A flashlight is a very low thrust photon drive:...

A flashlight is a very low thrust photon drive: it shoots a beam of light, composed of “photons”. Each photon has momentum, so a flashlight with really long-lasting batteries, left on, would eventually pick up a LOT of speed, in the direction opposite to the beam. Not practical, because there are no batteries long-lasting enough.

But if you have two parallel mirrors with a beam traveling back and forth between them, a single photon can make maybe 1,000 reflections between the two mirrors before dying out. And each time each photon is reflected, it exerts a tiny force on the mirror. So the “thrust” of our flashlight spaceship is theoretically increased by 1,000 times, IF THERE IS ANOTHER MIRROR to reflect off of.

I think this is somehow the basis of Bae’s invention. But it seems to me that, unless the “outboard” mirror is discarded frequently, when it gets too far away to contain the beam any longer, this is not a practical enhancement to the thrust of the photon drive.

I’m probably missing something. It will be interesting to follow the continued claims of Bae.