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A couple of days ago I asked Can a laser be used to clear the launch path of a rocket? turns out this is not a good plan but the answer by Hobbes suggests the idea of clearing debris with a laser is not completely out of the question.

...laser on a satellite, where it can shoot at targets at leisure, and not care how long it takes. That way you can also do selective ablation on larger pieces, and produce retrograde thrust to deorbit them. Power's still a problem though.

If we wanted to put laser(s) in orbit to and use them deorbit junk, at a rate of say 10% quicker then we are currently creating orbital debris, what would it take?

Does the laser currently exist that can create the retrograde thrust in the target? Could it be powered by solar or would it need another power source?

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  • $\begingroup$ It would primarily take wise and calm politicians who won't fear, nor attempt to use the laser on ground targets and active satellites. And I'm really not seeing that happening anytime soon. $\endgroup$
    – SF.
    Commented Jan 4, 2017 at 7:56

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Truth be told, they don't even need to be in orbit to make it work. There are plans to deorbit small objects using Earth based lasers (Fire as they are approaching you). For an object in LEO, it only take a few m/s of delta-v change to really make a difference, which can be imparted by a fairly powerful laser on a small object pretty easily. According to this article:

“Focused onto a piece of junk for an hour or two every day, they calculate that a 5 KW laser could do the trick”

Note that for objects that are trackable from Earth, that would be enough to prevent a collision if planned enough in advance, but not enough to deorbit. It will work for small paint flakes and that size of object, which are difficult to track. There are methods in place to track these smaller debris objects, using on-orbit sensors, but they do have their limits. A more powerful laser (~ 1000 times more powerful) would work to deorbit debris that can be seen, but those are considerably more expensive.

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    $\begingroup$ But you should read more of the article: "The “trick” is to only displace the object by a tiny amount, thereby preventing a collision. This laser’s effect would be far too weak to rapidly affect the decay of the object’s orbit. To actually de-orbit a debris object with a laser requires forces about 1,000 times more powerful. To “ultimately de-orbit it entirely” would take about the same amount of time as if we had not illuminated it - this may well take decades, depending on the object." A small change of the orbit and a real deorbit, thats a very big difference. $\endgroup$
    – Uwe
    Commented Jan 3, 2017 at 15:38
  • $\begingroup$ It depends on the size of the object, but I'll add some more details. $\endgroup$
    – PearsonArtPhoto ♦
    Commented Jan 3, 2017 at 17:07
  • $\begingroup$ A 5 MW laser in orbit? If we assume an efficiency of about 15 % for the laser, we will need 33 MW of electrical power. If a square meter of solar panel generates about 150 W we will need a total area of 222,222 square meters. If we use solar panels of 3 m width and 20 m length, we will need 3704 of them. $\endgroup$
    – Uwe
    Commented Jan 5, 2017 at 8:36
  • $\begingroup$ On orbit the requirement would be considerably less. Also, the laser wouldn't be used full time. $\endgroup$
    – PearsonArtPhoto ♦
    Commented Jan 5, 2017 at 12:55

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