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Old September 10th 18, 11:46 AM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Elliptical orbit question

In article ,
says...

What I don't understand is that the point where the satellite starts to
go faster than needed for that altitude happens before perigee. How
come it continues to drop even if it is going faster than needed to
remain in that orbital altitude?


Because it is not going faster IN THE RIGHT DIRECTION. So it
continues to drop and gain speed until its velocity IN THE RIGHT
DIRECTION is too high, at which point it starts going back up and
slowing down.


So what is magical about perigee that causes the satellite who is
already going way faster than necessary to finally stop losing
altitude/accelerating and starts to behave normally for a satellite that
is going faster than needed at that altitude? (gain altitude, lose speed)


Resolve the velocity into two components, one tangential to a circular
orbit and one normal to that. When your tangential velocity exceeds
orbital speed you start going back up.


This. You have to use vector math to analyze orbital mechanics, not
scalar math. For a two body problem, the motion is at least planar,
which reduces the complexity to a 2D vector math problem.

Jeff
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