he first stage uses RP-1 (kerosene) and liquid oxygen (LOX) as propellants, powering two Aerojet AJ-26 engines, which are modified Soviet-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 diameter of 3.9 m (150 in) with a matching 3.9 m payload fairing. The fairing is manufactured by Applied Aerospace Structures Corporation of Stockton, California, which also builds other composite structures for the vehicle, including the fairing adaptor, stage 2 motor adaptor, stage 2 interstage, payload adaptor, and avionics cylinder.
The second stage is a solid-fuel rocket, the Castor 30. Developed by ATK as a derivative of the Castor 120 solid stage, the Castor 30B produces 293.4 kN (65,960 lbf) average and 395.7 kN (88,960 lbf) maximum thrust, and uses electromechanical thrust vector control. Antares' Castor 30 solid stage was based on the Castor 120 solid motor used as Minotaur-C's first stage. The first two flights of Antares used a Castor 30A, followed by two flights of the Antares 120 using an enhanced Castor 30B. The longer Castor 30XL second stage will be used on subsequent ISS resupply flights, allowing Antares to carry larger Enhanced Cygnus.
Orbital Sciences offers two optional third stages, 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
Test firing of the Castor 30 upperstage engine
The first two test flights used the Antares 110 configuration, with a Castor 30A second stage and no third stage. Subsequent flights will use either a Castor 30B or 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.
No third stage
Standard first stage
(2 × AJ26-62)
(3 × IHI BT-4)
Main article: Antares A-ONE
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 (now Planet Labs) 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...
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