WASHINGTON – A Falcon 9 first stage did not land after a launch last month because one of its engines shut down during the flight after hot gas broke through a worn cover.
During a NASA press conference on March 1 about the next commercial flight of the Crew-2 crew, Benji Reed, senior director of human space flight programs at SpaceX, said that while the booster used on that February 15 launch was doing its sixth flight, some components were “life leaders” who flew more often than any other in the Falcon 9 fleet.
This included “boots” or covers around parts of the Merlin engines in the first stage. “This was the highest flight count this particular boot project has ever seen,” he said.
However, one of these boots had a “small hole” that allowed hot gas to enter parts of the engine during the flight, he said. “A little hot gas got to where it shouldn’t be and made the engine stop,” he said.
Reed did not mention at what point in the launch the engine shut down, but suggested that this occurred during the ascent. “A great thing about Falcon 9 is that we have the ability to turn off the engine,” he said, which means that one of the nine engines in the first stage can shut down without compromising the mission. “The vehicle was able to orbit and place the satellites exactly where they want to be. The main mission has been accomplished. “
The engine shutdown, however, prevented the first stage from landing. “When that booster came home, because of the problem with that specific engine, we didn’t have enough thrust to get back where we needed to be and we didn’t land where we wanted to be,” he said.
Reed’s comments have provided most of the details so far about why the booster failed to land, breaking a string of two dozen consecutive landings that date back almost a year. Hans Koenigsmann, a longtime executive at SpaceX who is currently a senior consultant for flight construction and reliability at the company, said on February 23 that it was “heat damage” to blame, but gave no further details.
Falcon 9 has not been launched since the February 15 mission, although the company tried to launch another set of Starlink satellites on February 28. The launch was scrubbed 84 seconds before the scheduled eastern takeoff at 8:37 pm, and the company did not set a new launch date or provide more information about the cause of the erosion.
During the webcast of this launch attempt, SpaceX hosts did not discuss the failed landing. However, they noted that there would be no video of the first phase of this release, a break with standard company practices.
Reed said the engine problem was “a great lesson we learned” as the company works to better understand the life of Falcon 9 boosters and which components are most susceptible to wear. The company is also working to update the vehicle’s control systems “to further detect and control what the vehicle needs to do” in circumstances like this.
NASA is following the investigation to understand if there are any problems that could pose security problems for Falcon 9 that will launch the Crew-2 mission, currently scheduled for no earlier than April 20. “We will continue with the SpaceX investigation,” Steve Stich, NASA’s commercial crew program manager, said at the briefing, including making sure they understood the problem before giving approval to launch the mission.
A big difference between the Starlink and Crew-2 missions is the number of flights. “We are about to embark on our first reuse here for a manned vehicle,” he said. The Falcon 9 booster that will launch Crew-2 had already launched the Crew-1 mission in November 2020, but with no flights between them. “SpaceX Starlink flights are a long way away” in terms of the number of booster reuses, he noted.
Astronauts flying on Crew-2 are also following this and potentially other problems with Falcon 9. “We have been informed every month about updates to our spacecraft as well as the rocket, so we are very confident that they will find out what it’s going wrong. ” said Shane Kimbrough, the NASA astronaut who will command Crew-2. “There were just a few small things in some of those rockets.” He did not elaborate on what these “little things” are.