Characterizing Propellants for Variable-Thrust/Specific Impulse Colloid Thrusters

Onset voltage modeling of micromachined colloid thrusters

The onset voltage of a colloid thruster is an important parameter in the design of micromachined thrusters. Because dimensions in MEMS thrusters are in the range of several tens of micrometers and because extractor electrodes can be only 5 μm from the capillary emitters, the aspect ratios for MEMS thrusters are much lower than the one of individual stainless steel or silica glass needles. There...

Studies on the Ion-Droplet Mixed Regime in Colloid Thrusters

Characterizing Variable Task

For the schedulability analysis of hard real-time systems it is important to use task and resource models that appropriately capture the characteristics of the underlying system. In this paper a general task model, the Variable Task Model, most appropriate for tasks with bursty release characteristics, is formalized. Also, a new processor model, the Variable Processor Model, is suggested which ...

Large Carbon-Carbon Grids for High Power, High Specific Impulse Ion Thrusters

NASA is investigating high power, high specific impulse propulsion technologies that could enable ambitious flights such as multi-body rendezvous missions, outer planet orbiters and interstellar precursor missions. Ion engines can efficiently operate at very high specific impulse, but accelerating voltages of many kV result in greater ion optics wear rates due to high energy ion bombardment. Th...

Constitutive Equations for Solid Propellants

Mechanical behavior of the Space Shuttle redesigned solid rocket motor (RSRM) propellant is studied from a phenomenological point of view. Motivated by the study of the experimental data three initially isotropic constitutive models have been developed. All models represent the e ect of strain rate, superimposed hydrostatic pressure, and cyclic loading on the stress and dilatation response of t...