Experimental investigation of the flow over a toroidal aerocapture ballute

NASA proposals for future planetary spacecraft involve the use of aerocapture to save propellant mass needed to enter planetary orbit. One concept that is being studied uses inflatable structures (ballutes) towed behind the spacecraft to provide the necessary drag while minimizing vehicle heating and flow unsteadiness. Experiments of the tandem body configuration of a toroidal ballute towed behind a spacecraft were performed in the T5 Hypervelocity Shock Tunnel. The test gases studied were carbon dioxide, nitrogen and hydrogen to simulate actual future missions to Mars, Titan and Neptune, respectively. Stagnation point heat transfer measurements were made and were found to compare well with theoretical estimates. In addition, flow visualization shadowgraphs were used to confirm that the flow was steady. The carbon dioxide and nitrogen tests successfully matched both the Reynolds number and enthalpy similarity criteria for the specific NASA missions. The hydrogen shots, however, failed to match the enthalpy criteria for the intended mission and care must be taken when using those results.