The Experts below are selected from a list of 24774 Experts worldwide ranked by ideXlab platform
Mark A Cappelli - One of the best experts on this subject based on the ideXlab platform.
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dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
Journal of Applied Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in the very low Earth orbit. A dual mode operation is achieved by leveraging propellant gasdynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely, magneto-deflagration and magneto-detonation, respectively. These modes form the basis of using gasdynamics to enable responsive thruster performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes as gas is allowed to expand in the thruster, with exhaust velocities ranging from 10 to 55 km/s in the deflagration and detonation regimes, respectively. Simulations of the processed mass bit offer the first glimpse into possible thruster performance and trade-offs between Specific Impulse and thrust. An Impulse bit tunability of ∼22% is predicted, with differing propellant fill fractions when operating in a burst mode.
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dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
arXiv: Plasma Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in very low Earth orbit. Dual mode operation is achieved by leveraging propellant gas dynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely a magneto-deflagration and magneto-detonation respectively. These modes can be chosen by changing the time propellant is allowed to diffuse into the thruster based on the desired performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes, with exhaust velocities ranging from 10 km/s to 55 km/s in deflagration and detonation regimes, respectively. Simulations of the processed mass bit offers a first glimpse into possible thruster performance confirming a broad range and tradeoff between Specific Impulse (2600 - 5600 sec) and thrust (up to 31 mN) when operating in a burst mode.
Richard R. Hofer - One of the best experts on this subject based on the ideXlab platform.
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1 Efficiency Analysis of a High-Specific Impulse Hall Thruster
2016Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limite
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American Institute of Aeronautics and Astronautics Efficiency Analysis of a High-Specific Impulse Hall Thruster
2015Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limite
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efficiency analysis of a high Specific Impulse hall thruster
2013Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:*† Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiplycharged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limited range of Hall parameters.
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high Specific Impulse hall thrusters part 1 influence of current density and magnetic field
Journal of Propulsion and Power, 2006Co-Authors: Richard R. Hofer, Robert S. Jankovsky, Alec D GallimoreAbstract:A laboratory-model Hall thruster with a magnetic circuit designed for high-Specific Impulse (2000‐3000 s) was evaluated to determine how current density and magnetic field affect thruster operation. Results have shown for the first time that a minimum current density and optimum magnetic field shape exist at which efficiency will monotonically increase with Specific Impulse. At the nominal mass flow rate of 10 mg/s and between discharge voltages of 300 and 1000 V, total Specific Impulse and total efficiency ranged from 1600 to 3400 s and 51 to 61%, respectively. Comparison with a similar thruster showed how efficiency can be optimized for Specific Impulse by varying the shape of the magnetic field. Plume divergence decreased from a maximum of 48 deg at 400 V to a minimum of 35 deg at 1000 V, but increased between 300 and 400 V as the likely result of a large increase in discharge current oscillations. The breathing-mode frequency continuously increased with voltage, from 14.5 kHz at 300 V to 22 kHz at 1000 V, in contrast to other Hall thrusters where a sharp decrease of the breathing-mode frequency was found to coincide with increasing electron current and decreasing efficiency. These findings suggest that efficient, high-Specific Impulse operation was enabled through the regulation of the electron current with the applied magnetic field.
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high Specific Impulse hall thrusters part 2 efficiency analysis
Journal of Propulsion and Power, 2006Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:Performance and plasma measurements of a high-Specific Impulse (2000‐3000 s) Hall thruster were analyzed using a phenomenological performance model that accounted for a partially ionized plasma containing multiply charged ions. Anode efficiency over discharge voltages of 300‐900 V ranged from 57 to 69%, which corresponded to 89‐97% voltage utilization, 86‐90% mass utilization, 77‐81% current utilization, and 97‐99% charge utilization. Although the net decrease of efficiency due to multiply charged ions was at most 3%, the effects of multiply charged ions on the discharge current could not be neglected because the increase of the discharge current with voltage was primarily due to the increasing fraction of multiply charged ions. This and the fact that the maximum deviation of the electron current from its average value was only +5/−14% illustrated how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. The electron Hall parameter, defined by acceleration zone plasma properties, was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400 to 900 V.
Alec D Gallimore - One of the best experts on this subject based on the ideXlab platform.
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1 Efficiency Analysis of a High-Specific Impulse Hall Thruster
2016Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limite
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American Institute of Aeronautics and Astronautics Efficiency Analysis of a High-Specific Impulse Hall Thruster
2015Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limite
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efficiency analysis of a high Specific Impulse hall thruster
2013Co-Authors: Richard R. Hofer, Alec D GallimoreAbstract:*† Performance and plasma measurements of the high-Specific Impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300-900 V, the results showed that although the net decrease of efficiency due to multiplycharged ions was only 1.5-3.0%, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300-900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14%. These findings revealed how efficient operation at high-Specific Impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300-900 V, the voltage utilization ranged from 89-97%, the mass utilization from 86-90%, and the current utilization from 77-81%. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400-900 V. These results confirmed our claim that efficient operation can be achieved only over a limited range of Hall parameters.
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Maximizing Payload Mass Fractions of Spacecraft for Interplanetary Electric Propulsion Missions
Journal of Spacecraft and Rockets, 2006Co-Authors: Prashant Patel, Daniel J Scheeres, Alec D GallimoreAbstract:Optimization of a spacecraft’s interplanetary trajectory and electric propulsion system remains a complex and difficult problem. Simultaneously solving for the optimal trajectory, power level, and exhaust velocity can be difficult and time consuming. If the power system’s technology level is unknown, multiple optimizations must be conducted to map out the trade space. Trajectories with constant-power, solar-power, variable-Specific-Impulse, and constant-Specific-Impulse low-thrust propulsion systems are analyzed and optimized. The technological variables, power system Specific mass, propellant tank coefficient, structural coefficient, and the launch vehicle are integrated into the cost function allowing for maximization of the payload mass fraction. A classical solution is reviewed that allows trade studies to be conducted for constant-power, variable exhaust velocity systems. The analysis is expanded to include bounded-power constant Specific Impulse systems and solar electric propulsion spacecraft with constant and variable exhaust velocity engines. The cost function and mass fractions are dimensionless to allow for scaling of the spacecraft systems.
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high Specific Impulse hall thrusters part 1 influence of current density and magnetic field
Journal of Propulsion and Power, 2006Co-Authors: Richard R. Hofer, Robert S. Jankovsky, Alec D GallimoreAbstract:A laboratory-model Hall thruster with a magnetic circuit designed for high-Specific Impulse (2000‐3000 s) was evaluated to determine how current density and magnetic field affect thruster operation. Results have shown for the first time that a minimum current density and optimum magnetic field shape exist at which efficiency will monotonically increase with Specific Impulse. At the nominal mass flow rate of 10 mg/s and between discharge voltages of 300 and 1000 V, total Specific Impulse and total efficiency ranged from 1600 to 3400 s and 51 to 61%, respectively. Comparison with a similar thruster showed how efficiency can be optimized for Specific Impulse by varying the shape of the magnetic field. Plume divergence decreased from a maximum of 48 deg at 400 V to a minimum of 35 deg at 1000 V, but increased between 300 and 400 V as the likely result of a large increase in discharge current oscillations. The breathing-mode frequency continuously increased with voltage, from 14.5 kHz at 300 V to 22 kHz at 1000 V, in contrast to other Hall thrusters where a sharp decrease of the breathing-mode frequency was found to coincide with increasing electron current and decreasing efficiency. These findings suggest that efficient, high-Specific Impulse operation was enabled through the regulation of the electron current with the applied magnetic field.
Thomas Underwood - One of the best experts on this subject based on the ideXlab platform.
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dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
Journal of Applied Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in the very low Earth orbit. A dual mode operation is achieved by leveraging propellant gasdynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely, magneto-deflagration and magneto-detonation, respectively. These modes form the basis of using gasdynamics to enable responsive thruster performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes as gas is allowed to expand in the thruster, with exhaust velocities ranging from 10 to 55 km/s in the deflagration and detonation regimes, respectively. Simulations of the processed mass bit offer the first glimpse into possible thruster performance and trade-offs between Specific Impulse and thrust. An Impulse bit tunability of ∼22% is predicted, with differing propellant fill fractions when operating in a burst mode.
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dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
arXiv: Plasma Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in very low Earth orbit. Dual mode operation is achieved by leveraging propellant gas dynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely a magneto-deflagration and magneto-detonation respectively. These modes can be chosen by changing the time propellant is allowed to diffuse into the thruster based on the desired performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes, with exhaust velocities ranging from 10 km/s to 55 km/s in deflagration and detonation regimes, respectively. Simulations of the processed mass bit offers a first glimpse into possible thruster performance confirming a broad range and tradeoff between Specific Impulse (2600 - 5600 sec) and thrust (up to 31 mN) when operating in a burst mode.
William Riedel - One of the best experts on this subject based on the ideXlab platform.
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dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
Journal of Applied Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in the very low Earth orbit. A dual mode operation is achieved by leveraging propellant gasdynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely, magneto-deflagration and magneto-detonation, respectively. These modes form the basis of using gasdynamics to enable responsive thruster performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes as gas is allowed to expand in the thruster, with exhaust velocities ranging from 10 to 55 km/s in the deflagration and detonation regimes, respectively. Simulations of the processed mass bit offer the first glimpse into possible thruster performance and trade-offs between Specific Impulse and thrust. An Impulse bit tunability of ∼22% is predicted, with differing propellant fill fractions when operating in a burst mode.
-
dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and Specific Impulse
arXiv: Plasma Physics, 2021Co-Authors: Thomas Underwood, William Riedel, Mark A CappelliAbstract:We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and Specific Impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in very low Earth orbit. Dual mode operation is achieved by leveraging propellant gas dynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely a magneto-deflagration and magneto-detonation respectively. These modes can be chosen by changing the time propellant is allowed to diffuse into the thruster based on the desired performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes, with exhaust velocities ranging from 10 km/s to 55 km/s in deflagration and detonation regimes, respectively. Simulations of the processed mass bit offers a first glimpse into possible thruster performance confirming a broad range and tradeoff between Specific Impulse (2600 - 5600 sec) and thrust (up to 31 mN) when operating in a burst mode.
