Rd 181 To Replace Antares Aj 26 Engine
The company has signed a contract with NPO Energomash to supply 60 new built RD-181s, including firm orders for 20 engines.
Orbital on Dec. 16 announced its decision via Twitter and through an article in Aviation Week and Space Technology, saying "RD-181 engine meets schedule and technical requirements. No other options do."
Orbital decided to replace the engine following the catastrophic failure of Antares on its fifth launch from Mid-Atlantic Regional Spaceport in Virginia on October 28, 2014.
Two RD-181s will replace the two AJ-26 engines, without requiring major modification to the vehicle structure, and totaly provide a 864,000 lb. thrust with a specific impulse of 311.9 sec.
The upgraded Antares will be used to complete the Cargo Resupply Contract (CRS) with NASA using the Cygnus spacecraft to International Space Station from early 2016.
On Dec. 9, Orbital announced that at least one, and possibly two, Cygnus flights would be launched on Atlas V rockets from Cape Canaveral Air Force Station, following the crash. The first RD-181 engine delivery is expected in mid 2015.
Orbital says the greater lift capacity of the Atlas V and upgraded Antares vehicles, will allow the company to complete all currently contracted ISS deliveries in four missions instead of the five previously planned flights over the next two years.
Under a 1.9 billion CRS contract with NASA, Orbital was to use Antares and Cygnus to deliver up to 44,000 pounds (20,000 kilograms) of cargo to the ISS over eight missions through late 2016.
The Anatres first stage is powered by two Aerojet AJ 26 engines, which are modified Soviet-built NK-33 engines. The turbopump onboard the 40 year old engines has been suspected for the failure.
The engines which are refurbished by Aerojet, has failed multiple times during ground tests due to fuel leak resulting from stress corrosion cracking. The NK-33 engines were developed for the ill fated Soviet moon rocket N-1.
Energomash also supplies the RD-180 first stage engines for the ULA's Atlas V launch vehicle, which launches US national security payloads. But tensions between Russia and the United States over the unrest in Ukraine has led to a Congressional ban on the future purchases of Russian-made rocket engines.
But orbital says the 2015 National Defense Authorization Act, does not affect its decision as its program is for civil purpose.
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