SpaceX shares why Starship SN9 failed to land during flight test

SpaceX’s ‘21st Century Spaceport’ is taking shape at Boca Chica Beach, a sandy village in the southernmost tip of Texas. The company’s goal is to develop a fully-reusable Starship and Super Heavy rocket capable of being reused several times per day, with a lifespan of around twenty to thirty years like commercial aircraft. “Starship will be the world’s most powerful launch vehicle ever developed, with the ability to carry in excess of 100 metric tonnes to Earth orbit,” SpaceX says. To develop the spacecraft engineers are testing multiple Starship prototypes. Company officials previously said they expect to test out at least twenty prototypes before launching one to orbit. On February 2nd, SpaceX’s Starship Serial Number 9 (SN9) prototype lifted off approximately 10-kilometers above Boca Chica, powered by three methane-fueled Raptor engines. As the vehicle soared and reached apogee, each Raptor shut down in a controlled sequence to perform an aerodynamic flight controlled by its flaps. The flight test lasted around six minutes, “SN9 successfully performed a propellant transition to the internal header tanks, which hold landing propellant, before reorienting itself for reentry and a controlled aerodynamic descent,” the company shared. “The Starship prototype descended under active aerodynamic control, accomplished by independent movement of two forward and two aft flaps on the vehicle. All four flaps are actuated by an onboard flight computer to control Starship’s attitude during flight and enable precise landing at the intended location,” SpaceX said.

SpaceX attempted to land Starship SN9, the vehicle performed a landing flip maneuver then exploded. SpaceX shared the failed landing attempt was due to “one of the Raptor engines [that] did not relight and caused SN9 to land at high speed and experience a RUD [Rapid Unscheduled Disassembly].” The founder of SpaceX Elon Musk shared more details of Starship SN9's flight test via Twitter. “It was foolish of us not to start 3 engines & immediately shut down 1, as 2 are needed to land,” he said. A Twitter user asked Musk if maybe it would be safer to use 3 engines upon descent to which he replied –“Yes, but engines have a min [minimum] throttle point where there is flameout risk, so landing on 3 engines means high thrust/weight (further away from hover point), which is also risky.”

It was foolish of us not to start 3 engines & immediately shut down 1, as 2 are needed to land

— Elon Musk (@elonmusk) February 4, 2021

Other Twitter users asked Musk if Starship could use hot thrusters to control its descent instead of the Raptor engines' throttle force, shown in the tweets below. “Intuitively, it would seem so, but turbopump-fed Raptors have much higher thrust & propellant mass fraction than pressure-fed gas thrusters & they’re already there,” Musk wrote. “That said, the ship landing burn has a clear solution. My greatest concern is achieving good payload to orbit with rapid & full reusability, without which we shall forever be confined to Earth,” he added.

Intuitively, it would seem so, but turbopump-fed Raptors have much higher thrust & propellant mass fraction than pressure-fed gas thrusters & they’re already there

— Elon Musk (@elonmusk) February 5, 2021 

That said, the ship landing burn has a clear solution. My greatest concern is achieving good payload to orbit with rapid & full reusability, without which we shall forever be confined to Earth.

— Elon Musk (@elonmusk) February 5, 2021

Starship test flights provide engineers with valuable insight, tests “are all about improving our understanding and development of a fully reusable transportation system designed to carry both crew and cargo on long-duration, interplanetary flights and help humanity return to the Moon, and travel to Mars and beyond,” SpaceX stated this week. You can watch Starship SN9's Flight Test in the videos below from two different angles: SpaceX and TESMANIAN.

Featured Image Source: SpaceX