This note investigates the minimal number of unilateral thrusters required for diierent versions of nonlinear controllability of a planar rigid body. For one to three unilateral thrusters, we get a new property with each additional thruster: one thruster yields small-time accessibility on the body's state space TSE(2); two thrusters yield global controllability on TSE(2); and three thrusters yi...

This work employs in situ measurement data and constructive simulations to examine the underlying physical mechanisms that drive spacecraft plume interactions with the space environment in low-Earth orbit. The study centers on observations of the enhanced flux of plasma generated during a maneuver of Space Shuttle Endeavour as part of the Sensor Test for Orion Relative Navigation Risk Mitigatio...

Vessels conducting dynamic positioning (DP) operations are usually equipped with thruster configurations that enable generation of resultant force and moment in any direction. These configurations are deliberately redundant in order to reduce the consequences of thruster failures and increase the safety. On such vessels a thrust allocation system must be used to distribute the control actions d...

Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been ...

A neutral gas background pressure map of the Large Vacuum Test Facility (LVTF) at the University of Michigan is presented. The LVTF was mapped at a series of cold anode flow rates corresponding to P5 Hall thruster operating conditions of 1.5, 3.0, and 9.0 kW. The chamber pressure was mapped at nominal xenon pumping speeds of 140,000 and 240,000 l/s with a rake consisting of five calibrated Baya...

The Coaxial High ENerGy (CHENG) Thruster is a high power coaxial pulsed plasma accelerator that was first proposed in 1970 by D.Y. Cheng. Reported exhaust velocities on the order of 10m/s, thrust densities on the order of 10N/m and low erosion rates make this thruster attractive for a variety of space missions. However, little work has been published since 1970 and the acceleration mechanism is...

The effects of anode temperature on the performance of a 4.5 kW Hall-effect thruster are investigated. The approach separates the location of gas injection from discharge current collection using an anode band, which removes the main mechanism that heats the gas distributor. A thermal model predicts a 270 K reduction of the gas distributor temperature, which corresponds to a 28% increase in the...

Accurate modeling of the anomalous electron mobility is absolutely critical for successful simulation of Hall thrusters. In this work, existing computational models for the anomalous electron mobility are used to simulate the UM/AFRL P5 Hall thruster a 5 kW laboratory model in a two-dimensional axisymmetric hybrid particle-in-cell Monte Carlo collision code. Comparison to experimental results i...

We propose a laser induced fluorescence heterodyne approach to resolve the timedependent ion velocity distribution (IVDF) in a Hall thruster. This approach is motivated by studies of low frequency modes of oscillations in Hall thruster, including azimuthal or so-called spoke and axial or so-called breathing oscillations. In this paper, we present the first successful application of this method ...

The current interest in ion thrusters for near-Earth and deep-space missions has occurred because of long-term development efforts yielding an understanding of the physical phenomena involved in thruster operation and hardware that is suited to a wide range of missions. Features of state-of-the-art thrusters are described in terms of the various physical processes that occur within them. Tradeo...