Joseph Lukas

Electric propulsion for small satellites

Propulsion is required for satellite motion in outer space. The displacement of a satellite in space, orbit transfer and its attitude control are the task of space propulsion, which is carried out by rocket engines. Electric propulsion uses electric energy to energize or accelerate the propellant. The electric propulsion, which uses electrical energy to accelerate propellant in the form of plasma, is known as plasma propulsion. Plasma propulsion utilizes the electric energy to first, ionize the propellant and then, deliver energy to the resulting plasma leading to plasma acceleration. Many types of plasma thrusters have been developed over last 50 years. The variety of these devices can be divided into three main categories dependent on the mechanism of acceleration: (i) electrothermal, (ii) electrostatic and (iii) electromagnetic. Recent trends in space exploration associate with the paradigm shift towards small and efficient satellites, or micro- and nano-satellites. A particular example of microthruster considered in this paper is the micro-cathode arc thruster (µCAT). The µCAT is based on vacuum arc discharge. Thrust is produced when the arc discharge erodes some of the cathode at high velocity and is accelerated out the nozzle by a Lorentz force. The thrust amount is controlled by varying the frequency of pulses with demonstrated range to date of 1‐50Hz producing thrust ranging from 1 µN to 0.05mN.

High thrust-to-power ratio micro-cathode arc thruster

The Micro-Cathode Arc Thruster (μCAT) is an electric propulsion device that ablates solid cathode material, through an electrical vacuum arc discharge, to create plasma and ultimately produce thrust in the μN to mN range. About 90% of the arc discharge current is conducted by electrons, which go toward heating the anode and contribute very little to thrust, with only the remaining 10% going toward thrust in the form of ion current. A preliminary set of experiments were conducted to show that, at the same power level, thrust may increase by utilizing an ablative anode. It was shown that ablative anode particles were found on a collection plate, compared to no particles from a non-ablative anode, while another experiment showed an increase in ion-to-arc current by approximately 40% at low frequencies compared to the non-ablative anode. Utilizing anode ablation leads to an increase in thrust-to-power ratio in the case of the μCAT.

Periodical plasma structures controlled by external magnetic field

Periodical structures in propulsion type magnetized plasma are detected both in kinetic simulations and laboratory experiment. Stationary two-dimensional double layers with a several potential steps appear both parallel and across (more pronounced) the magnetic field. The double layers are weak with a potential jump much smaller than the electron temperature. The electrical current is found to be stratified and aligned with magnetic field vector. The channels of current flow coincide with the ridges of the plasma density.

Micro-Cathode Arc Thruster for small sattelites attitude control

Summary form only given. A low-mass, low-volume propulsion subsystems based on electrically activated micro-thrusters that utilize chemically-inert solid propellants are beneficial for small satellite attitude control applications. Micro-thrusters are able to deliver small impulse bits of about several μNs to satellites and characterized by simplicity, scalability, low cost, low weight and high reliability. In this work measurements of the key parameters of micro-Cathode Arc Thruster (μCAT) are presented and μCAT performance compared with other commercially available thruster technologies operating at the same power range.