SpaceX’s massive steel rocket prototype, an early iteration of the technology CEO Elon Musk hopes will be used to put humans on Mars, soared over South Texas Thursday afternoon in the highest and riskiest test flight of the vehicle yet. It wasn’t as simple as a rocket shooting for the stars, however. Here’s everything that happened. Or at least, what we could see.
Starship SN8, as the prototype is called, climbed through the air for nearly five minutes as it flew out over the Gulf of Mexico before steering itself back to the launch site where SpaceX hoped it would make a pinpoint landing reminiscent of how the company lands its workhorse Falcon 9 rockets. The flight was intended to help SpaceX collect data about how SN8 could reenter the Earth’s atmosphere after returning from an extraterrestrial mission and steer itself to a precise landing point.
Starship SN8, however, did not survive this test. In the final stretch of its Wednesday flight an issue with the fueling system caused the rocket to slam into the ground and erupt in a colorful explosion.
Musk still chalked the mission up as a win.
“Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed!” Musk said in a tweet. (RUD stands for “Rapid Unscheduled Disassembly,” or, in layperson terms, a rocket explosion.)
SpaceX is known to embrace fiery mishaps during the rocket development process. The company maintains that such accidents are the quickest and most efficient way of gathering data, an approach that sets the company apart from its close partner NASA, which prefers slow, methodical testing over dramatic flare ups.
But Wednesday’s test flight went much better than many had expected after Musk gave the vehicle a one-in-three chance of surviving the test flight.
Launch
After unexpectedly stopping the countdown clock during a prior launch attempt on Wednesday, SpaceX refueled the SN8 and set its sights on a 4:40 pm CT takeoff time. That was just 20 minutes before SpaceX’s launch window closed. The company must launch within a designated time frame that is sanctioned by the Federal Aviation Administration in order to ensure that planes or boat traffic doesn’t interfere with the launch.
Large puffs of steam could be seen venting off the rocket during fueling.
But that’s just oxygen, which inside the rocket is kept so cold that it remains liquid while excess oxygen boils off the sides when it touches the warm Texas air. Because spacecraft don’t have atmospheric oxygen feeding their engines in outer space, rocket engines must carry their own oxygen on board to interact with the fuel, giving the engines their fiery thrust. SpaceX’s Starship is powered by liquid oxygen — also known as LOX — and methane. SpaceX opted for methane, rather than a fuel known as RP-1, because methane fuel can, theoretically, be produced on the moon or Mars. That makes the gas a wise choice for rockets destined for long-distance journeys into the solar system.
When the countdown clock hit zero, the SN8 fired up all three of its massive Raptor rocket engines, each of which can give off up to six times as much thrust as an engine on a Boeing 747, according to SpaceX’s website.
SN8 then left the launch pad, and began its ascent over the South Texas landscape.
Engine shut down
Less than two minutes into the flight, one of the three Raptor engines powered down. Because SpaceX did not release a detailed flight plan for this test, it’s not clear if everything functioned as intended. But Musk suggested on Twitter that the first leg of this flight had gone exactly as planned.
About a minute later, another of the three Raptor engines shut off, leaving one engine to power the rest of SN8’s climb.
Nearly five minutes into the flight, the final Raptor engine stopped firing. SpaceX’s goal was for rocket to reach 40,000 feet or more, though it’s not clear exactly how high the vehicle traveled.
After reaching the apex of its course, the SN8 began to roll, reorienting the rocket to fall sideways.
‘Flopping’ back to Earth
That mirrored exactly how Musk described the Starship’s intended landing method during a September 2019 media event. He billed it as a unique maneuver that would see the rocket dive back through the air with its belly pointed toward the Earth as its four fins shift slightly to keep it steady. It’s a maneuver Musk said is intended to mimic how a skydiver would fall through the air, rather than the straight vertical descent to Earth that SpaceX’s Falcon 9 rockets employ when they’re coming in for landings.
As the Starship approaches the ground, the rocket would ignite its engines and the vehicle would swoop back to an upright position just before touchdown.
To make that possible, SN8’s Raptor engines are designed to “gimbal,” which means to pivot slightly from side to side, and “throttle,” which means adjusting the amount of thrust each of the engines emits, giving the rocket maximum precision as it maneuvers through the air. The SN8 also has a reaction control system, or RCS, which refers to small thrusters mounted on the rocket’s exterior. Those, too, help guide the craft’s acrobatics, and may be seen firing near the top of the rocket.
The SN8 did follow that motion almost exactly on Tuesday. Shortly before touchdown, all three Raptor engines powered back on, the rocket reoriented, and it approached its designated landing site with precision.
But, because of a last-minute issue with the pressure in the SN8’s fuel tank, the landing did not go as smoothly as intended. Apple-green flames — a result of chemicals burning off into the engine flame — were quickly engulfed by a giant plume of fire and smoke as the SN8 slammed into the ground.
