Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

7 Platform one Unmanned Systems Technology | June/July 2021 Revector has reduced the size, cost and power consumption of its cellular phone monitoring system to fit onto a UAV (writes Nick Flaherty). The system captures the 15-digit unique IMSI number on the SIM card of a mobile phone. It acts like a base station, capturing data about the location of a target phone by measuring the signal strength from a silent call. Revector has used a software-defined radio (SDR) architecture to enable a two-channel system that weighs 750 g. Installing the IMSI-catcher on a UAV also meant using new plastics to reduce the weight of the aircraft and avoid issues with radio emissions. “We can connect to the 12 V supply in a 5 kg UAV but we had to use the plastics to replace the metal in the UAV to reduce the weight; this gives us 90 minutes of flight time,” said Andy Gent, CEO of Revector. “We have a number of SDR channels, and we scan the airwaves to detect cell sites and switch on a spoof base station to look at the IMSI. If it is the target we can hold onto it and make a silent call to it,” he said. “Our skillset is in developing the user interface and building our own 2G, 3G and 4G software stacks, and going from there we are building power amplifiers and SDR filters.” “We have to keep the wattage down with lower weight,” he added. “What we have developed works with five UAV manufacturers, with two channels with power amplifiers that produce up to 5 W, although they typically consume 1 W alongside a number of filter banks. “The filters provide isolation between the power amplifiers, the SDR and control channels to avoid damaging other parts of the UAV with the emission harmonics. The key thing here is not to interfere with the GPS and management of the UAV. To do that we have the UAV’s antennas pointing down, and we are trying techniques such as having antennas on all four legs of the UAV pointing down in a tight beam, for example when over a target,” he said. The IMSI-catcher has a range of 3-4 miles when in the air. Phone monitor fits on UAVs Cell needs no hydrogen Airborne vehicles A spin-off from Swiss laboratory EPFL has developed a compact, lightweight solid-oxide fuel cell for UAVs (writes Nick Flaherty). The cell, developed by Inergio, measures 20 cm long by 14 cm high and wide, and generates 25 W of continuous power. It is designed to use butane or natural gas rather than hydrogen to feed the anode, with atmospheric oxygen serving as the oxidising agent. “After 15 years of research we have been able to confine the high- temperature zone to a small area in the battery’s core,” said Inergio’s CEO Mahmoud Hadad. “This keeps insulation to a minimum and allows the smaller size for the same power output. “The big advantage of our system is that butane and propane are available commercially at a low price,” he said. “In liquid form, they are much lighter and easier to transport than hydrogen. We can generate 500 W of power with a 4 kg cell, which would give a delivery UAV 7-8 hours of flight time, compared with current flight times of around 60 minutes.” The cell’s design is scalable and can supply between 25 and 500 W. It operates over a -30 C to + 70 C range with an efficiency of 0.47 litres/kWh (0.37 kg/kWh) and has an energy density of 2.1 kWh/litre (2.7 kWh/kg). The next step for Inergio will be to test its system with various companies in the Lake Geneva area and develop a pilot production line. Fuel cells The fuel cell design took Inergio engineers 15 years to develop