Asri-unix.736
net.space
utcsrgv!utzoo!decvax!ucbvax!C70:sri-unix!csin!cjh@CCA-UNIX
Tue Feb 9 18:47:41 1982
orbital speed
I suppose a lot of people will wake up on this one, but I might as
well put in my nickel's worth. High orbits \are/ slower in linear
velocity than low orbits. Local example (remember, earth orbits are
measured from the surface, so add ca. 3900 miles to these figures):
A satellite at LEO is ca. 150 miles up and has ca. 90-minute orbit;
orbital velocity ca . 140 miles per minute.
A satellite at GEO is ca. 22,300 miles up and has (by definition) a
24-hour orbit; orbital velocity ca. 57 miles per minute.
The moon is around .25e6 miles up, orbits in 28+ days; orbital velocity
ca. 19 miles per minute.
Need more data? Start with Pluto being at 39 AU (earth-orbit radii) with
a period of 200+ years.
All of these figures are out of my head, but date from a grade-school
infatuation with space and so are tolerably accurate. More precise figures
are welcome.
What happens when you add energy to an orbiting body is not that simple;
the only way the body can maintain a stable orbit is by turning all that
energy (and some of its own kinetic) into potential energy, i.e. take a
higher orbit. What the shuttle is doing when it turns around and blasts in
the direction it was going is throwing away enough KE that it can't keep
a stable orbit above the Earth's surface; if you got rid of the atmosphere
and dug a trench it could drop into a stable orbit below the net surface.
C'mon, guys, even Brunner got this right (and used it to make an effective
point in THE SHOCKWAVE RIDER).
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