Spaceflight Insider

Aerojet Rocketdyne AJ-26 engine fails on the test stand

The AJ-26 is based off of the Russian-built NK-33 rocket engine. Photo Credit: Elliot Severn / SpaceFlight Insider

On Thursday afternoon, May 22, a routine test of an Aerojet Rocketdyne AJ-26 engine, at NASA’s Stennis Space Center in south Mississippi ended in failure. The engine was being tested for Orbital Sciences Corporation prior to its use in an early 2015 flight of Orbital’s Antares rocket

Reports indicate that the failure happened approximately 30 seconds into the scheduled 54 second test and may have resulted in an explosion causing “extensive damage to the engine.”

Photo Credit: Scott Johnson / SpaceFlight Insider

Photo Credit: Scott Johnson / SpaceFlight Insider

It is unknown to what extent, if any, the E-1 Test Stand was damaged. A NASA spokesperson stated that “Stennis will perform checkouts to the facility to ensure its operational integrity.”

A statement has been released by Aerojet Rocketdyne confirming that none of the personnel on hand were injured. The cause of the failure is, as yet, unknown – the statement reads as follows:

During hot-fire testing earlier today at NASA’s Stennis Space Center, Aerojet Rocketdyne’s AJ26 engine experienced a test anomaly. There were no injuries. The company is leading an investigation to determine the cause.

Two AJ-26 engines power the first stage of Orbital’s Antares rocket.  Orbital utilizes Antares as the launch vehicle which powers the company’s Cygnus spacecraft to orbit. Cygnus in turn is the spacecraft which ferries supplies to the International Space Station under the $1.9 billion contract that Orbital has with NASA under the space agency’s Commercial Resupply Services contact.

The AJ-26 is actually an NK-33 engine manufactured over forty years ago by the Soviet Union and originally intended for use on the failed Soviet N-1 Moon rocket. Rocketdyne imports, refurbishes and upgrades the engines for use by Orbital.

The next Antares launch is currently slated to take place in early June. Photo Credit: Mark Usciak / SpaceFlight Insider

The next Antares launch is currently slated to take place in early June. Photo Credit: Mark Usciak / SpaceFlight Insider

Rocketdyne purchased over forty of the NK-33 engines in the 1990’s and Orbital has purchased 20 of those engines for use on Antares. Rocketdyne has upgraded the engines by adding, among other items, electronics and a gimbaling / steering capability.

The AJ-26 has experienced one prior failure, in June 2011, when an engine caught fire in the same E-1 Test Stand.  The 2011 failure was determined to be caused by a fuel leak resulting from “stress corrosion cracking of the 40-year old metal” contained in the engine.

It is unknown at this time as to whether the AJ-26 engine failure will delay the next Antares launch scheduled for June 10 from NASA’s Wallops Flight Facility in Virginia. As with the last flight of Antares, this will be a resupply run to the space station.

Orbital has, to date, flown Antares three times. The first was a test flight, the second was under the Commercial Orbital Transportation Services (COTS) contract with NASA and the last launch of Antares, in January of this year, ferried some 2,780 lbs (1,261 kilograms) of supplies to the ISS.


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Scott earned both a Bachelor's Degree in public administration, and a law degree, from Samford University in Birmingham, Alabama. He currently practices law in the Birmingham suburb of Homewood. Scott first remembers visiting Marshall Space Flight Center in 1978 to get an up-close look at the first orbiter, Enterprise, which had been transported to Huntsville for dynamic testing. More recently, in 2006, he participated in an effort at the United States Space and Rocket Center (USSRC) to restore the long-neglected Skylab 1-G Trainer. This led to a volunteer position, with the USSRC curator, where he worked for several years maintaining exhibits and archival material, including flown space hardware. Scott attended the STS - 110, 116 and 135 shuttle launches, along with Ares I-X, Atlas V MSL and Delta IV NROL-15 launches. More recently, he covered the Atlas V SBIRS GEO-2 and MAVEN launches, along with the Antares ORB-1, SpaceX CRS-3, and Orion EFT-1 launches.

Reader Comments

As a materials inspector, having just witnessed the explosion of the Antares rocket, I find it hard to understand why we are flying 40 year old modified Soviet engines on brand new spacecraft. Especially when one exploded this year and the first one failed from stress corrosion cracking.

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