RESOURCE_DEFINITION { name = Nitrous Oxide density = 0.0085 flowMode = STACK_PRIORITY_SEARCH transfer = NONE isTweakable = true } RESOURCE_DEFINITION { name = HTPB density = 0.0065 flowMode = STACK_PRIORITY_SEARCH transfer = PUMP isTweakable = true } Hybrid Rocket fuel combination. This was the most promising fuel combination, thank you wikipedia.