Ballutes for supersonic deceleration at Mars

Mars landers are mass limited by the available entry, descent, and landing technology. The Mars Science Laboratory rover pushed the boundaries of EDL technology to land 900 kg of rover at an elevation of -4.5 km MOLA (Mars Orbiter Laser Altimeter) on Mars. A ballute, a portmanteau of parachute and balloon, is a ram-air pressurized isotensoid trailing aerodynamic drag device. Unlike a parachute, the ballute can be deployed and is stable at higher Mach numbers because of the closed quasi-rigid structure. The NASA Low Density Supersonic Decelerators project developed a 4.4 meter diameter isotensoid ballute and successfully deployed it at Mach 2.8 at the top of the Earth's stratosphere and used it as a pilot device for a main parachute. The design and performance of that ballute is discussed, as well as possible infusion into a future Mars landing mission. The advantages of a ballute as a parachute deployment device are discussed, as well as the capability of ballutes as primary supersonic aerodynamic decelerators. Potential Mars Sample Return-class mission concepts can realize mass savings by using a ballute, rather than an attached Supersonic Inflatable Aerodynamic Decelerator (SIAD), in combination with a parachute. Future entry vehicles with high ballistic coefficients can utilize ballutes as the sole supersonic aerodynamic decelerator to realize retropropellant savings. A ballute mass model was developed to assess the limit of scaling. A number of technology developments still remain for future users of ballutes for Mars missions.