Defence technology shows vision

Tom Shelley reports on the latest low cost technologies for remote observation and communications, from an organisation often featured in the magazine

Qinetiq, and its predecessor, DERA, continues to pioneer remote techniques for surveillance and observation, advances in communications and leading edge materials.

The plastic bodied tank, described in May 2000, showed state of the art in composite construction, enhancing protection for its crew while saving 30% in weight.

Now part privatised, its latest venture to the edge of space in a large balloon, shows a way forward for global communications, earth observation and advanced materials, not least in the unmanned aerial vehicle that will accompany the balloon to take pictures.

The project goal is to send a manned balloon up to 132,000 feet, or 40km. In order to photograph it, Zephyr 3, a 12kg, 12m wing span solar powered UAV will fly round and round it on the end of a tether. Zephyr 3 is merely a lightened version of a long standing project to develop a low cost UAV system capable of continual data collection at high resolution at an altitude of 30km and provide remote sensing or communications over a 300km swathe.

Project manager Christopher Kelleher told Eureka that his team had already built and tested a half scale model of the balloon accompanying version. The altitude attempting version has five brushless DC motors driving propellers through gearboxes at 5,000 rpm. The motors, designed to power competition models for short periods at 1.5 kW, are down rated to 200W each because of high altitude cooling problems where air has only 0.1 per cent of its density at sea level. For the same reason, the UAV will be flying at 70 m/s at maximum altitude as opposed to 5.5 m/s at sea level.

One of the longer terms aims of the UAV project is to develop aerial vehicles that could stay aloft day and night. In order to do this, Kelleher reckons the machines will need a system capable of storing 450 kWh/kg, three times as much as can be managed by the best lithium ion batteries made presently, and 15 times as much as is possible with lead acid batteries. The most promising option at present would appear to be reversible hydrogen oxygen fuel cells.

NASA has been pursuing similar goals with its Helios UAV project but Kelleher insists the Qinetic approach would allow coverage of "More ground with smaller, cheaper systems." One of the goals being pursued by NASA, Qinetiq and others is to come up with an economic system of locally boosting mobile phone bandwidth, particularly for major sporting events. Since the balloon requires no energy to get up to altitude, Eureka asked whether balloons might do the same job, and gathered that they might. The Qinetiq record attempt balloon is made out of nothing more exotic than thin polyethylene, similar in thickness to a household freezer bag, although 1.2 million cubic metres in volume in order to be able to lift two pilots and their Russian made life support systems.

Qinetiq balloon altitude attempt


* UAV accompanying balloon will likewise have to be able to fly at an altitude of 132,000 feet (40 km)

* UAV weight is 12kg, able to support a camera payload of just over 2kg

* The slightly more robust Zephyr 5, designed for longer term usage is designed for use at up to 30km and weighs 17kg. It is hoped eventually to operate such platforms for a year at a time

Tom Shelley

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