*Originally posted by mtthw*

**He didn't say it had to be a circular orbit.**

Sonhouse: "The question is, can you drive it into some sort of orbit, even if its only a cm above the ground?"

Let's define the concept of orbit: I say that a orbit is off ground all the way round. If it is 1 cm off ground all the way round it is circular, if not it is elliptic. I think we can rule out a parabolic oand hyperbolic orbit here, because it is a closed orbit. If it tuoches the ground anyware round the moon, it is not an orbit. Do we agree on this?

If I say the orbit must be circular I am wrong, it doesn't matter if it is elliptic. But the main question stands: Can the vehicle leave the ground?

I say that when the vehicle has the speed it can leave the ground it cannot gain more speed so it actually

*can* leave the ground becous the wheel lose its contact and friction with the ground. That's why it cannot leave the road. (The road has no bumps.)

Once I read a book about astronautics and from that got some insights about planetary (and lunary) orbits...