On 5/8/2010 8:56 AM, Frogwatch wrote:
OK, here is my attempt to revive things.
I recently did a simple calculation concerning lightsails and how fast
they could go. I used a graphene film coated with 100 nm of Au as my
sail. I was surprised that no matter how big you make the lightsail,
it cannot exceed solar escape speed using only solar photons. Of
course, the closer you start to the sun the faster you can go but
still cannot exceed suns escape velocity.
I do not have that calc in front of me now but does this seem right to
others? My conclusion is that your lightsail has to be initially
accelerated to escape speed before deploying

Was this using a straight-out trajectory from the Sun, or an orbit that
was getting larger and larger in radius as the lightsail was picking up
speed?
One would think that by setting the lightsail at a 45 degree angle to
the incoming sunlight, its orbit would eventually get large enough to
leave the solar system, no matter how low the acceleration from the
incoming photons was at a great distance from the Sun.

Pat