Gravitational slingshots: could they be used to decelerate a spacecraft traveling at a small fraction of light speed?
I have heard of gravitational slingshots being used to theoretically accelerate a spacecraft using a planet's gravity and momentum in orbit. But how about decelerating a ship? If it is at all possible, could it be done without g-forces killing the entire crew and destroying the ship if said spacecraft were traveling at a fraction of the speed of light, say .1c?
plot synopsis: a ship traveling at sub-light speed is too low on fuel to decelerate in time to keep from blowing through and past its target solar system. Radical measures are considered.
Any help would be appreciated, thanks!
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1 answer
Yes, in theory.
Gravity assist braking is a thing
The problem is the speed. Going that fast you'd need to do a lot of maneuvers in order to lose enough velocity to enter orbit around the sun, and that means that the planets would need to be in just the right places.
In the book Aurora, a ship traveling around .1c has to do something like this, and it ends up making something like 14 passes over the course of 20 years, gradually slowing until it got to a point where there would be no planet in its path for the next maneuver.
So not impossible.
Edit: getting crazy
OK, say that your crew is really really desperate. There is a very risky way to shed a lot of velocity really fast, but only if you're going really fast to start with...
The trick is to fly through the star.
If the structural integrity is really really good, and all the passengers are protected from the sudden deceleration, and you're going fast enough, you could pass through the sun so fast that the ship wouldn't have time to singe much, while hopefully losing enough speed to stay in the solar system and not just shoot it the other side. This would cut years off of the braking process. And hopefully a few passengers would not be crushed to jelly by the tidal forces.
Edit 2:
The sun isn't very dense near the surface. By aiming off center you'd be able to avoid the worst of the pressure. The heat wouldn't be an issue if you have some ablative material shielding the hull, since the heat would be removed before it can do damage, providing you get through fast enough that it cant all burn away.
Sun grazer comets have been observed passing through the outer layers of the sun and surviving.
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