WASHINGTON — NASA’s Space Launch System heavy-lift rocket may not be ready for its first launch until November 2018, nearly a year later than previously scheduled, based on the assessment of a major cost and schedule review that NASA unveiled Aug. 27.

NASA announced that the SLS completed a development milestone known in agency terminology as Key Decision Point C (KDP-C), a review that confirms that the SLS program is ready to proceed with full-scale development. The review established an estimated cost of $7.021 billion for SLS development from February 2014 through its first launch.

NASA had been targeting an initial launch of SLS, carrying an uncrewed Orion spacecraft on a flight named Exploration Mission 1 (EM-1), for December 2017. However, NASA said that they were now planning a first launch for no later than November 2018. Both the budget and schedule estimates from the KDP-C review are based on a 70-percent joint confidence level model.

In a teleconference with reporters, William Gerstenmaier, NASA associate administrator for human exploration and operations, said the SLS project was still working towards an earlier launch date than November 2018 by mitigating risks raised in the review. “If we don’t do anything, we basically have a 70-percent chance of getting to that date,” he said. “We will be there by November of 2018, but I look to my team to do better than that.”

However, he acknowledged that it was likely the EM-1 launch would slip from December 2017 into 2018. “It’s probably sometime in the 2018 timeframe,” he said, “but we don’t want to get too specific now.”

The November 2018 readiness date is based only on development of SLS. A separate KDP-C review is planned later this year for the ground systems that support the rocket, followed by one early next year for Orion. Only when all those reviews are complete will NASA be able to provide a better estimate for the EM-1 launch date, NASA Associate Administrator Robert Lightfoot said.

The cost estimate for SLS, according to Lightfoot, is consistent with the $1.6 billion NASA received for the program for 2014 and the administration’s request for fiscal year 2015 and beyond.

The White House has requested $1.35 billion for the program for 2015, with a relatively flat budget projected through 2019. However, a House appropriations bill passed in late May would give SLS $1.6 billion in 2015, while a Senate version would provide $1.7 billion.

The KDP-C review comes after some mixed news about the progress of SLS. In July, a report by the Government Accountability Office warned of a significant risk of insufficient funding that would delay the first SLS launch by six months and add $400 million to the program’s overall costs.

However, in an Aug. 8 speech at the 17th Annual International Mars Society Convention in League City, Texas, SLS program manager Todd May said that there was three to five months of slack in the critical path for SLS development. “We’re just clicking off milestones,” he said.

May said the GAO report warnings about cost and schedule risks were based on older data, before the program received additional funding from Congress for 2014, with another increase anticipated for 2015. “In December of 2017, my hardware will show up to support that flight,” he said of the EM-1 launch.

In the Aug. 27 teleconference, Gerstenmaier said that NASA was addressing technical and budgetary concerns raised in the GAO report. He added that there are currently no plans to seek additional funding to accelerate the SLS development schedule. “I still think we have a good chance of SLS being there some time in the December [2017] timeframe, maybe slightly into 2018 depending on what happens,” he said.

Jeff Foust has more than a decade of experience writing about space policy, entrepreneurial ventures and regulatory affairs. In 2001, he established spacetoday.net to aggregate and summarize the day's space-related news stories. In 2003, he started The...