Drastic miniaturization of electronics and ingression of next-generation nanomaterials into space technology have provoked a renaissance in interplanetary flights and near-Earth space exploration using small unmanned satellites and systems. As the next stage, the NASA’s 2015 Nanotechnology Roadmap initiative called for new design paradigms that integrate nanotechnology and conceptually new materials to build advanced, deep-space-capable, adaptive spacecraft. This review examines the cutting edge and discusses the opportunities for integration of nanomaterials into the most advanced types of electric propulsion devices that take advantage of their unique features and boost their efficiency and service life. Finally, we propose a concept of an adaptive thruster.

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 1-50 Hz producing thrust ranging from 1 µN to 0.05 mN.

Arc discharge is one of the most efficient and environmental friendly method to synthesize Single Wall Carbon Nanotube (SWCNT). However, due to the ultra-fast synthesis procedure, localization of the SWCNT synthesis in an arc discharge plasma volume in situ has been a long standing problem. This relates to the ability of controlling volumetric synthesis of nanostructures in plasmas in general. In order to better understand the mechanism of the nanotube growth in plasma, we have developed an actuator driven high-speed system that is able to extract material from the arc plasma volume during the synthesis procedure. The majority of the SWCNTs produced using arc discharge method are semiconducting with diameter of about 1.5nm. It is shown that the growth region of SWCNTs is between 3mm to 11mm away from the center of the arc

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.

A simple approach to modeling the plasma layer similar to that appearing in the vicinity of a hypersonic vehicle is demonstrated in a laboratory experiment. This approach is based on the use of a hypersonic jet from a cathodic arc plasma. Another critical element of this laboratory experiment is a blunt body made from a fairly thin foil of refractory material. In experiments, this blunt body is heated by the plasma jet to a temperature sufficiently high to ensure evaporation of surface deposits produced by the metallic plasma jet. This process mimics reflection of gas flow from the hypersonic vehicle in a real flight. Two-dimensional distributions of the hypersonic plasma flow around the blunt body were measured using electrostatic Langmuir probes. Measured plasma density was typically 10 12 cm −3 , which is close to the values measured for real hypersonic flight. The demonstrated laboratory experiment can be used to validate numerical codes for simulating hypersonic flight and to conduct ground-based tests for efficiency validation of various radio communication blackout mitigation techniques.