Rapid evolution of miniaturized, automatic, robotized, function-centered devices has redefined space technology, bringing closer the realization of most ambitious interplanetary missions and intense near-Earth space exploration. Small unmanned satellites and probes are now being launched in hundreds at a time, resurrecting a dream of satellite constellations, i.e., wide, all-covering networks of small satellites capable of forming universal multifunctional, intelligent platforms for global communication, navigation, ubiquitous data mining, Earth observation, and many other functions, which was once doomed by the extraordinary cost of such systems. The ingression of novel nanostructured materials provided a solid base that enabled the advancement of these affordable systems in aspects of power, instrumentation, and communication. However, absence of efficient and reliable thrust systems with the capacity to support precise maneuvering of small satellites and CubeSats over long periods of deployment remains a real stumbling block both for the deployment of large satellite systems and for further exploration of deep space using a new generation of spacecraft. The last few years have seen tremendous global efforts to develop various miniaturized space thrusters, with great success stories. Yet, there are critical challenges that still face the space technology. These have been outlined at an inaugural International Workshop on Micropropulsion and Cubesats, MPCS-2017, a joint effort between Plasma Sources and Application Centre/Space Propulsion Centre (Singapore) and the Micropropulsion and Nanotechnology Lab, the G. Washington University (USA) devoted to miniaturized space propulsion systems, and hosted by CNR-Nanotec—P.Las.M.I. lab in Bari, Italy. This focused review aims to highlight the most promising developments reported at MPCS-2017 by leading world-reputed experts in miniaturized space propulsion systems. Recent advances in several major types of small thrusters including Hall thrusters, ion engines, helicon, and vacuum arc devices are presented, and trends and perspectives are outlined.

Space micropropulsion systems for Cubesats and small satellites: from proximate targets to furthermost frontiers

The technological and commercial expansion of electric propulsion

CubeSats provide a cost effective means to perform scientific and technological studies in space. Due to their affordability, CubeSat technologies have been diversely studied and developed by educational institutions, companies and space organizations all over the world. The CubeSat technology that is surveyed in this paper is the propulsion system. A propulsion system is the primary mobility device of a spacecraft and helps with orbit modifications and attitude control. This paper provides an overview of micro-propulsion technologies that have been developed or are currently being developed for CubeSats. Some of the micro-propulsion technologies listed have also flown as secondary propulsion systems on larger spacecraft. Operating principles and key design considerations for each class of propulsion system are outlined. Finally, the performance factors of micro-propulsion systems have been summarized in terms of: first, a comparison of thrust and specific impulse for all propulsion systems; second, a comparison of power and specific impulse, as also thrust-to-power ratio and specific impulse for electric propulsion systems.

https://www.mdpi.com/2226-4310/4/4/58/pdf

An Overview of Cube-Satellite Propulsion Technologies and Trends

As small satellites become more popular and capable, strategies to provide in-space propulsion increase in importance. Applications range from orbital changes and maintenance, attitude control and desaturation of reaction wheels to drag compensation and de-orbit at spacecraft end-of-life. Space propulsion can be enabled by chemical or electric means, each having different performance and scalability properties. The purpose of this review is to describe the working principles of space propulsion technologies proposed so far for small spacecraft. Given the size, mass, power, and operational constraints of small satellites, not all types of propulsion can be used and very few have seen actual implementation in space. Emphasis is given in those strategies that have the potential of miniaturization to be used in all classes of vehicles, down to the popular 1-L, 1-kg CubeSats and smaller.

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Space Propulsion Technology for Small Spacecraft

Over 2500 active satellites are in orbit as of October 2020, with an increase of ~1000 smallsats in the past two years. Since 2012, over 1700 smallsats have been launched into orbit. It is projected that by 2025, there will be 1000 smallsats launched per year. Currently, these satellites do not have sufficient delta v capabilities for missions beyond Earth orbit. They are confined to their pre-selected orbit and in most cases, they cannot avoid collisions. Propulsion systems on smallsats provide orbital manoeuvring, station keeping, collision avoidance and safer de-orbit strategies. In return, this enables longer duration, higher functionality missions beyond Earth orbit. This article has reviewed electrostatic, electrothermal and electromagnetic propulsion methods based on state of the art research and the current knowledge base. Performance metrics by which these space propulsion systems can be evaluated are presented. The article outlines some of the existing limitations and shortcomings of current electric propulsion thruster systems and technologies. Moreover, the discussion contributes to the discourse by identifying potential research avenues to improve and advance electric propulsion systems for smallsats. The article has placed emphasis on space propulsion systems that are electric and enable interplanetary missions, while alternative approaches to propulsion have also received attention in the text, including light sails and nuclear electric propulsion amongst others.

Electric Propulsion Methods for Small Satellites: A Review

The characterization of a miniaturized ionic liquid electrospray thruster for nanosatellite applications is presented. The thruster investigated features an emitter array of 480 emitter tips per sq...

/pdf/emission-characteristics-of-passively-fed-electrospray-1rlxn4iwg1.pdf

Emission Characteristics of Passively Fed Electrospray Microthrusters with Propellant Reservoirs

Theoretical and experimental methods were developed to investigate the charging characteristics anticipated to be observed on spacecraft during the operation of electrospray thrusters These devices produce positively and negatively charged particles of similar mass and velocities An electrical model of this configuration was created to predict the charging properties of electrically isolated systems This model simulates a bipolar electrospray-thruster system Experiments were conducted on a test bed, in which a mock-up satellite is magnetically levitated inside a vacuum chamber The mock-up is equipped with batteries, power conditioning, radio transmitter, and electrospray thrusters The results from the experimental tests demonstrate that neutralization with heavy ionic species is indeed possible The thrusters are able to fire in a bipolar configuration for long periods of time inducing bounded spacecraft charging in the range from −400 to +600  V when emitting currents of about 20  μA It was found 

Spacecraft-Charging Characteristics Induced by the Operation of Electrospray Thrusters

The purpose of this work is to describe the use of electrospray propulsion devices as miniaturized actuators for precise attitude control of small satellites, including CubeSats. Electrosprays are ...

Electrospray Thrusters as Precise Attitude Control Actuators for Small Satellites

Plasma drilling on Martian ice: Enabling efficient deep subsurface access to Mars' polar layered deposits

We present the Sample Recovery Helicopter (SRH) element that serves as the primary backup for tube retrieval as part of the Mars Sample Return (MSR) Campaign. SRH was officially incorporated into MSR in July 2022. Concept of operations, aerial and ground mobility, manipulation, avionics, thermal and telecom will be described in the context of SRH's Mission Concept Review held in June 2022. The summarized Concept of Operations (ConOps) of SRH is as follows: 1. SRH would ride along with the Sample Retrieval Lander to Mars and deploy onto the surface. 2. SRH would perform mapping flights to aid in localization during the nominal mission. 3. SRH flies, and lands close to the tube sample depot. 4. SRH drives towards the selected sample tube and acquires it using a manipulator. 5. SRH + sample then take off, fly and land a safe distance from the lander. 6. SRH drives towards the lander and drops the sample tube onto the lander's robotic arm workspace. SRH drives away from the robotic arm workspace. 7. The lander's robotic arm picks up the tube from the ground and places it inside the rocket. 8. Process repeats, go to step 3. No functionality validation or design analysis is included in this work.

Fernando Mier-Hicks

Papers

Emission Characteristics of Passively Fed Electrospray Microthrusters with Propellant Reservoirs

Spacecraft-Charging Characteristics Induced by the Operation of Electrospray Thrusters

Electrospray Thrusters as Precise Attitude Control Actuators for Small Satellites

Plasma drilling on Martian ice: Enabling efficient deep subsurface access to Mars' polar layered deposits

Sample Recovery Helicopter