The mass referred to is the mass of the Earth. While the mass of the vehicle can be neglected, orbital velocity is very much a function of the mass of the body that is being orbited. The mean angular motion of an Earth orbitting satellite is sqrt(G*m/a**3) where is the G is universal gravitational constant, a is the semimajor axis, and m is the mass of the Earth. In a circular orbit, the speed is mean motion * radius.