# Can Nuclear Pulse Propulsion (Project Orion) accelerate a 100,000 ton M-type (metallic) asteroid to a LEO? [closed]

Project Orion: specific impulse in the range of 6,000 seconds.

For example – Starship Interplanetary (SpaceX):

Max Fuel (after refueling at orbit) - 1,950 ton

Fuel left after arriving at NEO asteroid – 1000 ton (half burned).

Raptor Engine:

Thrust: 2,200 kN

Mass Flow: 650 kg/s

Maximum burning time (one engine): 1000,000 kg / 650 kg/s = 1,538 s

Propellant mass loss fraction (linear average) = 0.5

Total propellant mass adjusted to propellant mass loss fraction = 1000,000 * 0.5 = 500,000 kg

Total mass: 10,000,000 kg[rock] + 100,000 kg [Spaceship dry mass] + 500,000 kg[fuel] = 10,600,000 kg

Speed after final burn: 2,200,000 N / 10,600,000 kg * 1,538 s = 319 m/s

Fully refueled Starship - can possibly bring back to LEO a 10,000 ton asteroid.

NASA’s OSIRIS-REx mission - acceleration from NEO Asteroid Bennu towards Earth - 277 m/s.

• Can it? Yes, of course, given enough nukes. Maybe you should be asking how many it would take.
– GdD
Commented Jan 17, 2023 at 20:17
• GdD - I don't think this is an abstract question. There is a spacecraft specification, there is an approximate orbit velocity change (minimal requirement for NEO), and there is a limited amount of fuel (nukes) spacecraft specification allows to be brought to NEO object (without refueling).
– anon
Commented Jan 17, 2023 at 21:20
• I'm not clear on how Starship specifications are relevant to a question about a completely different propulsion method. Commented Jan 18, 2023 at 0:07
• This question would make a lot more sense if you further specified the configuration of the Project Orion craft instead of having a long aside about a Starship. Commented Jan 18, 2023 at 0:47
• it's quite a leap between saying a 60-ton meteorite landed intact (and seems to be notable as the LARGEST METEORITE FOUND INTACT) and a 100,000 ton asteroid (which is 100,000 tons heavier!) landing intact / in usable form / without causing massive problems. There are many layers of inquiry you should probably pursue before the "should we use nuclear weapons to throw this at Earth." Commented Jan 18, 2023 at 12:21

Pulling some numbers from project Rho which appear to be quoting the original studies, we get 16M Newton from a 5 kt device onto a 20 meter pusher plate. This assumes optimal plate design that a random asteroid does not have but works for a best case.

100,000 tonne asteroid is 100,000,000 kg so F/m=a gives us 0.16 ms. Assuming we find an ideal near earth Asteroid that we can nudge to intercept and just need to drop from escape velocity to LEO we need 3210ms so with 0.16ms per device we need 20,100 of them. 5 kt are relatively small so the ~10k bombs currently available on earth could conceivably do the job, either rebuilt or just at higher yields than ideal.

The Orion propulsion units massed in at 1 tonne each, so our system mass for this looks to be at least 20k tonnes, so looks like we need at least another 4000 devices to get out from Earth.

In practice we probably cannot find a handy massive asteroid on an intercept so we would be looking at an additional couple of kilometers per second to get out, intercept and redirect.

So overall this might be something humanity could in fact do, but we'd be probably only be able to do it once (not counting the other ways this might end civilization by accident). In particular having used our entire inventory of bombs bringing it home, getting rid of the non useful parts of that 100,000 tonnes of now pretty radioactive rubble might be a serious problem.

Based on the comments by OP, if the aim is just to plonk an asteroid into the Sahara then things are much easier, only needing to do the re-direct and a couple of thousand bombs. The problem is that while a random calculator suggest much of it reaches the ground, it does so in pieces and then makes a kilometer or so of crater so there will be a non trivial mining effort scraping all the debris up.

Doesn't matter if you could, you're going to find every major military power in the world on your doorstep telling you that it's absolutely unacceptable and they're prepared to use whatever force it takes to stop you.

Orbital mechanics 101: Barring gravity maneuvers your orbit will include the point where you shut down your engine. You want to circularize at say 400km (ISS altitude), your engine is running 400km above the Earth. However, your engine is based on nuclear explosions--you're setting off nukes 400km up. We did that once--it was called Starfish Prime. That shot taught us never to do it again.

While a bomb up there won't directly kill anyone it would likely be worse than if you actually nuked them--you'll blow electronics over a large region. With everything not working the land becomes basically uninhabitable. And note that any reasonably modern vehicle is included, you can't even flee.

• "Loren Pechtel" - thank you for your note. You described a common opinion on the issue.
– anon
Commented Jan 18, 2023 at 4:00
• "Loren Pechtel" - thank you for your note. You described a common opinion on the issue. I get it. But in my case, I am trying to look a little bit beyond. We discussed difficulties with practical refueling stations in space (Hydrogen liquefaction). Without refueling stations, private ventures expansion in space will be limited. But Nuclear Pulse Propulsion - at least, has potential. The common opinion about Nuclear Power Plants was similar to what you've described above. But Bill Gates showed a safe and reliable way to use it in the future.
– anon
Commented Jan 18, 2023 at 4:07
• I would envision something like a Nuclear Space Tug - that could safely accelerate Starship to it's destination (starting maneuver beyond Moons orbit) and have Starship to arrive to destination with a full tanks (not half empty).
– anon
Commented Jan 18, 2023 at 4:12
• @TheMatrixEquation-balance And why do you think you won't get the devastating EMP from your Orion drive? The fact that your bomb goes off near a pusher plate doesn't change the energy that hits the atmosphere. The only safety is from being small enough & distant enough that the EMP doesn't cause a problem. Political opinion doesn't change whether you get to fry the planet below or not. Commented Jan 18, 2023 at 23:15