The newly formed Aerojet Rocketdyne is crafting a plan with the Russian Kuznetsov Design Bureau to restart production of the NK-33 rocket engine to assuage concerns from NASA that enough propulsion systems will be available for missions planned to resupply the International Space Station.

NK-33s overhauled by Aerojet, designated the AJ-26, are used to power Orbital Sciences’ new Antares medium-lift rocket for upcoming NASA Commercial Resupply Services (CRS) missions; Orbital also is trying to re-ignite a market for smaller military satellites by offering the Antares as an alterative to building large satellites for use exclusively on the Evolved Expendable Launch Vehicles managed by the United Launch Alliance. NASA is requiring that Orbital use an engine in production to power the Antares, and the NK-33 has long been out of production. Aerojet previously purchased 43 of the NK-33 engines from Kuznetsov to overhaul into AJ-26s as needed for missions.

Under its CRS-1 contract with NASA, Aerojet is overhauling 20 NK-33s for use on Antares. The motors have experienced stress and corrosion, which are addressed through the overhaul process.

At issue is concern from NASA that there may not be enough suitable engines to support CRS-2, which would require 20 more.

NASA, however, has requested that Orbital seek a production source for its Antares propulsion system. Aerojet Rocketdyne President Warren Boley is in talks with Kuznetsov to begin delivering new NK-33s in late 2016, he told reporters during a June 17 roundtable at the Paris air show. The total production rate depends on the demand for Antares, but Boley says it is likely to be at least 4-6 engines annually.

The strategy is to use the new engines for deliveries to Antares and use the remaining 23 engines requiring overhaul as a “buffer” if problems arise in restarting the production process, Boley says.

A signed deal with Orbital is needed in the fall to begin deliveries in late 2016.

Meanwhile, Orbital Sciences could use the Russian RD-180 engine, but it is currently sold exclusively in the American market to the United Launch Alliance for use on the Atlas V Evolved Expendable Launch Vehicle.