A timing error that caused two segments of a privately built Falcon 1 rocket to collide after liftoff doomed the booster's third flight test by the California-based firm SpaceX, the company's chief said Wednesday.
SpaceX's chief executive officer, Elon Musk, said his engineers have traced the cause of the Aug. 2 launch failure to a timing error between the shutdown of the low-cost Falcon 1 rocket's first-stage engine and the separation of its upper stage, causing the two segments to bump into one another instead of separating harmlessly.
"We have quite a definitive understanding of what went wrong on the last flight," Musk told reporters during a teleconference, adding that the timing error was on the order of seconds. "If we were to increase that gap by even a second or two, this problem would not have arisen."
Based in Hawthorne, Calif., SpaceX — short for Space Exploration Technologies — launched its third Falcon 1 rocket late Saturday ET from the U.S. Army's Reagan Missile Test Site on Omelek Island in Kwajalein Atoll, which sits about 2,500 miles (4,023 kilometers) southwest of Hawaii in the central Pacific Ocean.
Musk said SpaceX would be releasing video of the staging event that clearly shows the first and second stages separating as planned about 2 minutes and 20 seconds into the flight. The video also shows that unanticipated residual thrust from the redesigned Merlin engine caused the first stage to bump the second stage just as it began to fire, he said.
Both halves of the rocket then fell into the Pacific Ocean, well east of the Marshall Islands, and were destroyed along with its payload of two small NASA satellites and the Trailblazer demonstration satellite for the Pentagon.
A container containing the cremated remains of more than 200 people — including astronaut Gordon Cooper and actor James Doohan — was also lost, according to the space memorial firm Celestis, Inc. Doohan played the engineer Montgomery ("Scotty") Scott on the original "Star Trek" TV series.
New engine used
The rocket was powered by SpaceX's Merlin 1C engine, which uses a regenerative cooling system that funnels propellant through a series of channels along its engine nozzle before ignition. Previous Merlin engines used ablative cooling systems that burned away material to shed excess heat.
Musk said that simply extending the Falcon 1 rocket's 1.5-second separation sequence should solve the problem. SpaceX engineers pinned the glitch down for sure on Tuesday and are determined to aim for orbit a fourth time, he added.
"If we had a rocket on the launch pad tomorrow we could make this timing change, launch and be OK," Musk said.
The recent failure marked the third in a row for SpaceX, starting with the Falcon 1's debut in March 2006, when a fuel-line leak and fire thwarted the inaugural launch just after blastoff. A 2007 test flight lasted about five minutes, enough to undergo stage separation, but that rocket also failed to reach orbit.
Musk said that in contrast to the second test, which turned up other potential problems after analysis, SpaceX's post-launch assessment of the Aug. 2 flight has found no other near-miss issues that need to be worked before the next launch. As a result, Musk is confident that Falcon 1 will be flying again before the end of the year.
Components for the fourth Falcon 1 rocket to are expected to head to SpaceX's Omelek Island launch site in a few weeks, Musk added.
(On Monday, Musk announced that SpaceX accepted a $20 million investment from Founders Fund, a $220 million venture capital firm managed by his fellow PayPal co-founders. Musk said he accepted the investment before Saturday's launch "as a precautionary measure" in case the mission failed.)
First of the Falcon family
SpaceX's Falcon 1 rocket is a two-stage booster that stands about 68 feet (21 meters) tall and carries a reusable first stage designed to be recovered in the ocean and refurbished for future flights. The $6.7 million rocket is designed to loft satellites up to 1,256 pounds (570 kg) into low-Earth orbit.
The rocket is the first of SpaceX's family of Falcon boosters, with engine test firings also underway for the larger Falcon 9 launch vehicle.
As it stands, SpaceX expects to have its next Falcon 1 in place for a fourth launch attempt as soon as September.
That launch will now be a demonstration launch, Musk said, since SpaceX had previously promised to its next customer, the Malaysian space agency, that it would prove Falcon 1's ability to reach orbit before attempting to launch the company's Razaksat spacecraft.
"I've never given up and I've never lost," Musk said. "And I'm not going to start now."
Space News Staff Writer Brian Berger contributed to this story from Washington, D.C.