Issue 39 Unmanned Systems Technology August/September 2021 Maritime Robotics Mariner l Simulation tools focus l MRS MR-10 and MR-20 l UAVs insight l HFE International GenPod l Exotec Skypod l Autopilots focus l Aquaai Mazu

68 Dossier | HFE International GenPod very high quality and their performance is excellent – but we’re confident the new mufflers will match the unusual packaging, mounting and noise optimisations our GenPods need. “At a vibration frequency of 1000 Hz, the insertion loss and noise reduction of the new mufflers is expected to be around 70 dB, and around 30 dB across most of the range of operating vibrational frequencies.” As with all Slimline mufflers, the new ones from GenPod are built from aluminium parts that have been brazed together (rather than welded) to avoid stressing the metal components. Generator Designing the generator was a joint effort between HFE and Sullivan UV, with a degree of back-and-forth in terms of fitting it and its brackets into the GenPod’s design. Configuring the alternator and power electronics was handled largely by the latter (as were the decompression valves), with Sullivan’s power management unit (PMU) integrated for starter functionality and to operate the power bus between the generator and the GenPod-fitted UAV. The main rail of the PMU outputs a 24-28 V DC supply, with a secondary rail producing a 12-15 V DC output, and 5 V from a third one. “That provides for powering a wide range of onboard electronics, and for recharging a battery if needed,” West notes. “The generator is a similar design to those previously used on the DA-100 engines, and is cooled in the same way – using the air rush from the forward speed of the engine as it flows back over the propeller and spinner.” HFE asked for the generator to be as lightweight and compact as possible, while still being large enough to provide starting power. The 500 W it is rated to may be oversized for the GenPod’s needs, although the decompression system has contributed significantly to reducing the size of the generator. Future iterations of the electric machinery will be designed with hybridisation in mind. “In fact, the original concept for the GenPod was a hybrid powertrain with an electric prop drive on the back,” West recounts. “The current version of the GenPod is the first of several iterations that will eventually lead to a hybrid powerplant.” Propeller The standard-issue propeller is a 23 x 10 in, fixed-pitch carbon fibre prop from Mejzlik, which HFE and its development partners have simulated, tested and characterised to determine the August/September 2021 | Unmanned Systems Technology A fixed-pitch carbon fibre propeller from Mejzlik is issued as standard with every GenPod Future GenPods will incorporate larger Desert Aircraft engines and eventually hybridisation