The environment of weightlessness is the single significant difference a designer must consider for human beings and machines in space vehicles. This characteristic fascinates the journalist, intrigues the space enthusiast, and provides a new challenge to the man-machine designer. Weightlessness literally lifts the burden of gravity from mankind's shoulders. This, in itself, may be as near as man will come to soaring into unpowered free flight. Even with these newly found capabilities, effective designs for man to live and work in (and with) require diligent attention to the subleties of the changes that are peculiar to the weightless environment.