Engineers probing the May 22 failure of an Aerojet Rocketdyne AJ-26 engine during an acceptance test for a future Orbital Sciences Antares mission to the International Space Station (ISS) have yet to determine whether the mishap will delay the next Antares launch.

Preparations for that mission, set to launch from Wallops Flight Facility, Va., on June 10, continue as planned, according to Orbital spokesman Barry Beneski.

"The team will continue to progress toward the June 10 launch until they are told not to," he said May 27.

The refurbished Soviet-era engine suffered "significant damage" in the failure at NASA’s Stennis Space Center, where the reworked engines are hot-fire tested before shipment to Wallops for integration into an Antares.

The engine failed about midway through the test, Beneski said, a little less than a minute after ignition. Aerojet Rocketdyne has taken the lead on the failure analysis, which was "gathering all the data" on the mishap before drawing conclusions, he said.

The engine that failed wasn’t scheduled for flight until next year. The June 10 Antares already has its engines, and engines are on hand for another cargo mission to the ISS in October, according to the Orbital spokesman.

"Farther out, in 2015, we’ll figure out which engines go on which rocket," Beneski said.

The May 22 engine failure was the second in the Antares program. A kerosene-fuel leak from a manifold in one of the 40-year-old engines caused a test-stand fire in June 2011. Orbital rejected a third engine and sent it back to Aerojet for repairs, according to Beneski.

"Every AJ-26 that ... flies on Antares goes through a hot-fire acceptance test first," Beneski said. "Fourteen of them have done fine."

Orbital integrates the Soviet-era engines, originally designated the NK-33, in pairs into a first stage built by PA Yushmash, a state-owned company in Dnipropetrovsk, Ukraine. Although the company is located in the eastern part of the country, where pro-Russian sentiment runs strong in the ongoing Crimean crisis, Beneski said so far the political unrest has not disrupted production.

Dulles, Va.-based Orbital has three of the Ukrainian-built stages on hand for the two launches this year and one early in 2015, and expects to receive two more by ship in the second half of this year.

"We take a daily check of how it’s going over there," Beneski said, noting that aside from humanitarian concerns over the escalating violence, "from a business standpoint we watch for quality and schedule, and we haven’t detected any changes."