Thursday, February 23, 2017

Give me a home where the asteroids roam

Astronomers discover seven Earth-like planets around a nearby star

Or so the headlines tell you. But what does "Earth-like" mean? To give you a sense of what I mean, if we were studying our own solar system from afar, Mercury, Venus, Earth, and Mars would all qualify. And yet, three of the four aren't especially habitable.

Human beings are very clever about adapting to environments on Earth. Populations of humans are found all over, from the equator to above the Arctic circle. But all of those environments have constants which do not change, like gravity and the mix of gasses in the atmosphere. We already know that variations in the air we breathe can be deadly, and variations in the amount of sunlight over a 24-hour period effects long term human health. What if the day was something other than 24 hours? What if the gravity was 90% of Earth?

I'm pessimistic that humans can adapt to environmental factors which are especially different from Earth. Even if there are a dozen planets in every solar system, the odds of any planet being a close-enough match to earth (atmospherically, gravimetrically, and otherwise) to be a good fit for unmodified humans are slim.

However that does not mean I am pessimistic about human settlement of the solar system or the galaxy. It just means we should stop focusing on planets. Planets can be pretty hostile, they exist at the bottom of an gravity well that's very hard to safely enter and exit, and as a percentage of possible habitable real estate they're not even especially large.

Also, if you've read anything about the efforts that would be required to terraform a planet such as Venus, you know that's not a reasonable amount of work for the payoff. Not when there's a better alternative.

Much better than a planet is a small moon or large asteroid belt that can be mined for resources. Ordinary steel from a nickel-iron asteroid could be transformed into an O'Neil Cylinder habitat with an inner surface area of 10,000 square miles. Assuming (within reason I think) that we improve our ability to mass-produce carbon materials such as nanotubes and grapheme, the carbon from an asteroid could be turned into a Bishop Ring with an internal surface area of 1.2 million square miles (about the size of Argentina or India).

And those surface areas are just the top deck where people would probably choose to live, on account of the Mediterranean weather that's maintained year-round. There's no reason you couldn't have multi-level habitats with sub-levels for agriculture, infrastructure, and industry. Fields of rice won't care they only have 50' of headroom. So the upper deck numbers are pure residential land area.

The real benefit of ring habitats is you can produce 1g of gravity for the inhabitants without going down into a gravity well. This is important because if you think about a future where most humans live in space (not on Earth), you want to be closer to the trade networks connecting the many nations. From an energy point-of-view, living at the bottom of a gravity well is sort of like living on a remote mountaintop, whereas living in orbit is like being at a major sea port close to the world's shipping lanes. From earth the only way to get to the shipping lanes is taking a rocket; but from a Bishop Ring you can take an elevator.

So it's nice and all that we found seven planets. That's fine. Science is cool. But from the point of view of whether these planets will ever serve as a home to future humanity, the answer is "Probably not ever". Instead a colonization ship will set up shop in orbit around these worlds and produce 1,000 Earths worth of Mediterranean real estate from their moons, while on the (probably very hostile to human life) surfaces below we will only send robots for mining or scientific inquiry.

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