An Integrated RF Power Delivery and Plasma Micro-Thruster System for Nano-Satellites

Abstract

Progress in satellite technologies is ongoing and eventually finds applications back on Earth. Electric propulsion systems have been proven effective on large scale satellites (NASA DAWN) with better propellant efficiency than chemical or cold gas propulsion, and if miniaturized can be promising for long term operation of nano-satellites (e.g., CubeSats) in low Earth orbit or in deep space (NASA MarCO). However, the power supplies often used to power these electric thrusters, particularly those involving radiofrequency (RF) plasma, typically comprise power inefficient linear mode RF power amplifiers (e.g., class AB). These are simple systems designed to operate reliably under a wide range of loads for versatility, but they suffer low power efficiencies when operating at conditions significantly different from the nominal operating point. The required bulky and heavy thermal management components deem these electric propulsion systems impossible to fit on board nano-satellites. Here we present a compact and efficient switched mode dc-RF power inverter integrated with an electro-thermal plasma micro-thruster for nano-satellite (e.g., Cubesats) propulsion. The integrated system can serve as side panels and structural support of CubeSats, saving precious on-board volume for propellant and/or payloads. A complete assembly has been operationally tested in a space simulation system. This development opens a route for a new generation of power supplies applicable to the space sector, the microelectronics industry as well as the field of bioengineering.

Helicon-type radiofrequency plasma thrusters and magnetic plasma nozzles

“…It should be mentioned that the class-D amplifier is operational in the wide range of the frequency less than typically 1 MHz because of the switching loss of the transistors, while the class-E amplifier operational at higher range of the frequency is operational in a narrow range of the frequency than that of the class-D amplifier to realize the zero voltage switching under a LC resonance condition. These were tested in several helicon source and capacitive thruster experiments, where the driving frequency ranges from a few hundreds of kHz to several tens of MHz (Ziemba et al 2006;Ando et al 2010;Biggs et al 2015;Liang et al 2018). The switched rf power can be transferred to the load via a LC resonance circuit and the power would be controlled by the primary dc voltage.…”

An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster

“…The impedance was found not to vary significantly when the thruster is operated within its design range of power (20 W to 50 W) and argon gas flow (20 SCCM to 100 SCCM) At 40.68 MHz, this results in a ∼70 pF capacitor. Such direct impedance match has been successfully demonstrated for capacitive PR [31].…”

“…The technology to build suitable RF sources for the three lower ISM bands has been demonstrated and includes novel amplifier designs such as the Class-E [30]. Class-E amplifiers for the HF/VHF part of the spectrum have been constructed with 90% efficiency or better [31,32]. While the inductive PR thruster could in theory be designed to be powered by a microwave source, the strict restrictions of the cubesat platform make this choice a more challenging one due to generally lower efficiency achievable on these frequencies.…”

Commentary: On helicon thrusters: Will they ever fly?

“…The suitability criteria also include issues such as the allowed development timeframe and cost, the system's expected lifetime, and potential competitive advantages if successfully developed. There is on-going development work on RF thrusters of different types including the HT and the ICP, which aims at increasing performance and design based on space mission requirements; this includes improved designs of RF antenna, matching network, and RF power control, as shown in recent studies [22][23][24] including Godyak [1].…”