Summary. Research into reactive collision avoidance for unmanned aerial vehicles has been conducted on unmanned terrestrial and mini aerial vehicles utilising active Doppler radar obstacle detection sensors. Flight tests conducted by flying a mini UAV at an obstacle have confirmed that a simple reactive collision avoidance algorithm enables aerial vehicles to autonomously avoid obstacles. This builds upon simulation work and results obtained using a terrestrial vehicle that had already confirmed that active sensors and a reactive collision avoidance algorithm are able to successfully find a collision free path through an obstacle field.

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An electric thruster is presented that makes use of the properties of an asymmetric hollow cathode glow discharge that ejects a collimated plume of high velocity neutral atoms. Ions are accelerated electrostatically outwards from within the asymmetric hollow cathode and undergo charge exchange with the background gas resulting in energetic neutrals being ejected, thus producing thrust. This thruster is entirely self-contained allowing thrust generation and beam neutralization within the discharge. Doppler spectroscopy was used to determine the speed of atomic hydrogen in the plume and was found to produce a specific impulse greater than 3 × 10 4 s for applied voltages and powers of the order of 5 kV and 100 W, respectively. An estimate of the thrust of 1 mN for a power input in the order of 1 kW was obtained from previously measured ion densities in similar discharges.