Summary: I want to build a linear actuator that has a very fast actuating speed but fits in a very small space. Is igniting hydrogen/oxygen produced from an electrolysis fuel cell in a combustion chamber to drive an air cylinder a feasible option?

My Question/Idea: Electric gearmotors, c02, and air pressure, are all ideas that come to mind for this but they all have drawbacks. Gearmotors can only be so small before the power output to rpm is too low. C02 cartridges are stored at very high pressure and the small canisters are not very suitable as regulators and fittings seem to be scarce for their use in non purpose built applications. Air compression requires the compressor and air tank which are too large for my application. This leads me to wonder is it possible to drive a pneumatic cylinder using an ignited hydrogen oxygen mixture created using a very small electrolysis hydrogen fuel cell? When considering this I think of how a combustion engine works much the same way. Igniting a gas to drive a cylinder. I'm not sure whether pressure is maintained after ignition within the cylinder like in standard pneumatics with an air compressor. I would expect not. But if using a spring return cylinder would it not be possible to drive that cylinder forward with a very small amount of ignited hydrogen and let the spring return it to its original position? If this works we get a powerful and very small linear actuator with a regenerative gas supply that only requires water and a battery as inputs as well as electrolyte at a less frequent rate. I am interested in doing some experiments to test this idea but before I do I would like to hear from the physics community. I have asked the engineering community but so far the response has been alternatives to this idea and not answers to whether or not it's possible. Do you think this feasible? Is there something I have not considered?