Aerodynamics of a highly irregular body at transonic speeds—Analysis of STRATOS flight data

In this paper, we analyze the trajectory and body attitude data of Felix Baumgartner’s supersonic free fall through the atmosphere on October 14, 2012. As one of us (UW) was scientific advisor to the Red Bull Stratos team, the analysis is based on true body data (body mass, wetted pressure suit surface area) and actual atmospheric data from weather balloon measurements. We also present a fully developed theoretical analysis and solution of atmospheric free fall. By matching the flight data against this solution, we are able to derive and track the drag coefficient C(D) from the subsonic to the transonic and supersonic regime, and back again. Although the subsonic drag coefficient is the expected C(D) = 0.60 ± 0.05, surprisingly the transonic compressibility drag coefficient is only 19% of the expected value. We provide a plausible explanation for this unexpected result.