3 ms·

I choose a "meticulously deconstructed" variant. I call it the "onion method". First, invent a self-replicating robot. It does not need to be miniaturized.

I choose a "meticulously deconstructed" variant. I call it the "onion method". First, invent a self-replicating robot. It does not need to be miniaturized. It would actually probably work better if they were all stadium-sized. Allow replication, using solar energy and near-surface resources, until the entire planet is covered by a uniform layer one robot deep. The robots then securely connect to their nearest neighbors. You now have a uniform robot tensegrity shell around the planet. The linkages expand until the shell rises to a uniform altitude above the surface. This likely requires a material with tensile strength higher than any currently known, and a material with compression strength higher than any currently known. I haven't done the math. Reasonable strengths may require that the shell robots run on the surface a bit to start the whole thing spinning faster than the planet. A circular section of the shell directly facing the sun de-links, falls back to the surface, and begins replicating as before. The remainder of the robot shell opens like a jellyfish mantle, to catch the solar wind and reflect additional solar energy to the dark side of the planet. The shell sails to a different orbit, so as to not re-collide with the planet. Repeat until all shells have sailed away.

ars 10y ago
Solar wind is not strong enough to put something in orbit.
- teraflop 10y ago
  I dunno. Given a self-supporting spherical structure around the planet, you could raise it above the atmosphere and set it up to experience a net torque from solar radiation pressure. Just add "sails" that are black on one side and mirrored on the other. Then sit back as it very very slowly spins itself up to orbital velocity. Of course, there would be plenty of practical difficulties. (For one thing, radiation pressure is a hideously inefficient use of energy; for another, your spherical shells will be unstable and require constant maneuvering to keep them centered.) So if you have an army of self-replicating robots, it's probably easier to just have them build millions of solar-powered mass drivers and fire rocks directly into space.
- logfromblammo 10y ago
  The center of gravity of the shell starts coincident with the center of gravity of Earth. So as long as the shell keeps its integrity, and the center of mass of the Earth is inside the spherical shell, it is effectively unattached to the Earth by gravity. Let's also assume that the first round of robot-building made the Earth a perfectly smooth ellipsoid. So now you have a spherical shell on a spherical planet, standing on trillions of robot wheels. All the robots sync up, and do some math, and at the same millisecond mark, start turning their wheels. So the shell starts spinning faster than Earth. Its increase in angular momentum is subtracted from Earth's angular momentum. The robots now have to link arms pretty tightly to keep their wheels in contact with the surface. They connect to each other with cables of adjustable length. Escape velocity at Earth's surface is about 11.2 km/s. That's not practical due to atmospheric drag. Even a stable orbit at 200 km altitude requires 7.8 km/s. So the shell runs as fast as it can in air. Then all the robots simultaneously jettison their legs and spool out their cables, and the whole thing jumps in altitude. Now they start sacrificing. The robots nearest the spin axis twist as hard as they can on their own cables, slowing their own spin and increasing that of the remaining robots in the shell. Then they let go and drop back to Earth. The next opposing rings of robots do the same. Eventually, you reach a point where a spherical ring section of the shell is spinning fast enough to keep the linkages under a reasonable amount of tension, entirely outside the atmosphere. Now each robot deploys a solar sail, and angles it to accelerate the ring towards the winter end of Earth's axis, until Earth gravity starts pulling it back. Then the sails tack, and start pushing in the opposite direction. It's like pumping your legs on a playground swing. Eventually, the entire ring achieves Earth-escape velocity and flies off. Then you repeat with a new shell. [Edit:] Actually, let's make the shell an ellipsoid with greater eccentricity than the Earth during the spin-up phase. The robots nearest the poles can therefore keep running with wheels on the surface until their arms get torn off. Then the polar discs get sacrificed.

ars 10y ago

Solar wind is not strong enough to put something in orbit.

teraflop 10y ago
I dunno. Given a self-supporting spherical structure around the planet, you could raise it above the atmosphere and set it up to experience a net torque from solar radiation pressure. Just add "sails" that are black on one side and mirrored on the other. Then sit back as it very very slowly spins itself up to orbital velocity. Of course, there would be plenty of practical difficulties. (For one thing, radiation pressure is a hideously inefficient use of energy; for another, your spherical shells will be unstable and require constant maneuvering to keep them centered.) So if you have an army of self-replicating robots, it's probably easier to just have them build millions of solar-powered mass drivers and fire rocks directly into space.
logfromblammo 10y ago
The center of gravity of the shell starts coincident with the center of gravity of Earth. So as long as the shell keeps its integrity, and the center of mass of the Earth is inside the spherical shell, it is effectively unattached to the Earth by gravity. Let's also assume that the first round of robot-building made the Earth a perfectly smooth ellipsoid. So now you have a spherical shell on a spherical planet, standing on trillions of robot wheels. All the robots sync up, and do some math, and at the same millisecond mark, start turning their wheels. So the shell starts spinning faster than Earth. Its increase in angular momentum is subtracted from Earth's angular momentum. The robots now have to link arms pretty tightly to keep their wheels in contact with the surface. They connect to each other with cables of adjustable length. Escape velocity at Earth's surface is about 11.2 km/s. That's not practical due to atmospheric drag. Even a stable orbit at 200 km altitude requires 7.8 km/s. So the shell runs as fast as it can in air. Then all the robots simultaneously jettison their legs and spool out their cables, and the whole thing jumps in altitude. Now they start sacrificing. The robots nearest the spin axis twist as hard as they can on their own cables, slowing their own spin and increasing that of the remaining robots in the shell. Then they let go and drop back to Earth. The next opposing rings of robots do the same. Eventually, you reach a point where a spherical ring section of the shell is spinning fast enough to keep the linkages under a reasonable amount of tension, entirely outside the atmosphere. Now each robot deploys a solar sail, and angles it to accelerate the ring towards the winter end of Earth's axis, until Earth gravity starts pulling it back. Then the sails tack, and start pushing in the opposite direction. It's like pumping your legs on a playground swing. Eventually, the entire ring achieves Earth-escape velocity and flies off. Then you repeat with a new shell. [Edit:] Actually, let's make the shell an ellipsoid with greater eccentricity than the Earth during the spin-up phase. The robots nearest the poles can therefore keep running with wheels on the surface until their arms get torn off. Then the polar discs get sacrificed.