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

62 Digest | Sky Eye Systems Rapier X-25 fibre materials, with an impregnation technology developed specifically for the Rapier programme. Notably, the structural architecture of the aircraft is designed to mitigate the transmission of vibrations from the engine to the payload, in order to maximise the image quality regardless of the payload. The aerodynamics have been designed in line with the US Mil-F-8785C standard, contributing to the X-25’s stall resistance, controllability, trajectory stability, and the prevention of inertial roll couplings between yaws, pitches and rolls. Its aerodynamic efficiency is such that if its engine fails, it can glide for about 60 km (assuming an initial altitude of about 4 km). That potentially enables a return flight to the launch & recovery point, or at least to non-hostile territory for recovery, all while flight control and stability are maintained. The hull’s aerodynamic shape and materials have also been chosen to minimise the craft’s radar and acoustic signature, preventing excess conspicuity for ISR operations. “OpenFOAM was the main tool we used to model the aerodynamic field around the Rapier’s hull shape,” says Schettini. In the course of its structural and aerodynamic simulations, the company also created a digital twin of the X-25 using Dassault’s CATIA V5, MSC Nastran, NX Nastran and Hyperworks, enabling detailed simulations for testing and optimising the hull’s characteristics. Schettini continues, “We have not done extensive tests of the whole aircraft’s performance in wind tunnels, but we have carried out considerable ‘specific point’ wind tunnel tests, for example in characterising the air intake for improved cooling qualities. Most of our validations of the overall aerodynamics have been completed in flight tests, which offer real- world conditions, and turned up very close matches in performance numbers with those predicted by our mathematical models and flight simulators.” He adds that the flight control software was also rigorously tested in those flight simulators in order to validate its safety and robustness, to minimise the risk of control failures in flight. These simulations were performed by plugging X-25 prototypes into the simulator inputs to maximise the realism with which mission- critical systems were being tested. Dassault’s ENOVIA PLM (product lifecycle management) software was also used for configuration management, to help ensure the Rapier’s life cycle in terms of its maintenance, use, and modifications or upgrades for example. Flight control architecture The core hardware and software of the flight control system (FCS) are designed in-house, so each module and line of code is accessible and configurable to its engineers. That avoids relying on a potentially closed architecture from an external supplier. The flight control computer (FCC) module contains the main autopilot CPU and is stored in the upper section of the fuel sector, along with an air data processing unit that connects to a pitot tube mounted slightly further back on the side of the fuselage. Additional navigation and localisation data comes from a GPS unit and INS supplied by Advanced Navigation (connected to each other and the FCC via a separate I/O expander board) installed approximately between the wings. Control outputs go out to four Volz servo actuators, one in each aileron, and one in each tail ruddervator. Having been written following the guidelines of the Software Safety Critical aspects of DO178-C DAL B, which Schettini notes is the highest level of software certification for (typically) unmanned aircraft, the FCC software can be automatically reconfigured in the event of a system failure, to help October/November 2021 | Unmanned Systems Technology Sky Eye’s proprietary GCS features four touchscreen monitors, military-grade data encryption, and numerous devices for manual interfacing and control