Photon thruster

Bae claims to have solved these problems by integrating an optical cavity into a laser that traps the beamed photons, thereby amplifying their light pressure by 3000-times, while easing targeting with a centrally located laser in space.

An article in EE-Times describes how a new photon thruster has been demonstrated by placing a cavity around an active gain medium. This has some interesting implications, one of which is the increase in light-pressure. Other implications are not so promising, however.

I love the combination of science and public interest in this report. Hearing about the demonstration of a photon thruster that could send people to Mars in a week conjures images of at least some cool laser-driven projectile motion, or maybe even a nice big outdoor demonstration with a huge fire-risk. But no, instead the demonstration is almost as simple as it could possibly be:

photon thrusteroriginal image

A laser going through a mirror, a gain medium, and bouncing off another mirror… which is on a lab scale. I’ll have to say I was surprised when I saw the apparatus, but it makes sense. This is really where you have to start in order to send people to mars. I bet the first rocket engine wasn’t much more than a firecracker on a balance.Simple as it may be, I would say calling this a “proof of principle” experiment is a bit of a stretch. The principle of using this as a thruster also says that these two mirrors (both free floating in space) have to maintain cavity alignment. Coming up with a way to ensure alignment is really going to prove the principle. Talk to the folks at LIGO about keeping big mirrors aligned over long distances. It’s a pain on earth let alone in space over interplanetary distances.

Not to be too critical, the side of this experiment that I most enjoy is that it clearly demonstrates optical forces on a macroscopic scale (no pun intended). An air-rail version would be a very cool science-museum exhibit.

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