Analysis of Temperature-Constrained Ballute Aerocapture for High-Mass Mars Payloads

Abstract

We investigate trajectories and heating environments of ballute-assisted, low- to high-mass Mars aerocapture systems. Ballutes permit aerocapture at higher altitudes and allow for lower thermal protection system (TPS) mass than traditional aeroshells, due to lower heat fluxes. Trajectory calculations are presented for capture into a 4-day parking orbit about Mars with varying vehicle masses (of 1-100 tons) and with a ballute temperature constraint of 500 degrees C. We note that, for the same ballistic coefficient, a higher mass payload will require a larger ballute and consequently will have a lower ballute temperature (due to a larger nose radius). Compared to a payload of 1 ton (requiring a ballistic coefficient of 0.76 kg/m(2)), a higher ballistic coefficient (of 3.45 kg/m(2)) can be employed for the high mass payload (of 100 tons) while satisfying the temperature constraint, thus allowing for capture of high-mass payloads with smaller ballutes than previously estimated. To substantiate these conclusions, which are based on analytical heating calculations, we conduct a detailed aerothermodynamic analysis at maximum heat flux conditions (for payloads of 1, 10, and 100 tons). We use the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) to analyze the ballute in the continuum flow regime where the Navier-Stokes equations apply.