Dual Mode Operation of a Hydromagnetic Plasma Thruster to Achieve Tunable Thrust and Specific Impulse

TL;DR

This study introduces a pulsed hydromagnetic plasma thruster capable of dual mode operation with tunable thrust and specific impulse, demonstrated with nitrogen propellant, suitable for low Earth orbit applications.

Contribution

The paper presents the first demonstration of a hydromagnetic plasma thruster with switchable modes based on propellant flow dynamics, enabling adjustable performance parameters.

Findings

Exhaust velocities range from 10 km/s to 55 km/s.

Specific impulse varies from 2600 to 5600 seconds.

Thrust reaches up to 31 mN in burst mode.

Abstract

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.