Yann LeCun calls Tesla's flying Roadster a marketing stunt, then does the arithmetic

Tesla put a car in the air on 15 October, and the argument since has been about what the flight was for. At an unveiling at SpaceX's rocket test facility in McGregor, Texas, the next-generation Roadster left the ground on cold-gas thrusters, rolled, and came back down. Yann LeCun called it a "marketing stunt," as Live Science reported.

What actually left the ground

Two stunts ran back to back. In the first, the car drove up a half-circle ramp and stopped upside down, pinned by underbody fans that Aviation Week reports Tesla rates at roughly 4,700 kg-equivalent of downforce. It then launched off the top, thrusters rolling it upright. The second cleared a row of parked Teslas. Both runs were remote-controlled, with nobody aboard.

The hardware splits three ways. Performance gets the suction system and no thrusters. Thrust adds rear cold-gas thrusters that Tesla credits with a 0 to 60 mph time of about 0.81 seconds. Only the single-seat Rocket carries the full set, sells by invitation, and is, on Tesla's own site, not approved for public roads. The thrusters borrow from SpaceX, and Tesla claims the system produces four to five times the force the tires can.

The thrust budget

LeCun, Meta's chief AI scientist and a Turing Award winner, did the arithmetic in public. "Okay, so it's just compressed air," he wrote on X on 17 October. "Easier. But crappy specific impulse (less than 50 seconds)." Assume half the mass is compressed air, he went on, and you get "less than 10s of useful thrust." "Probably more like 5 seconds, actually." The car, he concluded, "must be an empty, lightweight shell containing big compressed air tanks."

Live Science's round-up of expert reaction reached the same word: impractical.

A hop is not transport

Five seconds is the right thing to argue about, and beside the point. A car that leaves the ground needs control authority for a second or two, and the demo had it: the flip, the roll, the landing. What it did not show is a vehicle that goes anywhere. Tesla has not said how high the Rocket gets or how long it stays up, and no price exists for the variant.

The comparison Tesla invited is with aircraft, and the regulatory gap is where the hop lands: Aviation Week notes that even the non-flying Thrust variant expels a plume of gas and will face hurdles, while the Rocket raises "a series of novel legal and safety issues."

What would settle it

A duration, an altitude, and a price, from Tesla rather than a fan account. Until those exist, the hop is a demonstration of thrusters that work, held where loud controlled explosions are the business, on a car nobody can buy.