The cover art depicts a type of space tugboat. The controls include a steering wheel and crane-like levers. Astronauts do not fly spaceships with steering wheels. A steering wheel provides two-dimensional control while a hand controller is a three degree of freedom (three dimensional) device. Space navigation is not limited to a two dimensional plane of reference since the effect of gravity is all but removed. Though this is the case, the inclusion of the lever system offers a third degree-of-freedom for control of the spacetug. Actually, a crane used to construct buildings and scoop dirt from the Earth is a three dimensional machine. It is a able to move its lifting scoop in three directions at right angles from one another.