Remote Recession Sensing of Ablative Heat Shield Materials

Characterization of Candidate Materials for Remote Recession Measurements of Ablative Heat Shield Materials

“…obtained during mArc testing. 5 In preliminary experiments in a subscale developmental arcjet facility (mArc) at NASA Ames, the feasibility of this method was demonstrated by testing samples made of phenolic impregnated carbon ablator (PICA) which were…”

“…A feasibility study in a NASA Ames arcjet facility was successfully conducted and showed promising results. 5 Applications besides ground testing are recession and possibly char depth measurements during actual re-entry. Detection through emission spectroscopy could be accomplished through ground based or airborne observation as performed during the Stardust 4 and Hayabusa 6 re-entries, through on-board spectrometers, or even through formation flight.…”

“…For detection, no spatial resolution of the optical system is needed as confirmed during the feasibility demonstration experiments at NASA Ames. 5 Spatial resolution through the thickness of the heat shield material, however, is achieved through a local deposition of the seed material in the TPS. The emission of the seed elements is then observed through external observation of the post shock plasma.…”

“…seeded with rods made of a polymer matrix which contained NaCl and MgCl2. 5 The heat flux to the sample was measured to about 1,000 W/cm 2 . The emission lines of magnesium and sodium were shown to be clearly visible on top of the thermal emission of the glowing sample.…”

Airborne Observation of Re-entries - Lessons Learned and Future Perspectives (Invited)

“…The concept has been experimentally proven in arc-jet experiments at NASA Ames where PICA was seeded at a known depth with small amounts of magnesium chloride. 57 The emission of magnesium and sodium was seen to register in the emission spectrum as the recession reached the seeding depth and then disappear after a given test time. The time during which these emission lines were visible correlated with the estimate of the total recession rate.…”