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@pirrer · 2026-10-16 23:25

@Tesla says it put “a rocket in Roadster.” At the October 15 unveiling, @Tesla said the new Roadster borrows technology from @SpaceX. Two pieces stand out. The first is a carbon-overwrapped pressure vessel: a thin metal liner wound in carbon fiber, much lighter than an all-metal tank built for the same pressure. Falcon 9 uses this construction for helium tanks inside its liquid oxygen tanks. The Roadster has two, with a combined capacity of 600 liters, holding about 250 kg (550 lb) of air, according to Tesla. The second is cold-gas thrusters. Nothing burns; high-pressure gas goes out a nozzle and pushes the car the other way. Falcon 9's first stage uses nitrogen cold-gas thrusters to flip around after stage separation. The Roadster has four nozzles at the rear, and an engineer at the event said they make more than 80 kN of thrust. How long can that air last? Tesla hasn't released the car's weight. Assuming 4,400 lb and typical thruster efficiency, all four nozzles wide open would run out in about 2 seconds; just holding the car up, about 7 to 9 seconds. Tesla's footage shows roughly 4 to 5 seconds of hover. The estimate fits, but the footage can't show how much thrust was used. The fans that hold the car to the wall are a 1970s racing technique, not rocket tech. And unlike propellant on a typical rocket launch, the Roadster's air can be pumped back into its tanks on board.

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