SpaceX readies the third test launch of its massive Starship rocket

SpaceX's next-generation mega rocket is set to launch on a key test flight Thursday morning in a bid to demonstrate new technologies and techniques that will be crucial on future missions to the moon and beyond.

The upcoming launch will be the rocket’s third and most ambitious test flight, according to SpaceX. The event will be closely watched because the nearly 400-foot-tall booster, known as Starship, is expected to play an important part in NASA’s return-to-the-moon program.

Starship will launch from SpaceX’s Starbase test site in Boca Chica, Texas. Liftoff is expected at 9:25 a.m. ET, but that timing is tentative and could change based on the rocket’s status and weather at the launch site. The 110-minute launch window opened at 8 a.m. ET but SpaceX adjusted its targeted liftoff time as it worked to clear boats away from danger in the Gulf of Mexico.

SpaceX said early Thursday that weather conditions were 70% favorable for the test flight, but later added that teams were monitoring winds.

The launch will be streamed live on SpaceX's website beginning around 8:50 a.m. ET.

With this flight, SpaceX is hoping to demonstrate that Starship can carry out a controlled re-entry through Earth’s atmosphere before splashing down in the Indian Ocean. Before that finale, the test also includes several different objectives from the rocket’s previous two outings. SpaceX will attempt to fire one of Starship’s Raptor engines while in space, open and close the vehicle’s payload door and transfer propellant between two of Starship’s tanks in orbit.

Many of these techniques could help SpaceX carry out future missions to deploy satellites, as well as set the stage for moon missions as part of NASA’s Artemis program.

Starship was selected by NASA to carry astronauts to the lunar surface in the upcoming Artemis III mission, which could launch in 2026.

Starship's debut flight last April was a destructive one, ending with the rocket exploding several minutes after liftoff. A second Starship launch in November achieved several milestones, including separation of the first-stage booster known as Super Heavy and the upper-stage Starship spacecraft, but the company ultimately lost contact with the vehicle.

Denise Chow

Denise Chow is a reporter for NBC News Science focused on general science and climate change.