32 fact that “so many companies make sensors and comms systems for mission capabilities as boxes – rectangular things with 90° edges that don’t fit easily into Insitu’s predominantly cylindrical fuselages”, Todorov observes. “So we offer a few different variants of that square payload bay, one of which has an outer skin that serves as a structural fairing, and another where all the structure-critical parts mount up into the aircraft, and the outer fairing for that version is non-structural, hence giving that base design a lot of flexibility for whatever customers want to put into the bay. Being a simple, rectangular component also allows us to customise for different internal mounting or cooling needs fairly easily too.” Also key to this has been judicious selection of components such as electromagnetic (EM)-shielded connectors and cables to minimise the RF emissions of both UAVs, as a sizeable portion of Insitu’s customers fly highly EMI-sensitive solutions, such as signals intelligence, non-communications-based signals and communications relays. In addition to the wide range of EO and IR cameras compatible with the nose turrets of both UAVs, today’s ecosystem of core payload offerings encompasses numerous high-end systems embedded with critical image-processing algorithms for actionable wide-area surveys, including Overwatch Imaging’s PT-6 EO/ LWIR maritime gimbal, Sentient Vision Systems’ ViDAR (typically integrated as a slice), and Logos Technologies’ wide area motion imagery (WAMI) and middle wavelength infrared (MWIR) sensors. Structure and hull The defining factor behind the structures of ScanEagle and Integrator is the highly energetic catapult-launch event that has kicked off the majority of their missions over the years. The shock and force of catapult launching places a minimum structural-strength requirement across numerous key points of both aircraft. As a result, the shapes and structures of both UAVs have remained mostly unchanged over their years of development, with the most noticeable evolutions including ScanEagle’s move from a fixed nose globe turret to an articulated dome that can roll 360o. The remainder have been minor tweaks for qualities such as structural strength, vibration damping and the packaging of internal systems. While the catapult launch is far less vital a consideration for customers relying on the modern VTOL-capable version of either UAS, Insitu is determined to maintain backwards compatibility with the SkyHook, just in case customers need to use them in rare instances. “We use some complex, finite element analytical tools to generate effective heat maps of any mechanical stresses that get communicated through the monocoques of our aircraft during launch and recovery, and we know from routine analysis that loads during cruise are very stable and straightforward,” Todorov says. “It is in launch and recovery where we get highly dynamic forces acting on the UAVs, and load-paths changing very rapidly, and coming in from directions that you might not normally expect. We use all that data to inform our carbon lay-up structures, and from there it’s just a matter of close interaction with and deep trust in our composite suppliers.” Pearce adds: “We control our part designs and stocks to very tight tolerances, and there is a lot of ‘coupon testing’, where we put samples of materials through rigorous validation processes. When we release a design for a structural part every numerical parameter that can be specified, verified and validated in the material is specified, verified and validated at Insitu.” Significant interactions tend to follow the validations of structural parts to achieve secondary (though still important) goals such as manufacturability and weight optimisation. Despite the minimum structural strength requirements, Insitu’s engineers constantly evaluate every structural part in terms of the mathematical relationships between grams added onboard either UAV and the corresponding number of minutes that endurance would shrink by. GNSS and MEMS Insitu primarily partners NovAtel for its navigation systems, with a variety of GPS and multi-constellation GNSS receivers (with MEMS IMUs) from the Hexagon company having been installed on the ScanEagle and Integrator over the years, largely for their high positioning accuracy. June/July 2024 | Uncrewed Systems Technology Non-gimbal payloads such as Overwatch Imaging’s PT-6 are often installed and flown on Integrator
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