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Nuclear Conversion for Starship

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Re: Nuclear Conversion for Starship

#71

Post by dgacmu »

jaggederest wrote: post #28
idlewords wrote: post #15

Earlier quoted context omitted.

Name me a country willing to give Elon Musk control of fissile material, however indirect.

Starship and the booster already collectively carry 70 kiloton-tnt-equivalent masses of liquid methane and oxygen. As a weapon of mass destruction, it's hard to beat relativistic impact.

How do you calculate this? Starship has a propellant capacity of 1200 metric tons - 1.2 kilotons. Super heavy booster has 3400 tons, total of 4.6 kilotons, per wikipedia [1]. By weight, you need about a 4:1 ratio of O2:Methane for complete combustion (Starship is rumored to carry 22% methane). Which means you're getting about 0.92 kilotons of methane completely combusted. At 50-55MJ/kg, that gives you - roughly - 50 thousand gigajoules. A ton of TNT is 4.184 thousand gigajoules[2], which means that Starship+Super Heavy carries the energy-equivalent of about 12 kilotons of TNT [3][4].

[1] https://en.wikipedia.org/wiki/SpaceX_Starship

[2] https://en.wikipedia.org/wiki/TNT_equivalent

[3] It can't explode all at once unless pre-mixed in perfect proportion, of course. What you'd really expect is an awfully big fireball + fire but not the same massive force all at once of a nuclear detonation.

[4] Or 50 terajoules (the ship) and .184 terajoules (TNT), which come out to the same thing, but I find gigajoules both more intuitive and more a more fun BTTF reference.

Re: Nuclear Conversion for Starship

#72

Post by lifeisstillgood »

psunavy03 wrote: post #66
Kim_Bruning wrote: post #56

Earlier quoted context omitted.

That was (part of) the original plan, post Apollo program. Somehow it got stripped down to to just a space shuttle. :-( https://en.wikipedia.org/wiki/Space_Transportation_System

The "we haven't solved all of our problems on Earth yet" crowd . . . as if we ever will.

Hell we put humans on another planet, we can fix the stuff down here if we really want

Re: Nuclear Conversion for Starship

#73

Post by Kim_Bruning »

lifeisstillgood wrote: post #72
psunavy03 wrote: post #66

Earlier quoted context omitted.

The "we haven't solved all of our problems on Earth yet" crowd . . . as if we ever will.

Hell we put humans on another planet, we can fix the stuff down here if we really want

It's a different kind of problem, unfortunately.

Re: Nuclear Conversion for Starship

#74

Post by marcinzm »

idlewords wrote: post #69
xwdv wrote: post #67

Earlier quoted context omitted.

Not really any more terrifying than driving around in vehicles powered by thousands of tiny explosions per minute.

If someone siphons your gas tank, they're not going to be able to nuke Paris. But a nuclear pulse rocket needs thousands of bomblets the size of coke cans. That's the scary part.

> size of coke cans.

Not really, each one would be 6 inches in diameter and weight over 300lbs.

Re: Nuclear Conversion for Starship

#75

Post by [deleted] »

klyrs wrote: post #54
CarVac wrote: post #27

Earlier quoted context omitted.

For specific impulse. When you have unlimited power, you want the lightest possible molecular mass exhaust for the best total delta V.

So, since beta radiation is even lower mass... just put a block of nickel-63 into a magnetic lens?

[deleted]

Re: Nuclear Conversion for Starship

#77

Post by api »

idlewords wrote: post #38
maxcan wrote: post #9

AFAIK, the only nuclear rocket that makes sense is landing a reactor on an icy comet and using it to shoot super heated steam wherever you want thrust. #seveneves

The Project Orion design (shoot hundreds of fission bombs out the back and ride the shock wave on a reaction plate) is surprisingly practical, and probably our only way to get humans past Mars. It's just kind of terrifying.

Ahh the old "devil's pogo stick."

Re: Nuclear Conversion for Starship

#79

Post by idlewords »

marcinzm wrote: post #74
idlewords wrote: post #69

Earlier quoted context omitted.

If someone siphons your gas tank, they're not going to be able to nuke Paris. But a nuclear pulse rocket needs thousands of bomblets the size of coke cans. That's the scary part.

> size of coke cans. Not really, each one would be 6 inches in diameter and weight over 300lbs.

Dyson's book hints that they ended up far smaller, but the details of that are classified to the gills.

Re: Nuclear Conversion for Starship

#80

Post by bluescrn »

Nuclear doesn't work with Elon's approach to development. You can't blow up multiple nuclear rockets within the atmosphere just to learn what needs fixing for the next attempt.

Then again, it's looking like the whole 'fail fast' approach is over anyway, with Starship grounded by red tape.

A full-stack Starship failure is seemingly too big/dramatic/risky to get away with doing repeatedly, especially admidst the politics of Twitter/X.

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