November 18, 2023

— The world's largest and most powerful rocket to leave the ground flew a mostly-successful test flight on what was only its second launch.

SpaceX ignited the 33 engines at the base of its integrated Starship and Super Heavy vehicle on Saturday (Nov. 18), seven months after its first test flight ended just four minutes into flight. This time, the launch at 7:02 a.m. CST (8:02 a.m. EST or 1302 GMT) from SpaceX's Starbase facility in Boca Chica, Texas, continued beyond stage separation, with Starship almost reaching its near-orbital velocity.

The test flight did not conclude, however, as planned with both the booster and spacecraft dropping into Gulf of Mexico and the Pacific Ocean, off the coast of Hawaii, respectively. Instead, the Super Heavy experienced a "RUD" — a rapid unplanned disassembly, or explosion — after separating and the Starship self-destructed near the end of its six-engine burn.

"What we do believe right now is that the automated flight termination system on the second stage appears to have triggered very late in the burn as we were headed downrange out over the Gulf of Mexico," said John Insprucker, a SpaceX engineer who co-hosted the company's webcast of the flight.

Despite that, Insprucker categorized the test flight as a success. It was the first time SpaceX was able to light all 33 Raptor engines on the Super Heavy without any failing and Starship reached space, flying 92.5 miles (149 kilometers) above Earth before telemetry was lost.

"The first stage looked beautiful with 33 Raptor engines firing," said Insprucker. "We got the hot staging, the thing that we really wanted to see and test. We saw the separation, we saw the flip maneuver, we saw the light up of the six Raptor engines on Starship and as it headed away everything really looked good."

Launch of SpaceX Starship Flight 2. Click to enlarge video in a new pop-up window. (SpaceX)

Saturday's successful ascent and stage separation could be attributed in part to the design changes SpaceX made to both vehicles since the first launch in April. During the previous flight, the rocket sustained fires from leaking propellant in the aft end of the Super Heavy booster, which severed connection with the primary flight computer. This led to a loss of communications to the majority of booster engines and, ultimately, control of the vehicle, according to a statement posted by SpaceX on its website.

SpaceX implemented leak mitigations and improved testing on both its engines and boosters. The company also expanded the Super Heavy's fire suppression system in order to protect against engine bay fires and made significant upgrades to the orbital launch mount in order to prevent a recurrence of a pad foundation failure suffered during the first flight test. The pad's foundation was reinforced and a water-cooled steel flame deflector was installed and tested.

The Federal Aviation Administration (FAA) oversaw and approved these changes before issuing a launch license for SpaceX to proceed.

Saturday's launch also incorporated upgrades that were unrelated to any of the issues observed during the first flight test. The integrated Super Heavy and Starship vehicle (also referred to as Starship) grew three inches taller; it now tops out at 397 feet tall (121 meters) as a result of a new hot-stage separation system.

Starship's six engines ignited on Saturday to push the ship away from the booster, rather than wait for the Super Heavy to drop away before firing. The same hot-fire technique was first used on NASA's Gemini-Titan rockets and is still in use by the Russian Soyuz.

SpaceX also engineered a new electronic thrust vector control system for Super Heavy's Raptor engines.

"This rapid iterative development approach has been the basis for all of SpaceX's major innovative advancements," the company said. "Recursive improvement is essential as we work to build a fully reusable transportation system capable of carrying both crew and cargo to Earth orbit, help humanity return to the moon and ultimately travel to Mars and beyond."

In April 2021, NASA awarded SpaceX a $2.9 billion contract to develop a modified Starship to serve as the human landing system (HLS) for the agency's Artemis III mission. Targeted to launch no earlier than late 2025, Artemis III is planned to touch down with the first woman and next American on the moon, where they will explore the lunar south pole for water ice.

SpaceX first intends as many as hundreds of additional flights of Super Heavy and Starship, in part to demonstrate the ability to land both vehicles and develop the ability to refuel Starship in orbit, a capability needed for the spacecraft to leave Earth orbit. The company also intends to use Starship to continue and accelerate the deployment of its Starlink broadband communication satellite network and has sold seats on at least three flights with passengers visiting Earth orbit or flying around the moon in the years to come.