For the Antares Return to Flight, Orbital ATK will rely on the Energomash RD-181 rocket motor. It is an all-new engine based on other successful liquid rocket engines Energomash designed and produced. The engines use an oxygen-rich staged combustion cycle that can be throttled, and has a variable mixture ratio for controlling relative flow rates of oxidizer and fuel.
The Antares second stage is powered by a CASTOR 30XL solid rocket motor produced and tested at Orbital ATK facilities in Utah. The CASTOR 30XL is based on the CASTOR 120, used in more than a dozen missions. The OA-5 mission will be the first use of this motor, allowing Antares to significantly increase its payload capability.
The Antares 230 rocket for this mission is a two-stage launch vehicle consisting of a liquid-fueled Liquid Oxygen/Refined Petroleum (LOX/RP) first stage powered by two Energomash RD-181s that will burn about 209 seconds. Antares employs a 9.9 m (32.5 ft.) long fairing to protect Cygnus as Antares accelerates through Earth’s atmosphere. It will separate at 250 seconds into flight, after which the second stage will burn about 163 seconds. The Cygnus cargo capsule will reach its initial orbit about 9 minutes after launch.