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SpaceX’s Starship, the most powerful launch vehicle ever built, is set to lift off on its fourth flight test on Thursday. The highly anticipated event is the company’s second uncrewed test of 2024.

SpaceX is aiming to mark new milestones this time around, such as showcasing the reusability of the Starship vehicle.

The 120-minute launch window opens at 7 a.m. CT (8 a.m. ET), with launch expected at 7:50 a.m. CT (8:50 a.m. ET), and the company will stream live coverage on X, formerly known as Twitter, about 30 minutes prior to launch. Weather conditions are 95% favorable for the launch, according to SpaceX.

The Starship launch system, which includes the upper Starship spacecraft and a rocket booster known as the Super Heavy, will attempt to take flight from the private Starbase facility in Boca Chica, Texas.

The flight test comes two days after the Federal Aviation Administration, which licenses commercial rocket launches, gave SpaceX its approval. And the test is occurring one day after SpaceX’s competitor under NASA’s Commercial Crew Program, Boeing, successfully launched the first crewed mission of Starliner, which is carrying two veteran NASA astronauts to the International Space Station.

Each of Starship’s test flights have different objectives that build on lessons learned and milestones achieved during the previous flight.

SpaceX is now focusing on “demonstrating the ability to return and reuse Starship and Super Heavy. The primary objectives will be executing a landing burn and soft splashdown in the Gulf of Mexico with the Super Heavy booster, and achieving a controlled entry of Starship,” according to a company release.

Starship is expected to splash down in the Indian Ocean.

The Starship team made software and hardware upgrades to the launch system to incorporate lessons learned from the third flight.

“The fourth flight of Starship will aim to bring us closer to the rapidly reusable future on the horizon,” according to SpaceX. “We’re continuing to rapidly develop Starship, putting flight hardware in a flight environment to learn as quickly as possible as we build a fully reusable transportation system designed to carry crew and cargo to Earth orbit, the Moon, Mars and beyond.”

Three wild test flights

The first two attempts to get Starship to orbital speeds in 2023 ended in explosions, with the spacecraft and booster erupting into flames before reaching their intended landing sites.

SpaceX is known to embrace fiery mishaps in the early stages of spacecraft development, saying these failures help the company rapidly implement design changes that lead to better results.

SpaceX has said its approach to rocket development is geared toward speed. The company makes use of an engineering method called “rapid spiral development.” This process essentially boils down to a desire to build prototypes quickly and willingly blow them up to learn how to construct a better one — faster than if the company solely relied on ground tests and simulations.

After the explosive first and second Starship test flights, the company immediately sought to frame these mishaps as successes.

The nearly hour-long third test flight, conducted in March, achieved several milestones before breaking apart after reentry, rather than splashing down in the Indian Ocean.

First, Starship reached speeds close to what would be required to put the vehicle in orbit. Typically, such a feat requires speeds topping 17,500 miles per hour (28,000 kilometers per hour). Starship reached its orbital speeds goal and did not aim to enter orbit on the third flight.

The Starship’s payload door — a hatch that must open for the spacecraft to deploy satellites into space after reaching orbit — swung open before resealing in a crucial test of that mechanism.

SpaceX also carried out a “propellant transfer demonstration,” or moving some of the propellant on board the Starship vehicle from one tank to another. SpaceX engineers designed the demo to test how Starship will be refueled on future missions while it’s in orbit.

But after a bright halo of red plasma, created by extreme heat and pressure as Starship reentered Earth’s atmosphere, glowed around the vehicle, the team lost communication with the spacecraft.

However, SpaceX never intended to recover Starship after this flight test.

The Super Heavy booster was also expected to make an autonomous, controlled landing in the ocean, but the booster was lost after all its engines failed to light.

But both the Starship spacecraft and booster made it farther into flight than the two previous tests in 2023.

Starship’s gargantuan goals

Much is riding on Starship’s eventual success. SpaceX CEO Elon Musk has repeatedly characterized the rocket as central to the company’s founding mission: putting humans on Mars for the first time.

NASA has selected the Starship spacecraft for a key role in its Artemis program to return humans to the moon for the first time in more than five decades. Under the federal space agency’s current road map, Starship would complete the final leg of a crewed mission to the moon, taking the astronauts from a spacecraft in lunar orbit and ferrying them to the surface. The United States is in a race with China, vying to become first to develop a permanent lunar outpost and set the precedent for deep-space settlements.

Milestones such as the propellant transfer from the third flight test objectives for the future. Topping off the spacecraft’s fuel will be critical for Starship’s high-profile missions down the road.

When Starship makes a journey to the moon under Artemis — it will have to sit in orbit close to Earth as SpaceX launches separate support vehicles that will transport fuel to the spacecraft. To get to the moon, SpaceX may have to make more than a dozen refueling trips.

The first astronaut landing under the Artemis program is slated to occur as soon as September 2026.

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