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starship-design: still some hope
Let's not give up on this light-deceleration quite yet.
Sure, light pressure can't do it alone, but there's more than just light.
There's also the solar wind and gravity. Here's a way we could maybe use
The sail doesn't come in straight toward the sun, but rather in a tight
parabolic orbit around it. We'd have to figure out how close we could get,
but the closer the better. The details of the star probably matter quite
a bit as well.
So on the way in we slow down from light pressure (although keep in mind that
we're getting deeper into the star's graivty well, which will speed us up
a little bit) When we're close enough, the solar wind acts as a drag;
charging up the ship might help matters even more. As we get close to the
nearest approach to the star the light pressure is now coming at the wrong
angle to slow us down much, but the solar wind keeps getting denser and
denser. Then we start to move away from the star, still braking in the
solar wind, although nowthe light pressure is speeding us up again.
At some optimal point we dump the sail (with as much velocity as we can
handle, slowing us down even more) and let the star's gravity apply the final
braking as we coast away.
I don't have time to look at numbers, and I'm not even sure where I'd
start. The first question to answer, though, would be: how close to a
star can we get without frying the ship? From that we can compute the plasma
density, and I should be able to give some braking numbers. (I'm supposed to
be a plasma physicst, after all...)