Post-Flight Aerothermal Analysis of the Stardust Sample Return Capsule

Abstract

The Stardust Sample Return Capsule (SRC) was launched in February 1999 on a mission to retrieve samples of interstellar dust from the tail of comet WILD-2. Stardust returned to Earth in January 2006 entering the atmosphere with a velocity of 12.6 km/s, the fastest Earth reentry and highest energy reentry of any artificial vehicle to date. Several optical instruments captured the reentry of Stardust through an observation campaign aboard the NASA DC-8 airborne observatory. Flow environments obtained from Computational Fluid Dynamics (CFD) solutions are loosely coupled with material response modeling to predict the surface temperature of Stardust throughout the reentry. The calculated surface temperatures are compared with the data from two spectral instruments onboard the airborne observatory, the Echelle camera and SLIT telescope. The gray body curves corresponding to the average and area-averaged surface temperatures predicted by the material response simulation have excellent agreement with the recorded Echelle data at lower altitudes. At these altitudes the CFD/material response coupling can predict the surface temperature to within 50 K. The CFD calculations alone overestimates surface temperatures because it does not take into account ablation, as the material response modeling does. At higher altitudes, the presence of paint on the heatshield could have contribution to the lower observed surface temperatures and explain the over-prediction by the simulated data, which does not account for the paint. The over-prediction of the simulated surface temperature coincides in time with the high emission intensity lines corresponding to paint products. The average surface temperatures resulting from the SLIT telescope analysis agree to within 5% with the average surface temperatures predicted by the material response. Surface temperature is one of the critical parameters used in the design of thermal protection systems since it is an indicator of material performance. The combined CFD/material response approach employed in the present analysis can thus be reliably used for future missions such as CEV Orion.

Significance of Nonequilibrium Surface Interactions in Stardust Return Capsule Ablation Modeling

“…Because the temperatures were optically measured during the SRC reentry and averaged over the entire heat shield, they cannot be compared with the computed stagnation point surface temperature [13,28]. Initial equilibrium calculations by Olynick et al [9] and Chen and Milos [10] predicted a recession near 1 cm at the stagnation point.…”

Resolved CN Band Profile of Stardust Capsule Radiation at Peak Heating

“…The data provide highspectral-resolution measurements at the time of peak heating in three wavelength intervals: from about 382 to 409 nm, from 535 to 577 nm, and in a small interval around 615 nm. The derived rotational and vibrational temperatures of the CN molecules are of order Tv Tr 8000 1000 K. Oxygen line emission is detected at 615 nm, and perhaps also at 394 nm, the intensity of which may be used to evaluate the level of radiative heating [11]. A broad emission feature centered on 563 nm (if second order) remains unidentified.…”

Multiscale Approach to Ablation Modeling of Phenolic Impregnated Carbon Ablators

“…In the phase of the reentry trajectory for which ablation is nonnegligible, the flow dynamics are in the continuum regime at the scale of the reentry body [8]. However, inside the porous medium, the length scale of interest is small and the dynamics may be in the rarefied gas regime.…”

“…These estimations are provided by current simulation tools. The aerothermal environment for the entry of Stardust was modeled [8] using the computational fluid dynamics (CFD) code Data Parallel Line Relaxation (DPLR) [9], assuming a ballistic entry and using the estimated flight trajectory (EFT) [10,11]. From the knowledge of the aerothermal environment, the material response for the Stardust EFT has been modeled [4] using the Fully Implicit Ablation and Thermal Analysis (FIAT) code [12].…”