Postflight 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.

Remote observations of reentering spacecraft including the space shuttle orbiter

“…The data were analyzed to reveal quantities of importance to atmospheric reentry aerothermodynamics: apparent temperatures, shock radiation spectra from high temperature gases, ablation species spectra (if present), and their temporal evolution during reentry. The first successful collaboration was for NASA's Stardust in 2006 [48][49][50][51][52][53][54][55][56][57][58][59][60] followed by JAXA's Hayabusa in 2010 [61,62]. These reentry observation campaigns used aerial based imaging systems.…”

“…The instrument was designed to capture emission from N2+ and CN at high resolution. When correlated to the reconstructed trajectory, these altitude-resolved measurements indicate the relative variations of shock radiation and ablation processes during reentry [48][49][50][51][52][53][54][55][56][57][58][59][60].…”

Superorbital re-entry shock layers: flight and laboratory comparisons

“…The spectrograph setup and calibration procedure is detailed by Jenniskens [2], and 100 frames were recorded between 9:57:15 UTC and 9:57:26 UTC over a wavelength range of 336 nm to 880 nm. The first frames captured the spacecraft at approximately 82 km altitude and its extremely high entry velocity of 12.8 km · s −1 , which is on the edge of the non-continuum regime [25]. Stardust was at approximately 69 km altitude and travelling at 12.2 km · s −1 when the last spectra were recorded; in comparison, peak heating occurred at 9:57:33 UTC once the vehicle had slowed to about 10.8 km · s −1 , at an altitude of 62 km [25].…”

“…This extends from the assumption that Hayabusa and Stardust follow ballistic trajectories at high altitudes, hence the simulated flowfield can be oriented with zero angle of attack [35] [1]. The grid has been sized to include the forebody shock layer only, extending slightly around the shoulder for Stardust as the shoulder radius is commonly defined [25]. It is assumed that the majority of the radiation captured in flight observations emanates from the forebody and the expansion tube measurements followed this assumption, imaging only the forebody region.…”

“…Low test flow densities require reasonable pressures in the shock tube but low pressures in the acceleration tube and test section, as well as an extremely high flight equivalent speed for an air flow, push the edge of the X2 operating envelope. The 9:57:26 UTC trajectory point was therefore selected due to having the highest density of the observed spectral data, and the flight parameters are quoted in Table 3.5 [25].…”