Issue 40 Unmanned Systems Technology October/November 2021 ANYbotics ANYmal D l AI systems focus l Aquatic Drones Phoenix 5 l Space vehicles insight l Sky Eye Rapier X-25 l FlyingBasket FB3 l GCS focus l AUVSI Xponential 2021

66 Digest | Sky Eye Systems Rapier X-25 Propulsion The X-25 is powered by a Corvid-29 engine from Currawong Engineering (also sold as the B29i in North America). It is a single-cylinder two-stroke, built around a 3W-28 design with a number of modifications. These include an altered crankcase design, a bespoke intake manifold and throttle body, and a self-priming fuel pump. Numerous electronic components including Currawong’s compact ECU, manifold and cylinder head temperature sensors, and EFI system, as well as a starter/generator allow it to output up to 250 W for powering UAV subsystems. A low-noise exhaust system has been selected to enhance the Rapier’s stealth. The engine weighs 2.4 kg, is air-cooled and produces a maximum power of 1.8 kW at 9000 rpm, with a specific fuel consumption rate of 500 g/kWh during cruise. It mounts at the back of the rearmost sector of the fuselage, with a two-blade pusher propeller providing traction. The various engine electronics and the CDI module are mounted in the forward part of this section. The lower floor of the fuel sector contains the UAV’s fuel tank. Also integrated here are a fuel level sensor running to the ECU, and a board for power distribution and management systems. The engine was selected for its high reliability as well as low fuel consumption, and for the convenience and weight efficiency of coming with a built-in starter/ generator. The X-25’s FCC governs the throttle width to optimise engine performance and flight endurance depending on the operating altitude and ambient temperature readings, while the ECU provides data on barometric pressure, throttle position and additional telemetry to the autopilot. “This 29 cc engine is key to how we obtain endurances from 10 to 16 hours, depending on the payload configuration,” Schettini says. To prevent vibrations propagating from the engine through to the payload cameras or other sensors, an engine restraint system is built into the ribs of the fuselage. This, combined with the Currawong engine muffler, means that no noise from the UAV can be sensed by the human ear so long as flight is maintained at more than 100 m overhead. SES adds that an alternative engine running on JP-5 heavy fuel can be integrated if required, for example by navy operators seeking a higher- flashpoint fuel than gasoline. Launch & recovery systems The X-25 is launched using a pneumatic catapult. SES has opted for this type of system over an elastic launcher (as used by some craft in this weight and mission class) as it can hamper the repeatability of launches, and its performance can be affected far more by the local environment and ambient temperatures. A transceiver in the catapult enables the X-25 to be launched as part of an automated sequence, which can be pre- planned and automatically managed by the flight software. Also, a proprietary (patent pending) system is available for launching the UAV from atop a road vehicle if the vehicle is moving at 80 kph or faster (also as part October/November 2021 | Unmanned Systems Technology The middle section of the X-25’s fuselage contains a parachute and airbag for safe landings The engine was selected for its high reliability, low fuel consumption and for the convenience of having its own starter/generator