[pfdietz]

I don't think that's the case, if launch costs are low enough. The options you describe there are quite expensive. Reprocessing costs somewhere in the neighborhood of $1000/kg. Even fast reactor have trouble disposing of the seven very long lived fission products. A fully reusable launcher might get costs down to $10/kg to LEO. Even if one had to wrap the waste in 10x its mass in launch armor this could be much cheaper than reprocessing.

[lenerdenator]

The problem with launching anything into orbit using current rocket motor technologies is that heavier stuff costs more to put into orbit.

The elements that are used in nuclear reactors (particularly Uranium and Plutonium) are pretty dense, and thus heavy.

[pfdietz]

That's true, but the cost of reprocessing is also very high, per kg. And aren't the nuclear bros always telling us how little nuclear waste is actually produced? There's about 30 tons of spent fuel per GW(e)-year from today's burner reactors. At $10/kg to space that would be just $300,000 (yes, ignoring lots of costs there, at $10/kg is aggressive, but this is for comparison), a pittance compared to the value of energy produced from the power plant: at $0.05/kWh it produces > $300 M in electrical energy, three orders of magnitude higher.

[dpark]

Why would launch costs be low? $10/kg is fantasy land. UPS won’t ship a kilogram across the country for $10.

And who wants spent nuclear fuel in low earth orbit? This is a far worse location for spent fuel than buried in a bunker. This is a worse location than Times Square.

[fc417fc802]

> UPS won’t ship a kilogram across the country for $10.

I can purchase produce grown on a different continent for less than that at the grocery store so something isn't right here.

[dpark]

It was a metaphor for how absurd the statement was. But if you try to ship a 1kg package across the country it will likely cost way more than $10.

Freight cost is certainly way lower.

[pfdietz]

Why wouldn't they be low? In the limit, if launch becomes operationally similar to air travel, costs will be a few times propellant cost. And propellant is very cheap. LOX is almost free (the second cheapest industrial liquid after water) and liquid methane isn't very expensive either.

Low earth orbit would just be where it's transferred to something to carry it farther out, for example using solar-electric engines.

For all this, remember it isn't done immediately, it's done in (say) 300 years when the short lived fission products are mostly gone.

[dpark]

I think the onus is on you to explain why costs would drop by >3 orders of magnitude (>4 accounting for the 10x launch armor). It’s something like $1500/lb on a fully loaded Falcon Heavy and all indications are that SpaceX isn’t making money at that price.

Plus even if this were free, “shoot 180k tons of nuclear waste into space” seems like a terrible idea in general. It’s one of those ideas that make sense only until you think about the ramifications. What happens when inevitably one of the 3 thousand Falcon heavy rockets explodes and the armor fails and we spread nuclear waste over 3 states?

[pfdietz]

Falcon Heavy is more expensive per kg than F9, because it throws away more things. SpaceX flies it for certain military missions but you will note they launch their own stuff on F9.

A full launch on F9 (with recovered S1) is estimated to cost $15M and can put up to 17,600 kg into LEO, or $850/kg.

> (>4 accounting for the 10x launch armor).

You're double counting there. 3x would be just fine even with 10x launch armor.

> seems like a terrible idea in general

And here's the problem: you started from an emotional reaction and are trying to rationalize that.

[dpark]

> A full launch on F9 (with recovered S1) is estimated to cost $15M

Estimated by who? SpaceX charges 74 million for this. Nothing credible I can find indicates that SpaceX is running an amazing 80% profit margin on Falcon 9 launches.

> And here's the problem: you started from an emotional reaction and are trying to rationalize that.

No, your premise is “just launch the trash into space” and you’re hand waving away the complexity, costs, and danger.

[pfdietz]

SpaceX charges what the market will bear, and because they have no good competitor their profit margins can be very large.

Anyway, the number is from fairly old Musk interviews. Costs have likely decreased since then.

https://www.nextbigfuture.com/2026/02/spacex-falcon-9-true-c...

> No, your premise is “just launch the trash into space” and you’re hand waving away the complexity, costs, and danger.

At least I didn't trot out a string of obvious errors like you did.

When people do that, it's a strong tell they're engaging in broken thinking. What you did, I think, is believe something, then try to rationalize it. When your thinking reached a justification you liked you just stopped thinking (because, after all, thinking more could break the pleasing argument you just constructed, and that would feel bad).

[api]

$10/kg isn’t fantasy land if we have fusion rockets, but then we don’t need fission power anymore. :)

[pfdietz]

Fusion would be useless for launch to orbit. Even fission sucks for that. It's really hard to beat the cost and power density of chemical rockets.

[api]

Depends. If we get explosive inertial confinement fusion to work you could build a pure fusion version of a nuclear pulse rocket. Look up Project Orion.

Orion (in its fission bomb form) is impractical and would be insane to launch from Earth, but it holds the title of being the only “torch ship” drive we know how to build. We could technically build it.