Future Possibilities

This is long term speculative stuff. Mostly it shows that we can bypass most conceivable limits to growth if we move most of our power production, communications, computation, and industrial processes into space and away from the biosphere.

Terascale Arrays and Beam Power

The m288 orbit region can hold perhaps 10 to 100 trillion thinsats. However, in the worst case (total loss of control) the thinsats will reflect some light into the night sky. The full moon provides about 1 lux of night-time illumination at the equator, about 0.5 lux at 45 degrees north latitude. On a clear moonless night, the illumination is 0.001 lux. The difference between full moon and no moon synchronizes some biological processes on earth, such as the spawning of coral. Some plants are also night-light aware, since they close up their leaves at night, and unfurl them at the first glimmerings of dawn, so they will be fully open and properly oriented when the sun rises.

If we arbitrarily assume a maximum worst case night time illumination of 0.03 lux ( 3% of the full moon, 30 times moonless darkness), that limits the total number of 20cm sthinsats in m288 orbit to 80 billion. Note that under normal conditions, fully under control and oriented to minimize night-time light pollution, the night-time illumination from 80 billion thinsats will be far less than that. 80 billion thinsats should be able to handle most of the near-realtime computing needs of the world population for some time.

For non-realtime calculation, big compute jobs like weather prediction or animation rendering, a much larger latency is tolerable. Thinsats in the Earth-Moon Lagrange positions will be 60 times further away from earth, so under similar conditions as before, they will produce 1/3600 of the worst case illumination as a thinsat in m288. There is room for quintilillions of thinsats in these Lagrange positions, with round trip ping times of 2.5 seconds.

This is far more than is needed to provide foreseeable computation and communication needs, so many of the later generations of thinsats may become "compute-light" and "transmit-heavy", beaming the power as microwaves to rectenna arrays on the ground, producing power for the electrical grid. Because the microwave beams are steerable, they can move from peak load center to peak load center as needed, reducing long-lines requirements. They can even be steered in circles around 6 rectenna grids, generating 3 phase AC power. This is an old idea - solar power satellites - but arrays of thinsats are much lower mass, cheaper, and easier to deploy than large rigid systems of solar cells, structure, and antennas.

However, high density microwave beams are not healthy. They can be stopped by a thin layer of metal, but birds are not shielded. Unless birds can be reliably kept away from the rectennas, the rectennas should only be placed where birds aren't. Perhaps the best place for rectennas is over deep ocean, far from land and far from the paths of feeding and migratory birds. A few centimeters of ocean water will stop the power that leaks through the rectenna, so sea life is safe from the leakage.

With good ground-based telescopes and pattern recognition, and huge orbiting arrays with very small ground spots, it should be possible to create nulls in the ground pattern where individual or flocks of birds are observed. With 2.5 seconds of latency in beam steering, the nulls must include not just where the birds are, but where they can get to in the next 3 seconds. It may be possible to constrain the bird's flight path with small robot airplanes, noises, and other stimuli so that the behavior of the birds is a little more predictable and constrained.

With these and many other constraints, it should be possible to supply most of the Earth's energy needs from huge arrays of thinsats in space.


High Orbit Arrays

For the first decade or two, server sky will coexist with traditional geosynchronous satellites, but as the traditional satellites age and become a very small part of the total communication bandwidth around the earth, they will likely be replaced by more thinsats. Very high orbits will be perturbed too much by the moon, but orbits above m720 ( 20295 km radius ) and below 5 day sidereal orbits ( 123300 km radius ) are probably usable. Lets assume the thinsats are deployed "thickly" around the 5 day orbit shell, and that they intercept 4% of the total sunlight reaching this region ( reducing the light to the earth by about 1%, much more around the edges of the thinsat "globe". The total power intercepted is 2.4E18 watts. If 1E15w = 1000Terawatts are beamed to earth, that equals the power that is blocked by the thinsats, and provides 100kW of electrical energy for each of 10 billion inhabitants (US usage in 2009 is around 10kW per capita). The rest of the power stays in orbit for orbital computation, industrial processes, etc.


Lunar and Asteroidal Materials

Most of the mass of a thinsat is aluminum and silicon, which are also most of the mass of rock, including lunar rock. It may be a long time before we can manufacture solar cells off the planet, and much longer before we could manufacture deep submicron integrated circuits. But the materials on the moon are in a lower gravity well, and there are few ecological risks to using large amounts of lunar material to manufacture aluminum, and launching it with electromagnetic launchers. A cubic meter of lunar regolith could be used to manufacture perhaps fifty thousand 5 gram aluminum thinsat "chassis", which could be mated to earth-manufactured integrated circuits in an automated facility in orbit. A cubic kilometer of regolith could manufacture fifty billion thinsats. Lifting those thinsats off the moon and placing them in an m288 orbit would require about 1e18 joules (depending on how they were captured), as much energy as the thinsats would produce in half an hour.


Deep Space Arrays

There is a lot of room in the solar system. Outside the orbit of the earth, most of the light is dumped into interstellar space. thinsats orbiting between Earth (1.5E11 meters from the sun) and Mars (2.3E11 meters) could capture much of the light of the sun. If there were enough of them, it would increase the apparent infrared temperature of the sky, which would in turn increase the temperature of the Earth. If the earth temperature increase was limited to 1C, then the effective sky temperature could increase from 2.7K to 100K. If the thinsats were at 1.9E11 meters distance from the sun, receiving 800 watts per square meter and at an equilibrium temperature of 270K, then they could cover about 2% of the sky. That intercepts about 7E24 watts of light, and might generate about 1E24 watts of usable electric power for computation and industrial purposes.


Low cost launch

The launch loop is an electrically powered earth-to-high orbit launch system. The main construction and operating cost of a launch loop is electricity. At 10 cents per kilowatt hour, and a quick payback of capital, a launch loop can put a kilogram into orbit for about $5, and a small launch loop can launch 80 tons into high orbit per hour.

Assuming extra mass for the satellite bus and the apogee insertion motor, the cost of orbiting a 5 gram, 2 watts-to-ground-collector thinsat will be on the order of 5 cents. If that 2 watts can be collected for another 10 cents of rectenna infrastructure, and the mechanism that does so lasts 20,000 hours, that is 100 kilowatt hours per dollar invested. This drops the cost of further launches, and thinning the thinsats down to 1 gram will save more. In time, the cost can drop still more by building apogee capture systems such as rotating tethers (with some payloads sent around the moon to add momentum back to the tether system).

The result will never be free space launch, or "power too cheap to meter", but it can result in very low cost space launch and electric energy on the earth - 50 cents per kilogram, and a 50 cents per megawatt-hour, may be possible someday.


Scientific sensors


Updated for 20cm thinsats

FuturePossibilitiesV01 (last edited 2014-09-13 07:17:30 by KeithLofstrom)