you are one of those victims), but not as much as you might expect.
pfdietz 4y ago
Another problem with it is that, unlike an ordinary rocket engine, it cannot be tested on a test stand. The injection of nuclear units, as well as the interaction of the unit with the pusher plate, are intimately affected by the surrounding environment (all that hot gas from previous explosions in the atmosphere). Getting this thing to work reliably for launch from Earth would be a nightmare. It might be easier to test the engine in space, say with an upside down unit on the Moon.
mikewarot 4y ago
It wasn't as bad as you would expect. The total fallout on Earth from a launch would have been about the same as a single 10 Megaton air burst, which we were doing all the time back then.

nwah1 4y ago

Launching from lunar orbit would obviate EMP and terrestrial radiation concerns. But those are the least of the concerns.

ianburrell 4y ago
The problem with that is Orion is that it is heavy. It only makes sense when launching the whole thing from the ground. Orion has been proposed for interplanetary propulsion since it is pretty efficient. But would need to be convertible from ground-launch to space propulsion. Nuclear rockets are pretty good and safer to launch. The other problem is that nuclear weapons are expensive. Something like Davy Crockett is 2kg of plutonium, and mid-sized Orion would use 800 to get to orbit. Plutonium is $4000/g which means $6.4 billion to launch Orion. Orion that puts 1600t in orbit. Or 10 Starships which is less as disposable rockets and way less if reuasable.
- philipkglass 4y ago
  In 1965 the Atomic Energy Commission put the cost of plutonium 239 at $10/gram, which by simple consumer price indexing (only a rough guide, admittedly) would make it $96/gram today. See Table I in this publication "Values In Spent Fuel From Power Reactors": https://www.osti.gov/servlets/purl/4618921 https://www.osti.gov/servlets/purl/4618921 At $96 per gram instead of $4000, that's a much more attractive $154 million to put 1600 tons in orbit. Uranium enrichment costs have fallen greatly since the 1960s as centrifuges have replaced gaseous diffusion, so uranium-fueled units would probably cost less (despite the greater mass of uranium required). I'd say that the main modern problems of a terrestrially launched Orion are treaty violations and giving a plausible cover for nations to again pursue developing "peaceful" nuclear explosives.

tomatotomato37 4y ago

Not as "spicy" an idea as the Nuclear saltwater rocket however, which instead of discrete bombs involves dissolving a load of bomb-grade fissiles into water and then ejecting them out a conventional rocket engine, with the idea the solution goes critical somewhere in the vincinity of the exhaust nozzle. Now if you're thinking "Does that replace singular discrete nuclear explosions with a continual nuclear explosion shrouded in an expanding cloud of radioactive superheated steam?", the answer is yes, yes it does. Weirdest thing is the design doesn't actually have as much potential ISP as a pulsed detonation system like an Orion, despite being a bonafide torchship. Go figure https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket

hermitcrab 4y ago

IIRC the estimate was that the extra radiation from a launch would kills tens of people per launch, not thousands. Still not great (especially if you are one of those victims), but not as much as you might expect.

pfdietz 4y ago

Another problem with it is that, unlike an ordinary rocket engine, it cannot be tested on a test stand. The injection of nuclear units, as well as the interaction of the unit with the pusher plate, are intimately affected by the surrounding environment (all that hot gas from previous explosions in the atmosphere). Getting this thing to work reliably for launch from Earth would be a nightmare. It might be easier to test the engine in space, say with an upside down unit on the Moon.

mikewarot 4y ago

It wasn't as bad as you would expect. The total fallout on Earth from a launch would have been about the same as a single 10 Megaton air burst, which we were doing all the time back then.