Orbital ATK returned to market of commercial space launch services with their modified Antares rocket. Company finished period of cooperation with United Launch Alliance and again will conduct launches under CRS program with own rocket.
This mission was important moment for Orbital ATK. Finally, after two years of utilizing Atlas V rockets for launching Cygnus robotic cargo spacecraft, Orbital ATK managed to perform launch of Antares rocket with Cygnus on atop. But last two years were not wasted - Antares 230 launched yesterday is not exact same rocket as rocket used during ORB-3 mission on 28 October 2014, when launch vehicle exploded shortly after start. It should not be surprising, that Orbital ATK tried to do everything to avoid next bad day on Pad 0A at Wallops Flight Facility in Virginia. Launch was postponed multiple times, and when it was announced on August, that OA-5 mission will be again moved in time, company declared that delay is caused by following reasons:
“Due to a variety of interrelated factors, including the company’s continuing processing, inspection and testing of the flight vehicle at Wallops Island and NASA’s scheduling of crew activities on the International Space Station in preparation for upcoming cargo and crew launches...”
Without knowledge on any specific reason of delay of Antares, Orbital ATK finally announced, that launch will be conducted in second half of October. Originally launch was planned for October 17, but due the small problem with launch pad’s hold-down system spotted on launch day, Orbital ATK and NASA decided to wait for another 24 hours. Luckily spare parts were available at Wallops, and launch was set for Monday for 23:45 GMT.
Fueling of the rocket started yesterday at around 22:32 GMT, just after finishing control of engines, thrust control system and hydraulic sub systems of the rocket. At 23:39 GMT, Cygnus was switched to internal power. At 23:45:38 GMT rocket ignited its engines and started to rise over Wallops Flight Facility. Shortly after, rocket performs pitch maneuver to set course for 110.2° and was continuing flight over Atlantic Ocean. First stage was planned to burn for 3 minutes 20 seconds. At 23:49 GMT first engine performed cut off of its propulsion and separated from second stage. At 23:49:44 GMT payload fairing (long for 9.9 m with diameter at 3.9 m) was jettisoned along with round cover of second stage. Propulsion of the second stage was ignited on altitude of 149.5 km ten seconds later. Cut off was performed at 23:52:34 GMT on altitude of 219 km. Cygnus was continuing ballistic flight still attached to second stage until 23:54:33 GMT, when separation was conducted on altitude of 217 km. Cygnus passed self-tests successfully, deployed its 3.7 m circular solar arrays at 01:28 GMT and begun its flight to International Space Station with over 4800 kg of cargo onboard. It will to dock to ISS on 23rd October - two days after docking of Soyuz MS-02 with members of Expedition 50 on 21st October.
Antares is medium sized launch vehicle (able to deliver 6120 kg to LEO in previous version) and comparing to other rockets by Orbital ATK (Pegasus, Taurus and Minotaur launch vehicles), the largest one. It was designed in the cooperation with Yuzhnoye Design Bureau under Commercial Orbital Transportation Services NASA program; first test flight was performed on 21 April 2013. Propulsion of the Antares was based on modified by Ukrainian Yuzhnoye Design Bureau NK-33 engines manufactured in seventies in Soviet Union. First stage was powered by two engines, which were able to provide thrust at 3265 kN. Second stage was designed by Orbital ATK with one in-house manufactured solid fueled Castor-30 engine with thrust up to 293.4 kN. Antares in basic configuration was 40.5 m long with diameter at 3.9 m and mass at 240000 kg. First stage was liquid fueled (RP-1/LOX propellant); second stage was solid fueled with HTPB (12815 kg of propellant). New version marked as "200" will use two RD-191/181 engines manufactured by NPO Energomash with thrust at 3700 kN in the first stage, combined with enlarged second stage. During OA-5 mission Orbital ATK will use "230" configuration based on first stage with two RD-181 and Castor-30XL solid fueled (HTPB) second stage with max thrust at 393 kN. Rocket in 230 configuration is longer comparing to Antares 100 (41.9 m) with unchanged diameter of 3.9 m. Launch mass is 298000 kg. Antares 230 is able to lift to GTO orbit 2700 kg, to LEO payload capacity is 7000 kg.