Why are they not experimenting with using photon momentum from a laser to push debris into the atmosphere? It seems ideal for small high-velocity garbage. Perhaps that's too close to weaponizing a spacecraft?
If you can track something accurately enough to hit it with a laser (especially for the length of time needed for photon pressure to work) then it's better to leave it alone- you know where it is and it's predictable enough that you can screen against it.
This is one of the (many) things Philip Lubin has looked at. The momentum transfer from photons is far too low. However this can be partially fixed. A laser can vaporize part of the trash and then heat up some of the vaporized material, effectively turning the ablated material into a small rocket. I am not entirely sure how much more effective this is, and if it is enough to be a viable technology.
alignment of forces would be a real pain. I expect the little rockets would just spin the item around. Also, I would expect much of the existing space junk to already be spinning in random directions for this approach to be really difficult. (didn't read the article - perhaps it's explained there?)
You could disperse* the beam over the entire object to even out any added rotational force. *whether by increasing beam diameter or sweeping beam across the object's face.
I think there are issues with weaponization. Developing a space laser with sufficient power and the guidance system to go with it may trouble international treaties against weapons in space. I love the idea of dragging the rubbish down in a net, very low-tech.
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.
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.
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...
The cost of failure is rather high. In 2007, China used a missile to destroy one of their satellites:
"This event was the largest recorded creation of space debris in history with more than 2,000 pieces of trackable size (golf ball size and larger) officially cataloged in the immediate aftermath, and an estimated 150,000 debris particles.[24][25] As of October 2016, a total of 3,438 pieces of debris had been detected, with 571 decayed and 2,867 still in orbit nine years after the incident."
