Fuel limits on a Covenant-style fusion reactor

Could a Covenant-style pinch-fusion reactor draw hydrogen from a planet's atmosphere, fuse it into helium, and then use the helium as a second-stage fuel?

Only where hydrogen is sufficiently abundant and cheap to extract; on Earth it would have to be cracked from water, while gas giants offer a more plausible supply.

Earth's atmosphere contains too little free hydrogen for direct harvesting to be useful. Cracking hydrogen from water is possible, but the process consumes energy and therefore has to fit inside the reactor's overall energy balance. Hydrogen is much more abundant around gas giants and stars, making those environments more plausible refuelling locations for the fictional system. The panel treats the design as workable science fiction only if its fuel cycle returns more energy than extraction and handling require.