Engineering topics
Publications and source records attributed to Sims, J. A..
Interplanetary missions which use low-thrust, high specific impulse propulsion can further capitalise on the capabilities of the propulsion system by using it to effect escape from the launch body or capture at a target body.
An application of the new optimization algorithm called Static/Dynamic Control (SDC) to design low-thrust escape and capture trajectories is presented.
With the complexities in computing optimal low thrust trajectories, easily-computed, good sub-optimal trajectories provide both a practical alternative for mission designers and a starting point for optimisation. The present paper collects in one place for easy reference and comparison several exact solutions that have been obtained in the literature over the last few decades: the logarithmic spiral, Pinkham's variant thereof, Forbes spiral, the exponential sinusoid, the case of constant radial thrust, Markopoulos's Keplerian thrust arcs, Lawden's spiral, and the analogous Bishop and Azimov spiral.
Several methods for determining the characteristics of low-thrust transfers around minor planets are examined and compared.
An application of the new optimization alorithm called Static/Dynamic Control (SDC) to design low-thrust escape and capture trajectories is presented.
Direct return to Earth after rendezvousing with a comet entails a very high entry velocity. Several methods for reducing the entry velocity, including using additional propellant on a direct return or using planetary gravity assists, are presented.
An application of the new optimization algorithm Static/Dynamic Control (SDC) to the design of low-thrust interplanetary trajectories is presented. The interplanetary trajectory is integrated with a multi-body force model and may include gravity assists.
An application of the new optimization algorithm called Static/Dynamic Control (SDC) to the design of low-thrust interplanetary trajectories is presented.
The Deep Space 4/Champollion mission will be the first to land a spacecraft on the surface of a comet, perform in-situ science, and collect a subsurface sample which it will return to Earth for analysis. This paper describes the trade studies resulting in the current reference mission, which uses solar electric propulsion to rendezvous with the comet Tempel 1 in December 2005 after launching in April 2003. An option which uses a chemical propulsion system to return to Earth is discussed.
Zerodur is a low coefficient of thermal expansion glass-ceramic material. This property makes Zerodur an excellent material for high precision optical substrates. Functioning as a high precision optical substrate, a material must be dimensionally stable in the system operating environment. Published data indicate that Zerodur is dimensionally unstable when exposed to large doses of ionizing radiation. The dimensional instability is discussed as an increase in Zerodur density. This increase in density is described as a compaction. Experimental data showing proton-induced compaction of Zerodur is presented. The dependence of compaction on proton dose was determined to be a power law relationship.