Could one lase accelerated probe, slow another probe behind it down?

2 points·Pica_soO··3 comments

I remember reading on HN a article on small probes, that could be accelerated to near 0.25 c with lasers. My Question is- could one such probe, aim a laser on a probe behind it, and slow it down?

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Laser light has very little mass but it does have some. The problem is the immense amounts of energy created to generate the laser beam.

The idea behind using a laser to push a probe is interesting because the power generation required can be kept on Earth.

On it's face, yes, a probe using a laser could fire it in the opposite direction in order to slow down... But the amount of power required would easily dwarf anything you could generate on a probe.

Could it redirect the beam it recived from earth, back unto a probe behind itself in mid flight?

Yes, with a giant mirror. And that's the best way to do it. But note that all lasers spread out in a cone -- they aren't a perfect column. The angle of this cone can only be made smaller by making very large optical equipment (I'd guess in the form of a large parabolic mirror collimating an earlier stage as best it can) which means far away probes only get a fraction of the energy Earth is sending. This also means the reflection only has a small portion of the initial light, and then the reflected beam spreads out with its own cone as well. So the deceleration stage is vastly longer than the acceleration stage.

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