Showing papers on "Arcjet rocket published in 2009"

Two-Dimensional Ablation, Thermal Response, and Sizing Program for Pyrolyzing Ablators

Abstract: The purpose of this paper is to describe and demonstrate new capabilities in the two-dimensional implicit thermal response and ablation program. These expanded capabilities include grid options for flight and arcjet geometries, a sizing algorithm for the flight-type geometry, and an orthotropic thermal conductivity model. Applications to analysis of an orthotropic low-density carbon-phenolic material in arcjet and flight environments relevant to the Orion crew module are presented. For the arcjet environment, multidimensional conduction effects strongly influence the in-depth thermal response. For a lunar return flight environment, in the shoulder region of the crew module (where the radius of curvature is smallest), the thermal response is influenced by multidimensional conduction and by the orientation of the orthotropic material.

Development of a High-Fidelity Thermal/Ablation Response Model for SLA-561V

Abstract: This paper describes the properties and parameters derived and/or developed to model the thermal/ablation response of SLA-561V. The model is based on arcjet data taken in the NASA Ames IHF and AHF arcjet facilities during 2004–2005. As such, this model does not account for potential ablation mechanisms associated with aerodynamic shear, as all of the aforementioned tests were conducted on 4-inch diameter flat-faced cylindrical samples. The model contains two interdependent elements: (1) a thermal response model to predict in-depth temperature response and (2), a surface ablation model to predict surface temperature and surface recession. As will be discussed, these two elements were developed separately and then integrated to comprise the high-fidelity response model (HFRM) for SLA561V. The properties and parameters included in the in-depth model will be described first, followed by a description of the surface ablation model, and, finally, the assumptions required to integrate the two.

Thrust Measurement of the Hybrid Electric Thruster TIHTUS by a Baffle Plate

Abstract: A novel, two-stage, electric thruster is under development at Institut fiir Raumfahrtsysteme at Universitat Stuttgart. The first stage is an arcjet, and the second stage uses inductive heating of the arcjet plume. Because of the complex setup of the thruster, it is impossible to mount the two-stage system on a thrust stand without causing unwanted momentum onto the stand by the numerous supply lines. Thrust is, therefore, inferred using a baffle plate by means of a variation of power- and mass-flow ratios between the two stages. To interpret the results, the present paper also provides radially resolved measurement of total pressure from which thrust can be determined. It is shown that the thrust obtained from the two measurement methods are in good agreement with each other and range between 1.7 and 2.5 N for the respective operating conditions of the thruster. At constant total input power of 50 kW to the thruster, thrust decreases as power is diverted from the first stage to the second (inductive) stage at a constant mass-flow rate. However, when power is applied to both stages, thrust increases as the mass-flow rate is diverted to the second stage at a constant total mass-flow rate of 300 mg/s.

Thrust Measurement of Pure Magnetic Sail

Abstract: A Pure Magnetic Sail is a deep space propulsion system consisting of a coil mounted on a spacecraft. In order to predict the thrust characteristics of a Pure Magnetic Sail in space, thrust measurement and magnetic field measurement were conducted using a scale model in a laboratory. To simulate the solar wind, a magnetoplasmadynamic arcjet provides a high density (2×1019 m-3) and high velocity (47 km/s) plasma flow that impinges on a 20-turn 25-mm-radius coil simulating a Pure Magnetic Sail. When the magnetic cavity size of the scale model (L) is increased from 0.12 to 0.17 m, the thrust increases from 0.47 to 0.92 N. Scaling up, this experiment corresponds to a 300-km diameter Pure Magnetic Sail in space. The thrust also depends on the coil tilt angle, which is the angle between the direction of the solar wind flow and the coil axis. The maximum thrust of 1.5 N is obtained for a tilt angle of 90 degrees.

AMC-1 (GE-1) Arcjets at 12-plus Years On-Orbit

Abstract: The paper describes the first twelve plus years of arcjet use to perform all North South Stationkeeping on the SES AMC-1 (originally designated GE-1) A2100TM Geostationary Telecommunications Satellite (Figure 1). More than 600 hours of arcjet operation were employed in approximately 600 separate maneuvers to achieve the desired orbit maintenance. The spacecraft involved is the very first A2100TM and almost all maneuvers have been done on a single arcjet pair. This pair of Aerojet MR-510 arcjets has now provided more than 800,000 N-s of total-impulse, corresponding to a throughput of approximately 140 kg of hydrazine. Details of the arcjet subsystem, spacecraft bus and an overview of mission plan from an arcjet utilization point of vie will be provided.

Effects of Anode Temperature on Working Characteristics and Performance of a Low Power Arcjet Thruster

Abstract: An arc-heated thruster of 130–800 W input power is tested in a vacuum chamber at pressures lower than 20Pa with argon or H2-N2 gas mixture as propellant. The time-dependent arc voltage-current curve, outside-surface temperature of the anode nozzle and the produced thrust of the firing arcjet thruster are measured in situ simultaneously, in order to analyze and evaluate the dependence of thruster working characteristics and output properties, such as specific impulse and thrust efficiency, on nozzle temperature.

An Experimental Study on Thermal Response of Low Density Carbon-Phenolic Ablators

Abstract: Coking phenomenon for low density carbon-phenolic ablative material exposed to aerodynamic heating is examined experimentally. The low density ablators with the nominal virgin density of 0.24g/cm3 are heated in arcjet wind tunnels with nitrogen and air as a test gas. The material in-depth density, in-depth and surface temperatures are measured. The density increase within the char layer is observed for the test specimens heated in the nitrogen arcjet freestream. In contrast, the coking behavior is not clearly seen for the case of air arcjet testing. The present study shows that the nature of the in-depth density distribution is very sensitive to the heating conditions.

Spatially Resolved Spectroscopic Study of Arcjet Helium Plasma Expanding through a Rectangular Converging and Diverging Nozzle

Abstract: An arcjet discharge device with a rectangular converging and diverging nozzle was developed, which allowed us to optically observe high-density plasma inside the anode nozzle. Spectroscopic observation along the plasma expansion axis was carried out to examine the characteristics of the arc plasma inside the nozzle. Analyzing intense continuum and line emission spectra, we successfully obtained spatial variations in electron temperature and density. Moreover, we found that two-dimensional optical measurement is highly useful in visualizing the transition from atmospheric thermal plasma to a strongly nonequilibrium recombining plasma due to adiabatic expansion.

Development of arc root attachment in the nozzle of 1 kW N2 and H2-N2 arcjet thrusters

Abstract: Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

Simulation of carbon-carbon crack growth due to carbon oxidation at high temperatures

Abstract: High-temperature gas-dynamic computational techniques are employed to study microflows in expanding crack channels caused by the oxidation of the channel carbon walls. Wall regression rates for three reinforced carbon- carbon samples that were tested in a high-enthalpy arcjet environment were modeled. The test geometries and flow conditions span flow regimes from the transitional through the continuum, but the same mechanism for wall material loss, atomic oxygen reaction with bare carbon, was used in all three cases. Kinetic (direct simulation Monte Carlo) and continuum (Navier-Stokes) gas-dynamic approaches were used. The predicted wall regression rates were found to agree with arcjet measurements, and the general specimen shape change was predicted. Local gas flowfield results were found to affect the oxidation rate in a manner that cannot be predicted by previous mass loss correlations. The method holds promise for future modeling of materials gas-dynamic interactions for hypersonic flight.

Design and Experiment of Thrusters Using Dimethyl Ether

Abstract: We proposed new thrusters using Dimethyl ether (DME) as propellant: DME arcjet thruster and liquid propellant thruster using plasma assisted combustion. DME has a freezing point of −143oC, a boiling point of −54oC, and liquefies at 6atm under room temperature. Thus, DME can be stored as a liquid without cryogenic device. DME has little toxicity and is chemically stable. A DME arcjet thruster prototype operated in a discharge power range from 1000W to 1600W and a plenum chamber pressure reached 160kPa. We also designed a liquid propellant thruster prototype using DME plasma assisted combustion. The plasma successfully sustained the combustion of DME and Hydroxyl Ammonium Nitrate oxidizer. At a discharge power of approximately 3kW, the measurement of the thrust chamber pressure yielded a C* efficiency of 0.39 and an estimated specific impulse of 114s.

Hollow cathode thrust mechanisms

Abstract: This paper investigates propellant acceleration mechanisms within hollow cathode thrusters based on the results of previous experimental testing. Experiments were conducted on a T5, T6 and ¼ inch cathode. An indirect pendulum micro-thrust-balance was built for the measurement of thrust production in the T5, T6 cathodes while a hemispherical energy analyzer was used for ion energy measurements in the ¼ inch hollow cathode. The data suggest that the thrust mechanism of hollow cathodes is composed primarily of gas dynamic mechanisms, particularly as a result of an intense electron pressure at the cathode exit, and magneto-hydro-dynamic (MHD) forces at high currents and very low flow rates arising from the self-induced azimuthal magnetic field within the orifice. While this initial characterization can only loosely attribute the relative magnitude each mechanism plays it does show evidence for each. Smaller cathodes, such as the T5, operate at lower currents in a more arcjet like mode and show the necessary performance and efficiency to compete with conventional propulsion systems at a mission level.

Two-Dimensional LTE Modeling of a Low-Power Argon Arcjet Thruster

Abstract: The extension to a higher specific impulse of an arcjet requires deeper understanding of the physics process in the thruster. In this paper, low-power arcjet thrusters are studied numerically using argon as the propellant. The all-speed SIMPLE algorithm is used for the solution of the governing equations, including temperature- and pressure-dependent gas properties. Computed results are presented concerning the temperature, pressure, axial velocity and Mach number distributions within in the thruster nozzle under typical operating conditions. It is found that the heating of the propellant takes place mainly in the constrictor. Under typical operating conditions studied here, the computed specific impulses and mass flow rates of the argon arcjet thruster are roughly consistent with corresponding experimental data. The effects of the geometrical sizes of the arcjet are also investigated.

Performance of Solid Propellant Rocket Motors with Variation in Nozzle Geometry

Abstract: The nozzle geometry affects the performance achieved by a solid propellant rocket motor to a great extent. In order to improve the development of a small home made solid propellant rocket motor these effects on performance from the nozzle geometry need to be understood. This thesis project involves the design of a small solid propellant rocket motor with materials readily available to a hobby rocket enthusiast. A specific investigation is then carried out into the effects that nozzle geometry has on the thrust and impulse performance of the rocket motor. The thrust-time profiles of the rocket motors are achieved by conducting a static firing in a cantilever beam thrust measuring apparatus. A secondary study is also done on these different nozzle geometries using computation fluid dynamics simulations to determine the predicted thrust performance. This also gives the advantage of visualizing the entire flow field and assists in identifying the features that drive the differences in performance. Overall this project develops a high performance nozzle geometry for use on a small home made solid propellant rocket motor as well as outlining various engineering issues involved with the development of a solid propellant rocket motor.

Simulation of RCC Crack Growth Due to Carbon Oxidation in High-Temperature Gas Environments

Abstract: The carbon wall oxidation technique coupled with a CFD technique was employed to study the flow in the expanding crack channel caused by the oxidation of the channel carbon walls. The recessing 3D surface morphing procedure was developed and tested in comparison with the arcjet experimental results. The multi-block structured adaptive meshing was used to model the computational domain changes due to the wall recession. Wall regression rates for a reinforced carbon-carbon (RCC) samples, that were tested in a high enthalpy arcjet environment, were computationally obtained and used to assess the channel expansion. The test geometry and flow conditions render the flow regime as the transitional to continuum, therefore Navier-Stokes gas dynamic approach with the temperature jump and velocity slip correction to the boundary conditions was used. The modeled mechanism for wall material loss was atomic oxygen reaction with bare carbon. The predicted channel growth was found to agree with arcjet observations. Local gas flow field results were found to affect the oxidation rate in a manner that cannot be predicted by previous mass loss correlations. The method holds promise for future modeling of materials gas-dynamic interactions for hypersonic flight.

Simulation of RCC Crack Growth Due to Carbon Oxidation in High‐Temperature Gas Environments

Abstract: High temperature gas dynamic computational techniques are employed to study microflows in expanding crack channels caused by the oxidation of the channel carbon walls Wall regression rates for three reinforced carbon‐carbon (RCC) samples that were tested in a high enthalpy arcjet environment were modeled The test geometries and flow conditions span flow regimes from the transitional to the continuum, therefore kinetic (direct simulation Monte Carlo) and continuum (Navier‐Stokes) gas dynamic approaches were used The same mechanism for wall material loss, atomic oxygen reaction with bare carbon, was utilized in all three cases regardless of the computational techniques The predicted wall regression rates were found to agree with arcjet measurements Local gas flowfield results were found to affect the oxidation rate in a manner that cannot be predicted by previous mass loss correlations The method holds promise for future modeling of materials gas‐dynamic interactions for hypersonic flight

Laboratory Facility for Simulating Magnetoplasma Sail

Abstract: Magnetoplasma sail (MPS) is a deep space propulsion system, in which an artificial magnetic cavity captures the energy of the solar wind to propel a spacecraft in the direction leaving the sun. This paper describes an improved facility for the scale-model experiment of MPS. We employed a magnetoplasmadynamic arcjet as a solar wind simulator. It is observed that a plasma flow from the solar wind simulator reaches a quasi-steady state of about 0.8 ms duration after a transient phase while initiating a discharge. During this initial phase of the discharge, a blast-wave was observed to develop in a vacuum chamber. Then, a quasi-steady interaction continues when a solenoidal coil (MPS scale model) is immersed into a 45-km/s-velocity and 10-m-number-density plasma flow. As a result of the interaction between the plasma flow and the MPS scale model, a bow shock and a magnetic cavity were formed in front of the coil. Thrust measurement was conducted for only a few limited cases, but the momentum of the simulated solar wind is found to decrease, and as a result, it is found that the solar wind momentum is transferred to the solenoidal coil simulating MPS consisting of only a solenoidal coil.