Andreas Steinbeck

Oxygen plasma flow properties deduced from laser-induced fluorescence and probe measurements

Estimation of the local dissociation degree and the local mass-specific enthalpy of a pure oxygen plasma flow determined mainly from laser-induced fluorescence measurements are reported. Measurements have been conducted for several generator parameters in an inductively heated plasma wind tunnel. Additional probe measurements of total pressure together with the deduced translational temperature are used to estimate the local mass-specific enthalpy. For a reference condition, full dissociation has been measured. The measured translational temperature of atomic oxygen for this condition is T = 3500 K. Subsequently, the local mass-specific enthalpy has been derived using these local density and temperature measurements. For the reference condition the estimated value of h = 27 MJ/kg is in good agreement with the probe measurements and results from diode laser absorption spectroscopy.

Local Mass-Specific Enthalpy Measurements with a New Mass Injection Probe

The results of local measurements of the mass-specific enthalpy in a high-enthalpy oxygen plasma flow are presented. The sensor measures enthalpy based on stagnation point heat flux measurements and its reduction by mass addition into the boundary layer. The efficiency of this boundary-layer cooling depends on the freestream enthalpy. Thus, an analysis of this heat flux reduction is a measure for enthalpy. The enthalpy probe is described and theoretically analyzed, and measured data are compared to locally resolved enthalpy measurements from optical diagnostic measurements. For the pure oxygen plasma flow, a simplified theoretical model neglecting chemical reactions and diffusion fits comparably well to the measurements based on optical diagnostics. The mass-specific enthalpy at the corresponding plasma condition applying optical diagnostics is h=27.47  MJ/kg, and the probe measures h=27.64  MJ/kg.

Enhanced Evaluation of Recombination Coefficient Measurements in Plasma Wind Tunnels

This paper describes the methodology of determining the recombination coefficients for candidate materials of the catalytic based sensor system PHLUX. The methodology was broadened in terms of evaluation of the specific heat flux on catalytic surfaces. This leads to the possibility of calculating species concentration and atom net fluxes on and at the surface directly. Recombination coefficients with an indication of temperature and pressure level at which they were determined is given. Total emissivities for these materials for temperatures up to 2300K are provided.

OVERVIEW ABOUT THE INSTRUMENTED NOSE ASSEMBLY DEVELOPMENT FOR THE EXPERT CAPSULE

The EXPERT mission aims at collecting precise in-flight data during atmospheric re-entry. For this purpose a vehicle was envisaged that is designed especially for that. Almost twenty payloads are on board of the EXPERT capsule which has the shape of a cone with a blunt nose. Four non-moveable flaps are located at the end of the capsule. The nose of the vehicle is made from a ceramic matrix (CMC) composite material. In the nose four exciting experiments are situated. Payload 1 is a Flush Air Data System that measures the pressure and the heat flux in five positions on the nose. Payload 2 collects temperature date on the inside of the ceramic nose at six locations via pyrometric measurements. Payload 10 is a spectrometer that investigates the chemical properties of the boundary layer around the nose via an optical window in the nose. Palyoad 11 is an experiment that deals with the catalycity of materials in the region of the interface of the nose to the adjacent metallic Thermal Protection System (TPS) of the capsule. This paper describes the development of the Instrumented Nose Assembly of the EXPERT capsule, referred to as the NAP, from the design concepts over the analysis and the tests up the flight hardware assembly.

The flight of EXPERT: Assessment of Nonequilibrium Effects with IRS Payloads PYREX, PHLUX and RESPECT

An overview of the IRS payload development for ESA’s EXPERT mission is given. The final design and performance parameters of the payloads PYREX, PHLUX and RESPECT are described. PYREX is a sensor system measuring the TPS rear side temperature. PHLUX is a catalysis based experiment to determine the dissociation degree of the boundary layer. RESPECT applies optical emission spectroscopy to measure spectrally resolved the radiation onto a TPS surface. I. Introduction pace vehicles encounter high thermal loads during re-entry. The design and layout process of the TPS requires a detailed consideration of various high-temperature effects because the mass of the thermal protection system (TPS) has a considerable impact on the total mass of the vehicle. Furthermore, the portion of the costs for the development of a TPS is significant compared to the total development costs. The investigation of TPS and TPS typical materials is performed by ground based means, e.g. plasma wind tunnels or shock tubes, as well as numerical simulations. Numerical tools used for the calculation of the flow around a vehicle performing an atmospheric entry manoeuvre have to be robust, accurate and efficient and be applicable in a wide altitude and velocity range. The models used in these tools must consider many complex high-temperature effects, such as chemical reactions as dissociation, ionization and recombination and different energy exchange mechanisms as well as thermal nonequilibrium and transport phenomena. The plasma state of the post shock regime and the boundary layer during atmospheric entry are primarily defined by the inflow conditions and the vehicle geometry. In the past, various numerical codes have been developed to numerically simulate these complex conditions. Unfortunately, it is not possible to reproduce all relevant parameters in ground test facilities in order to verify and improve the existing codes. Therefore, experimental data has to be gathered with in-flight sensor systems. A dedicated mission to improve the knowledge of atmospheric entry phenomena is the ESA mission EXPERT 1 , represented by a 1.6 m x 1.2 m large ballistic capsule with a mass of m = 436 kg and a nose radius of r = 0.55 m. Besides the technology development and demonstration aspect of the mission, the second key objective is to build up a database containing various measured re-entry data. At IRS the in-flight sensor systems PYREX, PHLUX and RESPECT were development to serve this purpose. PYREX is a flight-qualified pyrometric entry experiment which measures the TPS rear side temperature distribution. Hence heat fluxes on ceramic TPS can be calculated by solving the inverse heat conduction problem. PHLUX is a catalysis based sensor system which measures rear side temperatures of closely placed material probes