UK-based global major aerospace and defence group BAE Systems (BAES) has reported that the PHASA-35 solar-electric powered high altitude long endurance (HALE) uncrewed aerial vehicle (UAV) has successfully completed essential tests, known as ‘soak’ tests.

The UAV is a joint project involving BAES, small innovative UK UAV enterprise Prismatic and the UK Ministry of Defence’s Defence Science and Technology Laboratory (Dstl). These trials followed after the UAV’s first flight, in February, which took place less than two years after its initial design.

The tests were conducted in a dedicated facility at Prismatic’s site, near Farnborough, in the south of England. The UAV was set up as a fully-integrated system, including a communications sensor payload from Dstl. This took the form of a radio frequency sensing software defined radio, including a real-time and secure datalink. In the test hangar, the PHASA-35 was subjected to the same temperature and pressure stresses that it would experience when operating in the stratosphere. Day (when it would draw power from its solar array) and night (when it would be powered by its batteries) were also simulated.

Under these simulated conditions, the aircraft successfully operated for 72 hours. Its highly-efficient solar array and long-life battery give it the potential to fly continuously in the stratosphere for up to a year. The stratosphere is a layer of the atmosphere that starts at about 10 000 m (or some 33 000 ft) above the ground and extends upwards to about 50 000 m (although at the poles it can start as low as 7 000 m and at the equator as high as 20 000 m). The PHASA-35 is intended to operate at just under 20 000 m (at 65 000 ft).

“PHASA-35 is a great example of how we’ve brought together the best in British expertise and partnered to drive technological innovation and deliver critical capability.” affirmed BAES Air COO Ian Muldowney. “This latest success, only eight months after PHASA-35's maiden flight, further demonstrates how UK industry and our partners are accelerating pace  to deliver the UK’s vision for innovation, a Future Combat Air System and information advantage.”

“I am extremely proud of the efforts the team have put into making these trials a success and to do this despite the challenges that a global pandemic has brought to us all,” highlighted Prismatic MD Paul Brooks. “By taking the best from the large company experience that BAE Systems offers, together with the agility of a small, innovative company such as Prismatic, we’ve been able to drive the programme forward with continued pace, culminating in the seamless integration of this first payload. This is an important milestone in bringing PHASA-35 closer to market, working alongside Dstl in the process.”

“BAE Systems and Prismatic have put the integration and operation of the user payload at the heart of the PHASA-35 design and it has been very satisfying to work with the team in so clearly showing the benefits of this approach,” pointed out Dstl principal payload adviser Paul Mather. “Dstl has a proud tradition of rapid proving of new technologies which provide military and security advantage, which this latest success reinforces.”

The UAV has a wingspan of 35 m (the same as that of an Airbus A320 airliner) but a mass of only 150 kg, including a 15 kg payload. It is within the category of HALE UAVs which are also called pseudo-satellites, because they fly so high and have such long endurance. Missions that it could fulfil include border protection, disaster relief, environmental monitoring, maritime and military surveillance and mobile and Internet communications to remote areas.