Androcles wrote:
"Randy Poe" wrote in message
ups.com...

This is all from considerations of minimum energy. I
was thinking of minimum time, where I'm pretty sure
that you'd want to go TOWARD the body you're trying
to reach.

Actually it is a little more complex than that. You need to
match velocities as well, or you'll have a disaster from
which there is no recovery.

The recovery is to adjust your velocity before
landing. I think a slingshot maneuver can help you
save fuel in either gaining or shedding KE.

You can blast away from
the Earth radially from the Sun, but you'll still retain
Earth's tangential velocity of 30,000 km/sec.
If you give that up and head backwards to meet Mars
coming from behind, not only will you be wasting a
huge amount of KE but you'll impact as well. So now you
have to burn more fuel to gain the same tangential
velocity of Mars.

But a well-designed slingshot might help you do
most of that adjustment without burning fuel.

Yes, the best way to think of the problem is an absolute
frame of reference centred on the sun. What do you think
should be the velocity of light in such a frame?
What should it be relative to the vehicle?

All observers will measure the speed of light
to be 299792458 m/sec exactly.

- Randy