12 Platform one April/May 2025 | Uncrewed Systems Technology WaveAerospace has constructed a heavy-lift multirotor capable of highspeed, long-endurance flight in very harsh conditions, including in obstacleladen and GNSS-denied environments at night and in zero visibility. The company has been in active R&D of its portfolio of UAS solutions close to 10 years. Its MULE (Multi-Mission, Utility, Logistics, & Expedition) UAS has gained visibility in recent months through participation in US Military exercises such as Project Convergence. First conceived as a more efficient alternative to the actual mules (equus mulus) currently used for logistics in the Himalayan mountains, the rotorcraft may be configured for both sea level or highaltitude missions. At 3.5 m wide with a MTOW of 250 kg with a 40 kg payload the MULE uses a JP-8 powered APU hybrid power system with silicon-anode batteries to achieve up to four hours of flight, with heavy fuels or liquid propane powering its four electric rotors. The aircraft can function at -17 to 50 C, with cruising airspeeds of 50-70 knots (25-36 m/s, or 91-112 kph). Its fuselage and triple-bladed props have been optimised for aero efficiency giving the body a unique diamond-like shape that generates considerable lift in cruise, which takes some of the liftgeneration burden off the propellers. This ‘full-body aerodynamics’ philosophy extends across the rest of the company’s portfolio, its Falcon II LE being another visible example. “We’ve spent 10 years of research optimising our body, propellers, and powertrain to use less energy; in comparison to nearly any other UAV of equal weight, payload, current draw, and thrust profile, ours will almost certainly plugging in devices (Strauss adds that military generators can weigh as much as ten MULEs, for the same energy and power offering). The MULE’s navigation systems have been optimised to give the flight computer all the necessary information for making optimal decisions. Hence, while GNSS, inertial sensors, a magnetic compass, and air data sensors are installed, understanding that these systems can be rendered imprecise by well-covered sources of inaccuracy drove the installation of a phased radar altimeter as a source of mission-critical guidance data. “Even Lidars and cameras can be hampered by poor-visibility conditions like night, mountain fog, or dust storms; radar on the other hand is fast, precise, and cuts through just about everything, but traditional single-ping radar gives somewhat limited data,” Strauss says. “By using phased array radar and translating its data into a form that the flight computer can digest, we can send our radar ‘pings’ out in a pattern, and measuring the time each one takes to get back. The result is effectively a map of what’s around the aircraft, showing us everything in the direction we’re heading.” Airborne vehicles UAV flies through dust, night and obstacles use less energy to take-off and fly,” says Mark Strauss, CEO of WaveAerospace. “And many don’t realise that electrical losses are the largest source of inefficiency in a rotorcraft next to drag and weight,” Strauss continues. “So we’ve worked to move electricity as efficiently as possible, with minimised copper losses. That extra power can then be used to stabilise the aircraft in bad weather, instead of wasting it as heat or magnetic electrical losses.” The MULE’s endurance and durability are aided on one hand by judicious use of sealed components and joints, which render its airframe IP67-rated, a quality the company validates to us through sharing of army demo footage of successful spool-ups and takeoffs in a severely dusty dry lake bed. Also key is the craft’s drivetrain, which incorporates a battery pack that enables 45 minutes of purely electric flight, as well as an APU for the roughly 40X practical energy gain (once thermal efficiency is accounted for) of heavy fuels and liquid propane over battery energy storage, with the onboard tank storing up to 6 gal (22.7 L) of fuel. When on the ground, the MULE’s APU can also be run as a stationary generator, with accessible ports on the fuselage for The MULE's body is shaped to generate lift in cruise, reducing the energy expenditure needed from its rotors (Image courtesy of WaveAerospace)
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