British Armed Forces fixed-wing drone captures images of the stratosphere

In addition to conventional drones and satellites, a new unmanned aerial vehicle capable of surveillance operations could soon be deployed by the UK military. The British-developed drone, called PHASA-35, has the unique ability to fly in the stratosphere, which is not used by other conventional aircraft.

PHASA stands for “Persistent High Altitude Solar Aircraft”, while the number 35 in the name indicates the wingspan of the drone in metres. This is the same size as a Boeing 737 wingspan, but thanks to its carbon fibre frame, it weighs only 140 kilograms. “Thanks to the lightweight frame structure, it can stay in the air for a long time and can be used for large area reconnaissance. These are perhaps the two most important characteristics of aerial surveillance systems,” said Drew Steel, an aviation consultant for British company BAE Systems, which has bought the rights to manufacture and sell the drone from Prismatic, another British design company.

The unmanned aerial vehicle is equipped with long-life, solar-powered electric motors. It is designed to fly at an altitude of 20,000 metres in the airspace between the Earth’s atmosphere and space. By comparison, a passenger aircraft cannot fly above 12,000 metres, where the air is a thousand times thinner than on the Earth’s surface, and would need extremely long wings to stay airborne. “Solar power will allow PHASA-35 to stay aloft for up to a year. It can also make multiple landings and take-offs, which makes it cost-effective to operate. There is no need for the very expensive rockets used to launch satellites into orbit,” Steel stressed.

However, this drone is not designed to replace satellites as it can only carry a payload of 33 kilograms. However, this is already enough payload to lift the sophisticated camera system developed for the armed forces into the air, so that it can capture high-resolution images of the stratosphere. It is therefore suitable for observing people and vehicles of interest to the armed forces. The system can also be used for civilian operations, such as monitoring forest fires or oil spills.

The first test flights were carried out in February 2020, just two years after the start of design. The operations were conducted over unpopulated areas of South Australia, mainly to test the drone’s autonomous flight control system, its engine performance and the aerodynamics of the aircraft. Once the propulsion and energy efficiency indicators met expectations, the first real test flight was carried out a few months later, in October 2020, during which PHARSA-35 operated for three days in a live environment, i.e. in the stratosphere. The developers observed the effects of extremely low temperatures and extreme pressure on the drone. The company expects to complete testing and start mass production within the next four to five years.

Source: Popsci