Ion thruster | EPFL Graph Search

An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity. An ion thruster ionizes a neutral gas by extracting some electrons out of atoms, creating a cloud of positive ions. Ion thrusters are categorized as either electrostatic or electromagnetic. Electrostatic thruster ions are accelerated by the Coulomb force along the electric field direction. Temporarily stored electrons are reinjected by a neutralizer in the cloud of ions after it has passed through the electrostatic grid, so the gas becomes neutral again and can freely disperse in space without any further electrical interaction with the thruster. By contrast, electromagnetic thruster ions are accelerated by the Lorentz force to accelerate all species (free electrons as well as positive and negative ions) in the same direction whatever their electric charge, and are specifically referred to as plasma propulsion engin

Preliminary Design of a Lunar Reconnaissance Drone

Thomas Pfeiffer, Erik Uythoven

In this report, a preliminary design study of a compact lunar reconnaissance drone module which will assist exploration rovers is presented. It is designed to assist future exploratory rover missions in difficult environments such as PSRs or extreme topographies. Although similar concepts have been validated on Mars by NASA’s Ingenuity helicopter, only few such ideas exist for lunar applications. The main challenges of this project lie in the propulsion system to be used, the thermal system of the drone (due to extreme temperatures) and the 3D mapping of the lunar surface using a flash lidar system. These aspects were studied in detail with promising results: For a drone with a weight of 20 kg, 1 kg of green monopropellant is sufficient to cover a distance of a least 1 km before it needs refuelling. In this report, it is assumed that the lightweight flash lidar technology should be developed enough to allow for 10 cm resolution at 50 m flight altitude. This feasibility and initial design study sets a foundation for lunar drones and exploration of the Moon using flying spacecrafts, although many open questions remain to be solved and detailed designs to be performed.

2022

Micromachined electrospray thrusters for spacecraft propulsion

Renato Krpoun

Micromachining has enabled the downscaling of large, massive and power hungry systems into small batch-produced integrated devices. Recent progress in electrospray thruster technology, in particular the discovery of an ionic emission mode using the ionic liquid EMI-BF4 as fuel has sparked interest in miniaturizing this thruster technology, initially developed in the 1950's and lying dormant for several decades. Electrospray thrusters operate by applying a potential difference between a conductive liquid, usually on the tip of a needle or capillary, and an extractor electrode. Once a threshold voltage is reached the electric stress at the apex of the liquid surface overcomes surface tension and a spray of particles is ejected toward a counter electrode. The purely electrostatic nature of this type of thruster makes it an ideal candidate for miniaturization and the use of ionic liquids, also known as molten salts, as fuel allows operating the thruster in bipolar mode eliminating the need for an additional neutralizer. This thesis describes a process flow to fabricate planar arrays of silicon capillaries with integrated individual extractor electrodes. The developed process flow offers the possibility to manufacture arrays on the wafer scale allowing, in principle, to increase thrust from a fraction of micronewton for a single capillary to the millinewton level for large arrays. This process flow has been validated by microfabricating several thruster prototypes, which were packaged using Low Temperature Co-Fired Ceramic (LTCC) technology. In conjunction with this microfabrication process an onset voltage model was developed intended as design tool during thruster layout. This model allows to predict the voltage at which particle emissions initiate for complex geometries and to estimate the effect of dimensional variations on parameters such as crosstalk in large arrays. Tests carried out with thruster prototypes using single capillaries show a well defined energy distribution of the particles and the possibility to modulate spray current by changing the voltage. Controlled variations in the fluidic impedance of the emitters allow to spray in either ionic or droplet mode. Time-of-flight measurements with arrays show a beam composed of ions (monomers, dimers), thus yielding a high specific impulse. A first life test finally shows thruster operation for several hours with stable beam properties.

EPFL2009

Realization of a solid-propellant based microthruster using low temperature co-fired ceramics

Yannick Fournier, Thomas Maeder, Peter Ryser, Jaya Thakur

The introduction of micro-spacecrafts in the space industry has led to the development of various micro-propulsion techniques. Microthrusters are micropropulsion devices used in a microspacecraft for precise station keeping, orbit adjustment, attitude control, drag compensation and apogee kicking. The principle of operation of a solid propellant thruster is based on the combustion of a solid energetic material stored in a microfabricated chamber. In the current work, Low-Temperature Co-fired Ceramic (LTCC) technology has been used for the realization of a solid propellant based microthruster structure. Hydroxyl Terminated Poly-Butadiene/Ammonium Perchlorate (HTPB/AP) is used as the propellant. It is shown that geometric and dimensional variations in design, depending on the application requirements, can be easily implemented. Preliminary testing for micro-combustion has been done to verify the basic operation of the microthruster. A thrust value of 19.5 mN has been measured.

2010

Micromachined electrospray thrusters for spacecraft propulsion

Renato Krpoun

EPFL2009