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Cake day: June 8th, 2023

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  • The cheapest materials would be what can be acquired in space without having to launch from Earth. As a result, you’re going to want to build your O’Neill cylinder out of some combination of iron, aluminum, titanium, and silicon dioxide.

    The last of which might be particularly useful, as it is the main ingredient of fiberglass while also being the most common substance on Moon and asteroids. As a result, you probably want to build your cylinder primarily out of fiberglass. You can get pretty decently sized cylinders, as fiberglass has a higher strength-to-weight ratio than steel. Apparently, 24km diameter is a viable figure. Scale up length the same way, and you’ll get 96km. So a 24km x 96km O’Neill cylinder made out of fiberglass.

    That would be about 7238 km^2 of usable surface area. Half that to 3619 km^2 to make room for windows (as originally envisioned by O’Neill), and assuming a density comparable to New York City (about 11,300 people/km^2), you’ll get around 40 million people. Or about the population of Tokyo.

    That’s seems plenty for any sensible space colonization strategy we might adopt in the future. And what’s best is that you don’t really need any fancy technology. Just use solar power to power mass drivers and deliver raw materials from the moon or asteroid via electricity. And it won’t be any special materials either. Raw regolith can be made into fiberglass, so cost can be kept surprisingly low. The only question is scaling it all up, which may unfortunately be too expensive or will take a very long time to happen. Ultimately, this is still sci-fi, albeit on the hard side of it, since no fancy new technology is require.









  • At the end of the day, you are just turning sunlight/wind and water into a fuel. The marginal cost is nearly zero. Which is why the development trajectory will be the same as the rise of wind and solar energy. Both of those ideas also had nearly zero marginal cost. As a result, you can expect hydrogen fuel to be extreme cheap and basically inexhaustible. That is a major advantage and there is nothing batteries can ever do to match that.

    I wonder if you are projecting here: Hydrogen, not batteries, have many more applications. You can’t even make the steel used to make a car without a reducing agent like hydrogen. Same is true of the metals in the battery itself. So if we want to hit zero emissions for real, hydrogen is mandatory, but batteries are not. In fact, BEVs are totally dependent on green hydrogen to real reach zero emissions. Everything from industry to long-duration energy storage all requires hydrogen. You can skip BEVs altogether but you cannot avoid hydrogen.


  • Those are wildly exaggerated. The main limitation is that society hasn’t invested enough in hydrogen infrastructure. At least not yet. The problems would quickly go away if we did.

    You also forget that we’ve poured many billions of dollars into electrification and battery production. That amount of investment would have solved a lot of those limitations.

    As green hydrogen is made from water, there is basically no battery chemistry that can rival it in terms of availability. It is basically the best energy storage mechanism of this type already. Saying that batteries can get better is just misdirection. Also, you can have plug-in hydrogen cars too. The natural path is probably hybrids -> PHEVs -> plug-in FCEVs. Pure BEVs are in many ways a side-trip.