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The institute of aerospace engineering at TU Dresden is developing a highly miniaturized field emission electric propulsion (FEEP) system for Nano-satellites, called CubeSats. The presented propulsion system NanoFEEP is composed of the actual field emission thrusters and a carbon nanotubes silicon chip used as a cold electron source for neutralizing the electric charging behavior of the spacecraft. The NanoFEEP thrusters use Gallium as metal propellant and provide a continuous controllable thrust of up to 20 micro-newton. This thrust level is sufficient to control the attitude of the miniature CubeSat satellites and even perform orbit maneuvers. Two satellites missions will demonstrate these capabilities in the near future. One mission will show the feasibility of formation flying of CubeSats. The other mission will demonstrate the possibility of space debris avoidance with our propulsion system by deorbiting the satellite after mission completed.

Electromagnetic simulation is performed on two compact electrode designs to obtain higher electric field distribution between high voltage and ground electrode, which ensures high bacterial inactivation in liquid food. Electric field simulations are performed initially for test voltages of 1kV to 5kV to understand the nature of electric field distribution in the inactivation area. Then the applied voltage is gradually increased to induce transmembrane potential on the cell membrane. The microorganism modeled for field analysis is Staphylococcus aureus. For both the round edged and torus tube designs, the transmembrane potential of 0.5V to 1V is achieved with the spherical cell, modeled between the high voltage and the ground electrode, which shows pore formation possibility. Dimensions of the electrodes are maintained in mm and cm suitable for laboratory scale, continuous pulsed electric field treatments. In both the designs, emphasis is on the simulation to achieve higher electric field application in the inactivation area, which can be realized through satisfying electroporation phenomenon. From the observed results, it is understood that greater electric field application is achievable even using small efficient electrode designs, which in turn assures i) A greater bacterial inactivation in the liquid food and ii) A compact pulsed electric field experimental prototype.

For better integration of plasma thrusters into spacecraft and satellites, potential damaging effects of impinging high energy ions on the spacecraft surfaces should be taken into consideration. For analyzing the plume plasma in this regard, retarding potential analyzers (RPA) are used in electric propulsion as one of the most fundamental and widely used diagnostics tools. RPA determines the ion energy distribution of plume plasma which is in the downstream of a thruster. This paper reports on a successful design process of an RPA to be used with BURFIT-80 ion thruster. An in-house developed hybrid Particle-In-Cell Direct Simulation Monte Carlo (PIC-DSMC) code, which is previously applied for ion thruster grid region is implemented to simulate the flow in the RPA. Results are used to validate the effective operation of the RPA. Potential distributions in the RPA are investigated and the calculated currents collected by the collector is compared with an existing experimental study.

Considerable progress has been made in recent years in the study of the Earth's gravitational field by observing the motion of satellites in low altitude orbits. However, such observations are hampered by the aerodynamic drag caused by the residual atmosphere, which modifies the orbits of these satellites in an unpredictable way. In order to overcome this problem, an on-board propulsion system with wide range of thrust is needed which will exactly balance the drag experienced by the spacecraft while measurements are being made.

The cusped field thruster represents a new type of electric propulsion device incorporating cusped magnetic field profiles that keep high energy ions away from channel walls and mitigate erosion. Thus its lifetime will be longer compared with so me other type of electric propulsion devices. Recently, the cusped field thruster has been paid much attentions by many organizations, such as Thales Research Institute's HEMPT, MI T's DCFT and Stanford University's CCFT.

Studying the interaction of plasma and materials is very important in many plasma systems including those used in material processing applications, electric propulsion thrusters, or (bio-) surface treatment systems. For example, in the electric propulsion field, plasma-wall interactions influence thruster lifetime due to ion beam sputtering of the channel, and secondary electron emission can affect the sheath potential structure and plasma discharge conditions1. A better understanding of plasma-wall interactions will aid many practical plasma applications.

Summary form only given. Scaling down electric propulsion systems is of interest for the future development of propulsion systems for micro- and nano-satellites. Because of the low mass of nano-satellites, only a small amount of thrust, on the order of several hundred µN, is needed for tasks such as attitude control.

In this paper, we are interested to develope a protrusive (or higher dimensional) CL law to account for the sharpness of the emitters. We propose a method of calculating the maximum applied electric field Ec, which occurs when the emitter surface electric field Es is equal to the space-charge electric field Esp.

The ferroelectric plasma thruster (FEPT) is being developed for use in micro-spacecraft propulsion, large scale structure vibration damping, and proximity operations. An advantage of the FEPT over other thruster technologies such as colloid and field emission electric propulsion (FEEP) thrusters is that the FEPT operates with a single power supply. Additionally it is believed that the FEPT is self-neutralizing since both electrons and ions are accelerated to produce thrust. In order to test the self-neutralization capabilities of the FEPT, it must be operated with a power supply that is isolated from the ground of the vacuum chamber wall. Presented is the design of an isolated power supply to test the self-neutralization of the FEPT operating in a vacuum chamber.

Summary form only given. Micro-spacecraft are of current interest, due to the possibility of reducing mission cost and risk by flying several spacecraft in formation. The applicability of micro-spacecraft to certain missions is predicted to depend on the availability of compact, lightweight, high specific impulse micro-propulsion systems. In addition, micro-propulsion will be required for attitude adjustment of space-based telescope interferometers, and imaging arrays. Chemical propulsion systems are capable of specific impulses of /spl sim/250 s. This may not be adequate to ensure a lightweight propulsion option for attitude adjustment, for instance. Electric propulsion options are capable of impulses of 1000 s or greater, making them a potentially attractive micro-propulsion option. The most highly developed electric propulsion concepts, ion and Hall thrusters, have been developed for larger craft and higher powers. Scaling these concepts to micro-propulsion relevance can be difficult. Therefore, there is a need for new, high impulse, compact electric micro-propulsion concepts. A new micro-propulsion option based on ferroelectric plasma production, with ponderomotive acceleration to achieve high ion exhaust velocities will be presented. Recent studies of a ferroelectric plasma source excited by RF applied power have shown significant emission of negatively and positively charged species from the surface of the dielectric. Positive currents from 30 to 370 mA have been observed emanating from an RF driven ferroelectric cathode. Ions produced in the surface plasma of the ferroelectric cathode can be accelerated ponderomotively, resulting in high ion velocities. The RF driven ferroelectric emitter produces a strong electric field gradient, enabling ponderomotive acceleration of the ions. The high dielectric constant of the ferroelectric helps to amplify the applied field gradient. Calculations of the ion exhaust velocity indicates that specific impulses in the 1000 s range are possible. Data from ferroelectric emission experiments will be presented in the context of the ion accelerator and electric micro-propulsion concept.

Summary form only given, as follows. Expellantless neutralizers can improve the propellant utilization of very low-power colloid thrusters, field emission electric propulsion (FEEP) devices, ion engines, Hall thrusters, and gridded vacuum arc thrusters. In addition, spacecraft plasma contactors and electrodynamic tether systems could reap expellant mass reduction benefits from electron emitters that require very low gas flow rates or no gas flow to perform their functions. Ferroelectric emission (FEE) cathodes operating at minimized power are currently being studied as zero expellant flow rate cathode sources. Typical cathode operation requires 0.4 to 1 kV to be rapidly pulsed across a ferroelectric ceramic, triggering electron emission through a gridded electrode on the ceramic surface. Ceramics with painted-on Ag electrodes have produced peak current densities of 10s of mA/cm/sup 2/ with pulse voltages near current emission threshold (approximately 400 to 600 V). Additionally, thin film electrode grids have been deposited on two PZT ceramics with relative dielectric constants of 1000 and 4100. The thin film grids are composed of molybdenum and are 10 and 100 nm thick, 1 mm wide, and separated into strips by 1 mm. A parametric study of these FEE cathodes examines the effects of ferroelectric dielectric constant, grid thickness, and pulse geometry for low power operation. Additionally, cathode surface modification due to operation is studied.

Pumps utilizing electric traveling waves as the conveyor of liquids have already been presented in various publications. In those considerations, a dielectric liquid has been chosen as the media to propel. Inversely, it is conceivable to use pumps as propulsion motors for tiny vessels. Hereinafter, the proposed electrostatic propulsion motor is based on the electric tube device which has been introduced in an earlier paper by the first author for the task of particle mass transportation. The device is made by winding six parallel and insulated wires onto a cylindrical tube. The employed wires have a diameter in the range of 56 /spl mu/m-236 /spl mu/m. Upon the application of multi-phase voltages to the monolayer-electrodes, the created traveling electric field wave carries the charged liquid in the same direction. Various electrostatic propulsion motors have been fabricated and optimized through a series of experiments. Optimizing parameters involve electrode dimensions, fabrication materials, applied voltages and frequencies. As evaluative parameters, the propulsion pressure and the rate of liquid flow are determined. Constant and precise liquid propulsion is achieved. It is further shown that this tube structure has a high potential for miniaturization.

It has been shown that the values of the static and alternating current in a liquid-metal ion source (LMIS) are determined by the magnitude of the liquid-metal viscous flow on the needle surface, appearing under the action of negative electric pressure in the vicinity of Taylor's cone base. The strong decreasing of current modulation degree at high frequencies is determined by the inertia of the viscous flow. The obtained results allow one to determine the frequency range in which significant current modulation is possible when a comparatively low alternating voltage is supplied to the LMIS.

The stability of liquid metal layer in an electric field is considered, when the field has a temporal periodic component. This case is an extension of the known Tonks-Frenkel theory of conductive liquid instability in a DC electric field. A periodic field of moderate intensity makes the initiation of instability of surface perturbations easier than the application of a DC field alone. A linear theory of surface perturbation growth in a periodic electric field is developed and applied for the analysis of situations typical for droplet formation in high voltage devices. Two examples of the instability are assessed: behavior of a liquid metal ion source in an oscillating electric field and the motion of the electrode melt in a vacuum arc under fluctuating arc voltage.