Originally published January 4, 2015 at 5:25 PM | Page modified January 4, 2015 at 9:21 PM

Years before an unmanned rocket erupted in a fireball in October, NASA officials knew the metal in its 50-year-old Soviet-made engines could crack, causing fuel to leak and ignite, government documents show.

As early as 2008, a NASA committee warned about the substantial risk of using the decades-old engines, and a fire during a 2011 engine test in Mississippi heightened the agencys concern.

The engines had a fundamental flaw in the materials, said a top manager for NASAs contracted rocket builder, Orbital Sciences, in a 2013 interview with an agency historian. The Soviet engines were built in the 1960s and 1970s in a failed attempt to take cosmonauts to the moon.

They were never designed to be in storage that long, said the Orbital manager, Ken Eberly, deputy director for the rocket program.

The explosion, just seconds after liftoff from a Virginia launchpad on Oct. 28, destroyed tens of millions of dollars in taxpayer-funded supplies, experiments and equipment, all bound for the International Space Station.

The episode has raised questions about NASAs oversight of a new program to hire private contractors to carry cargo and astronauts to orbit, rather than operate the spacecraft itself.

NASA and Orbital officials knew the decades-old engines posed a danger before the agency awarded the company a $1.9-billion deal to launch eight missions. The company and NASA tried to address the risk by X-raying the engines to find cracks and patching them with welds.

NASA officials knew before the October explosion that the fix had not worked as well as intended. In May, an overhauled engine exploded during a test at NASAs Stennis Space Center in Mississippi.

Under NASAs contract with Orbital, taxpayers shoulder most of the risk of a catastrophe. The company receives as much as 80 percent of its fee for each launch even if the rocket explodes.

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Before explosions, NASA knew aging Soviet engines could crack, leak fuel