Die Engineering Wonders; Part 2

This image is one of the most spectacular pictures taken at Black Rock. The run occurred on October 6, 1997. The Mach number was approximately 0.95 and shock wave was formed near the front of the vehicle. Now I hear some of the more diligent noting that a Mach number of 0.95 is not actually supersonic and so shouldn’t produce shock waves. Which is a valid point, however, although the vehicle may not be supersonic the air that is being caused to flow around the body is and hence the formation of the shock wave.

Originally, it was thought that the differences in the lighting were due to refraction of light by the shock. It is now believed that a better explanation is that the "wind" induced by the shock has kicked up dust behind the shock. The bright region is just a scattering of the light off that faint dust cloud.

The THRUST team also reported that further evidence of the presence of shock waves during the transonic runs was found by inspection of the desert floor after passage of the vehicle. The dirt was seemingly pulverised with a "raked" appearance for a hundred or so feet to each side. This observation is consistent with the above "lofting-dust" explanation of the illumination.