The launch of an Antares 110 rocket
|Function||Medium expendable launch system|
|Country of origin||United States|
|Height||40.5 m (133 ft)|
|Diameter||3.9 m (13 ft)|
|Mass||~240,000 kg (530,000 lb)|
|Stages||2 to 3|
|>5,000 kg (11,000 lb)|
|Launch sites||MARS LP-0A
|Total launches||3 (110: 2, 120: 1)|
|Successes||3 (110: 2, 120: 1)|
|First flight||110: April 21, 2013
120: January 9, 2014
|Engines||2 × Aerojet AJ26-62|
|Thrust||3,265 kN (734,000 lbf)|
|Engines||1 × Castor 30A/B/XL|
|Thrust||30B: 293.4 kN (66,000 lbf)|
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 April 21, 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 December 12, 2011 Orbital Sciences renamed the launch vehicle "Antares" from the previous designation of Taurus II, after the star of the same name.
As of January 2014[update], Antares has made three successful launches to orbit of three launch attempts.
The NASA COTS award was for US$171 million; Orbital Sciences expects to invest $150 million in addition, split between $130 million for the booster and $20 million for the spacecraft. As of April 2012, development costs are estimated at $472 million.
On June 10, 2008 it was announced that the Mid-Atlantic Regional Spaceport, formerly part of the Wallops Flight Facility, in Virginia, would be the primary launch site for the rocket. Launch pad 0A (LP-0A), which is the former launch pad for the failed Conestoga rocket will be modified to handle Antares. A launch from Wallops would reach the International Space Station's orbit as effectively as from Cape Canaveral, Florida, while being less crowded. The first Antares flight launched a Cygnus mass simulator.
On December 10, 2009 Alliant Techsystems Inc. (ATK) test fired their Castor 30 motor for use as the second stage of the Antares rocket. In March 2010 Orbital Sciences and Aerojet completed test firings of the NK-33 engines. On February 22, 2013 a hot fire test was successfully performed, the entire first stage being erected on the pad and held down while the engines fired for 29 seconds.
The first stage uses RP-1 (kerosene) and liquid oxygen (LOX) as propellants, powering two Aerojet AJ-26 engines, which are modified Russian-built NK-33 engines. Together they produce 3,265 kilonewtons (734,000 lbf) of thrust at sea level and 3,630 kN (816,100 lbf) in vacuum. As Orbital has little experience with large liquid stages and LOX propellant, some of the Antares first stage work was contracted to the Ukrainian Yuzhnoye SDO, designers of the Zenit series. The core provided by Yuzhnoye includes propellant tanks, pressurization tanks, valves, sensors, feed lines, tubing, wiring and other associated hardware. Like Zenit, the Antares vehicle has a 3.9 m (150 in) diameter. It has a 3.9 m diameter payload fairing.
The second stage is a solid-fuel rocket, the Castor 30, developed by ATK as a derivative of the Castor 120 solid stage, with a 293.4 kN (65,960 lbf) average and 395.7 kN (88,960 lbf) maximum thrust, using electromechanical thrust vector control. The first two flights (Antares 110) will use a Castor 30A, the next two flights (Antares 120) will use an enhanced Castor 30B. The longer Castor 30XL second stage will be used on subsequent flights. 
The optional third stages planned, are the Bi-Propellant Third Stage (BTS) and an ATK Star 48-based third stage. BTS is derived from Orbital Sciences' GEOStar spacecraft bus and uses nitrogen tetroxide and hydrazine for propellant; it is intended to precisely place payloads into their final orbits. The Star 48-based stage uses a Star 48BV solid rocket motor and is planned to be used for higher energy orbits.
Configurations and numbering
The first two test flights will use the Antares 110 configuration, with a Castor 30A second stage and no third stage. Subsequent flights will use either a Castor 30B or an enlarged Castor 30XL. The rocket's configuration is indicated by a three-digit number, the first number representing the first stage, the second the type of second stage, and the third the type of third stage.
|Number||First digit||Second digit||Third digit|
|(First stage)||(Second stage)||(Third stage)|
|0||N/A||N/A||No third stage|
|1||Standard first stage
(2 × AJ26-62)
(3 × IHI BT-4)
|2||N/A||Castor 30B||Star 48BV|
Originally scheduled for 2012, the first Antares launch, designated A-ONE was conducted on April 21, 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 February 22, 2013, following an attempt on February 13 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 April 17, 2013, was scrubbed after an umbilical detached from the rocket's second stage, and a second attempt on April 20 was scrubbed due to high altitude winds. At the third attempt on April 21, 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[clarification needed] in the count.
|1||Antares A-ONE||Standard||21 April 2013||Antares 110||Success||Antares test flight. Castor 30A second stage and no third stage.|||
|2||Orb-D1||G. David Low Cygnus||Standard||18 September 2013||Success||Orbital Sciences COTS demonstration flight. First Cygnus mission, first mission to rendezvous with ISS, first mission to berth with ISS, second launch of Antares. The rendezvous between the new Cygnus cargo freighter and the International Space Station was delayed due to a computer data link problem, but the issue was resolved and berthing followed shortly thereafter.|||
|3||CRS Orb-1||C. Gordon Fullerton Cygnus||Standard||9 January 2014||Antares 120||Success||First Commercial Resupply Service (CRS) mission for Cygnus, first Antares launch using the Castor 30B upperstage|||
|4||CRS Orb-2||Cygnus spacecraft||Standard||1 May 2014||Planned|||
|5||CRS Orb-3||Cygnus spacecraft||Standard||3 October 2014||Antares 130||Planned||First Antares launch to use Castor 30XL upperstage|||
|6||CRS Orb-4||Cygnus spacecraft||Enhanced||2015||Planned||First Enhanced Cygnus mission|||
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Media related to Antares (rocket) at Wikimedia Commons
- Antares rocket at Orbital.com