Results for “Arcjet Testing” — Page 5

NASA NTRS1987

Long duration test of a 30-kW class thermal arcjet engine

This paper describes a recent long-duration test of a 30-kW arcjet engine. This engine performed very well for 573 hours at power levels between 24 and 29 kW and with ammonia as the propellant at a mass flow rate between 0.25 and 0.27 g/s. The specific impulse varied between about 850 and 950 s and the thrust efficiency between 36 and 40 percent. The cause of final engine failure and the conditions of the electrodes and insulator will be discussed in detail. An important part of this very long-term test effort was the performance and efficiency of the facility. The construction of this facility and the performance of the various critical components will also be discussed.

Pivirotto, T. J.↗

NASA NTRS2007

Testing Lunar Return Thermal Protection Systems using Sub-Scale Flight Test Vehicles

A key objective of NASA's Vision for Space Exploration is to revisit the lunar surface. Such an ambitious goal requires the development of a new human-rated spacecraft, the Orion Crew Exploration Vehicle (CEV), to ferry crews to low earth orbit and to the moon. The successful conclusion of both types of missions will require a thermal protection system (TPS) capable of protecting the vehicle and crew from the extreme heat of atmospheric reentry. As a part of the TPS development, various materials are being tested in arcjet tunnels; however, the combined lunar return aerothermal environment of high heat flux, shear stress, and surface pressure cannot be duplicated using only existing ground test facilities. To ensure full TPS qualification, a flight test program using sub-scale Orion capsules has been proposed to test TPS materials and heat shield construction techniques under the most stressing combination of lunar return aerothermal environments. Originally called Testing Of Reentry Capsule Heat Shield, or TORCH, but later renamed LEX, for Lunar Reentry Experiment, the proposed flight test program is presented along with the driving requirements and descriptions of the vehicle and the TPS instrumentation suite slated to conduct in-flight measurements.

heatshield↗

NASA NTRS1986

Power electronics for a 1-kilowatt arc jet thruster

After more than two decades, new space mission requirements have revived interest in arcjet systems. The preliminary development and demonstration of new, high efficiency, power electronic concepts for start up and steady state control of dc arcjets is reported. The design comprises a pulse width modulated power converter which is closed loop configured to give fast current control. An inductor, in series with the arcjet, serves the dual role of providing instantaneous current control, as well as a high voltage arc ignition pulse. Benchmark efficiency, transient response, regulation, and ripple data are presented. Tests with arcjets demonstrate that the power electronics breadboard can start thrusters consistently with no apparent damage and transfer reliably to the nondestructive high voltage arc mode in less than a second.

Gruber, R. P.↗

NASA NTRS1986

Power electronics for a 1-kilowatt arcjet thruster

After more than two decades, new space mission requirements have revived interest in arcjet systems. The preliminary development and demonstration of new, high efficiency, power electronic concepts for start up and steady state control of dc arcjets is reported. The design comprises a pulse width modulated power converter which is closed loop configured to give fast current control. An inductor, in series with the arcjet, serves the dual role of providing instantaneous current control, as well as a high voltage arc ignition pulse. Benchmark efficiency, transient response, regulation, and ripple data are presented. Tests with arcjets demonstrate that the power electronics breadboard can start thrusters consistently with no apparent damage and transfer reliably to the nondestructive high voltage arc mode in less than a second.

Gruber, R. P.↗

NASA NTRS1992

The 10 kW power electronics for hydrogen arcjets

A combination of emerging mission considerations such as 'launch on schedule', resource limitations, and the development of higher power spacecraft busses has resulted in renewed interest in high power hydrogen arcjet systems with specific impulses greater than 1000 s for Earth-space orbit transfer and maneuver applications. Solar electric propulsion systems with about 10 kW of power appear to offer payload benefits at acceptable trip times. This work outlines the design and development of 10 kW hydrogen arcjet power electronics and results of arcjet integration testing. The power electronics incorporated a full bridge switching topology similar to that employed in state of the art 5 kW power electronics, and the output filter included an output current averaging inductor with an integral pulse generation winding for arcjet ignition. Phase shifted, pulse width modulation with current mode control was used to regulate the current delivered to arcjet, and a low inductance power stage minimized switching transients. Hybrid power Metal Oxide Semiconductor Field Effect Transistors were used to minimize conduction losses. Switching losses were minimized using a fast response, optically isolated, totem-pole gate drive circuit. The input bus voltage for the unit was 150 V, with a maximum output voltage of 225 V. The switching frequency of 20 kHz was a compromise between mass savings and higher efficiency. Power conversion efficiencies in excess of 0.94 were demonstrated, along with steady state load current regulation of 1 percent. The power electronics were successfully integrated with a 10 kW laboratory hydrogen arcjet, and reliable, nondestructive starts and transitions to steady state operation were demonstrated. The estimated specific mass for a flight packaged unit was 2 kg/kW.

Hamley, John A.↗

NASA NTRS2014

Adaptable Deployable Entry & Placement Technology (ADEPT) for Cubesat Delivery to Mars Surface

The Adaptable, Deployable Entry and Placement Technology (ADEPT), uses a mechanical skeleton to deploy a revolutionary carbon fabric system that serves as both heat shield and primary structure during atmospheric entry. The NASA ADEPT project, currently funded by the Game Changing Development Program in STMD is currently focused on 1m class hypersonic decelerators for the delivery of very small payloads ( 5 kg) to locations of interest in an effort to leverage low-cost platforms to rapidly mature the technology while simultaneously delivering high-value science. Preliminary mission design and aerothermal performance testing in arcjets have shown the ADEPT system is quite capable of safe delivery of cubesats to Mars surface. The ability of the ADEPT to transit to Mars in a stowed configuration (similar to an umbrella) provides options for integration with the Mars 2020 cruise stage, even to consider multiple ADEPTs. System-level test campaigns are underway for FY15 execution or planning for FY16. These include deployment testing, wind tunnel testing, system-level arc jet testing, and a sounding rocket flight test. The goal is system level maturation (TRL 6) at a 1m class Mars design reference mission configuration.

3D Woven↗

NASA NTRSDate not supplied

Development and Sizing of the Mars 2020 Thermal Protection System

The Mars 2020 entry vehicle successfully delivered the Perseverance rover to the Martian surface on 18 February 2021. The entry vehicle aeroshell was shielded from aerodynamic heating with a thermal protection system (TPS) made of three different ablative materials. This paper provides an overview of the methodology and assumptions employed for the thermal sizing and design of the Mars 2020 aeroshell TPS. The sizing results demonstrate that the as-built thicknesses of the TPS materials were sufficient to withstand the predicted aerothermal environments without exceeding temperature limits of the underlying aeroshell structure. This paper also provides an overview of the ground testing performed in NASA arc jet facilities to verify the performance of flight lot TPS materials. Finally, temperature data returned by thermocouples embedded in the flight vehicle TPS are compared with predictions by the thermal response models used in pre-flight TPS sizing.

Mars2020↗

NASA NTRSDate not supplied

Development and Sizing of the Mars 2020 Thermal Protection System

The Mars 2020 entry vehicle successfully delivered the Perseverance rover to the Martian surface on 18 February 2021. The entry vehicle aeroshell was shielded from aerodynamic heating with a thermal protection system (TPS) made of three different ablative materials. This paper provides an overview of the methodology and assumptions employed for the thermal sizing and design of the Mars 2020 aeroshell TPS. The sizing results demonstrate that the as-built thicknesses of the TPS materials were sufficient to withstand the predicted aerothermal environments without exceeding temperature limits of the underlying aeroshell structure. This paper also provides an overview of the ground testing performed in NASA arc jet facilities to verify the performance of flight lot TPS materials. Finally, temperature data returned by thermocouples embedded in the flight vehicle TPS are compared with predictions by the thermal response models used in pre-flight TPS sizing.

Mars2020↗

NASA NTRS1985

Experimental performance of a 1-kilowatt arcjet thruster

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.

Nakanishi, S.↗

NASA NTRS1985

Experimental performance of a 1-kilowatt arcjet thruster

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 background 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.

Nakanishi, S.↗

NASA NTRS1993

Recent testing of 30 KW hydrogen arcjet thrusters

NASA is conducting efforts to evaluate high-power hydrogen arcjets for orbit transfer propulsion applications. As part of this program, an attempt was made to reexamine both radiatively- and regeneratively-cooled, 30 kW thrusters first demonstrated by the Giannini Scientific Corp. in 1963. The arcjets were configured to force arc attachment upstream of the throat in a subsonic chamber region. While thruster currents were steady, the voltage traces exhibited sawtooth waveforms at frequencies on the order of 20 kHz. Voltage variations per cycle were typically between 100 and 310 volts, indicating major changes in the position of the arc attachment with time. When operated at their respective design points, the performance of both thrusters fell below the values listed in the 1960's development reports. The reason for the discrepancies is not currently understood and further investigations are in progress. However, the recently measured efficiencies were high compared to those obtained with constricted-arc designs at similar conditions, and further arcjet performance optimizations may be possible.

Haag, Thomas W.↗

NASA NTRS1993

Recent testing of 30 kW hydrogen arcjet thrusters

NASA is conducting efforts to evaluate high-power hydrogen arcjets for orbit transfer propulsion applications. As part of this program, an attempt was made to reexamine both radiatively- and regeneratively-cooled, 30 kW thrusters first demonstrated by the Giannini Scientific Corp. in 1963. The arcjets were configured to force arc attachment upstream of the throat in a subsonic chamber region. While thruster currents were steady, the voltage traces exhibited sawtooth waveforms at frequencies on the order of 20 kHz. Voltage variations per cycle were typically between 100 and 310 volts, indicating major changes in the position of the arc attachment with time. When operated at their respective design points, the performance of both thrusters fell below the values listed in the 1960's development reports. The reason for the discrepancies is not currently understood and further investigations are in progress. However, the recently measured efficiencies were high compared to those obtained with constricted-arc designs at similar conditions, and further arcjet performance optimizations may be possible.

Haag, Thomas W.↗

NASA NTRS1990

Qualification and life testing of a flight design hydrazine arcjet system

This paper describes the design and the requirements of a low-power hydrazine arc jet system and presents the results of tests on the system's performance, vibration, and lifetime. The system consists of an arcjet, catalyst bed, power control unit, and interconnecting power cable. Operating at 1.4 kW input power, the system provides a minimum of 450 sec mission average specific impulse, yielding greater than a 100 kg propellant savings over standard monopropellant or bipropellant systems used on communication satellites.

Knowles, S. C.↗

NASA NTRS1992

Ammonia arcjet engine behavior in a cyclic endurance test at 10 kW

The behavior of a 30 kWe-class ammonia arcjet operated at 10 kWe during the 707 successful cycles of an endurance test is described. The propellant flow rate was 0.170 g/s, and the measured performance was about 630 s specific impulse at an efficiency of 0.34. Data obtained indicate that the terminal voltage increased over the first 300 cycles, and then remained approximately constant for the remainder of the test, which suggests that the cathode eroded initially and then reached a stable geometry. No major changes were observed in thruster performance. The test was terminated by a series of external arcs.

Polk, J. E.↗

NASA NTRS1994

ELITE/STAR Arcjet System End-to-End Test

UNKNOWN

ELITE/STAR↗

NASA NTRS2011

The Development of a CO2 Test Capability in the NASA JSC ARCJet for Mars Reentry Simulation

The Atmospheric Reentry Materials and Structures Evaluation Facility (ARMSEF) located at NASA Johnson Space Center is used for simulating the extreme environment experienced upon reentry for the development and certification of thermal protection systems (TPS). The facility supports a large variety of programs and was heavily leveraged for the certification and operational support of the TPS for the Orbiter and, more recently, the development of the heat shield for CEV. This paper will provide more detail into the heritage of the facility. Unique attributes of the facility include a modular aerodynamically stabilized arc heater and independently controlled O2 and N2 for the test gases. When combining the O2 and N2 in a 23:77 mass ratio respectively the Earth s atmosphere is accurately simulated and via modification of this ratio the investigation of the effects of atomic oxygen on a material s response is possible. In the summer of 2010 a development effort was started to add CO2 as a third independently controlled test gas such that, when combined with N2, opens up the possibility of accurately simulating a Martian reentry environment. This paper will discuss the test facility, especially the arc heater, in more detail. Initial testing involved relatively low concentrations of CO2 combined with N2 for the primary purpose of gathering data to answer two pressing safety concerns. The first being the rate of production of carbon monoxide (CO) within the ejector vacuum system. The main concern was that CO can be flammable and possibly explosive at high enough concentrations and pressures. The hazard control during the development phase involved the use of injecting N2 inside the test chamber diffuser to dilute and reduce the concentration of any and all CO present. A residual gas analyzer (RGA) was used to determine the relative amount of CO in the exhaust gas and provide a conversion rate of CO2 to CO. This paper will discuss in more detail the results of the RGA data and the calculated conversion rate. The second safety concern addressed is the possible formation of hydrogen cyanide (HCN) and cyanide (CN). HCN would primarily be present in the cooling water while the CN would most probably condense onto the interior surfaces of the test chamber. Water samples and wipes of the test chamber surfaces were analyzed by an industrial hygienist for the presence of HCN and CN. His paper will discuss these results in more detail. Throughout this development effort measurements of the CO2:N2 flowfield were made with heat flux and pressure probes and with laser induced fluorescence (LIF) of the atomic oxygen. This paper will discuss these results

DelPapa, Steven V.↗

NASA NTRSDate not supplied

Measurement of Material Recession and Shock Standoff in Plasma Windtunnel using Neural Nets

Arcjets are plasma wind tunnels used to test the performance of heatshield materials for spacecraft atmospheric entry. These facilities present an extremely harsh flow environment with heat fluxes up to 109 W/m2 for up to 30 minutes. The plasma is low-temperature (∼1 eV) but high pressure (> 10 kPa) creating high-enthalpy supersonic flows similar to atmospheric entry conditions. Typically, material samples are measured before and after a test to characterize the total recession. However, this does not capture time-dependent effects such as material expansion and non-linear recession. This work will present new analysis of arcjet test videos which measure both the time-dependent 2D recession of the material samples and the shock standoff distance. The results show non-linear time-dependent effects are present for some conditions. The material and shock edges are extracted from the videos by training and applying a convolutional neural network. Due to the consistent camera settings, the machine learning model achieves high accuracy (± 2 px) relative to manually segmented images with only a small number of training frames (80).

Neural network↗

NASA NTRSDate not supplied

Measurement of material recession and shock standoff in plasma windtunnel using neural nets

Arcjets are plasma wind tunnels used to test the performance of heatshield materials for spacecraft atmospheric entry. These facilities present an extremely harsh flow environment with heat fluxes up to 10^9 W/m^2 for up to 30 minutes. The plasma is low-temperature (~1 eV) but high pressure (> 10 kPa) creating high-enthalpy supersonic flows similar to atmospheric entry conditions. Typically, material samples are measured before and after a test to characterize the total recession. However, this does not capture time-dependent effects such as material expansion and non-linear recession. This work will present new analysis of arcjet test videos which measure both the time-dependent 2D recession of the material samples and the shock standoff distance. New results showing non-linear material erosion rates will be highlighted. The material and shock edges are extracted from the videos by training and applying a convolutional neural network. Due to the consistent camera settings, the machine learning model achieves high accuracy (~99%) on new data with only a small number of training frames (~80). The new results will be discussed in the context of temperature dependent plasma-surface interaction.

Magnus A Haw↗