Inside the 1960s-Era Soviet Engines That Downed the Antares Rocket

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Private space firm Orbital Sciences is facing criticism for the Aerojet AJ26 engines which powered the Antares rocket that exploded earlier this week at NASA’s Wallops facility. The story of the engines — refurbished versions of the NK-33s built by the Soviet Union at the height of the space race that bureaucrats stored in a warehouse for a decade — reads like a Ludlum novel.



Unlike the Challenger disaster that claimed the lives of seven astronauts, the Antares was unmanned and nobody was hurt during the spectacular failure. But because the explosion actually started while the rocket was still on the launch pad, it caused damage to NASA’s Wallops facility. NASA said that an initial examination showed that a number of support buildings in the immediate vicinity had broken windows and imploded doors, and a sounding rocket launcher beside the pad suffered the most severe damage. The transporter erector launcher and lightning suppression rods on the pad were also damaged during liftoff.

Orbital Science’s Frank Culbertson confirmed that the rocket suffered “disassembly,” after which, the range safety officer gave a self-destruct command, which is a standard procedure after a rocket goes off course. Rather than crash into a populated area, NASA sends a signal known as a “destructive abort” that destroys the vehicle.

Now the speculation is that the AJ26 engines were at fault.


The AJ26 engines are refurbished versions of the ex-Soviet Union NK-33 rocket engine. The engines were built in the late 1960s and early 1970s by the Kuznetsov Design Bureau, and were among the highest thrust-to-weight ratio rockets of any Earth-launchable rocket engine. Good for 339,000 lbf of thrust, the only one more powerful still is the SpaceX Merlin 1D.

The engines were originally designed to power the N1 heavy lift rocket, developed to compete with NASA’s Apollo Saturn V.


The NK-33 uses a highly unusual burner design, as they use oxygen-rich preburners to drive the turbopumps. The issue is that the exhaust is oxygen-rich and incredibly hot, which can cause burn-through failures as the exhaust attacks the metal of the nozzle. Soviet scientists perfected the metallurgy by corrugating the rocket nozzle, which was brazed to an outer and inner lining in a light, strong structure.

The Soviets built the rocket engines for the N1, but that rocket (pardon the pun) never got off the ground, because the race for the Moon was essentially over by the time it was developed. All the work on the rockets — the design, the rocket engines themselves, the plans — was supposed to be completely destroyed.

However, in perfectly pure Soviet bureaucracy fashion, they slipped out the back  door. Hundreds of the engines were squirreled away by a bureaucrat, who stored them in a warehouse. For years, the existence of the engines was a rumor, but three decades after they were built, a team of American rocket engineers were taken to the warehouse. One engine made its way to the United States and tested.

The first test is documented in this video:

About 150 of the engines survived, and in the mid-1990s, Russia sold 36 engines to Aerojet General for $1.1 million each. Aerojet also secured a license to produce new versions, known as the AJ26.

When Orbital Science’s Antares rocket took its maiden voyage on April 21, 2013 — from the Wallops Flight Facility where the ill-fated launch was supposed to happen this week — it was the first successful launch of the NK-33 heritage engines since they were originally built when Nixon was still president.

The most publicized part of the mission was to provide 5,000 pounds of supplies to the ISS. But this is about way more than just refilling the toilet paper dispensers up there. Antares had tens of millions of dollars of equipment on board.

According to Gizmodo: “Antares was also carrying the first payload from Planetary Resources. The fledgling asteroid mining company (formerly Arkyd Astronautics) raised $1.5 million last year on Kickstarter to construct and dispatch the first publicly controlled orbiting space telescope. According to Popular Mechanics, Antares was carrying 32 CubeSats—or mini research satellites—one of which was the Arkyd 3 (A3) from Planetary Resources, which was to act as a kind of prototype for future developments.”

Craig Fitzgerald

Craig Fitzgerald

Writer, editor, lousy guitar player, dad. Content Marketing and Publication Manager at