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23 Kevin Bean | In conversation that, shaping them to fit the aerodynamic profile of the front and rear of the UAV’s body.” Bean and his team have worked particularly closely with TWI in order to develop their liquid hydrogen storage solutions. While specific energy is measured in kWh/kg, and is thus the same between gaseous and liquid hydrogen, the company is opting for the latter, far newer fuel as it yields a significant energy density (kWh/litre) advantage, reducing the size of the tanks and ensuring they will fit inside the UAV. “Once you’ve dealt with the issue of volume, the next challenge is keeping the liquid hydrogen cold,” Bean explains. “We’ve designed our insulation system so that any heat coming into the tank is directed straight to the output of the tank. And to store it cryogenically, we’ve developed a carbon fibre, polymer resin composite tank that’s very lightweight, with a proprietary barrier and insulation layer to contain the liquid hydrogen and maintain the stable low temperature needed for storage. “We’ve partnered with several companies, mainly in the UK, to design the tank structures and which are now ready to be built, to hold the liquid hydrogen. And we developed our own labs and test equipment to validate that we can hold liquid hydrogen in them.” He adds that the fuel cell power system for providing electricity to the antenna system has been developed by himself and his team, and lab-tested in simulated stratospheric conditions, inside a chamber depressurised to 0.07 atm. Custom compressors were developed to ensure the low-pressure ambient air could still provide sufficient reactant oxygen to the cathode for the aforementioned 22 kW output. Propulsion, however, will not be electric but IC engine-based. A low- cost, reciprocating aircraft engine is to be supplied for combustion of the liquid hydrogen at high altitude, as it is viewed as the optimal route for propulsion efficiency, minimised maintenance costs, and ease of certifiability (compared with using a fuel cell for propulsion). “Hydrogen power systems for mobility applications are very well placed right now,” Bean observes. “There’s been so much work done in the car industry and aerospace to push hydrogen power and propulsion technology, not just in performance and efficiency but in the supply of parts and most importantly certifiability – if we’d tried to do this 10 years ago it would have been impossible. “So, unlike some aspects of the HAP’s subsystems, all the technology for hydrogen combustion already existed – the real trick is certifying it.” Project roadmap As well as Deutsche Telekom, Stratospheric Platforms is working with partners including Scaled Composites, NCC, Cambridge Consultants and several others to progress the various technologies of the HAP, and is now in the process of securing its next phase of funding. “We have effectively proven all the fundamental technologies,” Bean says. “For instance, the hydrogen engine concept is proven thanks to our [undisclosed] supplier, the fuel cell works in stratospheric conditions, we have everything we need to create the liquid hydrogen tanks, and we’ve tested their individual components separately. “Also, the antenna is built, fully ground- tested, and the next step is to use it in the air. Lastly, the aircraft concept is fully fleshed out and we’re at the start of developing the prototype system. We intend to have the prototype built and flying within 18 months, and have it certified and ready to start commercial operations by 2025. “The systems-within-systems aspect of UAVs has fascinated me for years, so I’m excited to see how the project will progress. One day we’ll be working on an electro-optical system, the next we’re talking about certification of the flight controls, and the next after that we’re talking about the logistics of fleet replenishment and maintenance.” Unmanned Systems Technology | February/March 2022 Kevin Bean was raised in Berkshire, England, where he attended various primary (elementary) schools before going on to secondary education to focus on mathematics, physics and computer science. He studied at the University of Warwick from 1995 to 1997, obtaining his BSc in Computer Science at the end of 1997, and started his career at Thales in January the following year. Initially he joined the French multinational as part of its software graduate programme, and over the next 18 years he worked on a range of projects as software engineer, software team lead, programme manager and systems engineer. During this period he also served as a Territorial Army infantry signaller for about 7 years with the Princess of Wales Royal Regiment. He also held the role of programme design authority for UAV projects and UAV Through Life Insertion programmes at Thales. Bean joined Stratospheric Platforms as VP of systems integration in November 2016, before being promoted in April 2019 to the dual roles of VP of operations & VP technical. Kevin Bean