Hypersonic Aerothermochemistry Duplication in Ground Plasma Facilities: A Flight-to-Ground Approach

Abstract

High conservative safety margins, applied to the design of spacecraft thermal protection systems for planetary entry, need to be reduced for higher efficiency of future space missions. Ground testing of such protection systems is of great importance during the design phase. This study covers a methodology for simulating the complex hypersonic entry aerothermochemistry in a plasma wind tunnel for a given spacecraft geometry without any assumption on axisymmetry or bluntness. A demonstration of this proposed methodology is made on the Qubesat for Aerothermodynamic Research and Measurements on AblatioN, QARMAN mission, which is a rectangular reentry CubeSat with a cork-based ablative thermal protection system in the front unit. The reacting boundary-layer profiles of the hypersonic entry probe compare well with the ones developing at the stagnation region of the plasma test model, defined with the proposed flight-to-ground duplication method.

Performance of cork-based thermal protection material P50 exposed to air plasma

“…To do so, an accurate methodology was needed to duplicate the flight conditions of QARMAN in the plasma wind tunnel, also because QAR-MAN nose geometry is rectangular unlike regular spherical entry vehicles. Such "Flight-to-Ground Duplication" methodology was developed and applied to QARMAN geometry and entry trajectory by Sakraker et al [23] for subsonic plasma wind tunnels testing, i.e., VKI Plasmatron facility. The outcomes of the duplication procedure lead to extensive testing, caring for three parameters, namely, enthalpy, pressure, and velocity gradient explained further in this section, and their effects on the ablation phenomena.…”

“…Unfortunately, duplicating these three parameters is not direct for nonaxisymmetric vehicles such as QARMAN and an iterative procedure involving CFD computations and experiments was needed [23]. It was shown in previous publications [23] that each trajectory point has a unique combination of pressure, enthalpy, and velocity gradient.…”

“…Unfortunately, duplicating these three parameters is not direct for nonaxisymmetric vehicles such as QARMAN and an iterative procedure involving CFD computations and experiments was needed [23]. It was shown in previous publications [23] that each trajectory point has a unique combination of pressure, enthalpy, and velocity gradient. This lead to the interest of plasma testing for the Cork P50 material in a range of pressure, heat flux (thus enthalpy), and sample sizes (thus velocity gradient).…”

Assessment of gas-surface interaction modelling for lifting body re-entry flight design

“…Although both diffusion tubes and plasma wind tunnels can be used to determine the recombination coefficient on TPS materials, the chemical regimes they provide can be very different. An extrapolation methodology is proposed by Kolesnikov [7,8] in the LHTS concept and has been adapted in the VKI by Barbante and Chazot [10], extended to ablative materials by Turchi et al [9] and applied in a non-spherical re-entry configuration by Şakraker et al [61]. introduces the geometry of the body in the heat flux equation.…”

Measurement of the aerothermodynamic state in a high enthalpy plasma wind-tunnel flow

“…with the freestream velocity u ∞ , the hemispherical diameter D HS and, assuming a fully dissociated gas, the ratio of specific heats γ=1.13. As the probe geometry in the present study is a flat faced cylinder, an equivalent hemisphere with radius R eff has to be defined [26]. This reproduces the velocity gradient in front of the flat faced cylinder, specified by the radius R. For this purpose, the work of Brown is used which applies potential flow theory to subsonic arc-heated flows [27].…”