Almost two years after a disastrous liftoff explosion, Orbital-ATK's Antares booster is back in service. At 7:45 pm EDT, an improved Antares 230 rocket blasted off from the MARS Pad 0A at NASA's Wallops Island facility in Virginia carrying the commercial OA-5 mission to deliver an Enhanced Cygnus unmanned cargo ship to the International Space Station (ISS). The launch, which was delayed 24 hours due to bad weather, went off without incident beyond a five minute hold to address a possible engine malfunction.

After first stage separation, the Cygnus spacecraft rose into low Earth orbit and separated from its second stage booster at 7:55 pm. Ninety minutes after liftoff, the cargo carrier completed initial systems checks and deployed the solar arrays that power the craft's avionics and other systems.

Over the next six days, Cygnus will carry out a series of engine burns to match orbits and rendezvous with the space station. When it arrives on Sunday, it will approach in a series of steps as safety checks are carried out before the station astronauts grapple it using a robotic arm and guide it to a docking berth.

Today's OA-5 mission marks the return to service of the Antares booster. According to Orbital ATK, the Antares 230 is an improved version of the model with all new RD-181 engines for greater performance and reliability. These were installed in the wake of a midair explosion that destroyed an Antares and its Cygnus payload six seconds after launch from Wallops on October 29, 2014.

This is the sixth Cygnus mission by Orbital ATK and the fifth operational mission to the ISS under a NASA commercial contract. The Cygnus is carrying about 5,300 lb (2,400 kg) of cargo and the capsule is named after the late Alan Poindexter, who was a NASA astronaut, Space Shuttle commander, and naval aviator, and who helped in the construction of the station.

Cygnus will remain docked at the ISS for up to 90 days, after which it will be loaded with waste and sent on a trajectory that will cause it to burn up in the Earth's atmosphere somewhere over the South Pacific. However, before it does so, the Cygnus will conduct a Saffire II experiment to study how substances burn in space, and will deploy several CubeSats.

The video below outlines the OA-5 mission.

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