space@mit-mc (03/02/85)
From: Rick McGeer (on an aaa-60-s) <mcgeer%ucbkim@Berkeley> Sure there is. Use various sails, of differing sizes, at varying angles and distances from your craft. The momentum vector of your craft is the sum of the momentum vectors of the various light sails, which are all radial to the sun (but the sum vector need not be). The restriction is that net momentum is always *away* from the sun: you can't accelerate in a sunward direction using a light sail. Actually, now that I think of it, there's no reason that the momentum vector of a sail need be radial to the sun: if the sail were forced to deform, so that pole of the sail was not in its centre, then the resultant vector *wouldn't* be radial to the sun. Further thought on tacking into the sun: yes, it can be done, if you use gravitational interactions. That is, tack in an outbound direction against your current elliptical solar orbit: you'll kill your radial velocity and fall inward. Rick.
space@mit-mc (03/02/85)
From: bsuper%ucbtopaz.CC@Berkeley
After reading Rick McGeers' description of momentum transfer between
photons and a light sail, it seems to me that all momentum imparted to the
sail must be radial to the sun. Is there any way to impart momentum to the
sail in a tangential direction?al@ames.UUCP (Al Globus) (03/04/85)
> > > After reading Rick McGeers' description of momentum transfer between > photons and a light sail, it seems to me that all momentum imparted to the > sail must be radial to the sun. Is there any way to impart momentum to the > sail in a tangential direction? Yes. The acceleration is normal to the plane of the sail. Draw the vectors in 2D in a piece of paper with the photon comming in at an angle. Take the vector sums and maintain conservation of momentum in all directions and you'll see what I mean. I wish I could put my Mac drawings on this thing.