The amateur radio STRaND-1 smartphone CubeSat is a joint project between SSTL and the Surrey Space Centre (SSC). It’s not only its smartphone that makes it exceptional. Engineers at the Surrey Space Centre have also developed a unique mass and power saving plasma propulsion system to fly on the satellite. This system will be the first propulsive technology to provide very precise attitude control and pointing.
STRaND-1 will carry both a Resistojet and a Pulsed Plasma Thruster (PPT) module on board. The PPT will consist of eight micro thrusters; four located at the top of the satellite stack and four located at the bottom. The micro thrusters operate by discharging a discrete train of pulses. Each pulse is a plasma discharge that forms between two metal electrodes, much like a small lightning bolt or electrical spark. The spark erodes the metal from the electrodes and electromagnetics accelerate the eroded mass out of the nozzle, which produces thrust. This is known as the Lorentz force.
Surrey Space Centre has developed two ways of minimising mass and volume. Firstly, the electrodes which form the plasma discharge also function as the propellant. As metal is highly dense, more propellant can be stored in a smaller volume than that of conventional chemical propulsion systems. The total weight of the propellant for the whole STRaND-1 PPT system is just 10g.
Secondly, Surrey Space Centre’s novel discharge initiation system uses a mechanical contact trigger built out of a tiny piezoelectric motor only 5mm in length. This takes up less space than the conventional spark plug system which requires volume intensive circuitry.
A video of the Pulsed Plasma Thruster firing can be seen st http://www.facebook.com/video/video.php?v=10150533409463432
A six page article on STRaND-1 appeared in the Spring 2011 issue of the AMSAT-UK publication OSCAR News available for download at http://www.uk.amsat.org/on_193_final.pdf
UK Amateur Radio Smartphone CubeSat STRaND-1 http://www.uk.amsat.org/1942
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