Harald Habiger

High-Power Hydrogen Arcjet Thrusters

A radiation-cooled thermal arcjet thruster named HIPARC-R has been developed and investigated. It has been designed for the 100-kW power level and is operated with hydrogen as its propellant. A specie c impulse of 1970 s was obtained with a mass e ow rate of 150 mg/s at the 100-kW power level and at a thruster efe ciency of about 28%. This equals a specie c input power value of 670 MJ/kg. Parallel to the experiments a numerical code system was developed to further optimize the next generation of hydrogen arcjet thrusters. This code system consists of a e nite volume e ow code coupled with program modules for the calculation of thermal, chemical, and electronical properties. In addition, a program module for the calculation of the heat e ow inside the thruster, including heat exchange, has been applied to model the heat transfer processes during thruster operation. The thruster has been operated over a wide power range and has been intensively investigated for the qualie cation of the numerical code system. Within this paper the experimental setup and the code system are described, the performance data are presented, and experimental and numerical results are compared.

Characterization of a nitrogen flow within a plasma wind tunnel

This article presents a comparison of numerical and measured results of a nitrogen high-enthalpy flow. Experimental data at a first cross section are used as initial and boundary conditions for a numerical simulation of the high-enthalpy flow, the results at a second cross section are compared with the numerical solution. The program system employed to examine the flow consists of a Navier-Stokes flowfield solver including models to investigate thermal and chemical nonequilibrium flows. Different measurement techniques were applied to determine the flowfield properties. The measurements made possible the calculation of the local specific enthalpy and mass flux distributions of the plasma plume by basic thermodynamic equations. These mass flux distributions are compared with measurements by mass spectrometry. Special emphasis is also placed on the investigation of the catalytic activity of different materials.

Experimental Investigation of a Nitrogen High-Enthalpy Flow

This article presents experimental results of a nitrogen high-enthalpy plasma flow obtained within a test campaign at the Institut fuer Raumfahrtsysteme. Different measurement techniques have been applied to determine the flowfield properties in flow direction and the distributions at two cross sections, i.e., pressure, heat flux, velocity, electron density, and temperature measurements. These measurements make possible the calculations of the local specific enthalpy and the mass flux distributions of the plasma plume. The experimental data at the first cross section are to be used as initial and boundary conditions; the comparison of the calculated and experimental results at the second cross section allow the verification of the models used in numerical codes. 24 refs.

Investigation of High-Enthalpy Air Plasma Flow with Electrostatic Probes

At the Institute for Space Systems of the University of Stuttgart, four plasma wind tunnels are in operation to investigate the thermochemical behavior of thermal protection systems of various space vehicles during planetary entries To achieve a detailed understanding of the plasma conditions in a plasma wind tunnel and of the erosion mechanisms of thermal protection materials, a specific flight condition on the re-entry trajectory of a winged vehicle was investigated experimentally and numerically in detail during the last few years. Electron temperatures, electron densities, plasma potentials, electron energy functions, and particle velocities of the air plasma flow generated by a magnetoplasmadynamic plasma generator were investigated by cylindrical electrostatic single, double, and triple probes. Plasma velocities were determined with time-of-flight probes, taking advantage of natural fluctuations of the ion current densities in the air plasma flow. Using the ratio of directed and thermal ion velocities related to currents of parallel- and perpendicular-oriented probes according to the Kanal theory, the ion temperature is estimated

DIAGNOSTICS OF HIGH ENTHALPY PLASMA FLOWS

For the qualification of materials for thermal protection systems of reentry vehicles the Institut fur Raumfahrtsysteme (IRS) operates several plasma wind tunnels where continuous plasma flows of high specific enthalpy and velocity are generated by thermal or magnetoplasma dynamic generators. The accuracy of the simulation of reentry conditions strongly depends on the ability to determine the flow conditions. This paper gives an overview of the diagnostic methods which are qualified and in use at the IRS so far. Both intrusive probe measurement techniques including mass spectrometry as well as nonintrusive, optical techniques, like emission spectroscopy and laser induced fluorescence (LIF) are used for the investigation of the high enthalpy plasma flows. For a better understanding of the interaction between the material and the plasma flow numerical prediction methods have been developed in addition to the diagnostic techniques.

Investigation of Arc Jet Plumes with Fabry-Perot Interferometry

For the development of arc jet thrusters, the investigation of fundamental plasma parameters is essential in order to improve the knowledge of the physics. Many parameters can be obtained by intrusive rnechanical and electrostatic probe methods, but as a major disadvantage many of those probes disturb the plasma flow and falsfy the measured parameters. The only way to avoid this is to upply uctive or passive optical diagnostic methods. While active methods like LIF are rather complicated, the passive emission spectroscopic methods provide easy access for a few fundamental parameters. Performing investigations with a high spectral resolution requires either large focal length spectrometer or a Fabry-Perot Interferometer (FPI). The application of a Fabry-Perot Interfrrometer means basically invesfigation of single emission lines and there the detection of Doppler-Effects. This paper shows results of optical investigations of basic emission lines emitted by the investigated plasma plumes of different propellants. The Doppler-ship of the spectral lines and so ,far the velocity of the emitting particle was determined by comparison with unshifed spectral lines of a quiescent plasmu, a laser or a discharge lamp. The FPI also allows the exact determination of .spectral line widths, which are governed by Dopplerand Stark-broadening effects, depending on the kinetic temperatures of the emitting particles and the electron number density. The data can be spatially resolved by an Abel inversion technique. The particle densities and temperatures in the plume and the exhnust velocity are of special interest to researchers developing analytical models, because they need detailed information about these parameter to validate and calibrate their results.