As Orbital Sciences Corporation looks for clues to Tuesdays catastrophic failure of its Antares launcher, three independent industry insiders tell Forbes that the blame squarely rests on one of two of the rockets Soviet-era engines.

Speaking on condition of anonymity, a launcher engineer and industry expert told Forbes that before the Antares vehicle lost thrust it was evident that there was a lot of unburned kerosene going into the exhaust stream which he says suggests that it also lost engine pressurization.

It wasnt a failure in the fuel tanks, avionics, or navigation, but definitely with an engine, said the launcher engineer.

The Orbital Sciences Corporation Antares rocket seen on launch Pad-0A during sunrise, Sunday, Oct. 26, 2014, at NASAs Wallops Flight Facility in Virginia. Credit: NASA/Joel Kowsky

The Antares two-stage launcher system, which NASA tasked with re-supplying the International Space Station (ISS), experienced a catastrophic failure which triggered a self-destruct scenario within seconds after liftoff at 6:22 PM EDT from NASAs Wallops Flight Facility on Virginias Atlantic shore.

The rockets two engines were modified Soviet-era hardware initially acquired from Russia in the late 1990s by the now defunct Kirkland, Wa.-based Kistler Aerospace Corporation. At the time, prior to its merger with Rocketdyne, the Sacramento, Ca.-based Aerojet Corporation had been subcontracted by Kistler to modernize the engines. However, Aerojet subsequently gained title to the engines as part of Kistlers bankruptcy settlement. They were originally developed by the Soviet Union for their N-1 manned lunar rocket which experienced several failures resulting in the Soviet cancellation of their manned lunar landing program, said Bill Ketchum, a retired General Dynamics General Dynamics Corporation aerospace engineer, familiar with such systems.

The Aerojet Rocketdyne modifications mainly were to allow the engines to gimbal (making them steerable); to inspect them for cracking and to integrate them with new control electronics, plumbing and wiring.

Aerojet Rocketdyne gave the engines the new AJ-26 designation number and eventually sold them to the Dulles, Va.-based Orbital Sciences; that is, shortly after Orbital Sciences entered into a commercial contract with NASA for unmanned cargo resupply missions to the ISS.

Those NK-33/AJ-26 engines had been stored in 1975 in a non climate-controlled warehouse, said Dennis Wingo, an engineering physicist and CEO of Skycorp Incorporated at Moffet Field, Ca. No one wanted them, until Orbital Sciences came along with their Antares vehicle.

Wingo says the most likely culprit in Tuesdays launch failure is hardware stress, corrosion and cracking leading to engine failure, but he notes it could have also been a fuel line crack or rupture.

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Antares Failure Casts Doubt On U.S. Commercial Launch Strategy