Crewed space flight, especially aboard spacecraft in low Earth orbit, is now commonplace. The space shuttle, able to carry the Spacelab module in its payload bay, provides an orbiting scientific laboratory in which scientists and astronauts can perform experiments in a low-acceleration (or nearly weightless) environment. Doing science in space is important for two reasons.

First, as more people work and live in a weightless environment, practical knowledge of how systems, materials, and even the human body perform in and respond to extended exposure to low gravity is critical to continued space exploration. Thus, many applied-science experiments are performed aboard the shuttle to gain insight into the effects of long-term weightlessness.

Second, the Earth's gravity is a dominant and pervasive force in ground-based laboratories and, in the case of experiments in fluids, can mask more subtle forces. In the relative absence of thermal and buoyant convection and their effects in orbit, surface tension becomes the dominant fluid force, and ideal experiments can be performed to provide absolute and rigorous tests of fluid-dynamic theories, which would be impossible on the ground. In one such experiment, liquid drops nearly 2.5 cm (1 in.) in diameter were allowed to float aboard the space shuttle, where they were deformed by an acoustic standing wave and then released to execute free oscillations about a perfect spherical equilibrium.