Re: Orbits Defined

>> >A spacecraft capable of moving under it's own power can 
>> >actually maintain geosynchronous orbit at any altitude, simply by
using
>> >it's drive system to maintain the correct velocity.
>> If you are using your drive system to maintain position, you are not
'in
>> orbit'. By definition to be in orbit you aren't using your drive
systems,
>By what definition? By the definition I know, if you are in a 'flight
path' which circles a 
>planet you are in orbit. Whether you are powered or not is irrelevant.
Does this mean a 
>space shuttle isn't 'in orbit' while it's firing it's manoeuvring
thrusters? Or the satellite 
>launching from it's bay isn't 'in orbit' until it's rocket stops
firing?

'By definition' was a poor choice of words on my part, I must admit. 'By
definition', any body which goes around another body (nevermind if it's
a
circular, elliptoidal, or spiral path) is considered 'in orbit'.

As for using drives to maintain orbit, I was thinking more along the
lines of
one's main drive system, not maneuvering thrusters. The shuttle doesn't
and
can't really use its main drives to 'maintain' an orbit; the manuevering
thrusters are primarily for that: maneuvering, to a higher or lower
orbit. It
really isn't using them to maintain it's current orbital level (whatever
that
may be). Their velocity and altitude will keep them sitting there 'in
orbit'
fine without need of fine controls of the maneuvering thrusters.

As for the satellite, I wouldn't consider it 'in orbit' until it's had
it's
orbit established. It's rocket firing to move it up to that orbital
level to
me isn't 'in orbit'. But then you can go back to the definition above
and blur
it some...actually, the more I think about that definition - gotten from
the
vaunted dictionary - the worse you can 'slur' what is and is not 'in
orbit'.
My brain hurts. Unless we come up with a more rigorous definition of
what is
'in orbit', I don't think debating it is going to be worthwhile.

Mk
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Only the bravest try where eagles and angels dare to fly
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