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De-orbiting from 200km+?


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Gravity wells are symmetric

True for Kerbin at least, not so much for any real body.

TuYW2.jpg

Except in reality where all spacecraft at low Earth orbit encounter a continuous small drag force from the thin atmosphere that doesn\'t have any clear border, just asymptotically approaches perfect vacuum.

All spacecraft in reality experience constant reduction in their peri- and apoapsis altitude.

And from solar pressure, and from non spherical gravity sources (see above), and the moon.

Their planes are also bumped around by earths lumpy gravity. This can be taken advantage of for special orbits such as a sun synchronous orbit.

There are no (unpowered) spiral orbits. If you\'re slower than escape, you\'re elliptical.

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

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

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

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

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The first two are not spiral orbits, and the last two are powered. Come on, I obviously meant that in order to have a spiral orbit, a force other than the gravity of the body you\'re orbiting needs to be acting on the ship.

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Then you said it wrong

Come on, I obviously meant that in order to have a spiral orbit, a force other than the gravity of the body you\'re orbiting needs to be acting on the ship.

Then you should have made your statements more clear.

Clever use Lagrangian points allow you to escape a gravity well (or damn close to it) without reaching escape velocity.

Horseshoe orbits have dramatic altitude changes with no other forces than gravity at work.

Aerobraking is not powered.

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