Good news from Orbital ATK - their Antares rocket should be ready for OA-5 mission of Cygnus cargo spacecraft scheduled for 31st May 2016.
Antares rocket remains official competitor of Falcon-9 in commercial resupply missions under CRS agreement between NASA, Orbital ATK and SpaceX. After last failed launch, performed on 28 October 2014 from Wallops Flight Facility, in Virginia, Antares was not utilized in any mission. All Cygnus flights under contract with NASA for resupply missions to International Space Station were performed with Atlas V rocket provided by United Launch Alliance. After unlucky fifth mission of Antares, rocket has been remained not operational for almost two years. It is a failure for sure; SpaceX after disaster of Falcon-9 in June 2015 was able to return to game in six months. Of course changes in construction of Antares were more advanced than in Falcon, but are almost two years of delay justified?
Antares rocket was designed by Orbital ATK especially to meet demands of NASA CRS contract. Rocket primary objective was lifting Cygnus robotic spacecraft with supplies for ISS eventually to deliver any other payload to LEO. It was largest launch vehicle in Orbital ATK fleet after Pegasus, Taurus and Minotaur launch vehicles. It was designed in the cooperation with Yuzhnoye Design Bureau; first test flight was performed on 21 April 2013 and was, just like further flights, successful. Antares represented most practical way of designing rockets - Orbital ATK focused on these parts of project where they were experienced, leaving these parts which could be done better by subcontractor. Yuzhnoye Design Bureau, most experienced design office in Ukraine, with potential comparable to best Russian design bureaus, was responsible for development and manufacturing first stage, including propulsion (in Antares 100 two NK-33 post-Soviet engines manufactured in late seventies). Second stage was designed and manufactured by Orbital ATK with one in-house Castor-30 engine. Antares in 100 version was 40.5 m long with diameter at 3.9 m and mass at 240000kg. Payload capacity for LEO mission was 5100 kg with 3.94 m payload fairing. First stage was liquid fueled with RP-1/LOX, second stage was solid fueled with HTPB (12815 kg of propellant). After failed mission in 2014 and due the limited number of ageing NK-33 engines, Orbital ATK decided to retire 100 version of Antares and switch as soon as possible to new version.
According to digit code for Antares, version scheduled for 31st may 2016 is 230. It means that it is equipped in second version of the first stage, third version of second stage (with Castor-30XL solid fueled with HTPB). First stage is powered with two Russian RD-181 engines manufactured by Energomash and fueled with RP-1/LOX, generating thrust at 3700 kN. RD-181 is offering thrust improved for about 435 kN comparing to old NK-33. Castor-30XL is larger version of Castor-30A. It is equipped with identical Electromechanical Thrust Vector Control System but it uses 2.4 m nozzle with expansion ratio of 56:1, dual density exit cone (for better efficiency on high altitudes) and 3.5° of vector angle for engine nozzle. Thrust provided by Castor-30XL is 300 kN, comparing to 259 kN in case of Castor-30A. According to Orbital ATK upgrading engines in first stage combined with Castor-30XL will give around 25% more payload capacity for LEO missions. At the moment core stages of Antares are modified for installing four RD-181 engines (two flight sets) which were delivered by Energomash and passed all tests in USA. One flight set will be used for hot fire test in Mid-Atlantic Regional Spaceport (MARS), and second pair will be installed in core stage of Antares intended for OA-5 mission. Comparing to Falcon-9 1.2V where changes were limited to new software in thrust control computers and lower temperature of LOX for better utilization of tanks capacity changes in Antares are definitely more advanced. Increasing payload capacity for 25% is success if we take under consideration that Falcon-9 1.2V has not improved payload capacity in such an extent as compared to 1.1V (according to SpaceX 1.2V has general performance increased for about 30%).
On picture above You can see Antares standing in launch pad in Wallops Flight Facility on January 2014.