stevel@haddock.UUCP (03/07/85)
/* Written 2:03 pm Mar 6, 1985 by al@ames in haddock:net.space */ /* ---------- "Re: Solar sail energy transfer mecha" ---------- */ > > Now (wave hands) consider a two or three dimensional system, and you see that > if the photon is absorbed, the sail can only change velocity in the direction > that the photon was moving. If the photon is reflected, you can "tack" by > tilting the sail and forcing the photon to bounce off at a non-pi angle, thus > generating a velocity change in the sail at an angle. > Actually, it turns out that the accelleration of the sail is ALWAYS normal to the plane of the sail. If I could draw on this thing (UNIX) the explination would be obvious, but I'll try anyway. This explanation is intuitive for me but may miss some basic physics (I never took it). The result is correct however. Assume an elastic collision. When the photon hits the sail it imparts momentum in the direction the photon is going. When the photon leaves the sail, it imparts momentum by 'action-reaction' opposite to the direction it leaves the sail in. If you sum the two vectors you get a vector normal to the plane of the sail. /* End of text from haddock:net.space */