Thursday, September 1, 2011

The Space Mirror Hack

by Glen Hendrix

Call me soft-hearted or a weeny-butt; I never fried ants with a magnifying glass when I was a kid. I did set pieces of paper on fire and burn my initials into a chunk of wood. What heady times those were. Those deeds were accomplished with a 2 ½” diameter magnifying glass at the bottom of a light-sapping 100,000-feet atmospheric well. Now imagine a magnifying glass 140 feet in diameter and sunlight that is twice as strong. That is what you have with an Orbital Adjustable Mirror.

The Orbital Adjustable Mirror is described in my science fiction novel Transmat World but is doable science. In the book the mirrors were first deployed to reflect sunlight to prevent the world from heating up due to an increase in greenhouse gasses. This has been proposed before by Lowell Wood, a senior staff scientist at Lawrence LIvermore National Laboratory. He states that reflecting 1% of sunlight striking the Earth’s surface would be enough to stabilize our climate, requiring a reflector of 600,000 square miles. The OAM is nowhere near that size but many of them were used in the book, taking advantage of the Space Elevators to get them into orbit cheaply. The OAM shown in the drawing is actually sized for the cargo bay of a Space Shuttle, a technology we know we are capable of even if it is not currently employed. It is a load that could easily be handled by Falcon Heavy to be launched this year.

Space Elevator illustration provided by Bruce Irving (FlyingSinger) under the creative commons license.
The OAM consists of two disc-shaped membranes approximately 8 thousandths of an inch thick. They are 140 feet in diameter and keep their shape via an inner-tube-shaped inflated tube 6 feet in diameter. One of the membranes is transparent and and the other is mirrored on the inside surface. Gas is introduced between these membranes to expand them, deforming them into spherical surfaces capable of focusing the sun’s rays on a small surface. The focal length ranges from several hundred feet to thousands of miles. Small thrusters around the outer surface of the tubular frame adjust the mirrors direction and its orbit. A small unit containing gas cylinders, computers, and solar panels attached by a flexible umbilical provides the essentials for directing and focusing the mirror. Even smaller, semi-autonomous robots roam the cavities of the framing tube and in between the membranes looking for and repairing small punctures.

Unlike the mirror proposed by Mr. Wood, the OAM does a lot more than prevent global warming. Once they have performed their climate-saving act, the mirrors can then be employed in their second job - creating space habitats. In the book the mirrors are focused on a mass of lunar regolith in orbit around the Moon. I propose that the mirrors be used to transform the asteroids captured and herded into orbit around Earth by the smart film I mention in an earlier post. If you will remember, smart film wraps the rock in a membrane that can change its albedo selectively over its surface to herd the meteor or asteroid using reflected or absorbed sunlight. The mirrors can be adjusted to focus on these captured chunks of material, melting them to extract metals or minerals. There is another reason to melt this detritus we’ve collected from the Solar System. Once they are melted, they form a spherical mass of molten material that can then be blown like pieces of glass into habitats. In future posts I will discuss further the fabrication of space habitations using the Orbital Adjustable Mirror.

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