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Antares, known during early development as Taurus II, is an expendable launch system developed by Orbital Sciences Corporation. Designed to launch payloads of mass up to 5,000 kg (11,000 lb) into low-Earth orbit, it made its maiden flight on 21 April 2013. Designed to launch the Cygnus spacecraft to the International Space Station as part of NASA\’s COTS and CRS programs, Antares is the largest rocket operated by Orbital Sciences.

NASA awarded to Orbital a Commercial Orbital Transportation Services (COTS) Space Act Agreement (SAA) in 2008 to demonstrate delivery of cargo to the International Space Station. For these COTS missions Orbital intends to use Antares to launch its Cygnus spacecraft. In addition, Antares will compete for small-to-medium missions. On 12 December 2011 Orbital Sciences renamed the launch vehicle “Antares” from the previous designation of Taurus II, after the star of the same name.

Originally scheduled for 2012, the first Antares launch, designated A-ONE was conducted on 21 April 2013, carrying the Cygnus Mass Simulator (a boilerplate Cygnus spacecraft) and four CubeSats contracted by Spaceflight Incorporated: Dove 1 for Cosmogia Incorporated and three PhoneSat satellites – Alexander, Graham and Bell for NASA.

Prior to the launch, a 27-second test firing of the rocket\’s AJ26 engines was conducted successfully on 22 February 2013, following an attempt on 13 February which was abandoned before ignition.

A-ONE used the Antares 110 configuration, with a Castor 30A second stage and no third stage. The launch took place from Pad 0A of the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia. LP-0A was a former Conestoga launch complex which had only been used once before, in 1995, for the Conestoga\’s only orbital launch attempt. Antares became the largest — and first — liquid-fuelled rocket to fly from Wallops Island, as well as the largest rocket launched by Orbital Sciences.

The first attempt to launch the rocket, on 17 April 2013, was scrubbed after an umbilical detached from the rocket\’s second stage, and a second attempt on 20 April was scrubbed due to high altitude winds. At the third attempt on 21 April, the rocket lifted off at the beginning on its launch window. The launch window for all three attempts was three hours beginning at 21:00 UTC (17:00 EDT), shortening to two hours at the start of the terminal count, and ten minutes later in the count.

Source: Wikipedia