Uncrewed Systems Technology 047 l Aergility ATLIS l AI focus l Clevon 1 UGV l Geospatial insight l Intergeo 2022 report l AUSA 2022 report I Infinity fuel cell l BeeX A.IKANBILIS l Propellers focus I Phoenix Wings Orca

86 Dossier | Infinity APWR fuel cell the application. In the Blue Origin New Shepard-23 flight for example, it was designed for remote activation, with its operation being automated. “After commencing the remote start, the system pressurised itself internally to its target pressure, before introducing reactants from the external hydrogen and oxygen storage units,” says Smith. “Then it went through a series of self- checks, making sure all the electronics and valves were working correctly, and finally introduced the initial load. That whole process took between 1 and 2 minutes, and that was after it had been switched off and in storage for an extended period without operational checks.” After start-up, the pressure regulators allow the hydrogen and oxygen reactant gases through to the fuel cell, which enter through one of the circular end plates and flow into their respective chambers within each BPP-MEA grouping via manifolds in the stack. The opposite end plate meanwhile vents the water collected via the APWR system, as well as any inert gases. Balance of plant Most often, Infinity uses mechanical pressure regulators to reduce the highly pressurised hydrogen and oxygen to levels ideal for the internal chambers in the stack, most often going from 100- 150 psia down to 45 psia, although it has used and can install electronic regulators depending on the application. “For instance, a wide dynamic range in the fuel cell might result in single- point mechanical regulators suffering significant droop when going from low power to high power,” Smith notes. “At that point it might be useful to have either multiple mechanical regulators or just electronic regulation to accommodate that change in demand and prevent the droop.” Although high-purity hydrogen and oxygen are used, Smith says that since Infinity’s fuel cell is a dead-ended design, any inert gases that enter with the reactant gases will accumulate and must be vented. “We have a way of concentrating the inert gases inside the stack, so that when we do vent, we’re minimising the amount of unused reactant gas that exits the stack,” he adds. “It’s a proprietary design that allows us to flow hydrogen and oxygen through the stack in a way that concentrates those gases down to one end of the stack, in a device we call the inert concentrator cell section. “That captures and circulates gas at one end of the stack, and when it reaches a level that we measure by passing a current or voltage through that individual cell, we vent that very small portion of the stack. That means we don’t have to vent the whole December/January 2023 | Uncrewed Systems Technology Infinity’s NASA-funded Advanced Modular Power and Energy System, which operated successfully aboard Blue Origin’s New Shepard-23 sub-orbital mission We concentrate the inert gases inside the stack, so when we do vent we’re minimising the amount of unused reactant gas that exits the stack