By Irene Klotz
MOJAVE Calif (Reuters) - An investigation into the explosion last week of Orbital Sciences' Antares rocket pointed to a likely problem with a turbopump in the booster's main engine, a refurbished Soviet-era motor that Orbital expects to discontinue, the company chief executive said on Wednesday.
The unmanned rocket, which was carrying a cargo ship to the International Space Station for NASA, exploded about 15 seconds after liftoff from Virginia on Oct. 28, the first of two recent accidents by privately owned U.S. space operators.
To fulfil its contractual obligations to NASA, Orbital Sciences will buy rockets from an unnamed outside source to launch Cygnus cargo ships, as it speeds up plans to incorporate a better, more powerful engine into its Antares rocket, CEO David Thompson told investors and analysts on a conference call.
He did not say which rockets Orbital would buy to fill the gap until the re-engined Antares was ready to fly, but said the options included two U.S. launch providers and one in Europe.
The U.S. companies that sell rockets suitable for launching Orbital's Cygnus capsules include Space Exploration Technology. The privately owned firm, also known as SpaceX, has a separate $1.6 billion contract to fly cargo to the station for NASA.
SpaceX declined to comment.
Steve Cahall, analyst with RBC Capital Markets, said the news reduced the chances that the mishap would derail Orbital's merger with Alliant Techsystems Inc.
"We see today's comments as a positive step for clarity on the merger/spin, though it's still early days," Cahall wrote in a note to investors.
Orbital shares surged on the news, trading nearly 4 percent higher at $26.10 on the New York Stock Exchange. Shares of Alliant Techsystems were $0.68 lower at $112.19.
Thompson said the cargo deliveries to the space station could be delivered in 2015 and 2016, as specified and within financial terms of its $1.9 billion NASA contract.
"We will purchase one or two non-Antares launch vehicles for Cygnus flights in 2015 and possibly in early 2016, and combine them with several upgraded Antares rocket launches of additional Cygnus spacecraft in 2016 to deliver all remaining … cargo," Thompson said.
"We expect to work with NASA to determine the most favourable combination for one or two gap-filler missions ... and are aiming to make final decisions on the best way forward over the course of the coming month," he said.
Orbital did not say which engine would replace the current AJ-26 motors, though the Russian news agency Tass reported last week that Orbital planned to buy another Russian engine, the RD-195 made by Moscow-based NPO Energomash.
Antares, which had made four previous successful flights before last week's failure, uses two heavily modified NK-33 engines originally built for a Soviet moon program that was abandoned after repeated in-flight failures. GenCorp Inc's Aerojet Rocketdyne division bought about 40 of the mothballed engines for refurbishment and resale as AJ-26 motors.
Thompson said more analysis was needed to confirm that the AJ-26 turbopump had caused the accident.
The Antares rocket explosion was the first accident since NASA turned to commercial providers to fly cargo to the space station following the retirement of the space shuttles in 2011.
On Friday, a passenger spaceship owned by Virgin Galactic crashed during a test flight in Mojave, Calif., killing one of the pilots and injuring the other.
(Additional reporting by Andrea Shalal in Washington; Editing by Bernadette Baum)