This lightweight solar-electric aircraft is an alternative to high-altitude satellites
Aircraft deployed for surveillance and communication missions usually need to be adequately fuelled before take-off. However, PHASA-35 – a high-altitude pseudo-satellite (HAPS) made by aerospace company BAE Systems – doesn’t rely on jet fuel. Instead it’s solar powered and charges up its batteries during daylight while in flight, so it can fly non-stop for months at a time. What sets this pseudo-satellite apart from standard satellites and aircraft is the layer of Earth’s atmosphere it operates in; PHASA-35 is designed to fly in the stratosphere, around 12.4 miles above Earth’s surface, as opposed to the troposphere, where commercial aircraft fly at around six to eight miles. Satellites orbit in the outermost layers of the atmosphere, the thermosphere and exosphere, upwards of around 50 miles.
PHASA-35 is unmanned and remotely operated from the ground. Its movements can be preprogrammed, but rely on careful weather monitoring for launch. Unlike a satellite’s, the payload on the HAPS can be replaced at any point, as it can be returned to Earth in one piece at any time. It weighs just 150 kilograms, which is about the same weight as a standard motorbike. Keeping its weight low during production was essential because the stratosphere isn’t an easy location to keep a vehicle aloft. The air density is lower at higher altitudes, reducing the air available to lift the aircraft. Its ‘monocoque’ structure means that all the components are attached to and supported by the external skin, and the lightweight materials used are a secret carbon-fibre composite.
