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Comment by randallsquared | Hacker News Reader

> You can't contain a bomb's hydrogen fusion reaction in a chamber

You certainly can, if you use a large enough chamber. Pacer was exactly this. You just have to accept high proliferation risk.

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Pacer took thinking about nuclear fuels in a lot of new and interesting directions. For the use case of interest, they really wanted to maximize the fusion yield fraction, minimize the radioactive products, and minimize the total yield. Had it ever been allowed to proceed to a commercial scale, these would have been very tight, very challenging, technical constraints.

If you relax one of those requirements, then it becomes instantly clear that limitless cheap energy is possible. For a somewhat absurd example, imagine that we build Pacer plants in space instead of on Earth. There's no longer any size constraint on the blast chamber. You can go to triple-stage (like Tzar Bomba) or more designs, at which point the fusion fraction gets extremely close to 100%, and the cost per unit energy becomes somewhat hard to fathom. But on Earth, it still would have been expensive.

We can also trigger fusion bombs with nice clean anti-matter instead of dirty fission. But we'd have to get better at making anti-matter.

Thank you for pointing me to Pacer, that was a fascinating read. They were apparently also considering digging a new panama canal with fusion bombs...

In 1972 they decided it wasn't economical based on fuel price compared to yellowcake, but fissile fuel isn't the primary cost of fission power and the engineering costs of pacer would seem to be much lower.

There's some old Asimov "Big Book of Science" sort of book I've got hanging around somewhere (dude definitely had aides/ghost-writers on some of that non-fic, right? Surely? At least researching and first-drafting for him to come through and punch up? Especially the more generic ones like that? I don't see how he'd have had the time to physically write that many words, otherwise, let alone also think about the words, considering his total output) that features the idea of nukes-as-tools pretty heavily, especially for canal digging and excavation generally.

He cranked out a ton of books. I'd believe it was just him, especially with his plain-English style.

True.

My crazy idea would be to use the heat and the pressure of these to pump water uphill. It is of course a crazy idea and you'd have to figure out a way to manage the pressure peak

But it would be very interesting

Pumped hydro has been a concept for a while now for grid storage of power; one of the limitations of it is just the rather unique geography required. Most places with adjacent reservoirs and enough vertical separation between them also have cottages, roads, and other infra that make it hard to be constantly draining and filling.

It is not just a concept, it represent the vast majority of grid energy storage today, we are talking about gigawatts.

Hydro is the best, so good in fact that most of the good spots are already taken, because as you said, it requires a very specific geography.

It’s less that (IMO) - cottages and roads are usually not as dense on steep hillsides and the like, though of course they can’t be ignored entirely. The pipes involved are usually not the big issue, and the pumping ops are usually not the big issue either.

The business model for pumped hydro requires relatively low cost to be economic and if it requires building a giant concrete water retention systems on top of large flat topped hills/mesas, near large drops in elevation, with water retention at the bottom of the large drop that is also really really expensive to build and requires specific geology to be economic.

And if something gets messed up, it’s a huge liability [https://en.m.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Powe...], as it can cause very damaging flooding and be expensive to repair/replace.

Worth doing when there is cheap power that can be stored and sold at higher rates later, but construction costs are really a huge part of it.

Or you can use multiple ordinary hydro power dams (i.e. ordinary lakes where one or more outlets are blocked).

I'm fairly certain we have these multi level semi natural systems here in Norway, but I am not sure if we use them for pumped hydro.

(Og course, if one doesn't care about ecology, one of those levels can be the sea.)

Of course, and they are. They are even more limited in quantity, geologically.

Yep, but just needs enourmous amounts if construction, not insane amounts.

> My crazy idea would be to use the heat and the pressure of these to pump water uphill.

This is a great idea, not crazy.

It ignores the steampunk future that awaits us all!

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