After nearly three months of investigation into what SpaceX at first only called an “anomaly,” the company on Monday announced the likely culprit of an explosion that blew apart its Crew Dragon astronaut capsule during a test on the Space Coast in April.
A leaking component in the vehicle’s propulsion system began the chain of events that ended in destruction, said Hans Koenigsmann, SpaceX’s vice president of build and flight reliability, during a press conference call Monday afternoon.
Because of delays caused by the accident, Koenigsmann said it’s going to be "increasingly difficult” to get astronauts aboard a Crew Dragon capsule and into space by the end of 2019, though not impossible.
The April 20 accident happened when the Elon Musk-owned rocket company was conducting static fire tests of the vehicle’s engines. The capsule on the test stand that afternoon had already successfully flown to space one month earlier, completing the first major test of SpaceX’s partnership program with NASA, which will carry astronauts back to space from U.S. soil for the first time since 2011 on vehicles built by SpaceX and Boeing.
The test was being conducted to prepare SpaceX for an in-flight abort test that would prove the capsule’s thrusters could safely move the vehicle and its astronauts away from the rocket in the case of an emergency mid-flight. A static fire of a set of thrusters that help the vehicle maneuver in space went by without incident.
But just about 100 milliseconds before SpaceX ignited the abort thrusters on the craft, the vehicle exploded.
At the time, SpaceX offered few details on the extent of the damage to the vehicle. A leaked video from the test started making the rounds online, showing that the craft, in fact, blew apart. SpaceX confirmed the spacecraft was lost 12 days after the explosion.
Following the accident, SpaceX and NASA, along with help from the Federal Aviation Administration and the National Transportation Safety Board, put together an accident investigation team to discover the root cause of the explosion.
With about 80% of that work now done, SpaceX offered its first breakdown of what went wrong.
The leak caused liquid oxidizer —a key component in the vehicle’s propellant — to cross over into the wrong set of pipes, the pressurization system. That’s when the high-pressure oxidizer reacted with a titanium valve leading to an explosion that “destroyed” the Crew Dragon capsule at Cape Canaveral Air Force Station’s Landing Zone 1, sending plumes of smoke over Cocoa Beach.
No one was hurt.
Burn marks found on the valve, as well as data and debris collected at the site confirmed the company’s suspicions. SpaceX also performed a series of tests of the flammability of the valve’s titanium components at the company’s rocket development facility in McGregor, Texas. The investigation, however, is still ongoing.
“We didn’t quite expect that [liquid oxidizer] driving into a titanium component could cause such a violent reaction,” Koenigsmann said. Titanium has been used safely on spacecraft for decades.
“Overall it’s something the components should not have done," he said. "[We learned] a very valuable lesson on something going forward that makes the Crew Dragon a safer vehicle.”
The abort thrusters, SpaceX said, were recovered from the test site intact, supporting the company’s belief that the abort system is not faulty. Koenigsmann said at a prior press conference that the safety thrusters have been tested more than 600 times with no issue.
Looking ahead, SpaceX has already replaced the valves, which allow liquid to flow in one direction, with burst disks that completely seal until opened by high pressure. Testing and analysis of the new system is underway, as well as testing of existing systems to make sure other versions of the Crew Dragon also in production don’t have the same vulnerability.
That means it will be unlikely that SpaceX will perform a test flight with astronauts aboard Crew Dragon by the end of the year, as previously planned. Boeing, meanwhile, is still moving toward a flight with humans aboard by year’s end.
Both programs have been plagued by delays. In 2018, Boeing, too, had a fuel leak that was discovered during a test of its abort system.
For SpaceX, the explosion means it won’t be able to use the spacecraft as planned for its in-flight abort test. Now, the craft that was meant to perform the first test with crew will be used for the abort test, and the Crew Dragon that was going to be assigned to the first operational mission will fly the test mission instead.
Kathy Lueders, manager of NASA’s Commercial Crew program, said NASA was at the console when the accident happened and has been working hand-in-hand with SpaceX since.
Bob Behnken and Doug Hurley, the NASA astronauts who will go on SpaceX’s first crewed test flight, “really appreciated SpaceX’s openness, SpaceX’s inclusion of NASA on the investigation team and the continued interchange that we’ve had over the past few months,” Lueders said. “This will help us fly safer.”
While the communication with NASA was good, NASA Administrator Jim Bridenstine has spoken to the company about improving transparency with the media and the public in the case of future incidents within the program.
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The Commercial Crew program is a taxpayer-funded undertaking. SpaceX got $2.6 billion from NASA to build its Crew Dragon, while Boeing was awarded $4.2 billion to build its CST-100 Starliner astronaut capsule.
Moving forward, SpaceX has agreed to be more transparent with the public after accidents, Bridenstine said in an interview with SpaceNews and The Washington Post last week.
“Within a couple of hours, we’re going to do a press conference," he said, "and get as much information out to the public as soon as possible.”
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