How much will it cost?
How much did Canada cost? Chicago? San Francisco? A lot. Space settlements will be even more expensive because all the basic life support the Earth gives us for free must be built, and transportation costs will be very high. On the other hand, children cost a lot of money and many people are only too happy to pay.
Space settlement is extraordinarily expensive because launch vehicles are difficult to manufacture and operate. For example, the current (2004) cost to put an individual into orbit for a short time is about $30 million. To enable large scale space tourism by the middle class, this cost must be reduced to about $1,000-$10,000, a factor of 3 to 4 orders of magnitude. Space tourism has launch requirements similar to space settlement suggesting that a radical improvement in manufacturing technology may be necessary to enable space settlement.
One candidate for a major improvement in manufacturing technology is molecular nanotechnology. An important branch of nanotechnology is concerned with developing diamonoid mechanosynthesis. This means building things out of diamond-like materials, placing each atom at a precise location (ignoring thermal motion). Diamond is 69 times stronger than titanium for the same weight and is much stiffer. If spacecraft were made of diamonoid materials rather than aluminum, they could be much lighter allowing more payload. For an excellent analysis applying nanotechnology to space development, see McKendree 1995.
Diamond mechanosythesis may enable a radical transportation system that could allow millions of people to go to orbit each year -- an orbital tower. An orbital tower is a structure extending from the Earth's surface into orbit. To build an orbital tower, start construction at geosynchronous orbit. Extend the tower down towards Earth and upwards at the same rate. this keeps the center-of-mass at geosynchronous orbit so the tower stays over one point on the Earth's surface. Extend the tower all the way to the surface and attach it. then an elevator on the tower can move people and materials to and fromorbit at very low cost. There are many practical problems with orbital towers, but they may be feasible.
An orbital tower is in tension so it won't collapse, but it must be very strong or it will break. The point of greatest strain is at geosynchronous orbit, so an orbital tower must be thickest at that point. The ratio of the diameter of the tower between geosynchronous orbit and the ground is called the taper factor. For steel, the taper factor is greater than 10,000 making a steel orbital tower completely impractical. However, for diamonoid materials the taper factor is 21.9 with a safety factor the same as McKendree 1995. Thus, a diamonoid orbital tower 1 meter thick at the ground would be only 22 meters thick at geosynchronous orbit. Fullerene nanotechnology, using carbon nanotubes, may be even better than diamonoid allowing a smaller taper factor. Calculations suggest that the materials necessary for construction of such an orbital tower would require one asteroid with a radius between one and two kilometers. These calculations assume the tower is built from diamonoid material with a density of 4 g/cm^3 and the asteroid has a density of 1.8 g/cm^3 and is 3% carbon.
Thus, molecular nanotechnology may enable space settlement.
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Author: Al Globus