Orbits:

The basic equation for orbits is:

	v**2=gr, where v is velocity, g is the gravity of the planet
		being orbited, and r is the orbital distance from
		the center of mass

This really is only going to work for small objects orbiting big ones
and neglects atmosphere and suchlike, but it should work for our
purposes.  So, for example, a scooter which can achieve a velocity of
10,000 km/hour (or say,  2,700 m/s) could orbit a planet with 1 G gravity,
such as Earth, at a maximum altitude of:
	2,700m/s*2,700m/s
        ----------------- =  r = 743,878 meters, roughly, or 743 km.
	    9.8 m/(s**2)


That's from the center of mass,though, and the planet itself has
a radius of 6,500 km.  So the scooter (see Space Opera
book 1) cannot achieve orbit under normal circumstances.  It can
however achieve orbit by first moving to outside of any atmosphere
and then accelerating continuously until orbit is achieved.