High Enthalpy Studies of Capsule Heating in an Expansion Tunnel Facility

Abstract

Measurements were made on an Orion heat shield model to demonstrate the capability of the new LENS-XX expansion tunnel facility to make high quality measurements of heat transfer distributions at flow velocities from 3 km/s (h 0 = 5 MJ/kg) to 8.4 km/s (h 0 = 36 MJ/kg). Thirty-nine heat transfer gauges, including both thin-film and thermocouple instruments, as well as four pressure gauges, and high-speed Schlieren were used to assess the aerothermal environment on the capsule heat shield. Only results from laminar boundary layer runs are reported. A major finding of this test series is that the highenthalpy, low-density flows displayed surface heating behavior that is observed to be consistent with some finite-rate recombination process occurring on the surface of the model. It is too early to speculate on the nature of the mechanism, but the response of the gages on the surface seems generally repeatable and consistent for a range of conditions. This result is an important milestone in developing and proving a capability to make measurements in a ground test environment and extrapolate them to flight for conditions with extreme non-equilibrium effects. Additionally, no significant, isolated stagnation point augmentation ("bump") was observed in the tests in this facility. Cases at higher Reynolds number seemed to show the greatest amount of overall increase in heating on the windward side of the model, which may in part be due to small-scale particulate.

Spherical Capsule Heating in High Enthalpy Carbon Dioxide in LENS-XX Expansion Tunnel

“…An exploratory series of experiments was performed in the new LENS-XX facility to assess the viability of a large-scale expansion tunnel facility to provide ground test data in a high-enthalpy reacting carbon dioxide environment without the uncertainties associated with the presumed behavior of the rapidly expanding freestream test gas observed in the reflected shock tunnel environment. To minimize the costs associated with this exploratory effort, tests were performed using an existing 17.8-cm (7-in) diameter spherical capsule model equivalent to a 4.5% scale Apollo or a 3.5% scale Orion/MPCV smooth-body heat shield 5 . Although NASA has never used the spherical capsule heat shield geometry for Mars entry, the goal of this effort was to acquire experimental data with which to make comparisons against CFD simulations.…”

“…A short test series has been conducted in the LENS-XX facility -a new, large-scale expansion tunnel facilityto assess its viability to fill in the ground testing gap for reacting carbon dioxide environments. These tests have been conducted using an existing spherical capsule model 5 with the intent of comparing the measured shock shape and surface data to CFD simulations for reacting CO 2 test cases. Six runs have been conducted with the model at angle of attack between 18 O and 20 O covering a range of effective total enthalpy between 7.6 and 23.5 MJ/kg (freestream velocity from 3.9 to 6.5 km/s).…”