Keith Henson: Current humans would have an awful time on Mars. They would have to live underground to avoid too much cosmic ray damage. Eventually, with medical nanobots, the radiation would not be a problem.

O’Neill cylinders are better suited for unmodified humans. The shell plus a few meters of dirt keeps the radiation down. Rotation gives normal gravity.

KH: By the time Engines came out, in 1986, the Space Colony meme (12 years old) had mostly burned out. It was clear by that point that mining the Moon and building power satellites was a long way off. The problem was cost: it was too expensive by a factor of about 300 for the would-be colonists to go into space on their savings. Freeman Dyson analyzed this in Disturbing the Universe (and that chapter was printed in the L5 News). L5 merged with von Braun’s National Space Institute in 1987, forming the National Space Society. NSI had around 25,000 members, and L5 had about 10,000. I don’t have exact numbers, but I understand that the combined membership fell for a long time. The meme of living in space was incompatible with reality.

There wasn’t any choice: it would take nanotechnology to reduce the cost to where we could go into space. Of course, we may or may not survive the AI and nanotech singularity. I wrote about this in 2006.

KH:  Space elevators have two problems: even the strongest materials are not strong enough to get a decent taper ratio. The other problem is that they will get hit by everything in orbit around the Earth.

Power satellites have different problems. The big one for business is that they don’t scale down; so you can’t start small. Microwave optics force the size into a few GW. They still look good in comparison to nuclear; perhaps $2.4 B/GW as opposed to around $10 B/GW for nuclear, but a 5 GW power satellite would cost $12 B, not counting the R&D or startup for the construction. If you can lift parts to GEO for $200/kg, they produce power for less than any other baseload method.

Space junk makes it hard to build them in LEO and move out to GEO.

It takes 1000 of them to replace 1/3rd of the energy humans now use. At 50 a year, it would take 20 years. 50 a year takes 25,000 StarShip launches, which may be at the ozone damage limit. Not likely to happen for 20 years, which puts it beyond the singularity.

KH:  In the mid 1800s, municipal gas was made from carbon (coke), steam, and heat. This proposal proposes using the carbon in trash, steam, and heat from intermittent renewable energy to make syngas. The syngas can be stored or used to make diesel or jet fuel.

KH: Los Angeles did reduce the waste flow by recycling. But there is still an awful lot of trash going into the landfills. This proposal turns the trash into valuable sustainable fuel. It has the advantage of no need to sort the trash; and, unlike incineration, generates no pollution.

KH: As part of the gas processing, the CO2 can be sorted out and sequestered. If you feed the vaporizer on biomass, you can make energy in the same process that takes CO2 out of the air. If you are making fuel, half the carbon winds up in the fuel.

I don’t think this is a big deal. I have been talking for many years about the problem when we take too much CO2 out of the air. Carbon—that is, diamond—is the best engineering material. We are likely to strip it out of the air for all sorts of projects.

KH: A lot of money, maybe a billion dollars—a very tentative number. On the other hand, the profit on sales of jet fuel pays off the investment in 5 years.

KH: Closing in. Despite being familiar with AIs from editing Drexler’s book, it was a shock when the recent crop of AIs was released. I spent a few pages interacting with an early one. It went out and read “The Clinic Seed” on the web. It was surreal talking to a real AI about a fictional one. I posted the exchange on the extropian mailing list.