If all goes to plan, SpaceX will test its huge fully-reusable rocket, Starship, again on Sept. 22.

It will be the 14th test for Starship. It will be the first time the upper stage enters a stable Earth orbit, completing six orbits on a 10-hour mission. SpaceX also plans to deploy Starlink V3—or version three satellites. (Starlink is SpaceX’s space-based broadband business, with more than 12 million subscribers.)

The launch window opens at 8:15 a.m. Eastern time.

The 13th test, launched in July, was a success. The booster stage successfully completed a boostback burn and landed offshore in the Gulf of Mexico. Starship’s upper stage deployed 20 Starlink V3 satellites and re-lit a Raptor rocket engine in space. The upper stage splashed down in the Indian Ocean. Surprisingly, the upper stage was recovered, giving SpaceX an unexpected look at the spaceship’s heat shield. (Typically, the upper stage explodes after falling into the ocean.)

It’s hard to overstate the importance of Starship to SpaceX. The larger rocket is needed to deploy the more capable Starlink satellites, which will help grow SpaceX’s communications business. It’s also needed to build SpaceX’s artificial intelligence business. SpaceX operates AI data centers on the ground. Eventually, its Starmind satellites will form a Starlink-like constellation of AI computers in orbit.

SpaceX believes using the sun to power the constellation will give it a cost advantage over ground-based data centers. A big part of the cost advantage is Starship, too. Fully reusing both the upper and lower stages of the rocket makes reaching space much cheaper. SpaceX pioneered reusable rockets, lowering costs to reach orbit. Still, the upper stage of its Falcon 9 rocket is expended on each flight.

SpaceX stock was up 5% in morning trading Wednesday at $150.71, while S&P 500 were up about 0.3%.

Coming into Wednesday trading, SpaceX stock was up about 6% from its $135 June IPO price. It’s a small move, but shares have traded as high as $225.64 and as low as $104.83. Investors have been balancing SpaceX’s trillion-dollar valuation with rising sales estimates, selling pressure from early investors, and corporate developments, such as Starship testing.