After calling off the maiden launch of its Falcon 1 rocket due to a computer glitch and a liquid oxygen supply tank problem, Space Exploration Technologies ( ) now expects the launch to occur no earlier than Dec. 17, said Elon Musk, the company’s founder and chief executive.
In a Nov. 29 telephone interview, Musk said the date is driven by range availability and the time it will take to have a new supply of liquid oxygen (LOX) delivered from Hawaii to the company’s launch site on the Kwajalein Atoll in the Pacific Ocean’s Marshall Islands chain.
Kwajalein is home to the Ronald Reagan Ballistic Missile Defense Test Site. Musk said the U.S. military has the range booked for missile defense tests between now and Dec. 17.
Musk said most of SpaceX’s roughly 25-member launch operations team had returned to the company’s home base in El Segundo, Calif., to await a new launch date.
He said the upcoming holidays would not be reason to put off the launch until January. “Myself and the rest of the crew will work through Christmas if need be,” Musk said. “It is important to get our launch off as soon as possible and show our customers we can do it. Many SpaceX employees gave up Thanksgiving with their families to be in Kwajalein to support the weekend launch attempt.
After being bumped from its originally scheduled Nov. 25 launch window by the Army Space and Missile Defense Command to facilitate preparations for a missile defense test, SpaceX was forced to scrub its Nov. 26 launch attempt as a result of the engine computer glitch and liquid-oxygen tank problems. The rocket is slated to launch the FalconSat 2 spacecraft built by students at the U.S. Air Force Academy .
Musk said the vent valve on one of the four liquid-oxygen supply tanks used to ready the Falcon 1 for launch was mistakenly left open during the fueling process, preventing SpaceX from completing the operation.
In addition, the rocket’s main engine computer reset itself prior to the final countdown due to what appears to have been a ground power source interruption, Musk said.
SpaceX engineers suspect, but are not yet certain, that ice might have fallen off of the Falcon 1’s liquid oxygen-filled first stage and struck a quick disconnect box, temporarily interrupting the flow of power to the computer, Musk said. Additional analysis is under way to confirm the cause of the problem, he said.
A lthough the unexplained engine computer reset would have been reason enough to scrub the launch, Musk said, the bigger problem that day was the liquid-oxygen issue.
The two-stage Falcon 1 rocket is designed to burn a combination of liquid oxygen and kerosene on its way to orbit. Additionally, liquid oxygen is used to chill the helium needed to pressurize the rocket prior to launch.
On launch day, SpaceX had less than a full inventory of liquid oxygen on hand. Three weeks prior to the Nov. 29 launch attempt, the company’s on-site liquid-oxygen plant broke down. Rather than postpone the launch until the equipment was repaired, SpaceX decided to ship the needed liquid oxygen from Hawaii.
But the tanks used to ship the liquid oxygen to Kwajalein were so poorly insulated, Musk said, that by the time the delivery arrived, about 80 percent of SpaceX’s order had boiled off.
Still, SpaceX determined it had enough liquid oxygen on hand to proceed with the launch.
Gusting tropical winds that had prompted a one-hour delay early in the countdown further exacerbated the liquid-oxygen situation by causing the chilled tanks to boil off their contents faster than usual. “It’s like having a hair dryer on the LOX tanks,” Musk said.
That alone would not have been reason to call off the launch. But by the time the tank valve problem was caught and corrected, the SpaceX flight team found itself fighting a losing battle to refuel and pressurize the Falcon 1 faster than its already stretched supply of liquid oxygen was boiling away.
“There was no way to close the gap, so the launch had to be called off,” Musk said.
Musk said the vent valve oversight was part of operating a new launch site for the first time and is the kind of mistake not likely to be repeated.
“We have a checklist and this particular valve wasn’t on it. Now it is,” he said.
Musk said although he hopes to get the on-site liquid-oxygen plant back in service before mid-December, he is going to go ahead and bring in more liquid oxygen from Hawaii to add to the 35,000 pounds SpaceX already has on hand.
Musk said he has no choice but to use the same Hawaiian liquid-oxygen supplier, but this time he is sending two of SpaceX’s own better insulated tanks back to Hawaii to be filled and shipped back out to Kwajalein.
Musk said he was working with the U.S. Army to find a ride to Hawaii for the tanks on a C-5 cargo aircraft in the days ahead. Once SpaceX’s tanks are filled with 80,000 pounds of liquid oxygen, they will be put on a ship for the 3,400-kilometer voyage back to Kwajalein.
Musk says he has invested nearly $100 million of his personal wealth in development of the Falcon rocket. The Falcon 1’s advertised price of $5.9 million per launch plus range fees already has attracted a six customer backlog. Comparable U.S. rockets in service today cost $25 million or more to launch.
When Musk started SpaceX in 2002, he expected to complete development of the Falcon 1 and conduct the first launch within about 18 months. He has since admitted that he underestimated the technical and budgetary challenges associated with getting a new rocket to the launch pad.
Still, Musk remains confident that the Falcon 1 and its larger successor, the Falcon 9, will succeed in dramatically lowering the cost of putting payloads into space.