Uncrewed Systems Technology 046

86 Dossier | Honeywell 600U, 600U-HV and 1200U fuel cells customise their components quickly and affordably, and we can’t pass that up if it means the customer gets to minimise or even not need any changes to their airframe to accommodate the heat exchanger.” The stock heat exchanger is typically square-shaped, measuring around 10 cm 2 . Most customisations stem not only from the aircraft’s shape but from the airflow rate, and integration is typically carried out in one of two ways. In fixed- wing UAVs it will probably sit inside the fuselage and receive airflow via a duct, whereas in multi-rotor aircraft there will be a pair of them, one each under an opposing rotor arm for balance, with direct cooling coming from the propellers. “As liquid is pumped through the fuel cell, we have a proportional valve system that can route more and more coolant through the heat exchanger as the temperature shows signs of rising,” Robinson says. “Obviously, the further you place the heat exchanger from the fuel cell, the more tubing weight you carry, and the harder the pump needs to work, but we tend to work closely with customers on optimising their hydrogen powertrains for both weight and thermal efficiency.” Future plans Although the move from Ballard to Honeywell was motivated primarily to best serve its DoD customer, interest in Robinson’s team’s fuel cell designs (and the range of partners it therefore works with) continues to widen. Robinson says, “We’ve recently started field trials with a couple of interesting companies and their platforms, which we can’t name at the moment. “One is a VTOL-transitioning aircraft, which is ideal for fuel cells as you can size the battery to the take-off and landing, and size the fuel cell for the cruise phase, getting the best of both worlds. The other is a UGV, specifically a quadrupedal robot, which is a commercial as well as a DoD platform. It’s a vehicle type we’ve not worked with before, which is quite exciting for us.” October/November 2022 | Uncrewed Systems Technology 600U Dimensions: 24.1 x 17 x 14 cm Weight: 1.8 kg Maximum continuous power output: 600 W Voltage: 12-33.6 V Maximum continuous current: 30 A Peak current: 50 A Specific fuel consumption: 53 g/kWh at 200 W 63 g/kWh at 650 W 600U-HV Dimensions: 23.1 x 15.5 x 13.7 cm Weight: 1.9 kg Maximum continuous power output: 600 W Voltage: 12-33.6 V Maximum continuous current: 60 A Peak current: 50 A Specific fuel consumption: 53 g/kWh at 200 W 63 g/kWh at 650 W 1200U Dimensions: 43.2 x 26.67 x 16.5 cm Weight: 4 kg Maximum continuous power output: 1200 W Voltage: 18-84 V Maximum continuous current: 60 A Peak current: 100 A Specific fuel consumption: 53 g/kWh at 400 W 63 g/kWh at 1300 W Specifications On multi-rotors, Honeywell will integrate the radiators beneath two of the propellers, with coolant pipes running parallel to the rotor arms