A review of low-power applied-field magnetoplasmadynamic thruster research and the development of an improved performance model

Abstract

Numerous thrust and voltage models for applied-field magnetoplasmadynamic thrusters (AF-MPDTs) exist, however, all have been formulated using data for conventionally high current AF-MPDTs. To address a perceived gap in knowledge about smaller thrusters, a review of low-power applied-field magnetoplasmadynamic thruster research and published thrust and voltage models is presented. Using available experimental data limited to a low-power high magnetic field strength regime, a database of pertinent physical and operational parameters is established and used in a comparative study to evaluate the accuracy of published performance models. Statistical analysis of the models was used to create a corrected low-power AF-MPDT performance model. When applied to the database, an improvement in model accuracy is achieved. It is found that AF-MPDTs in the low-power regime with high applied magnetic field strengths can present a feasible alternative to other electric propulsion methods. However, the resulting sensitivity of achievable performance to physical and operational parameters requires careful design and optimization for a given mission.

Unveiling the Future: A Survey of Electric Propulsion Systems and their Pivotal Role in Shaping the Next Frontier of Space Exploration

“…Thrusters that rely on self-generated magnetic fields are known as self-field MPD thrusters, while those utilizing externally generated axial magnetic fields are referred to as applied-field MPD thrusters. Applied field MPD thrusters operating at lowdischarge current have received much attention in terms of research and development due to their higher magnetic fields for potential future low-earth orbit and deep space missions (Zheng et al, 2021;Balkenhohl et al, 2023). However, the erosion of the cathode has been identified as one of the limiting factors that affect the operational life of the thruster (Peng et al, 2020).…”

Magnetic Disturbance Rejection in Spacecraft using Electromagnetic Propulsion

“…There exist numerous models of AF-MPDTs. In this thesis we base our model on that in [13], where the proposed model accurately encompasses the performance of low power AF-MPDTs (up to 10 kW). The total thrust of an AF-MPDT is comprised of three different components [14]:…”

A Central-Cathode Electrostatic Thruster Featuring a High-Temperature Superconducting Applied Field Module

“…As a result, low power AF-MPDT research was deferred in favour of forms of electric propulsion [55], and AF-MPDT technology was not developed to the same extent. Instead of being regarded as thrusters for high specific impulse missions, this has led to the current view: that AF-MPDTs will be important thrusters for future missions requiring high thrust density, high specific impulse and high power operation [37], [56], [57], with only a few AF-MPD thrusters targeting low power regimes but unable to compete with electrostatic thrusters in terms of maturity or electrical efficiency [54], [58], [59].…”

“…This means that charged particles must cross fewer field lines in order to establish a current between cathode and anode, improving the probability of thruster ignition. However, AF-MPDT thrust models [8], [42], [59] predict that thrust scales with anode radius and this means that in high current regimes, including the anode ring may result in a loss of thrust. Secondly, it encourages propellant flow towards the anode, raising the number density of neutral gas in the region close to the cathode.…”

“…Firstly, there are fundamental limits on low power operation in that the thruster will not ignite below a certain discharge voltage. Minimum discharge voltage depends on other operating conditions, such as mass flow rate and applied field [59]. With a rarified plasma in an axial magnetic field, electrons must diffuse across magnetic field lines in order to establish an anodecathode current.…”