[VadeRetro]

I think that's the final hurdle. Building to escape doesn't happen with tiny pressures. Also--a key point I had missed and you realized--if you really want to stabilize an orbit at a higher level, you have to add transverse (orbital) velocity, not directly outward pressure.

Because the radiation pressure is at right angles to the orbital velocity, you can basically ignore the orbital velocity. Radiation pressure becomes the act of holding a plate aloft by shooting BBs at it. The inverse square law for light means that the higher the plate goes, the fewer BBs even strike it.

The plate goes up until it hits an equilibrium point. The pressure has slackened--some of the BBs miss--to where it can't rise further. If the rate of BBs increases for a bit (a brightening phase), then the plate is pushed higher, but only to a new equilibrium point. If it slackens (dimming), the plate drops lower until the number of BB impacts required to keep it aloft is met.

A tiny pressure, no matter how unrelenting over the years, won't do any more than keep the plate at an equilibrium somewhere.

[RadioAstronomer]

Sigh. I am sorry to be taking so long. :-(

LOOK FOR A POST IN THE MORNING.

My sincere apologies.

[VadeRetro]

I think I finally realized what you are saying.

Going back to my own example, the plate would not be lifted from the ground by this particular ultra-feeble BB pressure. Rather, it would just "weigh" (press down on whatever is under it) microscopically less with the BB stream hitting it than without. In orbit, this means the equilibrium when it happens is slightly higher because of this pressure. But that's it. There is no constant new acceleration.

Am I getting close?