NEW ORLEANS — As NASA marked the completion of the core stage of the first Space Launch System rocket, the agency and the rocket’s prime contractor are in the midst of negotiations for a long-term production contract for additional vehicles.

NASA announced in October that it was starting negotiations with Boeing for a production contract that would cover up to 10 core stages for the SLS, starting with the third SLS rocket. Boeing is already under contract for the first two SLS vehicles and NASA has authorized initial funding for the third SLS in order for it to be ready in time for a human lunar landing mission in 2024.

NASA expects that, with a long-term contract in place, it will be able to bring down the costs of individual SLS vehicles. “If you buy one SLS rocket, the price is really high. If you buy two, the price goes down significantly, and if you buy the three it keeps going down,” NASA Administrator Jim Bridenstine said at a Dec. 9 event at the Michoud Assembly Facility here.

Bridenstine said at the event that the agency was seeking such economies of scale in any contract for future SLS vehicles, depending on how many the agency needed for its future exploration plans. “We need to look at the price based on a negotiation between NASA and our prime contractor,” he said, a reference to Boeing. “That negotiation, and how many we buy, ultimately will determine what that final cost will be per rocket.”

Bridenstine didn’t state a price target for the SLS under any new contract, although at a NASA town hall meeting Dec. 3 he estimated the per-vehicle cost to eventually reach $800–900 million. In an interview with CNN Dec. 9, he estimated a single SLS today costs $1.6 billion, but could get down $800 million under a long-term production contract.

Those contract negotiations are going well, according to a Boeing official. “I personally don’t think we’re that far apart,” Jim Chilton, senior vice president for space and launch at Boeing Defense, Space and Security, said in a Dec. 9 interview. “It’s actually going pretty fast.” The scope of that long-term contract, he said, would likely cover 10 vehicles, although initial funding would be for just the third and fourth SLS vehicles.

Another factor will be how quickly those vehicles will be produced. Some in Congress have sought to increase the SLS production rate to two vehicles a year as soon as 2024. That would enable another SLS to be available to support human lunar missions: Boeing, for example, has proposed developing a lunar lander that would be launched as a single vehicle on an SLS, rather than in modules launches on commercial rockets. Congress has also required that NASA use an SLS to launch its Europa Clipper mission.

Chilton said that, while Michoud was not designed for high production rates, he didn’t see many problems in going to two SLS vehicles a year. Despite the long delays in the production of the first SLS core stage, he said the company could produce future SLS core stages at a rate of one every eight months. “So we’re not that far off it,” he said of a two-per-year production rate.

While Chilton said he thought that Boeing could produce two SLS vehicles a year by 2024, Bridenstine was not nearly as optimistic. “Nobody has presented me a plan that says that that’s happening, but certainly I would fully support it if they could make it happen,” he told reporters at the event. “I’m not counting on that for 2024, quite frankly.”

“For 2024 we need to be focused on getting that Artemis 3 SLS complete, and using other rockets to do payload deliveries and that kind of thing apart from the SLS itself,” Bridenstine added. NASA’s current architecture calls on using commercial rockets for delivery of lunar Gateway elements and modules for the lunar lander, with SLS reserved for the launch of the crewed Orion spacecraft.

Another issue will be the transition from the original Block 1 version of the SLS, which uses the Interim Cryogenic Propulsion Stage as its upper stage, to the Block 1B with the more powerful Exploration Upper Stage. NASA’s current plans call for using the Block 1 SLS for the first three missions, then moving to the Block 1B, although some have called for a faster transition.

“Starting in 2024, the Exploration Upper Stage (EUS) will power NASA missions that carry crew and heavy cargo deeper into space,” Boeing said in a Dec. 9 statement about development of the stage. “NASA expects to fly the EUS on the Artemis 3 mission to deliver combined payloads, such as large elements of the Gateway lunar orbiter or an integrated Human Lander System, along with Orion.” A NASA statement in October said use of the EUS would begin with the Artemis 4 mission.

Chilton said that work on EUS, which was paused for a time, is proceeding, with the stage now between its preliminary and critical design reviews. The EUS, like the core stage, will be produced at Michoud. “Our target is ’24,” he said of having the EUS ready. “The Artemis 3, 4 time frame.”