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Nuclear Conversion for Starship

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Re: Nuclear Conversion for Starship

#81

Post by ben_w »

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?

Shooting just electrons out the back of your ship is fine for the brief period before your ship gains a positive electric potential comparable to the net potential those electrons experience due to the inside of the particle accelerator you were using, after which your ship's own field is a major source of drag.

If your ship has a positive electric potential of over 1.044 MeV[0], you also start getting positron-electron pairs forming on your hull.

[0] less in practice, because any electrons you're going to encounter were already moving

Re: Nuclear Conversion for Starship

#82

Post by jerrysievert »

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

which other planet have humans been to? I can only remember humans making it to earth, which isn't that far of a journey ... from earth.

we put humans on a moon, and we've put robots on another planet.

Re: Nuclear Conversion for Starship

#84

Post by ben_w »

renewiltord wrote: post #57
idlewords wrote: post #31

Earlier quoted context omitted.

That's like saying they carry 4400 tons of mass-energy, which could destroy the planet.

Would you not realize a lot of damage by just pointing Starship somewhere instead of at the sky?

Surprisingly little, as the thing is mostly fuel — by the time it hits anything[0] it's almost empty and therefore very light.

It wouldn't even be like the effect of the planes on the WTC in 9/11, as planes use fuel continuously during flight, whereas spacecraft use almost all of it just to take off.

[0] which implicitly assumes the self-destruct still isn't working right

Re: Nuclear Conversion for Starship

#85

Post by matheusmoreira »

Skunkleton wrote: post #2

First I am reading about nuclear engines applied to Starship. I wonder if it would be more practical to launch the reactor, fuel, and propellant into orbit using conventional rockets. Later a mission could pick up this Nuclear rocket engine and use it as a sort of booster while not inside a strong gravitational field. Ofc that doesn’t sound like Starship at all.

That's exactly what I do in Kerbal Space Program.

Re: Nuclear Conversion for Starship

#86

Post by ben_w »

idlewords wrote: post #15
politician wrote: post #7

I think we'll see nuclear propulsion for Starship variants that receive fuel rods in orbit and are not designed for reentry. Interplanetary logistics between Earth/Moon/Mars orbits.

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

If he really wanted to, he's rich enough to build the enrichment facilities himself. Could hide it underground in one of those tunnels, claiming the power consumption is a cryptocurrency mining rig or an AI server farm.

I suspect at least ten government agencies from various nations all have him/his assets under 24/7 surveillance just to make sure he doesn't do something at least this unwise.

Re: Nuclear Conversion for Starship

#87

Post by klyrs »

ben_w wrote: post #81
klyrs wrote: post #54

Earlier quoted context omitted.

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

Shooting just electrons out the back of your ship is fine for the brief period before your ship gains a positive electric potential comparable to the net potential those electrons experience due to the inside of the particle accelerator you were using, after which your ship's own field is a major source of drag. If your ship has a positive electric potential of over 1.044 MeV[0], you also start getting positron-elect…

Twin beta+ and beta- engines?

Re: Nuclear Conversion for Starship

#88

Post by asdff »

Animats wrote: post #45

That's a useful analysis. Nuclear power gives you more energy, but you're still limited by how much reaction mass you can carry. The plans that work look like early 1960s NASA plans - build infrastructure in orbit, assemble nuclear power interplanetary craft in orbit, nuclear power is from planetary orbit to planetary orbit only. That was Wernher von Braun's "Man Will Conquer Space Soon" plan.[1] The Apollo program,…

It makes you wonder though, should you set up such space based infrastructure, is it even worth publicizing lest you trigger an arms race?

Re: Nuclear Conversion for Starship

#89

Post by matheusmoreira »

andrewla wrote: post #36
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.

I need to play Kerbel Space Program. I have absolutely no intuition about this sort of thing. Some intuition around orbital mechanics from my physics days but rocketry is a bit of a mystery.

Do it! You'll know you got it when you're maneuvering the rocket on pure intuition without even using maneuver nodes.

Just steer clear of the planet Eve. It's been years and I still haven't been able to leave it.

Re: Nuclear Conversion for Starship

#90

Post by ben_w »

MrTortoise wrote: post #76

yay radioactive shit falling from space again

The sun is a giant fusion reactor known to cause cancer on a good day, and emit radiation bursts that can damage or disrupt power grids often enough that people can reasonably expect to read reports of them more than once in their lifetimes.
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