-Z- (Z@Gundam.Com)
Sun, 28 May 2000 13:20:49 -0700


At 09:35 5/28/2000, you wrote:
>>If you think about it, if the colony missed the atmosphere, it's trajectory
>>would end up looking an awful lot like the gravity assist manuvers used on
>>interplanetary voyages. I wonder if it would give enough of a boost to
>>allow the colony to escape earth's gravity and send it into a solar orbit?
>
> I have no idea about the physics of this. Maybe someone else can
help?

In the "slingshot" gravity assist maneuver, you're accelerating all the way
down the gravity well of the body that you're using for the assist, with no
intention of actually making orbit, just adding the planet's gravitational
attraction to your acceleration.

In the colony drop, you're decelerating the colony into a decaying orbit
that will eventually crash into the planet. It's deceleration all the way
and you'll only skip back off into space if you fail to reduce the velocity
enough to de-orbit.

Where the colony ends up is determined by how much velocity it retains
after the failed attempt to de-orbit. The most likely scenario is that it
will go into a highly elliptical orbit that brings it very close to Earth
at perigee and out past the Moon at apogee. In effect, it recapitulates
the near-miss colony drop, with diminishing energy on each orbit, with
greater and greater circularization, until it resolves into a stable mildly
elliptical orbit. That orbit is likely to be centered, not on the Earth,
but around the Moon or either of the stable Lagrange points, L4 or L5.

In short, it's most likely to end up close to where it started from, back
in L4.

-Z-

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