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ULA pinpoints cause of Atlas 5 premature shutdown

In the heat of competition: ULA has completed its investigation into the premature shutdown of the Atlas 5 first stage during its March launch of Orbital ATK’s Cygnus capsule and has corrected the problem.

An extensive review of all post-flight data observations determined that at approximately T+222 seconds, an unexpected shift in fuel pressure differential across the RD-180 Mixture Ratio Control Valve (MRCV) and a reduction in fuel flow to the combustion chamber caused an oxidizer-rich mixture of propellants and a reduction in first stage performance. The imbalanced propellant consumption rate resulted in depletion of the first stage oxidizer with significant fuel remaining at booster engine shutdown. The engine supplier has implemented a minor change to the MRCV assembly to ensure the anomaly does not occur on future flights.

Engine hot-fire testing, extensive component and assembly level testing and analyses have been performed to confirm the findings. Detailed inspections and minor hardware replacement on all engines will support the current launch manifest.

They have now scheduled the next Atlas 5 launch for June 24.

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

 
Unfortunately, that is exactly where that journey takes him.

 
The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

 
He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

 
Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.

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