[NicknamedBob]

One advantage of space travel is that the cruise control is automatic. Unless you change something, you just drift along on whatever course you're on.

Right now, we're getting ready to do another "sling-shot" maneuver around the Moon. Earth might be preferable, for having a higher mass, but it has way too many satellites for a close flyby.

Swinging around the Moon will not only increase our overall speed, it will also align us on the proper trajectory toward where Mars isn't.

We don't want to aim for where Mars is, because by the time we get there, it will have moved. We have to direct ourselves to that point in space where Mars is going to be when we get there.

Lead distance, you know. Like shooting at ducks -- sixty million miles away.

[TASMANIANRED]

Heisenberg principal of planetary uncertainty?

[MNJohnnie]

Is it true that if you accelerate to a certain speed in space you will maintain that velocity as long as you avoid a gravity well, an object of sufficent mass or don't wish to change directions? Trying to remember a half understood theory explained decades ago about space travel. Can you give a Freshman level explination how it all works?

[Monkey Face]

Yah...I get the "lead" thing...I was raised in the High Desert, and EVERYone had a rifle or handgun, and they were just part of growing up. One couldn't very well hit rabbits if one didn't know how to "lead." My dad had my sister and I out in the west desert with a rifle when I was eight years old. Or maybe seven...