Showing papers on "Arcjet rocket published in 1985"

MPD thruster performance with various propellants

Abstract: The thrust performance of a quasisteady MPD arcjet is studied with different propellant species. It is found that the thrust obtained with molecular gases is larger than that with monoatomic gases, and that the voltage increase with current is steeper for the monoatomic gases. These differences are attributed to the larger contribution of aerodynamic thrust by the molecular gases. The specific impulse ranged from 2000 to 6000 s by changing gas species. Selection criteria of gas species are discussed from the viewpoint of the thruster system.

Experimental performance of a 1-kilowatt arcjet thruster

Abstract: A formerly unused cathode and anode/nozzle assembly from a flight model arcjet was tested with nitrogen, hydrogen, and nitrogen-hydrogen mixture simulating ammonia decomposition products at arc power levels from about 300 to 950 W. Two different power sources and two nozzle configurations were tested at low back-ground pressures to exclude facility effects. Increased nozzle expansion ratio improved cold flow nozzle efficiency from 0.8 to 0.9. Hydrogen thrust efficiency of 0.26 at 872 sec specific impulse matched some 1964 performance on a similar device. Simulated ammonia thrust efficiency was 0.31 at 422 sec. Spontaneously occurring voltage mode changes at constant arc current could be partially stabilized with appropriate power source characteristics. In the higher voltage mode specific impulse was higher, but thrust efficiency changed only slightly from that of the lower voltage mode. Sustained tests of up to 2 hr duration exhibited no apparent performance degradation with time.

Initial results of SEPAC scientific achievement

Abstract: Electron beam injection of 5 keV, 300 mA (1.5 kW) and MPD arcjet plasma injection of 2 kJ/shot were successfully performed together with various kinds of diagnostic instruments including a high sensitivity TV camera observation in the Spacelab 1. Major scientific results obtained are studies of: (1) vehicle charge-up due to the electron beam emission and its neutralization by the MPD arcjet plasma; (2) beam-plasma interaction including the plasma wave excitation; (3) beam-atmosphere interaction such as the verification of critical velocity ionization effect; and (4) anomalous enhancement of ionization associated with a neutral gas injection into space.

Investigation of arcjet nozzle performance

Abstract: An investigation is performed to examine the feasibility of improving arcjet performance through the use of contoured nozzle designs. The results of preliminary experiments performed on two different nozzle configurations, a 19 degree half-angle cone and a 'bell' shaped nozzle, are described. A unique experimental arcjet apparatus, which effectively tests only the change in nozzle contour on arcjet performance is used in this investigation. The preliminary experimental results indicate approximately an 8 percent improvement in thrust and specific impulse for operation at 15 kW with an ammonia flow rate of 0.20 g/s for a 'bell' shaped nozzle compared to a conical nozzle.

An experimental study of energy loss mechanisms and efficiency considerations in the low power dc arcjet

Abstract: The potential utility of the low power dc arcjet in auxiliary propulsion was investigated. It was indicated that improvements in the areas of stability, energy efficiency, reliability, and electrode erosion are necessary to obtain a useful device. A water-cooled arcjet simulator was tested to investigate both the energy loss mechanisms at the electrodes and the stability of different conventional arcjet configurations in the presence of a vortex flow field. It is shown that in certain configurations only 25 to 30% of the input energy is lost to the electrodes. It is also shown that vortex stabilization is not difficult to obtain in many cases at the flow rates used and that a careful starting procedure is effective in minimizing electrode damage.

Thermal arcjet technology for space propulsion

Abstract: Advanced space propulsion systems are required to meet projected Air Force needs through the year 2000 Most of these missions require a large, on-orbit impulse capability High specific impulse (I sub sp) electric engines can provide this impulse while consuming relatively little propellant An arcjet engine system, which operates in the range of 800 to 2000 s I sub sp, is a promising candidate to meet these projected Air Force mission needs This electric propulsion system is ideally suited to missions currently under consideration, such as the Space-based Radar and other space platforms, because sufficient power is already installed for other functions on the spacecraft Also, arcjet systems are attractive for NASA near-term, low-cost Mariner Mark II missions to Saturn and Uranus Development of arcjet engines was an Air Force and NASA-sponsored activity that proceeded vigorously from its inception during the late 1950's up to the mid-1960's when the programs were terminated This paper describes thermal arcjet technology as it was developed over two decades ago and points to the direction this technology development should proceed in the future In particular, operation with storable propellants such as ammonia and hydrazine are considered The performance, applicability and advantages of these systems in terms of increased payload and/or decreased trip times are discussed

Development and life-testing of 10 kW class thermal arcjet engines

Abstract: A facility to develop and test thermal arcjet engines over extended periods of time has been constructed and is described in this paper. It consists of a large vacuum tank, high capacity vacuum pumps, a 100 kW power supply and a large ammonia propellant storage and delivery system. The facility is instrumented to measure electrical power dissipated in the engine, propellant mass flow rate and developed thrust. Pressures and temperatures up to 2400 K can also be measured. The entire facility is computer-controlled and can be operated unattended for many weeks. Two 30 kW thermal arcjet engines that have been designed, built and are being tested in this facility are also described.

Primary propulsion of electrothermal, ion and chemical systems for space-based radar orbit transfer

Abstract: An orbit transfer mission concept has been studied for a Space-Based Radar (SBR) where 40 kW required for radar operation is assumed available for orbit transfer propulsion. Arcjet, pulsed electrothermal (PET), ion, and storable chemical systems are considered for the primary propulsion. Transferring two SBR per shuttle flight to 1112 km/60 deg using electrical propulsion systems offers an increased payload at the expense of increased trip time, up to 2000 kg each, which may be critical for survivability. Trade offs between payload mass, transfer time, launch site, inclination, and height of parking orbits are presented.

Electrode erosion in arc discharges at atmospheric pressure

Abstract: An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexaboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, and external magnetic fields were all found to reduce electrode mass loss.

Hollow cathodes in high pressure arc discharges

Abstract: An orified hallow cathode was tested at high pressure to improve lifetime and efficiency in arcjet thrusters. It is indicated that the arc would not operate with emission from the insert above 200 torr in nitrogen regardless of insert material, orifice diameter, or gas flow direction. Emission occurred from the insert in argon and xenon although it could not be ascertained whether diffuse or spot emission existed within the cathode. Over the extended range of configurations and operating parameters explored the desired diffuse emission mode could not be obtained at high enough pressures for orified hollow cathodes to operate in the range which is considered for arcjet applications.

MPD arcjet system

Abstract: The current status and future prospects of the magnetoplasmadynamic (MPD) arcjet system are described. Recent research activities on the chemical rocket and electric propulsion are discussed. The characteristics of various MPD arcjet systems including the Komaba-I system developed by the Institute of Space and Astronautical Science of the Tokyo University are analyzed. The applications of the MPD arcjet system to the satellite test, lunar mission, free flyer test, space station test, and heliospheric exploration are discussed.