On October 28, 2014 an engine failure caused the destruction of an Antares rocket shortly after the launch of the Cygnus spacecraft which was supposed to bring various supplies to the International Space Station. This reinforced the doubts about those Soviet-made engines forcing Orbital Sciences, the rocket’s owner, to look for alternatives. A few days ago, the company announced plans for the upcoming launches, starting with a contract for at least one launch of an Atlas V rocket.

The October 28, 2014 mission was the third within the Commercial Resupply Services (CRS) contract with NASA. The Antares rocket used AJ26 engines, which are actually Soviet NK-33 engines built between the late ’60s and early’ 70s. They were modified by Aerojet to work with Americans electronics.

The NK-33 engines were designed for the rocket that was supposed to bring Soviet cosmonauts on the Moon but the Apollo 11 success led to the cancellation of the project. Abandoned in a warehouse for many years, after the USSR collapse they were sold to Aerojet and used on American rockets.

The AJ26 engines are tested before their use but over the years many doubts were raised about their reliability. After the failed October 28, 2014 launch, Orbital Sciences announced that it would give up using them. In recent days, the company confirmed that it will use a new main propulsion system for the Antares rocket. No details were given but the new version of the Antares is planned to fly in 2016.

Orbital Sciences has a contract with NASA that is worth a lot of money but also requires commitments to be fulfilled by the company. For this reason, after the decision to give up the current Antares version, it went looking for a new rocket. Among the possible candidates there was an ESA one but the launch would take place from French Guiana. Another candidate was even the Falcon 9 of its competitor SpaceX.

Eventually, Orbital Sciences managed to sign a contract for at least one launch with United Launch Alliance (ULA) on an Atlas V rocket. It’s one of the most important companies in the field satellite and occasionally space probes launch and is very reliable. The launch should take place in the fourth quarter of 2015 and there’s an option for a second launch, again on an Atlas V rocket, in 2016 if the new Antares isn’t ready.

There will be some delay from to the original schedule for Orbital Sciences in its launches to the International Space Station. However, the company will use a new version of the Cygnus spacecraft that is bigger thanks to the greater lift capability of the Atlas V. The new Antares will be more powerful as well so Orbital Sciences plans to complete its contractual obligations in 7 missions instead in 8 originally scheduled.

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