Engineers celebrate world’s first flight of ‘lighter than air’ UAV
SOUTHAMPTON: A new type of unmanned aerial vehicle (UAV) has made a successful maiden flight thanks, in part, to the expertise of engineers from the University of Southampton.
The 15-metre long Phoenix with a wingspan of 10.5 metres is the world’s first large variable buoyancy- powered UAV. Resembling an airship with wings, in appearance, the ultra-longendurance aircraft spends half its time as a heavier-than-air aeroplane and the other half as a lighter-than-air balloon. It is the repeated transition between the two which provides the sole source of propulsion for the Phoenix’s anticipated use as a pseudo-satellite.
Under a project funded by Innovate-UK approved by the Aerospace Technology Institute, and bringing together SME’s, High Value Manufacturing Catapults and Academia, the ultra-long-endurance aeroplane uses the concept of variable-buoyancy propulsion that has been exploited previously for underwater remotely-operated vehicles (ROVs) but has never before been used successfully for the propulsion of a large-scale aircraft.
The fuselage is made from a vectran-based woven material and contains ~120m3 of Helium, providing buoyancy sufficient to make the complete vehicle lighter than air and ascend like a balloon.
Within the fuselage is a separate air bag with a capacity of six cubic metres. Pumps located at the mouth of this air bag can inhale and compress air from outside and thereby add weight (without altering the displacement) sufficient to overcome the buoyancy.
This transition to heavier-than-air flight allows the aircraft to descend like a conventional aeroplane.
The release of the compressed air returns it to a lighter-than-air configuration and the process is repeated.
The forward inclination of the lift/buoyancy vectors with respect to the flight path, and the expulsion of the compressed air through a rearward facing vent, provide a thrust force that propels the aeroplane forwards without need of any other form of propulsion. — University of Southampton News