Abstract:A single-stage pulsed inductive plasma accelerator was modelled as an inductive mass-driver, with the plasma treated as a rigid slug that acts as the armature. We derive a set of coupled dynamic-circuit equations, with dimensionless coefficients. The functional form of the mutual inductance profile, M(z), was calculated using the magnetic field solver QuickField; an exponential form for M(z) was found to be accurate for a variety of coil-slug geometries. A parametric study of the solutions to the equations was… Show more
“…It is noted that the efficiencies are quite low, despite the simplifying assumptions in the model. However, only about 7%-8% of the energy is lost to ohmic dissipation, so the energy not utilized for acceleration can arguably be recovered through inductive recapture [22].…”
Section: Resultsmentioning
confidence: 99%
“…All of these parameters are highly dependent on the coil geometry, propellant distribution, and effective propellant distance from the coil. Typically, in modeling of inductively coupled thrusters, the aforementioned RLC model is modified to include a secondary coil (the plasma) which is coupled to the primary coil through a mutual inductance [15], [18], [22]. These models assume that the mutual inductance follows a function of the form L coil exp(−z/2z decouple ), where L coil is the coil inductance and z decouple is some empirically determined decoupling distance.…”
Section: Modelmentioning
confidence: 99%
“…One of the main drawbacks of inductively coupled thrusters is that the mutual inductance between the primary coil(s) and plasma appears to decrease exponentially [15], [16], [18], [22] with distance as the plasma is accelerated, thus making efficient acceleration challenging. One of the keys to unlocking the potential in these devices is to maximize the work done by the magnetic field pressure on the plasma.…”
Section: Introductionmentioning
confidence: 99%
“…While it has been investigated since at least the 1960s, only recently have efforts been made to model the acceleration process using simple coupled circuit and momentum equations [22]. A conical theta pinch consists of a capacitor bank, transmission line, external switch, and single-turn coil.…”
Pulsed electromagnetic plasma accelerators and, more specifically, those that are inductively coupled potentially have high thrust density, high specific impulse, and long thruster lifetime since there is limited contact between the plasma and coil(s). One-dimensional electromechanical models of these thrusters, which are important for identifying important relationships among circuit parameters, coil geometry, and plasma, usually make the same underlying assumption about the mutual inductance between the primary coil and induced plasma current, based on empirical evidence. This approach is inconvenient for arbitrary coil geometries and if trying to make comparisons with directly coupled plasma accelerators, such as coaxial plasma guns. A generalized slug model was developed in which RLC circuit equations are coupled to a mechanical force equation. The acceleration term was made to be thruster and geometry dependent, so that the same model could be used to study both coaxial plasma guns and conical theta pinches. The calculated mutual inductance from the coil model exhibits the same exponential falloff with distance as in previous models and experiments. Efficiency (plasma kinetic energy divided by initial capacitor bank energy) and exhaust velocity were calculated for the conical theta pinch coil over a 5-D parameter space. For the cases with highest efficiencies, peak coaxial plasma accelerator efficiencies were calculated under certain operating constraints. It was found that, while coaxial plasma accelerators are generally more efficient, under certain conditions, the conical theta pinch performance is higher.
“…It is noted that the efficiencies are quite low, despite the simplifying assumptions in the model. However, only about 7%-8% of the energy is lost to ohmic dissipation, so the energy not utilized for acceleration can arguably be recovered through inductive recapture [22].…”
Section: Resultsmentioning
confidence: 99%
“…All of these parameters are highly dependent on the coil geometry, propellant distribution, and effective propellant distance from the coil. Typically, in modeling of inductively coupled thrusters, the aforementioned RLC model is modified to include a secondary coil (the plasma) which is coupled to the primary coil through a mutual inductance [15], [18], [22]. These models assume that the mutual inductance follows a function of the form L coil exp(−z/2z decouple ), where L coil is the coil inductance and z decouple is some empirically determined decoupling distance.…”
Section: Modelmentioning
confidence: 99%
“…One of the main drawbacks of inductively coupled thrusters is that the mutual inductance between the primary coil(s) and plasma appears to decrease exponentially [15], [16], [18], [22] with distance as the plasma is accelerated, thus making efficient acceleration challenging. One of the keys to unlocking the potential in these devices is to maximize the work done by the magnetic field pressure on the plasma.…”
Section: Introductionmentioning
confidence: 99%
“…While it has been investigated since at least the 1960s, only recently have efforts been made to model the acceleration process using simple coupled circuit and momentum equations [22]. A conical theta pinch consists of a capacitor bank, transmission line, external switch, and single-turn coil.…”
Pulsed electromagnetic plasma accelerators and, more specifically, those that are inductively coupled potentially have high thrust density, high specific impulse, and long thruster lifetime since there is limited contact between the plasma and coil(s). One-dimensional electromechanical models of these thrusters, which are important for identifying important relationships among circuit parameters, coil geometry, and plasma, usually make the same underlying assumption about the mutual inductance between the primary coil and induced plasma current, based on empirical evidence. This approach is inconvenient for arbitrary coil geometries and if trying to make comparisons with directly coupled plasma accelerators, such as coaxial plasma guns. A generalized slug model was developed in which RLC circuit equations are coupled to a mechanical force equation. The acceleration term was made to be thruster and geometry dependent, so that the same model could be used to study both coaxial plasma guns and conical theta pinches. The calculated mutual inductance from the coil model exhibits the same exponential falloff with distance as in previous models and experiments. Efficiency (plasma kinetic energy divided by initial capacitor bank energy) and exhaust velocity were calculated for the conical theta pinch coil over a 5-D parameter space. For the cases with highest efficiencies, peak coaxial plasma accelerator efficiencies were calculated under certain operating constraints. It was found that, while coaxial plasma accelerators are generally more efficient, under certain conditions, the conical theta pinch performance is higher.
“…While Eq. 8 was developed for a planar coil geometry, it has been found to accurately represent the axial inductive coupling behavior of ring-shaped and conical geometries as well [16,17]. We nondimensionalize Eq.…”
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