In its simplest form, a wind tunnel is an enclosed structure that lets researchers simulate the same conditions an aircraft would encounter as it flies through the atmosphere. Wind tunnels allow researchers to safely take measurements often impossible to make while an aircraft is in flight.
Computers collect the instrument readings for later analysis.
Also, new design concepts are tested before any flights are made. No aircraft, spacecraft, or launch vehicle is built or committed to flight until its design and components have been thoroughly tested in wind tunnels. The National Aeronautics and Space Administration has 42 wind tunnels, representing the largest number and variety ever operated by a single agency or company. The NASA Glenn Research Center maintains and operates five of these tunnels in accordance with its commitment to researching innovative aircraft propulsion technologies and flight safety. Although it was designed to test supersonic engine components such as inlets and nozzles, some rocket applications have also been investigated.