109 superior corrosion resistance. “The robustness and corrosion resistance of these far outweighs any weight penalty they impose,” Kempley emphasises. Finally, specialist aerospace plastic inserts integrate components to complete the structure. Through stress analysis and load testing, critical areas were identified and selectively reinforced while lighter regions were optimized. This data-driven approach ensures a well-balanced structure, maximizing both strength and weight efficiency, he adds. Staying smooth For a UAV that must carry high-resolution cameras, minimising vibration is critical and preserving that smoothness through the platform’s evolution is equally important, as Kempley explains. “After any initial design, or iteration of the platform, we conduct vibration tests to identify any areas of concern. However, integral to the design of the platform is a number of “break” points, where vibrations are eliminated through material choice. We also ensure correct balance on all motors and propellers, again to minimise any disturbances.” For a UAV with military applications, a degree of stealth is always an asset, and this attribute is now incorporated into the company’s vehicles. “At the V2 revision of the Sensus M, we were asked to consider having a lower radar profile on the platform,” Kempley recalls. “This led to the now iconic zigzag pattern of the side hulls on our entire range of UAS. The idea is that it removes several flat/perpendicular surfaces, and it was tuned, to a degree, for the optimal reflection patterns.” Propulsion and control Propulsion and control forces are generated by either 4 or 8 brushless direct current (BLDC) motors, each rated at 100 Kv. The Kv rating relates the motor’s speed to the voltage applied to it without a propeller or any other load, so a 100 Kv motor will spin at 100 rpm per volt. A 100 Kv motor has a relatively low Kv rating, so it will spin more slowly for a given voltage but typically generate higher torque than a higher Kv motor of the same power rating, assuming similar design and efficiency. Such motors are well suited to large propellers and heavy loads. Each motor can generate 8 kg of thrust while consuming 900W at full throttle. In the Sensus L vehicles, however, they are generally run at just 55% of their capacity even when the UAV is loaded to its maximum weight. This puts them Uncrewed Systems Technology | April/May 2025 ISS Aerospace Sensus L heavy-lift multicopter | Digest Sensus L8 carrying a Radarteam Sweden Cobra CBD ground penetrating radar primary payload, pictured with a Boxer remote controlled howitzer (All images courtesy of ISS Aerospace)
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