Joe Hansen(@joehansen):Facts by #JoeHansenFacts That green flash right before a Falcon 9 lifts off is the engines being lit. The Merlin engines start with TEA-TEB, a chemical mix that bursts into flame the moment it touches oxygen. The boron in it burns green. Every start uses up a charge. At liftoff it comes from the pad, but in flight only the upper stage engine and the three landing engines carry their own. That puts a hard limit on how many times they can restart. Raptor on Starship skips the chemicals. Spark plugs light small torches, and the torches light the engine. No cartridges to run out of, and nothing extra to ship to Mars.

2026.10.19 02:56

Facts by #JoeHansenFacts# That green flash right before a Falcon 9 lifts off is the engines being lit. The Merlin engines start with TEA-TEB, a chemical mix that bursts into flame the moment it touches oxygen. The boron in it burns green. Every start uses up a charge. At liftoff it comes from the pad, but in flight only the upper stage engine and the three landing engines carry their own. That puts a hard limit on how many times they can restart. Raptor on Starship skips the chemicals. Spark plugs light small torches, and the torches light the engine. No cartridges to run out of, and nothing extra to ship to Mars.