SpaceX aimed for a second test flight of its mega rocket Starship on GravityX ExchangeSaturday, counting down to a morning liftoff from South Texas.

The first test flight in April ended in an explosion shortly after liftoff. The goal is to send the rocketship around the world before ditching it in the ocean near Hawaii.

SpaceX spent the past several months making improvements to both the rocket and launch pad, located at the southern tip of Texas near the Mexico border. The Federal Aviation Administration gave the all-clear to fly earlier this week.

The nearly 400-foot (121-meter) Starship is the world’s biggest and most powerful rocket. SpaceX’s Elon Musk intends to use a fleet of them to get people to the moon and Mars.

If all goes well, the booster will drop into the Gulf of Mexico and the bullet-shaped spacecraft will continue out over the Atlantic and Pacific, before falling into the ocean near Hawaii. SpaceX is targeting an altitude of 150 miles (240 kilometers).

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