🚀 go-pugleaf

In article <1505@boulder.Colorado.EDU>, huntting@boulder.Colorado.EDU (Bradley Enoch Huntting) writes:
> It occured to me the other day that when satalites launched from within the
> U.S., they are put into a transfer orbit which is inclined about 20 deg from
> the plane of the equator.  This means that the net change in velocity nessary
> to place the payload into geosyncronous orbit (sum of the instantainious
> acceleration nessary to attain transfer orbit (~10.1 km/s) plus the
> instantainious acceleration nessary to bump the object from transfer to
> geosyncronous orbit (~1.45 km/s if launched from the equator, or ~4.39km/s
> if launched from 20 deg latitude) is higher by ~3km/s!  That's a 26% increse!
> [..]

Whoa!  I don't know where you got that 4.39 km/sec figure, but it's way
off.  (Actually, I can guess: it sounds like what one might come up with 
by figuring the plane change first, in LEO, rather than at GEO).  There 
is definitely a penalty for launching from higher latitudes, but it's not
nearly that bad.  (Figure, figure).  Uhm, the back of the envelope numbers
I get--taking your 10.1 km/s and 1.45 km/s as correct--is about 1.65 km/s
for the appogee burn from a launch at 20 deg.  That's still a significant
penalty, but not unbearable.  The vector diagram for the two appogee burns
looks something like this (pardon my ascii):

	    ^
	    |\
	    | \
	    |  \
  1.45 km/s |   \ 1.65 km/s
	    |    \
	    |     \
	    ^      \
	    |  20  ^
	    | deg./
  1.55 km/s |    /
	    |   / 1.55 km/s
	    |  /
	    | /
	    o

- Roger Arnold					..ucsd!telesoft!roger