Speaker
Description
The critical design review status of the Dragonfly aerothermal environments and simulations will be presented. Titan’s atmosphere predominantly consists of nitrogen (~98% by mole) with small amounts of methane (~2% by mole) and other trace gases. CN is a strong radiator and is found in nonequilibrium concentrations for Titan entry, and is of particular importance on the backshell, where radiation dominates the heat flux.
The presentation will discuss the simulation methodology and assumptions, as well as the margin process in determining the aerothermal environments for Dragonfly’s entry at Titan. In particular, the presentation will focus on refining the aerothermal environments to mitigate thermostructural risks for the PICA-D heatshield. The PICA-D risks are related to possible in-plane stress/strain failure modes and has been the focus of several experimental campaigns. Typically, the initial approach for margining aerothermal environments for heatshield design is conservative. As the mission design matures, refinements to this process are investigated, when and if, the aerothermal loads preclude the design from closing. This submission will detail the various physics and parameters investigated to lower the total margined heat flux. These physics include surface catalysis, summation of aerothermal uncertainties, flowfield/radiation coupling, non-equilibrium radiative heat flux model improvements, choice of design trajectory and radiative heating margin reduction utilizing shock tube informed bias. Shock tube informed bias being a relatively new and innovative methodology based on comparison to shock tube experiments performed in EAST at NASA Ames. These EAST experiments were also critical for reductions in the nominal radiative heat flux predictions.
Summary
The critical design review status of the Dragonfly aerothermal environments and simulations will be presented. The presentation will discuss the simulation methodology and assumptions, as well as the margin process in determining the aerothermal environments for Dragonfly’s entry at Titan. In particular, the presentation will focus on refining the aerothermal environments to mitigate thermostructural risks for the PICA-D heatshield.
