Roger Myers

• PhD
• Consultant at R Myers Consulting

Hall effect thrusters operating at power levels in excess of several hundreds of kilowatts have been identified as enabling technologies for applications such as lunar tugs, large satellite orbital transfer vehicles, and solar system exploration. These large thrusters introduce significant testing challenges due to the propellant flow rate exceedin...

Findings and Recommendations of the 11-member National Academies' Committee on 'Space Nuclear Propulsion Technologies,' as a result of their 9-month study, are identified and characterized. in this report. Scope and focus of the study was to assess programmatic and technical issues associated with in-space nuclear thermal propulsion (NTP) and nucle...

The use of Electric Propulsion (EP) on satellites for commercial, defense, and space science missions has been increasing in recent decades, from the first successful operation in 1964 aboard the Zond-2 spacecraft to the present day. This paper provides an overview of the technological and commercial development of EP systems that have been deploye...

The use of electric propulsion for commercial and research purposes has been gaining terrain in the past few years. The focus of this paper is the technological and commercial development of electric propulsion systems since 1993, the year when the first commercial satellite with an EP system was launched. Since then, 248 satellites with EP systems...

In this paper, we review the expansion process of EP in the last 24 years. To do so, we focus on four particular spacecraft niches: (1) communication satellites in GEO, (2) satellites in LEO, (3) interplanetary or deep space missions, and (4) small satellite platforms under 100 kg. For each niche, we present statistics showing the chronological inc...

Future human exploration missions to Mars are being studied by NASA and industry. Several approaches to the Mars mission are being examined that use various launch vehicle configu-rations and different types of propulsion for the various phases of the mission.. Understand-ing the key impacts of key systems being considered for both cargo transfer a...

This study examines the impact of the launch capabilities provided by the planned Space Launch System (SLS) Block 2 vehicle on the solar electric propulsion (SEP) power levels required for large cargo prepositioning missions to Mars orbit. Our analysis shows that the additional launch capability planned for the SLS vehicle enables a dramatic reduct...

There is growing consensus within the international space community that the surface of Mars is the ultimate destination for human exploration efforts over the next two decades. As this consensus solidifies, the focus will turn to the necessary steps and associated capabilities that will be required to execute such a challenging mission. It is desi...

Aerojet Rocketdyne has completed mission analysis trade studies to support near-term NASA cislunar exploration mission concepts by comparing cargo delivery to the EarthMoon Lagrange points (EML1 or EML2) using a solar electric propulsion (SEP) stage (or “tug”) versus the most efficient all-chemical approach. The study examined the relationship betw...

Integration of pulsed plasma thruster (PPT) onboard spacecraft requires the evaluation of potential plume/spacecraft interactions. Important findings are summarized of our experimental and modeling plume investigations of rectangular-geometry Teflon® PPTs. Initial studies of the Lincoln Experimental Satellite 8/9 PPT plume used time-of-flight analy...

The Primex Aerospace Company has developed a hollow cathode assembly (HCA) for Hall thruster applications. The technical basis for its design is the NASA HCA, which is flight qualified for the Space Station plasma contactor mission. The primary objective of the Primex development effort is to significantly improve the manufacturability of the NASA...

A hollow cathode based plasma contactor will be flown on the international space station to control the station's potential to within +/-40 V of the local ionosphere. Extensive testing of the plasma contactor has been conducted in vacuum facilities at the NASA Lewis Research Center. Significant performance differences were observed between tests of...

Solar electric propulsion technology is currently being used for geostationary satellite station keeping. Analyses show that electric propulsion technologies can be used to obtain additional increases in payload mass by using them to perform part of the orbit transfer. Three electric propulsion technologies are examined at two power levels for geos...

The International Space Station (ISS) program is developing a plasma contactor to mitigate the harmful effects of charge collection on the station's large photovoltaic arrays. The purpose of the present test was to examine the effects of charge collection on the solar array electrical circuit and to verify the effectiveness of the plasma contactor....

Pulsed Plasma Thrusters (PPT's) are currently baselined for the Air Force Mightysat II.1 flight in 1999 and are under consideration for a number of other missions for primary propulsion, precision positioning, and attitude control functions. In this work, PPT plumes were characterized to assess their contamination characteristics. Diagnostics inclu...

Solar Electric Propulsion (SEP) has been shown to increase net geosynchronous spacecraft mass when used for station keeping and final orbit insertion. The impact of launch vehicle selection and power level on the benefits of this approach were examined for 20 and 25 kW systems launched using the Ariane 5, Atlas IIAR, Long March, Proton, and Sea Lau...

Pulsed Plasma Thrusters (PPTS) are a new option for attitude control of a small spacecraft and may result in reduced attitude control system (ACS) mass and cost. The primary purpose of an ACS is to orient the spacecraft to the desired accuracy in inertial space. The ACS functions for which the PPT system will be analyzed include disturbance torque...

A 2.3 kW Breadboard Power Processing Unit (BBPPU) was developed as part of the NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) Program. The NSTAR program will deliver an electric propulsion system based on a 30 cm xenon ion thruster to the New Millennium (NM) program for use as the primary propulsion system for the initial N...

Anode power deposition is a dominant power loss mechanism for arcjets and magnetoplasmadynamic (MPD) thrusters. In this study, a free burning arc experiment was operated at pressures and current densities similar to those in arcjets and MPD thrusters in an attempt to identify the physics controlling this loss mechanism. Use of a free burning arc al...

Pulsed plasma thrusters (PPT's) offer the combined benefits of extremely low average electric power requirements (1 to 150 W), high specific impulse (approximately 1000 s), and system simplicity derived from the use of an inert solid propellant. Potential applications range from orbit insertion and maintenance of small satellites to attitude contro...

Tests were performed to establish 30-cm ion thruster plume impacts, including plume characterizations via near and farfield ion current measurements, contamination, and sputtering assessments. Current density measurements show that 95% of the beam was enclosed within a 22 deg half-angle and that the thrust vector shifted by less than 0.3 deg during...

A thrust stand was modified, and a primary calibration technique was developed to evaluate the performance of applied-field pulsed magnetoplasmadynamic thrusters (MPDTs) for 10 kW class solar electric orbit transfer vehicle (SEOTV) missions. The NASA Lewis Research Center (LeRC) 30 kW thrust stand was modified to accept high current pulses delivere...

Solar electric propulsion (SEP) technology is already being used for geostationary satellite stationkeeping to increase payload mass. By using this same technology to perform part of the orbit transfer additional increases in payload mass can be achieved. Advanced chemical and N2H4 arcjet systems are used to increase the payload mass by performing...

Eight magnetoplasmadynamic thruster configurations were tested with argon propellant at power levels between 20-130 kW to study the effects of geometry and applied magnetic field strength on thruster performance. The discharge voltage, thrust efficiency, and specific impulse increased monotonically with increasing applied-Field strength for all geo...

A cathode in an MPD thruster has an internal heater and utilizes low work function material. The cathode is preheated to operating temperature, and then the thruster is fired by discharging a capacitor bank in a pulse forming network.

Advanced chemical and low power electric propulsion offer attractive options for small satellite propulsion. Applications include orbit raising, orbit maintenance, attitude control, repositioning, and deorbit of both Earth-space and planetary spacecraft. Potential propulsion technologies for these functions include high pressure Ir/Re bipropellant...

Xenon ion propulsion systems are being developed by NASA Lewis Research Center and the Jet Propulsion Laboratory to provide flight qualification and validation for planetary and earth-orbital missions. In the ground-test element of this program, light-weight (less than 7 kg), 30 cm diameter ion thrusters have been fabricated, and preliminary design...

Pulsed magnetoplasmadynamic (MPD) thrusters offer ease of power scaling, reduced test facility requirements, and the potential of launch cost reductions through efficient high specific impulse operation at power levels which make them attractive for several primary propulsion missions. This work addresses the operational design of 10 kW class pulse...

Stationary Plasma Thrusters (SPT's) are being investigated for application to a variety of near-term missions. This paper presents the results of a preliminary study of the thruster plume characteristics which are needed to assess spacecraft integration requirements. Langmuir probes, planar probes, Faraday cups, and a retarding potential analyzer w...

Recent interest in solar electric orbit transfer vehicles (SEOTV's) has prompted a reevaluation of pulsed magnetoplasmadynamic (MPD) thruster systems due to their ease of power scaling and reduced test facility requirements. In this work the use of externally heated cathodes was examined in order to extend the lifetime of these thrusters to the 100...

Pulsed magnetoplasmadynamic (MPD) thruster systems were analyzed for application to solar-electric orbit transfer vehicles at power levels ranging from 10 to 40 kW. Potential system level benefits of pulsed propulsion technology include ease of power scaling without thruster performance changes, improved transportability from low power flight exper...

Three electromagnetic propulsion technologies, solid propellant pulsed plasma thrusters (PPT), magnetoplasmadynamic (MPD) thrusters, and pulsed inductive thrusters (PIT), were developed for application to auxiliary and primary spacecraft propulsion. Both the PPT and MPD thrusters were flown in space, though only PPT's were used on operational satel...

A single thruster geometry with argon and hydrogen propellants under the same operating conditions was tested to determine the effects of propellant choice on thruster performance and power deposition. It is found that operating on hydrogen extended the stable operating range to higher values of applied magnetic field range. The extended operating...

A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrus...

Emission spectroscopy measurements were made of the plasma flow inside the nozzle of a 1 kW class arcjet thruster. The thruster propellant was a hydrogen-nitrogen mixture used to simulate fully decomposed hydrazine. The 0.25 mm diameter holes were drilled into the diverging section of the tungsten thruster nozzle to provide optical access to the in...

The NASA Lewis Research Center (LeRC) conducts and directs an electric propulsion research and technology program aimed at providing high-performance electric propulsion system options for a broad range of near and far-term missions. This evolutionary program emphasizes the development of propulsion systems for three classes of missions: (1) near t...

Component erosion and material deposition sites were identified and analyzed during tests of various configurations of 100 kW class, applied‐field, water‐cooled magnetoplasmadynamic (MPD) thrusters. Severe erosion of the cathode and the boron nitride insulator was observed for the first series of tests, which was significantly decreased by reducing...

Three cylindrical applied-field magnetoplasmadynamic thrusters were tested with argon propellant over a broad range of operating conditions to establish empirical scaling laws for thruster performance. Argon flow rates, discharge currents, and applied-field strengths were varied between 0.025 and 0.14 g/s, 750 to 2000 A, and 0.034 to 0.20T, respect...

Anode power deposition is the principal performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents,...

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Electric propulsion flight and technology demonstrations conducted in the USA, Europe, Japan, China, and USSR are reviewed with reference to the major flight qualified electric propulsion systems. These include resistojets, ion thrusters, ablative pulsed plasma thrusters, stationary plasma thrusters, pulsed magnetoplasmic thrusters, and arcjets. Ev...

A successful attempt has been made to gain optical access to the inside of an arcjet nozzle without changing internal thruster design or affecting performance characteristics. Both fiber optics and small open holes have been used for emission spectroscopy of a small, confined, high-temperature plasma source. The plasma was found to be in a highly n...

Performance and lifetime requirements for multimegawatt magnetoplasmadynamic (MPD) thrusters were used to establish a baseline 2.5 MW thruster design. The chamber surface power deposition resulting from current conduction, plasma and surface radiation, and conduction from the hot plasma was then evaluated to establish the feasibility of thruster op...

The topics are presented in viewgraph form and include the following: in house program elements; performance measurements; applied-field magnetoplasmadynamic (MPD) thruster performance scaling; MPD thruster technology; thermal efficiency scaling; anode fall voltage measurements; anode power deposition studies; MPD thruster plasma modeling; MPD thru...

An experimental examination of energy deposition in self-field, coaxial plasma thrusters revealed that the thrust efficiency ranged from 2-9 percent and that the dominant losses resulted from electrode heating and propellant ionization. Sensible enthalpy and radiative losses were negligible. Thruster specific impulse increased with current, ranging...

Mass-loss and surface-temperature measurement, filter photography, and scanning electron microscope surface characterization were used to study cathode phenomena in a steady-state, self-field magnetoplasmadynamic thruster operated at power levels between 15 and 30 kW. The steady-state cathode temperature was found to be above 3000 K over most of it...

MPD thrusters have demonstrated between 2000 and 7000 sec specific impulse at efficiencies approaching 40 percent, and have been operated continuously at power levels over 500 kW. These demonstrated capabilities, combined with the simplicity and robustness of the thruster, make them attractive candidates for application to both unmanned and manned...

Piloted Mars Mission Requirements of relatively short trip times and low initial mass in Earth orbit as identified by the NASA Space Exploration Initiative, indicate the need for multimegawatt electric propulsion systems. The design considerations and results for two thruster types, the argon ion, and hydrogen magnetoplasmadynamic thrusters, are ad...

Eight MPD thruster configurations were used to study the effects of applied-field strength, propellant, and facility pressure on thruster performance. Vacuum facility background pressures higher than about 0.12 Pa were found to significantly influence thruster performance and electrode power deposition. Thrust efficiency and specific impulse increa...

Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied-field MPD thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no meas...

Anode heat flux measurements of a water cooled segmented anode applied-field MPD thruster were made to investigate anode heat transfer phenomena. Pure argon and argon-hydrogen mixtures were used as propellants for a variety of thruster currents, propellant mass flow rates, and axial applied magnetic field strengths. The thruster was operated in two...

Electric propulsion has applications for orbit raising, maneuvering of large space systems, and interplanetary missions. These missions involve propulsion power levels from tenths to tens of megawatts, depending upon the application. General facility requirements for testing high power electric propulsion at the component and thrust systems level a...

Performance of four hollow cathode configurations with low work function inserts was evaluated in a steady-state 100 kW class applied magnetic field magnetoplasmadynamic (MPD) thruster. Two of the configurations exhibited stable discharge current attachment to the low work function inserts of the hollow cathodes. A maximum discharge current of 2250...

An experimental program initiated to characterize the near field of an arcjet plume is described. The complete emission spectrum from 3200 to 7200 A at the nozzle exit plane detected the electronically excited species N2, N2(+), NH, and H, indicating excitation, dissociation, ionization, and recombination in the nozzle. Axial intensity profiles ind...

Three applied-field magnetoplasmadynamic (MPD) thruster geometries were tested with argon propellant to establish the influence of electrode geometry on thruster performance. The thrust increased approximately linearly with anode radius, while the discharge and electrode fall voltages increased quadratically with anode radius. All these parameters...

An experimental investigation of a low power arcjet plume was conducted using emission spectroscopy. A laboratory model arcjet incorporating a segmented anode was run on simulated hydrazine at a flow rate of 5 x 10(exp -5) kg/s. The complete visible spectrum measured in the exit plane of the arcjet showed the presence of N2, N2(+), NH, and H. Radia...

A diagnostics facility for MPD thruster plume measurements was built and is currently undergoing testing. The facility includes electrostatic probes for electron temperature and density measurements, Hall probes for magnetic field and current distribution mapping, and an imaging system to establish the global distribution of plasma species. Prelimi...

Performance of a 100 kW, applied field magnetoplasmadynamic (MPD) thruster was evaluated and sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. Thermal efficiencies as high as 60 percent, thrust efficiencies up to 21 percent, and specific impulses of up to 1150 s were attained wi...

Mass loss and surface temperature measurements, filter photography and SEM surface characterization are used to study cathode phenomena in a steady state self-field MPD thruster operated at power levels between 15 and 30 kW. The equilibrium cathode temperature is found to be approximately 3200 K over most of its length, for which evaporation and th...

The energy deposition and acceleration mechanisms in the electrothermal-electromagnetic hybrid regime of coaxial plasma thruster operation are examined both theoretically and experimentally. Theoretical results show that the major trade-offs in the hybrid regime are between efficiency and specific impulse: increasing the influence of electromagneti...

The Energetic Transient Array (ETA) is a mission, proposed by the Center for Space Research (CSR) at MIT, to set up an interplanetary constellation of six microsatellites for Gamma Ray Burst (GRB) astrometry. The micro-satellites will be deployed into distinct heliocentric orbits by a carrier spacecraft which will be propelled by a stationary plasm...

Pulsed Plasma Thrusters (PPTs) are finding renewed user appeal due to the growth in small satellite applications. PPTs are especially well suited to small satellite applications because they are simple, low-mass, and high Isp propulsion systems. The solid Teflon fuel allows for a self-contained, inert and stable propellant system. With a power draw...