In order to fully characterize the performance of the colloid thruster system the electrospray (ES) beam must itself be fully characterized. This may be achieved by measuring various properties such as flow rate, current, droplet/ion charge to mass ratio and current profile. Beam properties of both standard electrospray mass spectrometry (ESMS) emitters and arrays of custom made micro-fabricate...

Measurements of the most probable time-averaged axial ion velocities and plasma potential within the acceleration channel and in the plume of a straightchanneled cylindrical cusped field thruster operating on xenon are presented. Ion velocities for the thruster are derived from laser-induced fluorescence measurements of the 5d[4]7/2 −6p[3]5/2 xenon ion excited state transition centered at λ = 8...

We present a new approach to generalised autoregressive conditional het-eroscedasitic (GARCH) modelling for asset returns. Instead of attempting to choose a speciic distribution for the errors, as in the usual GARCH model formulation, we use a nonparametric distribution to estimate these errors. This takes into account the common problems encountered in nancial time series, for example, asymmet...

It is well known that each thruster on the SPHERE produces slightly different thrust and behaves differently (see [Chen] and [Berkovitz]). Some methods were developed by [Chen] to compensate for the difference in thrust between thrusters and improve the open-loop performance of the SPHERE, but they were yet to be demonstrated. An experiment was performed onboard NASA’s KC-135, during microgravi...

Todays model-based dynamic positioning (DP) systems require that the ship and thruster dynamics are known with some accuracy in order to use linear quadratic optimal control theory. However, it is diicult to identify the mathematical model of a dynamically positioned (DP) ship since the ship is not persistently excited under DP. In addition the ship parameter estimation problem is nonlinear and...

The correct approach to electron transport modeling in Hall thrusters is an open question in the field and is compounded by a lack of comparative studies on the relative influence of various proposed electron transport mechanisms in the thruster plume. Lacking an analytical model for transport, empirical coefficients are used in most models to reproduce major discharge parameters like the total...

A rectangular gridded ion thruster discharge chamber is investigated for operation with multiple discharge cathode assemblies. The multiple-cathode approach attempts to increase thruster throughput and lifetime by operating three discharge cathode assemblies sequentially, possibly providing a threefold increase in discharge chamber life. Previous multiple-cathode electric propulsion devices, su...

A fault-tolerant control scheme with thruster redundancy is developed and applied to perform attitude tracking manoeuvres for an orbiting flexible spacecraft. Based on the assumption of bounded elastic vibrations, an adaptive sliding mode controller is proposed to guarantee that all the signals of the resulting closed-loop attitude system are uniformly ultimately bounded in the presence of an u...

Fluid codes are widely used to model Hall thrusters because of their simplicity and low computational demands. However, they have not been successful in describing all the physics of Hall thrusters. On the other hand, PIC codes (Particle In Cell) are powerful for simulating microscopic phenomena. Their drawback is the requirement in the number of particles in order to achieve good results. This...