The VARIES Antimatter Catalyzed Fusion Drive produces 1.71 units of solid hydrogen per second while running, resulting in a gain of 0.02 units per second.

This is caused by the method InterstellarReactor.UseProductForPropulsion, which seems to be missing a step: Instead of giving back some propellant, it gives back all of the propellant.

How is this supposed to work? I can create a pull request once I know how to fix it.

the idea is to give back the mass of the fusion products, so they can be used for propulsion. This is especially important for pure fusion mode where the engine is supposed to run on fusion products. The plan was to use the new temporary resource, Charged Particle (which now has a mass), so it can be used by ModuleEngine to generate force, and any excess could be thrown away.

I think I figured it out. Pull request is open