AJ-26 rocket engine being test fired. Credit: Aerojet Rocketdyne

COLORADO SPRINGS, Colo. โ€” An AJ-26 engine slated to power Orbital Sciences Corp.โ€™s Antares rocket on a 2015 mission to the international space station failed May 22 during a hot-fire test at NASAโ€™s Stennis Space Center in Mississippi. 

Orbital Sciences spokesman Barry Beneski confirmed the failure late May 22.

โ€œYes, there was an AJ26 engine test anomaly earlier today at Stennis. The cause is unknown at this point,โ€ Beneski said in an email. โ€œEngineering teams will gather and examine the data to determine the cause. It was an engine slated for a flight in 2015.โ€

The AJ-26 is a liquid oxygen- and kerosene-fueled engine originally built for Russiaโ€™s abandoned lunar program. Aerojet Rocketdyne of Sacramento, California, has a stockpile of the 1970s-vintage engines that it is refurbishing for Orbital. 

Two AJ-26 engines are used to power the Antares rocketโ€™s main stage.

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Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...