Live Video: Watch Launch of Starship on 4th Test Flight

Starship, the gargantuan rocket under development by Elon Musk’s SpaceX, launched on Thursday morning to make a fourth attempt to get to space and back.

The previous three flights of the vehicle all ended in explosions, but each got farther than the last. Such progress is regarded as success in SpaceX’s break-it-then-fix-it approach to engineering and has been celebrated by some of the company’s fans. Those include Bill Nelson, the administrator of NASA, whose agency is depending on Starship to land astronauts on the moon.

Here’s what you need to know about today’s ongoing launch attempt.

The Starship lifted off and the flight is ongoing.

The latest Starship lifted off from the launchpad at the SpaceX site in South Texas, outside Brownsville. As with the other three flights, there are no people on board. One of the Super Heavy booster’s 32 engines did not ignite, but the others powered the vehicle toward space. Minutes later, the booster stage separated successfully from the upper Starship vechile, which continued on its path to space.

The launch began 8:50 a.m. Eastern time on Thursday, almost halfway into a two-hour launch window that opened at 8 a.m. Moments before the scheduled launch, crews concluded loading propellants into the vehicle’s two stages.

SpaceX is providing live video coverage of the launch on X, Mr. Musk’s social media service, or you can watch it in the video player embedded above.

What is Starship and why is it important?

With the Starship spaceship on top of what SpaceX calls a Super Heavy booster, the rocket system is, by pretty much every measure, the biggest and most powerful ever.

The rocket is the tallest ever built — 397 feet tall, or about 90 feet taller than the Statue of Liberty, including the pedestal.

The rocket also has the most engines ever in a booster: The Super Heavy has 33 of SpaceX’s powerful Raptor engines sticking out of its bottom. As those engines lift Starship off the launchpad, they will generate 16 million pounds of thrust at full throttle.

For Mr. Musk, Starship is really a Mars ship. He envisions a fleet of Starships carrying settlers to the Red Planet.

For NASA, the vehicle is to be a lunar lander, carrying astronauts to the surface of the moon for the first time since 1972.

In the near term, SpaceX also plans to use Starship to deploy the next generation of Starlink internet communication satellites.

An even more transformative feature of Starship is that it is designed to be entirely reusable. That capability has the potential to cut the cost of sending payloads into orbit — such that sending 100 tons to space one day might cost less than $10 million, Mr. Musk has predicted.

What is SpaceX trying to accomplish with this flight?

A couple of weeks ago, after a successful launch rehearsal, Mr. Musk wrote on X that for this flight, “Primary goal is getting through max re-entry heating.”

In other words, he does not want the vehicle to burn up.

During launch, Starship reaches orbital speeds of more than 17,000 miles per hour while reaching an altitude of 145 miles. As the spacecraft belly-flops back into the atmosphere, it experiences temperatures up to 2,600 degrees Fahrenheit.

For a fully successful flight on Thursday, Starship would endure that heat, then land in a remote part of the Indian Ocean. Another goal is to softly land the first stage, the Super Heavy booster, in the Gulf of Mexico.

During future operational flights, both vehicles are to return to the launch site and to be caught in one piece by the launch tower. Those attempts are still in the future.

What happened during the last flight?

The previous launch in March for the first time reached speeds that were fast enough for Starship to enter orbit. The ascent included a successful new twist: hot-staging separation, when some of the second-stage engines ignited before the Super Heavy booster, or first stage, separated and dropped away.

The second-stage part of Starship accomplished some of its goals as it coasted in space, including opening and closing the spacecraft’s payload door and a demonstration of moving propellant between two tanks inside the vehicle.

But while coasting at the highest point of its trajectory, Starship began rolling out of control. Cameras on board captured the orange glow of hot plasma beneath the spacecraft. Some 49 minutes after launching, it disintegrated, with communications lost at an altitude of 40 miles.

Earlier in the flight, the Super Heavy booster was to simulate a landing over the Gulf of Mexico. But six of 13 engines used for that maneuver shut down early.

SpaceX blamed blockages in the flow of propellants as the most likely cause for losses of the Starship and the Super Heavy booster. The company said it had made changes to address those problems.