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22 “For another early unmanned project, we simulated how different payload pods for cameras, radars and other sensors would affect drag on the outer mould line of an existing UAV, and how performance could be preserved by optimising the aerodynamics of the payloads,” Leto says. “But really there are so many interplays with unmanned systems optimisation beyond just reducing drag. Say you have an air-cooled engine: you need to look at mass airflow, and how evenly distributed the shear stress is across heat exchangers or cylinder heads. We can do a full simulation with heat and everything, but in principle you primarily have an issue of getting air where it needs to go. “If we want more detail, we can go to something called conjugate heat transfer analysis, which investigates rates and kilowatts of temperature transfer from solids to air. That is eminently doable through our CFD and is fairly straightforward for us, as is minimising drag creation from the cooling approach, through the right ducting, air intake, minimal flow separations and more across the whole flight envelope.” Next-generation vehicles Leto notes that optimising for trade-offs in this and other subsystems becomes even more critical given the latest engineering trends in vehicle design. For instance, electrification increasingly comes with demands for the last 0.5-1% of efficiency, given the greater challenge of remote recharging compared with remote refuelling. Also, the surge in heavy UAVs and eVTOL designs comes with new challenges and questions raised over aerodynamics efficiency (not to mention safety) over the flight envelopes of some untested new aircraft architectures. “We’re adding real value there, because a lot of manoeuvres and flight conditions can actually be captured and analysed in a virtual way far better than they can physically,” Leto says. “Real-world tests are great, but being able to instrument the vehicle, collect the data and understand what’s going on from an aerodynamic or thermal side – and simulate interactions and deflections between peculiar new combinations of different rotors, wings, control surfaces, pods and so on – is horribly challenging. “We can study that through scale models and software models in our combined physical and virtual testing to iterate tens of thousands of hours of data about what’s going on with any flow separation, varying rotor rpm, efficiency differentials over different points of the flight envelope and across different conditions. This kind of mapping allows an entirely safe way to test the edges of the flight envelope. “The more we can model a vehicle, the more we can get on top of any feasible issue that could arise. Going forward, we can build flight control systems around the forces and physics we’ve mapped, which can then go into an autopilot and servo architecture to build an all-round safe and efficient aircraft.” Future plans As the company’s endeavours in unmanned systems engineering continue, Leto plans for his company to keep on top of new technologies while also pushing the science forward, be it in GPUs and other computing platforms for CFD calculations, or even newer areas such as physics-informed machine learning for AI simulations. “We produce dozens of gigabytes of data with each new simulation, and we need to wipe hundreds of terabytes each year to make space for new projects, so we’re closely studying new intuitive learning models for how they could help us optimise designs faster and with fewer resources,” he says. “There are other new techniques in maths and science we’re looking at as well, across software as well as computer advances. The technology’s getting better, and we’re getting better in what we do and how we can leverage new inventions quicker.” April/May 2022 | Unmanned Systems Technology In conversation | Ray Leto Ray Leto was born and raised in Kennett Square, Pennsylvania, and studied Aerospace Engineering at Penn State University, graduating in 1989. He initially worked as an engineer for motorsport team Truesports, which was absorbed by Rahal- Hogan Racing in 1992. Soon after, he became an aerodynamicist, before being promoted to technical director in 2000 and team manager in 2002. After several more years of race engineering and some aerodynamics consulting – as well as working as a race engineer for Sam Schmidt Motorsports and Luczo Dragon Racing between 2007 and 2009 – he co-founded TotalSim US, where he has served as CEO for 13 years. In addition to his professional work in leading the company’s CFD and engineering services, he also serves on the external advisory board at Ohio State University’s Modeling and Simulation Center, as well as on organising committees for the SAE World Congress’ Motorsport Engineering and Vehicle Aerodynamics sessions. He also volunteered as a medical scribe for the Ohio’s Medical Reserve Corps’ Covid-19 vaccine clinics from 2021 to ’22. Ray Leto