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Comment by nabla9 | Hacker News Reader

Very popular question.

The short answer is: Counterintuitively it would take less energy to launch a spacecraft to another star than our own sun

As for why not into the space in general:

Risk of rockets failing. Lancing probes with small nuclear batteries is controversial. Think about launching tens of tons of nuclear waste. Almost 100,000 tonnes of nuclear waste is produced per year. That's clearly too much to launch.

If we would use SpaceX Falcon Heavy to launch only the highly radioactive waste )12,000 tons per year) for $2,500 per kg. It would cost $30 billion per year and 240 Falcon Heavy launches per year. Some of them will fall down, explode etc. and that must be dealt with.

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https://www.forbes.com/sites/startswithabang/2019/09/20/this...

https://www.universetoday.com/133317/can-we-launch-nuclear-w...

https://astronomy.com/news/2016/07/heres-why-we-cant-just-ro...

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I'm a little baffled that the question is so perennial. You'd think it would start and end with "thousands of dollars per kilogram". Landfill fees are closer to "pennies per kilogram".

There's all kinds of technical reasons as well, and people love talking about space. But "five orders of magnitude in costs" seems like the conversation ends very abruptly.

Just speaking as OP, I think it's bc of the little information that gets into the public about nuclear science in general, much of it is about the cost and dangers of nuclear waste. I have the impression of this thing that has to be maintained by burying it under a mountain in North Dakota for the next 50,000 years.

So while 5 orders of magnitude makes the financial case clear, I don't have a good idea if the risks of keeping it around are potentially 6-7 orders of magnitude greater than getting rid of it.

> Risk of rockets failing

The thing is, we transport nuclear waste over sea or air all the time, don't we? I believe the spent fuel is put into "casks" which is then loaded onto ships or jumbo jets and flown around the world.

Planes crash and ships sink, but we judge the risk (with proper pre-cautions) to be low enough when transporting radioactive waste. To me this shows that people generally accept transporting nuclear waste when the danger of catastrophe is low enough - importantly this signals that the risk only has to be low enough, it doesn't actually have to be 0.

Presumably as rocket technology advances we will eventually enter a stage similar to that in air travel, where the risk of a crash is measured in 1-per-billions rather than 1-per-hundreds or 1-per-dozens.

At that point, would we accept launching radioactive waste into space?

Don't forget that those casks are really heavy. If you launch the "waste" into space in them you'll be launching a lot more mass than just the 30kt. I don't know the exact ratio between cask mass and waste mass, but it could easily be 10:1.

Also, I'll repeat that throwing away valuable nuclear material just because it's called a "waste" product is stupid. Paying a lot of money to throw it into space is even dumber.

Are there any practical uses for nuclear waste?

I think they are referring to fast reactors (Referring to the fast neutrons used to induce fission) that can burn high level nuclear waste from standard PWR plants as fuel.

Some types of fresh nuclear fuel can be transported trough air, with limited amounts at the time.

Used nuclear fuel in those flasks are not transported trough air. Always by land or sea. On the sea they are transported in purpose-built ships.

Small amounts of highly radioactive nuclear fuel are transported trough air but they be in extremely secure type C containers that survive crash from cruising altitude. Creating similar containers that survive crash from space launch would make launching very expensive. Most of the payload would be just the container and only small amounts would be radioactive material.

It's 1000 times cheaper to recycle nuclear fuel make nuclear reactors that use nuclear waste than shoot it into space. France does it in La Hague. The rest can be buried into the ground.

Totally different, a space ship failling would mean tons of nuclear dust in the upper atmosphere, wich would mean radioactive material spreading everywhere in the world, poisonning everything.

This is pretty fascinating. I naively assumed that if you got something outside of Earth's orbit and stopped pushing it, eventually the Sun's gravity would take it from there.

Regarding price, that's quite a bit more in volume and cost than I realized. Thanks for the info!

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