QinetiQ, a UK based development company that focuses on defence technologies has been developing a low cost, high altitude, long endurance (HALE) unmanned aerial vehicle (UAV) and product family named Zephyr. These platforms are capable of capturing and disseminating information while operating at altitudes of more than 30 km, and potentially deployed on long-term missions of up to three months.
The first steps
In 2003 Zehpyr had been announced by QinetiQ: a solar-powered, propeller-driven vehicle to reach 40 kilometres (132,000 feet) height, which earlier had been only surpassed by experimental rocket planes and the space shuttle. Reaching such height can be used for obvious military survaillance missions, but such planes could also be a cheap alternative to space satellites. These solar planes could be used for environmental montoring, civilian mapping, crop and forestry fire monitoring or to supply mobile phone coverage in remote areas or perhaps in a disaster zone. They can be quickly and relatively cheaply deployed in the skies. From such altitudes a camera built on the plane can see the whole UK for example, and contrary to low-Earth orbit satellites “these aircraft, if we meet the night-storage of power issues, would operate continously and indefiniately over a city or battle theatre” said Chris Kelleher, the chief designer of Zephyr four years ago.
The plane at that time had a wingspan of 12 meters, and weighed little more than 12 kilograms, while having a carbon composite frame. The solar cells on the top of the wing provided 1 kW of power to five motors. In such high altitude Zehpyr was to cope with extremes of temperature, as the sun-facing surfaces get very hot, while the shaded regions of the airframe would experience cooling down to about minus 50 Celsius.
The first tests
In December 2005, two prototypes of Zephyr had succesfully flown at the White Sands Missile Range, New Mexico, USA. The two aircraft were flown for four and a half and six hours respectively. The maximum altitude attained was 27,000 feet above sea level. By this time, Zephyr kept the original wingspan of 12 meters, but had grown in terms of weight to more than double: to 27 kilograms, as rechargeable batteries had been incorporated in the carbon fibre airframe. The batteries later proved to be useful and successfull in providing the required power after dusk fell as in July 2006 a third Zephyr had flown for 18 hours, including 7 hours of flying in the dark for the first time – thus tripled the maximum flight time. At the same time the first two, recovered Zephyrs were first used as communication relays and had carried other payloads as a trial, too. At this time Zephyr had ascended to a record 36,000 feet (up by 10,000 feet from six months eariler).
The latest achievements
It has been announced on 10SEP2007 that Zephyr has broken the longest flight of an unmanned air vehicle, with a 54 hour flight (tripled the flight time yet again and included two nights!) achieved at the same location as the earlier tests. This would be a world record, but as QinetiQ had not published the planned tests in time, the FAI (Federation Aeronautique Internationale – World Air Sports Federation) officials could not be present at the site, so it remains an unofficial world record for the time being. However, the QinetiQ team believes that air traffic controllers at the White Sands base will verify the second, 33-hour, 43-minute flight, which took place on the 31 August.
Zephyr now has a wingspan of nearly 18 meters and weighs just 30 kilograms. The trials validated recent modifications that have improved the efficiency of Zephyr’s power system. These have included new solar arrays supplied by United Solar Ovonic (that are amorphus silicon arrays no thicker than sheets of paper (!)), a full flight-set of Sion Power batteries (lithium-sulphur) as well as a novel solar-charger and bespoke autopilot developed by QinetiQ, all of which were being flown for the first time.
During the trials the same aircraft was flown twice while carrying a surveillance payload – first for 54 hours to a maximum altitude of 18,000 meters, or 58,355 feet (another 20,000 added to the 2006 record), and then for 33 hours 43 minutes to a maximum altitude of 52,247 feet. Both flights were achieved in the face of thunderstorms and debilitating heat in the hostile environment of the New Mexico high desert in the summertime, but as the Zephyr is capable of flying above commercial flight paths and most weather this would only influence the take-off and landing operations. Zephyr now uses solar power to fly at altitudes in excess of 60,000 feet during the day while storing sufficient energy in its rechargeable batteries to power it overnight without falling below 50,000 feet, while being used to conduct persistent surveillance using GPS waypoint navigation to remain on station.
Among several other companies trying to create an unmanned, solar powered vehicle is NASA, that had broken the altitude record in 2001 for non-rocket-powered winged aircraft when its Helios climbed to 96,863 feet (29.5 km) above sea level. Helios broke up on a flight in 2003 and had been lost.
But Zephyr seems to be more alive now than ever before and seems to try taking over all the available records for unmanned, solar powered aircrafts, and as it has proven just a few days ago, it’s very successfull in doing just that! Based on the previous path in climbing record numbers, for the next test, I believe we can expect an altitude of around 80-90,000 feet and a flight length of about 162 hours (if they keep on tripling the earlier record), which would be almost a week (6 hours short). But according to QinetiQ, the ultimate goal is about 3 months in the air, so they still need some more tests. As we find this a very interesting development, We will try to keep you informed on the subject, but it may be some months before we can report another new Zephyr record, whic we are actually very much looking forward to!