Keeping weight down is important, because of the high energy and cost needed to send even small amounts of mass into space. If manned, a spacecraft must have enough shielding to protect its occupants from such hazards as micrometeoroids and solar radiation.
Forces of Flight on this Page
Shaped for Space
How Does Space Affect Structure?
If a spacecraft flies only in space and not through an atmosphere, it does not have to deal with drag. Its shape and configuration can be sprawling and irregular. Instruments can be placed at the end of long booms; broad solar panels can be deployed to gather energy from the Sun.
Did You Know?
The International Space Station was not the first space station in low Earth orbit. In 1971 the Soviet Union (USSR) launched the first of several single-module, disposable space stations called Salyut. The first space station launched by the United States was Skylab, which orbited Earth from 1973 to 1979. And in 1986, the Soviet Union began construction on the multi-module space station Mir, which orbited Earth until 2001.
There is no drag in space.
True: If there is no fluid medium, then there is no drag. Drag is generated by the difference in velocity between an object and the fluid it’s moving through. Although space is filled with gas (like hydrogen and helium) and dust, the concentrations are so low that it does not behave like a fluid. Therefore there is no noticeable aerodynamic drag.