AJ-26 is a refurbished Russian NK-33 liquid fuel engine, a derivation of the NK-15 used in the Russian N-1 moon rocket. The N-1 program halted after 4 consecutive launch failures.
Now that Orbital has merged with ATK this will probably speed up their decision to ditch their Ukraine made, Russian engined Antares first stage with an ATK made solid rocket.
The solid is rumored to be based on the Dark Knight composite core solid booster tech ATK developed for the now cancelled SLS Advanced Booster program. Most likely a 1-2 segment vs SLS's 4 segments with a slower burning solid propellant.
The same diameter as the Shuttle SRB's, the Dark Knight tech will also be used in the first stage of the StratoLaunch Thunderbolt air-launcher.
Antares' AJ-26 Engine Suffers Test Stand Failure
COLORADO SPRINGS, Colo. -- An AJ-26 engine slated to power Orbital Sciences Corp.’s Antares rocket on a 2015 mission to the international space station failed May 22 during a hot-fire test at NASA’s Stennis Space Center in Mississippi.
Orbital Sciences spokesman Barry Beneski confirmed the failure late May 22.
"Yes, there was an AJ26 engine test anomaly earlier today at Stennis. The cause is unknown at this point,” Beneski said in an email. “Engineering teams will gather and examine the data to determine the cause. It was an engine slated for a flight in 2015.”
The AJ-26 is a liquid oxygen- and kerosene-fueled engine originally built for Russia’s abandoned lunar program. Aerojet Rocketdyne of Sacramento, California, has a stockpile of the 1970s-vintage engines that it is refurbishing for Orbital Sciences.
Two AJ-26 engines are used to power the Antares rocket’s main stage.
Dark Knight SLS Advanced Booster