The RD-181 is based on the RD-191 and is adapted for integration on the Antares rocket. While the RD-193 was designed as a close replacement for the NK-33, on December 17, 2014, Orbital Sciences announced that it would use the NPO Energomash RD-181 on the version 2 Antares launch vehicle and had contracted directly with NPO Energomash for up to 20 RD-181 engines.[8] Two engines are used on the first stage of each Antares, which is currently used to carry cargo to the International Space Station under contract to NASA.[9] While Russian press had stated that the contract was valued at US$ 1 billion with options, Orbital stated on 26 January 2015 that even when exercising all the options the contract was less than that amount, and that the initial contractual commitment was significantly less than that.