An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster

Abstract

The "cubesat" form factor has been adopted as the defacto standard for a cost effective and modular, nano-satellite platform. Many commercial options exist for nearly all components required to build such satellite; however, there is a limited range of thruster options that suit the power and size restrictions of a cubesat. Based on the prior work on the "Pocket Rocket" electro-thermal capacitively-coupled radiofrequency (RF) plasma thruster operating at 13.56 MHz, a new design is proposed which is based on an inductively-coupled radiofrequency plasma system operating at 40.68 MHz. The new thruster design, including a compact and efficient radiofrequency matching network adjacent to the plasma cavity, is presented, together with the first direct thrust measurements using argon as the propellant with the thruster immersed in vacuum and attached to a calibrated thrust balance. These initial results of the unoptimized first proof of concept indicate an up to 40% instantaneous thrust gain from the plasma compared to the cold gas thrust: typical total thrust at 100 SCCM of argon and 50 W RF power is ∼1.1 mN.

Current-Free Electric Double Layer in a Small Collisional Plasma Thruster Nozzle Simulation

“…The present simulations have been limited to a narrow range of external parameters; future studies will investigate the scaling of such DLs to initiate an experimental validation: although direct measurement of the localized ion acceleration would be challenging in small nozzles, experimental investigation of the plasma confinement mode may be possible using optical diagnostics. Recent demonstration of direct thrust measurement with increased sensitivity in the 0.1-1 mN range for a new prototype of such electrothermal thruster [57] suggests that additional experimental testing using this complimentary non-intrusive diagnostic can soon be envisaged.…”

Comparison of Submillinewton Thrust Measurements Between a Laser Interferometer and a Load Cell on a Pendulum Balance

“…The vessel is pumped down to a base pressure of about 10 −6 using the 70 m 3 /h scroll and 1,800 l/s turbomolecular pumps but not the cryogenic pump. Wombat is routinely used for the experimental testing of various types of thrusters and their propellant and electric subsystems (Tsifakis et al, 2020) and is equipped with a thrust balance validated in-house (Charles et al, 2013;Charles et al, 2016) and in a number of laboratories (Pottinger et al, 2011;Takahashi et al, 2011).…”

Naphthalene as a Cubesat Cold Gas Thruster Propellant

“…Naphthalene is also toxic to humans and nature, in particular aquatic life. To FIGURE 4 | Diagram of the naphthalene cold gas thruster mounted in the Wombat space simulation chamber thrust balance [17][18][19]. Not seen in the diagram are the feed through connections to valve control, heating elements, and thermocouples.…”

“…The thrust measurements were conducted in the previously described Wombat space simulation chamber [17,18] using a high sensitivity thrust balance [19], shown in Figure 4. This balance consists of a four arm pendulum suspended frame.…”

“…When a force is applied to the frame by the thruster, the pendulum starts oscillating. This oscillation is dampened by a previously described magnetic damper [19]. The time constant of the dampening system is in the order of a few seconds.…”