SpaceX called off the first flight attempt of its third generation Starship rocket on Thursday evening at the company’s Starbase facility in South Texas. Engineers tried multiple times to push through the countdown but ultimately stopped the launch at around T minus 40 seconds, with another attempt now planned for Friday at 5:30 p.m. local time.

Elon Musk said the issue was mechanical: a hydraulic pin holding one of the launch tower arms in place failed to retract on cue. The arms have to clear the booster cleanly before liftoff, so the launch director scrubbed rather than risk damage to the tower.

This is a milestone vehicle for SpaceX. It is the first flight of the Starship V3 design, which replaces previous test articles with a taller, more powerful stack standing roughly 124 meters tall and producing more than 18 million pounds of thrust at liftoff. The booster carries upgraded Raptor 3 engines and a redesigned grid fin layout meant to make tower catches easier on future missions.

The flight, the twelfth in the Starship program, will not attempt a full orbit. SpaceX plans soft splashdowns for both stages, with the Super Heavy booster targeting the Gulf and the upper stage aiming for the Indian Ocean. The company is also using this flight to validate fixes for propellant leaks that troubled earlier vehicles, with the goal of eventually flying Starship as reliably as Falcon 9.

The pressure on Starship is unusually high right now. SpaceX recently filed paperwork for an initial public offering expected within weeks, and the Starlink network reportedly produced 11 billion dollars in revenue last year, with future generations of Starlink satellites depending on Starship to reach orbit.