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Comment by jbert | Hacker News Reader

Is there any way to use drag to decay the orbit? We don't have to reach the sun quickly.

The solar wind is blowing past, is it possible to "sail" against that at an angle and - over time - dump orbital velocity and so end up in the sun?

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That's not how sailing works. The only reason you can sail upwind in a sailboat on the water is because you have a keel pushing against the water to prevent you from blowing downwind. Essentially, a sailboat sits on the interface between two fluids (air and water) that are moving relative to each other, and abuses that fact to go wherever it wants to. If you couldn't push against the water, or in the extremely unlikely case that the water and wind had identical velocities, you wouldn't be able to sail upwind. (Actually, if the water and wind had identical velocities, you wouldn't be able to sail at all. It would feel like no wind.)

To tie this back to solar sailing, there's obviously no fluid interface in space, so to the extent that solar sailing is possible, solar sailing "upwind" toward the sun is not.

There is a heliospheric current sheet[†], but it's not clear to me if/how it could be practically employed to achieve a sailing effect.

[†] http://en.wikipedia.org/wiki/Heliospheric_current_sheet

Don't use drag use gravity...

http://en.wikipedia.org/wiki/Gravity_assist

Basically you loop in front of a planet, and then it slingshots you back to the Sun.

Voila... done.

From my understanding, solar wind can only push the payload further away from the sun and there is no noticeable drag in space or the earth wouldn't orbit for very long.

You are probably thinking that you can sail upwind on a sail boat but it isn't the same in space. The boat's keel [1] and general shape keep it going straight which is necessary to sail upwind. That doesn't work in space.

Another factor is that a sail works much like an airplane's wing and isn't really 'pushed' by the wind. This allows the force to be perpendicular to the sail in some cases. To my knowledge (take this part with a grain of salt), solar sails works by receiving momentum as the photons hit. This could only push it away from the sun.

http://www.real-world-physics-problems.com/images/physics_sa...

The force will be perpendicular to the surface light reflects from, not perpendicular to the light arriving at the surface. Therefore if the sail was mounted at a 45 degree angle to the Sun, there would be a force that reduces angular momentum and puts the object in a spiral towards the Sun.

http://wiki.solarsails.info/index.php/Tacking_Solar_Sails You can tack a solar sail so that it gets closer to the sun, but solar sails need to be very light to work at all... and nuclear waste is heavy.

Yes, using a magnetic sail - which is this case is more of a magnetic parachute:

http://en.wikipedia.org/wiki/Magnetic_sail

The easiest way to use it might be to apply it in the direction perpendicular to the dumptruck - Sun axis. That way, you don't pick up radial speed, but you do lose orbital speed.

Assuming, that is, that i've understood how a magnetic sail works.

Solar wind won't help you but there are other ways of moving slowly - e.g. an ion drive.

For sub-millimeter particles, there is the Poynting-Robertson effect:

http://en.wikipedia.org/wiki/Poynting–Robertson_effect

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