SpaceX Rocket Destroyed on Launchpad
An explosion was seen from the site of a SpaceX rocket at the Cape Canaveral Air Force Station in Florida in September.
By U.S. LAUNCH REPORT, VIA REUTERS on Publish Date September 1, 2016. Photo by U.S. Launch Report, via Reuters. Watch in Times Video »Engineers investigating the explosion of one of SpaceX’s rockets in September have figured out what went wrong, and launches could resume in mid-December, Elon Musk, the company’s chief executive, said on Friday.
“I think we’ve gotten to the bottom of the problem,” Mr. Musk said during an interview on CNBC’s Squawk Box program. “Really surprising problem that’s never been encountered before in the history of rocketry.”
Mr. Musk described it as the toughest puzzle solved that the company has ever had to solve.
The cascade of explosions on Sept. 1 that destroyed the Falcon 9 rocket as well as a $200 million satellite was perplexing because it occurred before the ignition of the engines for a planned test. The actual launch was scheduled for two days later.
The accident has complicated NASA’s operations with the International Space Station. SpaceX is one of two companies ferrying cargo to the space mission. SpaceX’s next flight had been scheduled to launch this month but is postponed indefinitely.
On Friday, NASA juggled its order for the next flight from the other company, Orbital ATK of Dulles, Va., switching to a larger rocket that would allow additional cargo. That launch is scheduled for the spring.
SpaceX also has a NASA contract to carry astronauts to the space station beginning as early as late next year.
Mr. Musk indicated on Friday that the problem occurred during fueling. As liquid oxygen flowed into a tank on the second stage, the propellant was so cold that it froze solid, setting off a domino effect that destroyed the rocket in a succession of fireballs on the launchpad. At normal atmospheric pressures, oxygen turns solid at -362 degrees Fahrenheit.
Last week, SpaceX released a statement that it was focusing the investigation on one of three helium containers within the oxygen tank. During launch, as the liquid oxygen is consumed, the helium is heated up and released to maintain pressure within the tank. The company said that its tests had replicated the rupture of the helium containers, made of carbon fiber composite materials.
“It basically involves a combination of liquid helium, advanced carbon fiber composites and solid oxygen,” Mr. Musk said. “Oxygen so cold that it actually enters solid phase.”
Mr. Musk did not provide other details about how solid oxygen affected the carbon fiber composites.
In December 2015, SpaceX began using an upgraded Falcon 9 design that uses supercooled liquid oxygen at -340 degrees, 40 degrees colder than what is typically used for rocket propulsion. The lower temperatures make the oxygen denser and improve engine thrust, SpaceX has said.
If the helium were in a liquid state, it would be even colder (-452 degrees), and that appears to have provided unintended additional cooling that turned some of the oxygen solid.
The Wall Street Journal reported this week that hazards could be greater for future astronauts riding on SpaceX rockets. With supercooled fuel, the launch occurs soon after the fuel is pumped into the rocket. SpaceX has proposed that the astronauts would be strapped in before fueling begins instead of boarding after fueling.
In a letter last December, a space station advisory committee headed by retired Lt. Gen. Thomas P. Stafford of the Air Force strongly and unanimously objected to that idea, saying it was “contrary to booster safety criteria that has been in place for over 50 years, both in this country and internationally.”
SpaceX officials have suggested that a change of procedure would prevent a recurrence, and the rocket’s launch abort system would have carried the astronauts to safety in case of an emergency.
When SpaceX resumes launching, the first flight will be for one of its commercial customers, but company officials have not said where the next launch will occur. The accident damaged the Launch Complex 40 at Cape Canaveral Air Force Station that SpaceX has used for almost all of its Falcon 9 launches so far.
SpaceX has also been renovating Launchpad 39A at the Kennedy Space Center, once used for space shuttle launches, and it also has a launchpad at Vandenberg Air Force Base in California.
For NASA, the space station is not running short of supplies. But Orbital ATK is recovering from its own mishap, when an Antares rocket with NASA cargo exploded two years ago. It then launched two of its Cygnus cargo ships on a competitor’s rocket, the Atlas 5 built by United Launch Alliance, and last month, it launched with a redesigned Antares.
Russian and Japanese cargo ships are scheduled to head to the station before the end of the year.
Frank DeMauro, the vice president of Orbital ATK’s advanced programs division, said that a couple of months ago, NASA officials began discussions to launch the next cargo flight with an Atlas 5 instead of an Antares rocket. That would increase the cargo capacity by about 660 pounds.
Mr. DeMauro said that an Atlas, which has a track record of more than 60 successful launches, would decrease the chances of delays. “It highlights our focus on supporting our customer even if it means launching on another company’s rocket,” he said.
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