Development of a Hall-Effect Thruster Operating on Molecular Propellant: 1-Fluoronaphthalene
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Date
2025
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University of Southampton
Abstract
Modern small satellites demand precise orbit control and low mission cost. Electric propulsion (EP) supports these goals by providing high exhaust velocity in compact, efficient systems. Among EP technologies, Hall-effect thrusters (HETs) are widely used because they produce useful thrust at modest power levels with relatively simple and robust hardware.
Propellant selection strongly influences cost, storage complexity, and handling risk. Conventional noble-gas propellants each present limitations: xenon is expensive and supply-constrained; krypton typically yields lower performance and faces price and supply volatility; and argon, though abundant and inexpensive, performs poorly in HETs. These factors motivate interest in condensable alternatives.
However, molecular propellants can dissociate and generate fragment ions, creating additional electron-energy losses that may alter the ion distribution and increase plume divergence (the lateral spreading of the exhaust). For low-power HETs, the significance of these effects remains insufficiently quantified.
In this context, the present work investigates whether 1-fluoronaphthalene can be reliably vaporised, delivered, and used as a propellant in a low-power HET, and whether it can provide stable operation with acceptable performance.
Description
The purpose of this dissertation is to assess whether a 200-W Hall-effect thruster (HET) can operate on 1-fluoronaphthalene and to quantify the expected thrust, specific impulse, and erosion risks. To this end, we integrate a newly developed cartridge-heated vaporiser with an existing low-power HET (YC-200) from prior work. The methodology combines ideal and fragmentation-weighted performance modelling based on electron-ionisation mass spectra with a calculated correction; Larmor-radius assessments of electron and ion magnetisation; CFD-guided anode design selection; and thermal verification of the vaporiser in both ambient and vacuum environments.
Under fixed beam conditions, xenon is predicted to deliver 18.86 mN of thrust and 2140 s specific impulse. Among molecular candidates, adamantane yields 19.2 mN and 2101 s, while 1-fluoronaphthalene offers 19.90 mN and 2028 s ideally; 17.61 mN and 1795 s when weighted by composition; and a fully corrected thrust and specific impulse of 15.03 mN and 1533 s— the best overall performance of the molecular propellants evaluated. In vacuum testing, the vaporiser reached 250 °C within 25 minutes at 60 V and 0.60 A, exhibiting uniform heating. The anode exit remained near ambient temperature, indicating a cold interface during integrated operation.
Overall, the results show that 1-fluoronaphthalene is a promising dense, storable propellant and that the vaporiser enables clean, stable gas-phase delivery suitable for low-power HETs. By combining the previously developed capillary feed system with the new cartridge-heated vaporiser on the YC-200, this work establishes a practical propellant-feed architecture for low-power HET operation on 1-fluoronaphthalene.
Keywords
electric propulsion, rocket propulsion, satellite propulsion, space systems engineering