The federal government’s watchdog agency says getting NASA’s heavy-lift Space Launch System rocket off the ground is likely to take longer and cost more than the space agency says it will.

Any issues that crop up in the months ahead could push the first uncrewed SLS launch, known as Artemis 1, from its planned mid-2020 timetable to mid-2021, the Government Accountability Office said in a study issued today.

What’s more, the GAO says NASA has been shifting costs forward to make it look as if expenses for the first launch have grown by $1 billion, when the actual adjusted cost growth is $1.8 billion.

Schedule and cost issues for SLS are particularly problematic because the rocket has been selected to carry NASA astronauts to the moon by 2024.

When Vice President Mike Pence, who heads the White House’s National Space Council, announced the 2024 deadline in March, he issued a veiled warning to the Boeing Co. and other SLS contractors about the consequences of missing the date.

“If our current contractors can’t meet this objective, then we’ll find ones who will,” Pence said. “If commercial rockets are the only way to get American astronauts to the moon in the next five years, then commercial rockets it will be,”

During a conference held today in Boston at the John F. Kennedy Presidential Library and Museum to mark the 50th anniversary of the Apollo 11 moon mission, Boeing CEO Dennis Muilenburg insisted that SLS was on track for 2020.

“First launch is next year,” he said. “We’re looking forward to making that happen.”

Muilenburg acknowledged that “the technology challenges are very significant.”

“The first rocket is now about 80% assembled, and we’re going through the detailed system integration,” he said. “These are very complex, sophisticated machines, so the technology itself is a challenge. I think it’s manageable. It’s work we know how to do. But it’s tough, challenging work, and we have to do it in a way that ensures safety in the end.”

Muilenburg said having consistent political and funding support for such a big space project was at least as challenging.

“We’ve seen that to date on the Space Launch System,” he said. “If we’re going to get back to the moon by 2024, we can do that, but we can’t if we don’t have stable, consistent support and funding. So the political and funding side of this, I would say, is actually the greater risk.”

In its report, the GAO noted that between 2014 and 2018, NASA paid more than $200 million in award fees relating to contractor performance on the SLS stages and the Orion deep-space crew capsule.

“But the programs continue to fall behind schedule and overrun costs,” the GAO said. “Ongoing contract negotiations with Boeing for the SLS and Lockheed Martin for the Orion program provide NASA an opportunity to re-evaluate its strategy to incentivize contractors to obtain better outcomes.”

In its response to the study, NASA said it agreed with the recommendation to re-evaluate how it paid out incentives to Boeing and other contractors.

NASA is gradually moving away from a “cost plus” model and favoring a model that specifies a fixed price and development milestones for space projects. That’s the way its contracts with SpaceX and Northrop Grumman for cargo resupply missions to the International Space Station are structured, for example.

Muilenburg discussed other space issues as well: