Showing papers on "Arcjet rocket published in 2000"

New inductively heated plasma source for reentry simulations

Abstract: Apart from magnetoplasmadynamic plasma generators (MPG) and thermal arcjet devices (TPG) for re-entry simulation, inductively heated plasma generators (IPG ) have been developed for basic TPS material tests at the IRS. These inductively heated plasma generators consist mainly of a water-cooled coil surrounding a tube in which the plasma is located Due to this setup no electrode erosion appears; impurities in the plasma are minimized. Hence, both the behaviour of the gas components can be examined singularly and basic material tests such as the determination of the catalytic behaviour can be performed. With IPG3 an rf-source is provided where the coil is closer to the plasma than it was with previous designs. Therefore, the electromagnetic field loss is reduced. The water cooling system surrounds both the induction coil and the plasma container. IPG3 was qualified up to an anode power of 180 kW (argon), which is an essential improvement regarding the intended re-entry simulations in combination with the IRS MPG-simulations in the plasma wind tunnels 1 and 2 (PWK). The structure of the rf-plasma source IPG3 and the facility PWK3 are presented in this paper. This paper describes the design of IPG3 and the first experimental results for the plasma source. Power characteristics of IPG3, which were measured under variation of gas, are shown. Within this variation of gas frequency measurements were made, which will be a help for later numerical simulations of IPG3. A CID camera was used to measure the radial intensity of the plasma through an axial optical window of IPG3. The results led to a rough determination of the skin depth for the operation with air.

On-Orbit Demonstration of a Pulsed Self-Field Magnetoplasmadynamic Thruster System

Abstract: A repetitively pulsed self-Ž eld magnetoplasmadynamicarcjet thruster was integrated into a propulsion system, which was tested on-orbit using liquid hydrazine propellant. This space test was designated as Electric Propulsion Experiment (EPEX) onboardSpace FlyerUnit thatwas a Japaneseunmannedreusable space platformlaunchedby anH-II rocket inMarch1995,and retrieved by aU.S.SpaceShuttle in January1996.TheEPEX successfully veriŽ ed the propulsive function of the pulsed magnetoplasmadynamic arcjet thruster system by repetitively Ž ring over 40,000shots during a few days of allocated experiment period, and conŽ rmed that the on-orbit thrust performance was in good agreement with that obtained in the ground test. The residual hydrazinewas successfully dumped into space according to NASA safety requirements. The post ight inspection exhibited no signature of abnormal arc discharge and no hydrazine concentration in the EPEX system.

Nonintrusive Diagnostic Strategies for Arcjet Stream Characterization

Abstract: In the previous lecture, the issues related to arcjet flow modeling were introduced, and the limitations of conventional instrumentation in addressing these issues were discussed. The general level of understanding of the arcjet flows was seen to preclude the use of arcjets as aerothermodynamic test facilities beyond the current role in aerothermal material testing, despite their long test duration capability. In this section, the focus will be on new developments in spectroscopic instrumentation and techniques that can be brought to bear on the fundamental problem of arcjet stream characterization. Although a wide selection of arcjet facilities were introduced in the previous section, the discussion of nonintrusive diagnostic instrumentation will be restricted to the large-scale, segmented, constricted-arc heater facilities that are most widely used in thermal protection material testing for aerospace applications. After a brief review of the important features of arcjet flows, the topic of nonintrusive, optical diagnostics is introduced with a discussion of some of the basic aspects of radiative transitions. The lecture is then organized into two sections covering emission measurements and laser-induced fluorescence measurements. Emission measurements are presented next for different regions of arcjet flows, while the fluorescence measurements are presented for the free stream region only. Summaries are given for each of the two main sections, and observations on arcjet characterization by optical diagnostics in general are given at the end.

Density measurements in a DC arcjet using scanned beam deflection tomography

Abstract: We have demonstrated a scanned beam deflection technique, and applied this technique to imaging the free stream of a dc arcjet plasma plume. An acousto-optic deflector sweeps a HeNe beam transverse to the jet flow direction. A transform lens and split photodiode measure angular beam deflections produced by refractive index gradients in the arcjet plume. Line scans of beam deflection angle are collected at a 1 kHz sweep rate. Assuming axial symmetry, tomographic reconstruction is used convert the beam deflection data to refractive index. Multiple one-dimensional scans are stacked to produce two-dimensional refractive index images. Index of refraction is directly related to density for measurements in pure argon. Good images are obtained at chamber pressures as low as 4 Torr.Measurements were performed using both pure argon and argon/ hydrogen/methane mixtures in the arcjet reactor at a variety of reactor chamber pressures including conditions for diamond deposition. We found significant differences in the radial transport with chamber pressure and with feedstock composition. Comparison of index of refraction data with photographs of arcjet optical emission shows that the emission is not a good representation of the jet density. The simplicity and sensitivity of the scanned beam deflection technique may allow its use for process control when using arcjets for plasma deposition of material.

Oxidation of Hypervelocity Impacted Reinforced Carbon -Carbon

Abstract: Results from arcjet tests conducted at the NASA Johnson Space Center on reinforced carbon ‐carbon samples subjectedtohypervelocityimpactarepresented.Thetestspecimensarerepresentativeofreinforcedcarbon ‐carbon component used on the Space Shuttle Orbiter. The arcjet testing established the oxidation characteristics of reinforced carbon ‐carbon when hypervelocity projectiles, simulating meteoroid/orbital debris, impact the reinforced carbon‐carbon material.In addition, analytical modeling of theincreased materialoxidation in the impacted area, using measured hole growth data, to develop correlations foruse in trajectory simulationsisdiscussed. Entry e ight simulations are useful in assessing the increased Space Shuttle reinforced carbon ‐carbon component degradation as a result of impact damage and the hot gas e ow through an enlarging hole into the wing leading-edge cavity.

Flow Characterization of a Diamond-Depositing DC Arcjet by Laser-Induced Fluorescence.

Abstract: Laser-induced fluorescence (LIF) measurements of seeded nitric oxide and naturally occurring species in a diamond-depositing dc arcjet of hydrogen/argon/methane (0.8:1.0:0.005) at 25 Torr are used to determine the temperature and velocity fields in a gas jet. LIF measurements are also used to demonstrate the importance of gas recirculation on the chemical composition of the arcjet plume. The gas flow in the arcjet plume is supersonic, with a maximum axial speed of 2.6 km/s at the center of the nozzle exit. This axial velocity decreases with radius with a parabolic distribution in the plume. There is no measurable radial velocity in the free stream of the arcjet plume, and the radial expansion of the plume is consistent with diffusion. The maximum temperature at the plume center is 2400 K and varies less than 15% with chamber pressures of 10–50 Torr. The substrate is placed in the arcjet plume normally to the directed velocity, producing a stagnation point. The gas temperature above this stagnation point is observed to rise abruptly as a consequence of the supersonic shock. The radial velocity near the stagnation point becomes significant, and a maximum radial velocity of 1300 m/s is determined.

Low-Power Microwave Arcjet Testing: Plasma and Plume Diagnostics and Performance Evaluation

Abstract: The results of an experimental study of a microwave thruster are presented. Performance evaluation of a 7.5 GHz engine was done using different propellants under both atmospheric and vacuum conditions. Helium, nitrogen and ammonia were tested providing mean chamber stagnation temperature values. Other experiments include plasma and plume diagnostics. Emission spectroscopy of the plasma was made in order to measure the plasma electron temperature at different specific power levels, and the commonly-made assumption of Local Thermodynamic Equilibrium (LTE) was examined. In order to obtain thrust and specific impulse data under vacuum conditions, the Doppler shift between light emitted by the exhaust plume parallel to the gas velocity and perpendicular to the flow was measured using a high spectral resolution Fabry-Perot interferometer, yielding centerline specific impulse values for helium propellant at various specific powers. Thrust and mean specific impulses for all three propellants are being measured using a vertical mechanical thrust stand mounted inside a vacuum tank. Nomenclature

Determination of Parameters in Arcjet Plume by Tomographic Reconstruction

Abstract: The spatial temperature and atomic number density of the plume generated by a 3-kW-class arcjet thruster are determined with a small number of absorption measurements across the plume based on diode-laser absorption computerized tomography. The maximum temperature and atom number density increase with the massflow rate and discharge current. The increase trend is not always found with the specific input power, although there exists an increasing trend with it at a fixed massflow rate. The development of the plume is studied with the measurements of the plume at different locations. The technique should also be applicable to arcjet or other hypersonic flow systems without much modification.

Cathode Jet Structure in Quasi-Steady MPD Thrusters.

Abstract: Quasi-steady MPD (Magnetoplasmadynamic) arcjet PF-series were developed to understand the cathode jet structures, i.e., to mainly understand pumping acceleration processes of an MPD thruster. The ring anode of PF arcjets is located downstream from the cathode enough to generate a high axial current. Spatial current distribution, electron temperature and electron number density were measured in order to examine the plasma features in the cathode jet region. They were sensitive to the gas species and the anode radius of PF arcjets. Especially, a high-energy region was formed along the center axis of the PF-II arcjet with H2. The current distribution on the cathode cone and the pressure at the cathode tip were also measured with a divided cathode and pressure tap, respectively. Current fractions entering an inner cathode rod at large discharge currents were hardly dependent on gas species and the anode radius of PF arcjets. The pressure at the cathode tip of the PF-II arcjet was good agreement with the JJ2-dependence curve derived from the electromagnetic acceleration theory.

Analysis of high speed non-equilibrium chemically reacting gas flows. Part I. physical modeling and sensitivity studies

Abstract: A theoretical model for high speed flow of chemically reacting gases out of thermal and chemical equilibrium is presented. The main features of the physical model are discussed together with details for a new form of the kinetic rate coefficients for non-equilibrium flows and presentation of a two-layer radiation model used for a plasma torch problem. This model is implemented in a new hybrid finite volume/finite element scheme, which is developed in Part 2. Results from this physical model are compared with experiments and other results in the literature for an arcjet and non-equilibrium nozzle test case. Sensitivity studies are included for the nozzle problem to simulate the influence of the rate coefficients

An absorption sensor system for arcjet multi-parameter measurements

Abstract: Diode-laser absorption computerized tomography is applied to the diagnosis of the plume generated by an arcjet thruster. A protection stack is designed to carry a laser beam into the arcjet flow field at any location in the vacuum chamber. The experimental system is developed to reconstruct the maps of the temperature and the atomic number density by utilizing a small number of line-of-sight measurements. It has been demonstrated to be a convenient and useful method for the measurement of plume parameters and for monitoring the performance of the arcjet.

Energy Management in Rocket Propulsion

Abstract: The optimal management of the available energy in an ideal single-stage rocket produces a velocity increment that is larger than the value provided by Tsiolkovsky’ s equation. This result is immediately applicable when a limited amount of energy is available from a source that is external to the propellant. A storage device is instead necessary to delay partially the use of the energy that is produced by the combustion of a reactive working e uid. The penalty of the energy-source mass and the presence of an upper limit on the propellant temperature are also discussed; in the latter case, the addition of a low-molecular-weight, inert propellant to the reactive propellant is benee cial during the e nal phase of the rocket acceleration.

Investigation on Discharge Modes of Low Power DC Arcjet.

Abstract: In the regime of low power DC arcjet, a research how to stabilize the operation modes was conducted in the Institute of Space and Astronautical Science (ISAS) using a 2-dimension-like DC arcjet for internal visualization, designated as ISAS-VAJ. As the results, an intermediate-voltage operation mode was newly found between the conventional low-voltage and the high-voltage mode. In the new intermediate-voltage mode, it was observed that the electron density and the ionization features were locally enhanced in the upstream region of the nozzle. It was also found that these localized features turned to be relaxed just after the formation, and the operation mode transferred to a high-voltage mode. Applying Kuriki model to this phenomenon, the operation mode and the transition were understood in view of the conditions for arc column formation. A proposal to stabilize the operation mode was made to be applied to ISAS-VAJ by adding a second-cathode in the upstream region of the nozzle. Initiating high voltage pulsed discharges on it, the operation mode was successfully transferred from a low-voltage to a stable high-voltage mode.

30 KW Class Arcjet Advanced Technology Transition Development (ATTD)

Abstract: : The Arcjet Advanced Technology Transition Demonstration (ATTD) Program developed and demonstrated a flight qualified 30 kW arcjet propulsion flight unit. Once it successfully completed qualification testing, the flight unit was integrated as the Electric Propulsion Space Experiment (ESEX) flight experiment onto the Air Force Advanced Research and Global Observation Satellite (ARGOS). The objectives of the flight unit space test were to measure arcjet plume deposition, electromagnetic interference, thermal radiation, and performance in space. These measurements were chosen to address specific operational issues that are commonly raised for EP systems. There were a total of eight firings conducted over the course of the 60-day mission, for a total duration of 2,023 seconds. All of the demonstration aspects of the experiment were completed successfully and the arcjet, PCU, PFS and overall system operated very well. All of the data analyzed to date indicate the thruster operated nominally, and operated completely independently of the normal operations of the host spacecraft.

Experimental Results of the Impact of an Ion Thruster Plasma on Microwave Propagation

Abstract: Electric thrusters are being considered for a variety of space missions because of the significant propellant savings that result from the use of high performance, electric propulsion technologies, Propellant mass savings reduces spacecraft launch requirements and increases mission lifetime and payload The impact of electric thruster plasma plumes on microwave signal propagation however is an important spacecraft integration concern Arcjets were the first electric thrusters to be considered for operational missions Ling, et al, studied the effect of arcjet plumes on propagation Arcjets produce a lightly ionized plume and Ling's analysis predicted that the plume would have a negligible effect on communication Plumes from the higher performance ion thrusters being developed exhibit higher ionization levels, plasma temperatures and particle velo@ities than arcjets Therefore, there was a need to assess the impact due to these plumes To address this need, the authors designed and performed a series of experiments to examine propagation effects of plumes The challenge with these experiments was that they had to be performed in the operational environment of the thruster Therefore, the experiments were conducted inside a metal chamber which could be depressurized to simulate a near vacuum condition of space The metal chamber presents a potential large source of error to the propagation measurements due to the corruption of the desired data by multiple wall reflections within the chamber This chamber effect was minimized by employing a pulsed-continuous wave transmitter and receiver system This system, based on an HP8510 Network Analyzer, uses external hardware time gating to eliminate the clutter of the spurious reflections Additionally, high gain antennas were used in the measurements to ensure that minimal amounts of energy ",ere transmitted/received in undesirable directions The measurements took place in Vacuum Facility 5 of the Electric Propulsion Laboratory at the NASA Glenn Research Center This facility utilizes a cylindrical, stainless steel, vacuum chamber, which is 183 m long and 46 m in diameter For the tests being described here a 30 cm diameter, xenon ion thruster was used The thruster provided between 500 W and 23 kW of operating power The thruster was mounted on a stand along the axis of the chamber near one of its ends

Development of a Methodology for Conducting Hall Thruster EMI Tests in Metal Vacuum Chambers of Arbitrary Shape and Size

Abstract: While the closed-drift Hall thruster (CDT) offers significant improvement in performance over conventional chemical rockets and other advanced propulsion systems such as the arcjet, its potential impact on spacecraft communication signals must be carefully assessed before widespread use of this device can take place. To this end, many of the potentially unique issues that are associated with these thrusters center on its plume plasma characteristics and the its interaction with electromagnetic waves. Although a great deal of experiments have been made in characterizing the electromagnetic interference (EMI) potential of these thrusters, the interpretation of the resulting data is difficult because most of these measurements have been made in vacuum chambers with metal walls which reflect radio waves emanating from the thruster. This project developed a means of assessing the impact of metal vacuum chambers of arbitrary size or shape on EMI experiments, thereby allowing for test results to be interpreted properly. Chamber calibration techniques were developed and initially tested at RIAME using their vacuum chamber. Calibration experiments were to have been made at Tank 5 of NASA GRC and the 6 m by 9 m vacuum chamber at the University of Michigan to test the new procedure, however the subcontract to RIAME was cancelled by NASA memorandum on Feb. 26. 1999.