 A launch vehicle that uses hypergolic propellant must therefore carry a greater mass of fuel than one that uses these cryogenic fuels.The corrosivity, toxicity, and carcinogenicity of traditional hypergolics necessitate expensive safety precautions.Although not hypergolic in the strict sense (but rather pyrophoric), triethylborane with triethylaluminium, which ignites spontaneously in the presence of air, was used for engine starts in the SR-71 Blackbird, the F-1 engines used in the Saturn V rocket, and the Merlin engines used in the SpaceX Falcon 9 rockets.