The news was leaked a few days ago and later confirmed by Orbital Sciences. The American aerospace company has signed a contract with Russian NPO Energomash for the supply of the model RD-181 engines for the Antares rocket. They will replace the AJ-26 engines used so far and discarded after the fault that led to the explosion of Antares on October 28, 2014.
The RD-181 engines are one of the evolutions of the model RD-171 and are very similar to the model RD-191 (photo ©Vladislav Chernyy) adopted for the new Russian rockets Angara. Orbital Sciences chose the model RD-181 because it was the one that was best suited to the Antares rocket. It has many features similar to the AJ-26 engines starting from the use of RP-1, a very highly refined form of kerosene, as fuel and liquid oxygen as the oxidizer.
Orbital Sciences will proceed with the modifications to its rocket Antares for the engine change. The company worked with NPO Energomash to choose the engine model that required the least amount of redesign work. With the RD-181 engines the Antares core stage should remain nearly identical and this should allow the company to resume the launches in 2016.
The choice of the RD-181 engines was also made for their price and especially for their availability as a delivery of 20 of them is scheduled for mid-2015. Orbital Sciences has two options for two more supplies of 20 engines each. There are no official announcements on the total cost of the purchases. According to totally unofficial sources, the total contract value is close to a billion dollars. Orbital Sciences only stated that the total figure is significantly lower.
Eventually, after considering various alternatives, both American and foreign, Orbital Sciences has again chosen a Russian engine. Recently, the USA decided various sanctions against Russia following the tension due to the situation in Ukraine. Among them there’s a ban on the use of Russian engines for rockets used in launches related to national security. The Antares rocket engines can implement Russian engines because it has civilian uses, even more because it launches the Cygnus spacecraft carrying supplies to the International Space Station, managed in collaboration also with Russia.
2016 will be a pivotal year for Orbital Sciences. The company must demonstrate that the Antares rocket with the new engines RD-181 is reliable. It may do so by continuing with success the launches to the International Space Station still remaining in the contract with NASA. It’s the only way to hope for a renewal of the contract and for other contracts for commercial satellite launches.