Their is a problem with the FX engine, it is not generating any hydrogen. To fix it go into the part.cfg file. Make a backup copy (I used part.old). Open part.cfg The path to the part.cfg is something like: C:\…..\Kerbal Space Program\GameData\SMA\Parts\Engine\SM-BRJ This is the entry you need under the FX engine. It is near the bottom. MODULE { name = ModuleAlternator RESOURCE { name = CompressedHydrogen rate = 90 } } Change it to this. MODULE { name = ModuleGenerator RESOURCE isAlwaysActive = true OUTPUT_RESOURCE { name = CompressedHydrogen rate = 90 } } I wanted to add that the rate may be to high. I don’t know what the author had in mind. I just noticed that it was not generating any hydrogen. After looking over the file it seamed that 90 was what the author intended. If you are using Ferram Aerospace Research v0.12.5.2. The only way to get those engines into space is with Procedural Fairings. Or remove F.A.R.