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Cygnus grapple
The International Space Station’s robotic arm reaches out to grapple Orbital ATK’s Cygnus cargo ship in a video view with an overlay of computer data. (Credit: NASA TV)

Orbital ATK’s Cygnus commercial cargo ship had a smooth link-up with the International Space Station today, delivering about 7,500 pounds of supplies, equipment, experiments and high-tech gizmos. But a rocket glitch that cropped up while putting the Cygnus into orbit has led United Launch Alliance to postpone the next scheduled liftoff of its Atlas 5 rocket.

The good news is that Tuesday night’s anomalous rocket engine performance had no impact on the Cygnus sendoff. The uncrewed capsule made today’s rendezvous right on time, and astronauts used the station’s robotic arm to bring it in for its berthing.

Over the next two months, crew members will unload Cygnus’ cargo – including a 3-D printer, a meteor-watching experiment and tons of more mundane items. Then they’ll fill it back up with trash and send it loose to burn up during atmospheric re-entry. During the descent, mission managers will use an experimental apparatus to set a fire inside the capsule and study how the flames spread.

Meanwhile, United Launch Alliance is trying to figure out why the Aerojet Rocketdyne RL10C-1 rocket engine on the Atlas 5’s Centaur upper stage fired for more than a minute longer than projected. The extended upper-stage firing came after the Russian-made RD-180 engine on the rocket’s first stage shut down about five seconds earlier than projected.

ULA noted that despite the engine snags, Tuesday’s launch put the Cygnus in its proper orbit. That marked the 62nd successful Atlas 5 liftoff with no failures. However, the company said it will delay the next scheduled Atlas 5 launch, which is aimed at putting the U.S. Navy’s MUOS-5 tactical communications satellite into orbit.

The postponement from May 5 to no earlier than May 12 will provide additional time to review the launch data from the Cygnus launch, ULA said.

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