The rabbit hole I emerged from yielded this, it was interesting: their SpaceShipTwo was powered by the RocketMotorTwo engine [1] fueled by the solid fuel hydrox

The rabbit hole I emerged from yielded this, it was interesting: their SpaceShipTwo was powered by the RocketMotorTwo engine [1] fueled by the solid fuel hydroxyl-terminated polybutadiene (HTPB) [2]. HTPB's primary precursor compound is butadiene [3], which is a synthetic rubber precursor. No rubber plantations were sourced for rocket fuel, as green as that would have sounded in the marketing collateral; good 'ol hydrocarbons, mostly. [1] https://en.wikipedia.org/wiki/RocketMotorTwo https://en.wikipedia.org/wiki/RocketMotorTwo [2] https://en.wikipedia.org/wiki/Hydroxyl-terminated_polybutadiene https://en.wikipedia.org/wiki/Hydroxyl-terminated_polybutadi... [3] https://en.wikipedia.org/wiki/Butadiene https://en.wikipedia.org/wiki/Butadiene