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Comment by codefined | Hacker News Reader

Not looked into the technology, but wouldn't it need to put a ridiculously strong laser to have any effect on garbage at all? Solar sails have to have a really large surface area and a really low mass in order to get even a tiny amount of acceleration from photons, I don't see how we would be able to focus enough momentum onto tiny pieces of garbage in order to cause their orbit to decay.

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Depends on the size of the garbage? Even paint chips with sufficient relative velocity are a danger to the ISS. The laser would have as much time as it needs to de-orbit something and a limitless power source.

Suppose your laser-zapper spacecraft is solar powered. The force of the sun on its solar panels is approximately the same as the force imparted by its laser beam on the target garbage.

This is to say nothing of the propellant required to transfer the laser-zapper spacecraft into the same orbit as its target garbage.

The biggest benefit of a laser solution is that it doesn't need to be in the same orbit. It needs to regularly intersect the target's orbit (or at least close enough to get in the laser's effective range) but that's a much cheaper maneuver.

What would the effective ranger of a laser in nearly gas-free environment like space be? How precise of laser collimators are we able to build?

In general, at the power levels in question the limiting factor is diffraction, not beam quality. There are a lot of variables going into it, but the numbers I've seen bandied about for orbital systems are on the order of 100km. See e.g. here: https://www.sciencedirect.com/science/article/pii/S100093611...

(Or, for a more speculative take, here: https://childrenofadeadearth.wordpress.com/2016/07/02/the-ph...)

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