Complicated shock wave patterns envelope vehicles traveling at supersonic and hypersonic speeds. A shock wave is essentially a very tiny region–only a few mean free path lengths wide–over which flow conditions, including density, pressure, velocity, and temperature, change drastically. The image above shows a model of the Space Shuttle at a re-entry-like, high angle of attack at around Mach 20 in one of NASA Langley’s historic helium tunnels. The eerie glow outlining the shock structures around the model is a result of electron-beam fluorescence. In this flow visualization technique, a beam of high-energy electrons is swept over the model, causing the gas molecules to fluoresce according to temperature. (Photo credit: NASA Langley)
Tag: electron beam fluorescence
Fluorescing Shock Waves
Wind tunnel testing plays a major role in the planning of many space missions. Here a model of the Mars Sample Return Orbiter is tested at Mach 10 to determine the heat shield’s response to aerobraking off Mars’ atmosphere. The colors are the result of electron beam fluorescence, in which an electron gun is used to ionize molecules in the flow, which causes them to emit photons (light). The technique can be used for flow visualization–as in the case of the shock waves shown here–or to measure flow characteristics like density, temperature, and velocity. (Photo credit: Thierry Pot/DAFE/ONERA)
