3 May 2018
A British project to develop a high-altitude solar-powered unmanned aircraft capable of staying aloft for a year at altitudes up to 70,000ft has got a boost from BAE System. The aerospace major has agreed to work with Farnborough-based Prismatic to realise its PHASA-35 high-altitude long-endurance (HALE) unmanned system; a first aircraft is expected to begin flight trials next year.
PHASA-35 – Persistent High Altitude Solar Aircraft – features a 35m wingspan but mass of just 150kg. Designed for remote sensing, surveillance, communcations or environmental science, PHASA-35 should be able to operate year-round at latitudes up to 35°, or at the poles in summer, according to Prismatic. A quarter-scale version flew last year; PHASA-8 was designed to replicate at sea level the behaviour of a HALE at 65,000ft.
Whether such platforms are called HALEs, BAE and Prismatic’s choice, or HAPS – high altitude pseudo-satellites – there is growing interest in a capability seen as offering some of the value of a satellite at a fraction of the cost and, critically, deployable tactically, where persistent high-resolution coverage is needed of a particular region. They could also be deployed if needed to ensure reliable telecommunications to remote or challenging locations, for example to a steep-sided valley. HAPS have been referred to as bridging the gap between drones and satellites.
At least one HAPS platform is available today. Airbus Defence & Space’s solar-powered Zephyr in 2010 set a world endurance record, staying aloft for 14 days without refuelling. The improved Zephyr S version has a 25m wingspan and flies at 65,000′. The UK ministry of defence intends to buy at least three for unspecified uses.
Other HAPS projects include an autonomous airship called StratoBus, which its maker, Thales Alenia Space, describes as a cross between an aircraft and a balloon – and “halfway between a drone and a satellite”. And, California unmanned air systems maker AeroVironment earlier this year teamed up with Japanese telecommunications group SoftBank to develop a solar-powered HAPS; performance and applications have not been specified, but the project has a $65 million budget.
PHASA-35 brings another of the world’s leading aerospace companies into the HAPS arena. Managing director Paul Brooks describes Prismatic as a small company with skills in technology and systems development but not production or services, “which is where the real value lies”. As for BAE, air strategy director Michael Christie says his company was interested in space rather than high-altitude UAVs, but met Prismatic through its space activities and saw “great synergies” between the two.