Starship, the massive rocket being developed by Elon Musk's SpaceX, is scheduled to make its fourth attempt at a round trip to space on Thursday morning.
Starship's three previous flights have all ended in explosions, but each has traveled farther than the last. These advances are seen as a success of SpaceX's “break-and-fix” engineering approach and have been praised by some of the company's fans, including NASA Administrator Bill Nelson, who is relying on Starship to land astronauts on the moon.
Here's what you need to know about today's launch attempt.
When does it start and how can I watch it?
The latest Starship is sitting on the pad at the SpaceX facility outside Brownsville in southern Texas, and like the other three flights, there are no passengers on board.
The two-hour window for the launch begins at 8 a.m. ET on Thursday. SpaceX plans to start covering the launch on Musk's social media service, X, at 7:30 a.m. ET.
What is Starship and why is it important?
The rocket system, which mounts the Starship spacecraft on top of what SpaceX calls a Super Heavy booster, is by almost any standard the largest and most powerful ever built.
The rocket is the tallest ever built, standing 397 feet tall, or about 90 feet taller than the Statue of Liberty, including its pedestal.
The rocket has the most engines ever put on a booster: Super Heavy has 33 of SpaceX's powerful Raptor engines protruding from its bottom. At full throttle, these engines produce 16 million pounds of thrust to lift Starship off the pad.
To Musk, Starship is truly a Mars-bound spacecraft: He envisions a fleet of Starships ferrying colonies to the Red Planet.
For NASA, the spacecraft will be a lunar lander, carrying astronauts to the moon's surface for the first time since 1972.
In the near future, SpaceX also plans to use Starship to deploy its next-generation Starlink internet communications satellites.
One of Starship's more revolutionary features is that it's designed to be fully reusable, a feature that could reduce the cost of putting payloads into orbit, with Musk predicting that one day it could cost less than $10 million to send a 100-ton payload into space.
What is SpaceX hoping to accomplish with this flight?
A few weeks ago, after a successful launch rehearsal, Musk wrote to X that the flight's “primary goal is to survive maximum re-entry heating.”
In other words, he doesn't want the car to burn up.
During launch, Starship will reach orbital speeds of more than 17,000 miles per hour and reach an altitude of 145 miles. As the spacecraft re-enters the atmosphere, it will be exposed to temperatures of up to 2,600 degrees Fahrenheit.
Starship will have to survive that heat to successfully complete Thursday's flight and land in a remote area of ​​the Indian Ocean. Another goal is to soft-land the first stage, a Super Heavy booster, in the Gulf of Mexico.
Future operational flights will see both vehicles return to their launch sites and be captured intact by the launch tower, although such attempts are still planned for the future.
What happened on your last flight?
The previous launch, in March, was the first time Starship reached a speed fast enough to enter orbit. The ascent included a novel twist called hot staging, in which part of the second-stage engine ignited before the Super Heavy booster, or first stage, separated and fell.
Starship's second stage accomplished several goals during its flight through space, including demonstrating the opening and closing of the spacecraft's payload door and transferring propellant between two tanks inside the spacecraft.
But as it coasted through the highest point of its orbit, Starship began to spin out of control. Onboard cameras captured the orange glow of hot plasma below the spacecraft. About 49 minutes after launch, the Starship broke apart at an altitude of 40 miles and communication was lost.
At the beginning of the flight, the Super Heavy booster was scheduled to simulate a landing over the Gulf of Mexico, but six of the 13 engines used for that maneuver shut down early.
SpaceX said the most likely cause of the loss of Starship and the Super Heavy booster was a blockage in the propellant flow, and the company said it had made changes to address those issues.
