Spaceflight Insider

NASA: AJ26 turbopump likely to blame for loss of Orb-3 Antares

Launch of Orbital ATK Antares rocket with Cygnus cargo freighter on Orb-3 mission. Photo Credit Joel Kowsky NASA posted on SpaceFlight Insider

It has been little more than a year since the accident that saw the loss of Orbital ATK’s Antares booster and a Cygnus spacecraft. NASA has recently revealed its findings as to the root cause of the accident. Photo Credit: Joel Kowsky / NASA

NASA’s Independent Review Team (IRT) has released its findings on the Oct. 28, 2014, loss of an Orbital Sciences Corp. (now Orbital ATK) Antares rocket and the Cygnus spacecraft it carried. The cause of the accident was debated between Orbital and the supplier of the two AJ26 rocket engines that were used in Antares’ first stage – Aerojet Rocketdyne. That debate, through a recent settlement and the IRT’s findings, appears to have been put to rest.

Whereas Orbital ATK has stated that a fault in a turbopump on one of the two engines was responsible for the accident, Aerojet Rocketdyne has contended that Foreign Object Debris or “FOD” was to blame.

An Orbital ATK Antares booster explodes some 12 seconds after lifting off from Pad-0A at Wallops Flight Facility in Virginia NASA photo posted on SpaceFlight Insider

The Orb-3 mission only lasted for approximately 15 seconds before the mishap occurred. Photo Credit: Joel Kowsky / NASA

If FOD had been to blame, that would have meant Orbital ATK would have been accountable for the mishap as they are tasked with ensuring FOD is cleared from the launch site prior to flight. For their part, NASA has stated that while FOD could have been the issue, the preponderance of evidence suggests the AJ26’s turbopump was the likely cause.

NASA noted, however, that FOD was likely not the cause of the accident. The U.S. space agency stated the following in the roughly 10-page report: The lack of significant particle impact damage to the recovered impeller and other components indicates that there were not gross-levels of FOD present within the system. In addition, there is no clear forensic evidence that FOD directly or indirectly led to the E15 failure. 

This brought the discussion of what caused the accident back to the AJ26s themselves. The IRT noted the agency believed Orbital ATK’s take on the accident was likely correct, stating: Forensic investigation performed by Orbital ATK and NASA discovered the presence of a defect on the turbine housing bearing bore that was not consistent with baseline design requirements. The investigation determined that the defect was introduced during machining of the bearing bore housing and was therefore present prior to the engine ATP and Antares launch for Orb-3. 

The report went on to say that another AJ26, which underwent testing in 1998, had a similar flaw in it. At least two of these engines encountered failures at the E-1 Test Stand at NASA’s Stennis Space Center located in Mississippi.

The AJ26 engines, initially known as the NK-33, were built 40 years ago by the former Soviet Union for use on the N-1 Moon rocket. Aerojet Rocketdyne then refurbished the engines after they were purchased in the 1990s. It is unclear at this time if the issues with the turbopump that were noted by NASA and Orbital ATK were from the engines’ original production, incurred sometime during their long storage period, or happened accidentally during their refurbishment.

Recent events led many industry analysts to surmise that the cause of the Orb-3 accident was the AJ26 and not FOD even before the IRT’s report was made public. A report appearing on Reuters detailed how Aerojet Rocketdyne paid $50 million to Orbital ATK and took title to 10 AJ26 engines that had been tasked for Antares flights. In so doing, Aerojet Rocketdyne’s involvement with the Antares Program has come to a close. The Reuters article was published on Sept. 24, 2014 – more than two weeks before the IRT’s findings were released.

Orbital ATK enhanced Cygnus spacecraft at Kennedy Space Center in Florida photo credit Kim Shiflett NASA posted on SpaceFlight Insider

Orbital ATK is working to launch the new “enhanced” version of the company’s Cygnus spacecraft on Dec. 3, 2015. Photo Credit: Kim Shiflett / NASA

One of the recommendations NASA made was that Orbital ATK should not use the AJ26 rocket engine in the future without undertaking a more thorough inspection, qualification and acceptance test, and certification program. At present, this is a non-issue as Orbital ATK is working to field a new up-rated version of Antares – without the AJ26.

The Dulles, Virginia-based firm had been moving away from the AJ26 even before last year’s accident had taken place. Orbital ATK selected the Russian-built RD-181 rocket engine. The first flight of the “enhanced” Antares rocket with these new engines could take place as early as late spring of 2016.

When the new version of Antares returns to service, it will serve to resume commercial flights to the space station. At present SpaceX has stated that it will begin flying the Falcon 9 again sometime before the close of this year. However, sources have told SpaceFlight Insider that it is more likely that the Falcon 9 won’t resume flying until early 2016 – with Commercial Resupply Services missions likely to continue afterward.

At about 6:22 pm. EDT (20:22 GMT) on Oct. 28, 2014, the Antares-130 booster and Cygnus spacecraft lifted off from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) at NASA’s Wallops Flight Facility in Virginia. About 15 seconds into the flight, the rocket exploded, resulting in the loss of approximately 5,057 lbs (2,296 kg) of cargo that it carried. A standard Cygnus spacecraft was used for the mission, three other Cygnus have already been sent to the orbiting lab as part of NASA’s Commercial Orbital Transportation Services (COTS) and CRS contracts.

Orb-3 was the third operational cargo delivery flight that Orbital ATK worked to carry out under the $1.9 billion CRS contract the company has with NASA. In order to ensure it can meet its obligations, the aerospace firm has since purchased two United Launch Alliance Atlas V 401 rockets to launch the new “enhanced” version of Cygnus on supply runs to the orbiting lab.

For its part, the space agency has decided to focus on the numerous positive milestones both Orbital ATK and SpaceX have accomplished before both firms encountered mishaps (on June 28, 2015, a SpaceX Falcon 9 and uncrewed Dragon spacecraft were lost two minutes and 19 seconds into flight).

“The thorough work of the NASA team is essential to ensure the agency continues to learn and improve,” said William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate. “This unfortunate event provides a tremendous opportunity for the industry and NASA team to improve vehicle development, acquisition, and operations. The findings from this team will provide a basis to begin discussions on future areas for improvement. Even though not all recommendations will be implemented as written, all the recommendations will enable positive lessons for the agency.”

Launch of Orbital ATK Antares rocket with Cygnus spacecraft bound for the International Space Station. Photo Credit Joel Kowsky NASA

Orbital ATK is planning on launching the new “enhanced” version of its Antares rocket. This first of the uprated version of the booster could take place as soon as late spring of 2016. Photo Credit: Joel Kowsky / NASA



Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

Reader Comments

Thomas Williams

I think the FOD in question would enter the engine from the propellant tanks, not be sucked up from the launch site. The pre burner of these engines produce hot high pressure oxidising gas. Some magic coating protects the engine but any contamination can initiate a metal oxygen fire that rapidly destroys the engine.

Yea, this isn’t the ramp at an Air Force Base. No turbofan to suck in FOD. If FOD was ingested into the engine it was left in the tanks or plumbing. Still probably a drunk Soviet machinist from the early 1970s brought down this bird.

Just prior to Antares (Orb-3 accident) impacting the ground, safety officer sent a destruction command. The bulk charges were activated. Are we sure the explosions occurred following this sequence ensuing explosion of the vehicle before ground impact ?

⚠ Commenting Rules

Post Comment

Your email address will not be published. Required fields are marked *