SpaceX CEO Elon Musk told CNBC on Friday that investigators have found the root cause of the fire and explosion that destroyed a Falcon 9 booster on Sept. 1. The company expects to resume launches by the middle of December.
Musk, confirming earlier discussion about the investigation, said the failure involved liquid helium being loaded into bottles made of carbon composite materials within the liquid oxygen tank in the rocket’s upper stage. This created solid oxygen, which Musk previously said could have ignited with the carbon composite materials. However, he did not go into that level of detail in his CNBC comments.
“It’s never happened before in history, so that’s why it took us a while to sort it out,” Musk said, adding that SpaceX has been working with NASA, the U.S. Federal Aviation Administration and commercial customers on the accident investigation. “This was the toughest puzzle to solve that we’ve ever had to solve.”
…SpaceX’s last public statement about the accident investigation, published on its web site Oct. 28, said that the company had narrowed its focus to one of three helium bottles inside the liquid oxygen tank that burst, noting it was able to replicate the tank failure with helium loading conditions. “The root cause of the breach has not yet been confirmed,” the company said at the time.
Meanwhile, more details are emerging about safety concerns related to SpaceX’s plans for its Crew Dragon spacecraft, which is designed to fly NASA astronauts to the International Space Station beginning in 2017 or 2018.
Tom Stafford, chairman of the NASA International Space Station Advisory Committee, expressed concerns about SpaceX’s plans to fuel the rocket with the crew aboard Dragon and the company operating the launcher’s Merlin 1D engines “outside their design input conditions.”
Stafford wrote that the committee unanimously believes SpaceX’s plan to load astronauts aboard the Crew Dragon before fueling the Falcon 9 booster is counter to safe practices that have been in place for more than 50 years.
“Pump-fed chemical engines require a sufficient and consistent input pressure to reduce the likelihood of cavitation or unsteady flow operations. We are concerned that there may be insufficient precooling of the tank and plumbing with the current planned oxidizer fill scenario, and without recirculation there may be stratification of oxidizer temperature that will cause a variation in the input conditions to the oxidizer pump,” the letter read.
“In summary, we are deeply concerned about introducing the practice of fueling with the crew onboard, and about the lack of even a recirculation pump for oxidizer conditioning on Falcon 9,” the letter added.
The Wall Street Journal also reports that ISS Advisory Committee members had expressed concerns about the design of the booster at a meeting last week.
The Falcon 9 booster, according to industry officials, also is the only large rocket world-wide in decades with helium bottles installed inside its liquid-oxygen tanks. During launch, the helium inside the bottles is released into the tank to maintain pressure while the liquid oxygen is consumed….
At the same meeting, Joseph Cuzzupoli, a former senior NASA manager who worked on the agency’s Apollo, Gemini and space shuttle programs, also expressed misgivings about SpaceX’s plans and the lack of NASA response. “Are we in the dark on this whole thing?” he asked.
Mr. Cuzzupoli told the committee that installing helium containers within fuel tanks—which entails putting wiring, sensors and tubing inside a potentially explosive environment—is “very unusual in my world, in my experience.” Such designs, he said “have been a no-no ever since Apollo.”
In 1970, a spark from an exposed wire inside an oxygen tank caused a life-threatening fire on board Apollo 13, bound for the moon. The crew managed a safe return to Earth, but NASA changed designs to prevent a similar incident.
On Nov. 1, NASA released a statement sttessing the space agency’s rigorous review process for any vehicles flying astronauts.
“The agency has a rigorous review process, which the program is working through with each commercial crew partner,” the statement reads. “Consistent with that review process, NASA is continuing its evaluation of the SpaceX concept for fueling the Falcon 9 for commercial crew launches. The results of the company’s Sept. 1 mishap investigation will be incorporated into NASA’s evaluation.”