April 20th, 2023
The first integrated flight test of SpaceX’s massive Starship rocket failed just minutes into the booster phase of ascent.
The exact reason for the failure is not yet known, but since the 394-foot (120-meter) tall uncrewed rocket made it out over the Gulf of Mexico before the anomaly, the launch pad and surrounding infrastructure at the company’s Starbase facility in South Texas was spared.
“As if the flight test was not exciting enough, Starship experienced a rapid unscheduled disassembly before stage separation,” SpaceX tweeted shortly after the explosion. “Teams will continue to review data and work toward our next flight test.”
Launch of the 10-million-pound rocket occurred at 9:33 a.m. EDT (13:33 UTC) April 20, 2023. At liftoff, the 33-engine booster had a thrust estimated to be some 16 million pounds, nearly twice that of NASA’s Space Launch System rocket, making it the most powerful rocket to leave the ground.
During liftoff, it appeared that several of the first stage’s Raptor engines flamed out. Exactly how many and for what reason, planned or unplanned, is not known.
About two or so minutes into the ascent, the rocket began to spin and then tumble. Based on the company’s webcast, the rocket made it to a maximum altitude of about 24 miles (39 kilometers) and velocity of 1,330 miles (2,150 kilometers) per hour.
Eventually the rocket’s flight termination system activated to destroy the rocket about four minutes after launch.
This was the second launch attempt of the vehicle. The first attempt on April 17 was scrubbed with less than 10 minutes to launch because a pressurant valve appeared to be frozen. The company rescheduled for April 20.
The plan was to launch the two-stage rocket, placing the upper stage “ship” into a nearly orbital trajectory to reenter Earth’s atmosphere over the Pacific Ocean north of Hawaii.
While this was a test flight, it’s unclear if or how much this will set back SpaceX’s Starship program, which is also a critical part of NASA’s efforts to return humans to the Moon. A lot of it will depend on what needs to be modified and how fast the company can get the next rockets ready.
“With a test like this, success comes from what we learn, and today’s test will help us improve Starship’s reliability as SpaceX seeks to make life multiplanetary,” SpaceX tweeted.
The plan for Starship’s first integrated test flight
Starship is SpaceX’s super-heavy-lift launch vehicle, which the company has been developing in some form since 2012. The bulk of visible development has occurred since about 2019 at the company’s facility known as Starbase, located at the very southern tip of Texas.
The current iteration has two stages powered by methane and oxygen consuming Raptor engines. Both stage bodies are made of stainless steel and designed to be fully and rapidly reusable while still being able to place between 100 and 150 metric tons into low Earth orbit.
At 230 feet (70 meters) tall and 30 feet (9 meters) wide, the first stage, called the booster, has 33 Raptor engines at its base. It also has four grid fins to control its descent after stage separation — similar to how Falcon 9 first stages guide themselves back toward Earth.
The second stage, also called the ship, is 164 feet (50 meters) tall and the same width as the booster. It has six Raptor engines — three optimized for sea level and three optimized for vacuum operation.
To aid in recovery, the ship has thousands of hexagonal ceramic tiles on its broad side to act as a heat shield during reentry. Additionally, there are four flaps — two smaller units at the top and two larger units at the base — that are used to control the vehicle after it reenters Earth’s atmosphere.
For this launch, the company used Booster 7 and Ship 24. Neither were planned to be recovered for this first integrated test flight.
Had the in-flight anomaly not occurred, Booster 7 was expected to propel itself and the ship skyward over the Gulf of Mexico for about 2 minutes and 49 seconds. The booster and ship would have then separated.
Ship 24 would have then ignited its six engines and burned for just over six minutes to place it nearly into orbit with a high point of about 150 miles (240 kilometers). If all had continued to go well, it would have reentered the atmosphere heat shield first about 90 minutes later some 62 miles (100 kilometers) north of Hawaii where it would have used its body flaps to slow down to a terminal velocity and crash into the Pacific Ocean.
The ship was not expected to perform a landing-flip maneuver that was demonstrated during a high-altitude test campaign in 2021, which saw the flaps and engines ignite near the ground to pitch it up from a horizontal to vertical engine-down position.
Following separation three minutes into flight, Booster 7 was expected to perform a boostback burn, similar to what the Falcon 9 does to return to land. However, the vehicle was to target an area about 20 miles (32 kilometers) off the coast of South Padre Island, Texas.
Before hitting the ocean, Booster 7 would have reignited a subset of its engines to slow itself down to softly splashdown in the water roughly 8 minutes after launch. The plan was for the booster to fall on its side where valves would have been open to flood its propellant tanks, sinking the rocket.
SpaceX’s Starship ambitions
SpaceX plans to use this vehicle for a variety of purposes, including building up its Starlink internet constellation. Perhaps more importantly, however, Starship is part of the company’s overall plans to begin sending cargo and people to the Moon and Mars.
In fact, NASA has contracted SpaceX to build a version of the ship to be used for the space agency’s Moon lander during the Artemis 3 mission, likely not before 2026.
In order for Starship to accomplish anything significant beyond low Earth orbit, however, SpaceX will need to demonstrate the system can transfer cryogenic propellants while in orbit to refill tanks. This would enable the ship to send 100 or more tons of payload to nearly anywhere in the solar system.
In-space cryogenic refilling can only happen after SpaceX demonstrates the system can reliably reach orbit and return safely to Earth.
While the booster and ship for this integrated test flight were not expected to be recovered anyway, at some point the company plans to use the nearly 500-foot (146-meter) tall launch tower to catch a returning booster with arms that are also used to integrate the vehicle before liftoff.
During an operational flight the booster would slow down and slide between catch arms, which would then close to allow the grid fins to settle on the massive device.
After everything settles, the catch arms would reposition the booster on the launch mount to wait for another ship to launch.
It’s unclear when the first booster catch attempt will occur. SpaceX will need to first fix what caused the anomaly and retry the integrated flight test.
But in order for Starship to be ready to deliver a Moon lander for NASA’s Artemis 3 mission in 2026, the system will need to be able to reliably launch, use and recover boosters and propellent tanker ship variants.
Moreover, SpaceX will also need to design, build and fly a propellant depot and a prototype lunar Starship variant for a Moon landing demonstration by 2025 — an ambition timeline that could slip as issues crop up during the company’s development program.
Video courtesy of SpaceX
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity.