Unknown at this stage
Second stage of the two-stage Starship super heavy-lift launch vehicle.
The Starship second stage was testing during a number of low and high altitude suborbital flights before the first orbital launch attempt.
Space Exploration Technologies Corp., known as SpaceX, is an American aerospace manufacturer and space transport services company headquartered in Hawthorne, California. It was founded in 2002 by entrepreneur Elon Musk with the goal of reducing space transportation costs and enabling the colonization of Mars. SpaceX has many pads, on the East Coast of the US they own SLC-40 at Cape Canaveral and LC-39A at the Kennedy Space Center for their lower inclination launches. They also own SLC-4E at Vandenberg, California for their high inclination launches. Another site is also being developed at Boca Chica, Texas.