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The Zephyr 8 flies very slowly and above the high-speed jetstream winds and weather systems, loitering over selected areas under the guidance of a ground controller. It is very tolerant of high winds and has even flown backwards at over 100 mph. .

Pseudo satellite, potential disrupter, flies on sunlight

It used to be that the defense sector set the bar for hi-tech electronic developments, which were then adapted, subject to security veto, and then applied to commercial aviation. Examples included advanced avionics and navigational systems. In the 1990s global positioning systems were only used by the military, but now almost everyone has a hand-set of some kind with accurate GPS data available 24/7 in every location, and cars and boats have access to precision directions to wherever they need to go.

It is the military that has now been playing catch up in most cases, with front line troops still using secure tactical radios in the field that are little different to those used years ago, while in their free-time soldiers can use their own iPads and iPhones to access social media across the planet. Realistic computer-generated imagery that has emerged from studios in Hollywood and elsewhere, and can be seen in the latest movies and computer games, have out-paced the flight simulation sector, and are now finding new applications in training and aboard ISR (intelligence, surveillance, and Reconnaissance) special mission aircraft.

All these devices, civil or military, now depend to a large degree on the vast and growing global network of unseen space satellites that allow all these bandwidths and nodes to co-exist, delivering seamless interconnectivity.

Two big problems that come with this are cost and sustainability, and a third is obsolescence. Launching satellites is an expensive undertaking and so a new generation of relatively small and simple launchers are being developed to launch small low-cost space vehicles (smallsats or cubesats), which have a limited life. Once in a low-Earth orbit they can’t be upgraded or repaired.

As needs and capabilities are changing all the time, satellites can become obsolete and therefore have to be replaced on a regular basis. Satellites can remain in orbit and operating for up to 15 years and over this time the sophistication and miniaturization of components can change significantly. So as the near-space surrounding the Earth fills up with thousands of man-made platforms, how can the benefits of space-enabled services be sustained in a more affordable way? This where the so-called pseudo satellite comes into its own.

Think of a giant model airplane platform that has an entirely self-contained electric power system and which can stay on station above the highest flying manned or unmanned surveillance aircraft for months at a time. It can act as an airborne eye-in-the-sky or communications node, and do many of the tasks previously in the hands of small satellites.

When service is required to renew or upgrade any component or sensor, it can return to Earth and another such vehicle can take its place, so a continuous capability can be maintained at all times. And it costs just a fraction of the clutch of small satellites needed to do the same thing.

Such a vehicle exists now, and it looks as if it might eventually have a big impact on providing persistent communications links without needing an expensive space launch infrastructure and rocket to blast the individual space vehicles into position.

For several years, technology development company QinetiQ, based at Farnborough in the U.K., worked on developing a prototype solar-powered UAV, the Zephyr, that might have practical applications in a larger form, with provision for a useful payload. The concept was proven, with an ability to stay in the air for several weeks, extending into months, breaking world records in the process.

The project has since been bought by Airbus Defense & Space, and has won its first production order for two air vehicles from the U.K. Ministry of Defense. The new Zephyr 8 will fly at 65,000 ft or above and can provide surveillance over land or sea, hosting communications links over the same area for weeks or months without the need for any maintenance during that patrol period. The precise purposes for which the aircraft will be used have not been disclosed, though earlier references from the MOD said that Special Forces would be given enhanced surveillance and communications assets in their global tasks.

The Zephyr 8 flies very slowly and above the high-speed jetstream winds and weather systems, loitering over selected areas under the guidance of a ground controller. It is very tolerant of high winds and has even flown backwards at over 100 mph. The only aircraft capable of flying regularly at these heights were the Concorde supersonic transport and the SR-71 and U-2 spy planes.

As with the earlier Zephyr 7, which broke the world endurance record in 2010 with a 14-day continuous mission, lasting almost 340 hours, the latest version charges its batteries from sunlight during the day and maintains its height on stored power at night. No other UAV has flown unrefuelled and continuously for more than 80 hours.

Zephyr 8 has a wingspan of 25 m and can carry 50% more batteries than the earlier version, yet is 30% lighter. This translates into a vehicle that can carry a heavier payload and is designed to, typically, stay in the air continuously for over a month. The basis of the requirement was a military one but the Zephyr can also be used for humanitarian missions, precision farming surveillance, environmental and security monitoring, and also to provide internet coverage to remote regions with zero or poor connectivity.

With environmental performance now a major factor in developing new aircraft, Zephyr scores heavily by using just sunlight to fly and recharge its batteries, powering small electric motors and producing no carbon dioxide while consuming no fuel. Replacing just one conventional UAV with one Zephyr would save 2000 ton of fuel each year.

Although it can carry out a worthwhile mission it remains remarkably light—just 30 kg. It is so efficient in flight that if its power was switched off it still takes 30 hours to reach the ground, 12 mi below.

The structure can support five times its own weight but uses ultra-thin fibers, the thickness of a human hair. The detailed design of the complete aircraft, which involved cooperation at the component stage with a Formula One supplier, is so sensitive that even the design of the propeller tips is secret. Weights equivalent to two and a half times the expected loads are attached to every rib to test the aircraft’s strength. This can bend the airframe to an extreme degree, with the upturned wing tips deflecting to below the fuselage, demonstrating its robust characteristics, despite its low weight.

The concept of pseudo satellites is an exciting evolution beyond mere UAVs. They can be made relatively autonomous, flying pre-selected patrols, but able to be re-tasked if need be from the ground. At the extreme altitude at which they operate there is no need for sense-and-avoid equipment, which would add weight, and they don’t need self-defense measures.

Time will tell just how reliable or how much utility can be gained by having a few in use alongside more conventional manned and unmanned air platforms. The latter will always be able to carry heavier payloads, and even weapons, but the costs of operating large or medium-size UAVs is similar to that for manned aircraft when all the control and support infrastructure is taken into account.

Satellites today provide essential surveillance and communications capabilities that only space access can address, but as space platforms move out of position several are needed to provide continuous coverage, and this is an expensive exercise.

If the Zephyr-type pseudo satellite is looked at simply as another UAV it will appear to have limited capabilities. Similarly, if seen as just a substitute for satellites it may look an inferior replacement.

But if one looks at its potential from outside the box—as a breakthrough air platform and a disruptive new technology—then it might be appreciated more as an easily affordable air asset with enormous commercial value as well as providing safe and secure military communications at a very much lower ownership and operating cost than anything else in the air. From that perspective it could be really game-changing.

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