Wave J-1 | Engine dossier end of the COTS systems available,” Maqbool says. Control of the pump, injector and ignition is handled via pulse width modulation (PWM), both for its use in developmental fine-tuning and its ease in connecting with the full range of flight controllers (including non-CAN ones). Going forwards, Wave Engine plans to offer other forms of interfacing on customer request (and Maqbool reports they have built ECUs that communicate by CAN in-house), particularly to make detailed performance and health data available to end-users for diagnostics and maintenance tracking. Metalwork In pursuit of an inexpensive, rapidly producible engine, the three metal components of the J-1 have been predominantly made from 304 stainless steel, being the most commonly found steel and easy to work with. “There’s aluminium in a few key places where weight-saving has been prioritised over strength, but there are workshops all over the place that can do metalforming and -bending with 304 stainless, which means we have easy access to production suppliers, depending on our need,” Maqbool says. “We also have CNC-milled parts in a few places, but ultimately we want to reduce those because it’s just cheaper to stamp or bend metal.” Using more advanced materials such as titanium alloys could halve the J-1’s weight, although this would at least double the material and manufacturing costs. It would additionally go against Wave Engine’s targeted advantages in cost, manufacturability and simplicity, however, so it is not a priority for now. Once formed to shape, the two pipes and the combustion chamber are welded together to create a single, solid piece of metal. Mounting brackets and other peripherals may be bolted on afterwards. As of writing, no liners are being used inside the engine, although Wave has built several engines with liners, and anticipates applying coatings or other internal materials for special applications with specific thermal, noise, packaging or longevity requirements. “Though in theory, liners could reduce the amount of heat the engine radiates outwards, which is significant, that could improve performance by reducing thermal losses,” Maqbool notes. “In our experience, it won’t be a huge efficiency gain, but it won’t be a net boost of zero either, in theory.” Future With steady interest in the J-1 from UAV manufacturers, and optimisation plans for the engine laid out, Wave is now turning some attention and r&d resources to its larger sibling, the K-1, which produces 220 lb (99 kg) of thrust force. “UAVs are always going to be an important market for us, and I do expect to see a lot more aircraft with the J-1 before we see them integrating the K-1,” Maqbool says. “And, as important as defence markets have always been for pulsejets, there are commercial applications for pulsejet technology too, and we don’t want to lose sight of those, or what it will take to meet the standards those manufacturers and integrators have.” 73 Uncrewed Systems Technology | October/November 2024 J-1 Pulsejet Spark-ignited Air-cooled Gasoline (E85, Jet-A and JP-8 optional) Weight: 7.5 kg Maximum thrust: 236 N (24 kg of force) Thrust-specific fuel consumption: 54 g/kN.s Dimensions: 163 x 32 x 14 cm Key specifications The engine is predominantly made from 304 stainless steel (an easily sourced metal, driving home the J-1’s simplicity advantage) with some aluminium for weight saving
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