The Government Accountability Office issued a downbeat report on NASA’s major space projects today, saying that cost and schedule performance has deteriorated over the past year.

The full extent of the cost issues is unknown, primarily due to uncertainties surrounding the effort to build NASA’s Orion deep-space capsule, the GAO said in its 127-page “Quick Look” assessment.

NASA’s multibillion-dollar commercial space taxi program, which has SpaceX and Boeing as lead contractors, could face delays as well. The GAO said full certification for carrying astronauts to and from the International Space Station could slip to the end of 2019 for SpaceX, and to early 2020 for Boeing.

The space agency is already discussing contingency plans to get around that issue by expanding the scope of pre-operational test flights. Those test flights are planned in the 2018-2019 time frame.

For SpaceX, the concerns focus in part on the composite-wrapped pressure vessels for the Falcon 9 rocket. Flaws in the manufacture of the pressure vessels led to a launch-pad blow-up in 2016.

SpaceX says that its latest Falcon 9 model, known as Block 5, eliminates that risk as well as concerns about cracks in rocket engine turbines. But the GAO said the redesigned rocket will have to go through qualification testing to reassure NASA.

For Boeing, the GAO pointed to the potential for the Starliner to tumble in a pad abort scenario. Boeing says it will soon put its Starliner test vehicle through a pad abort test in New Mexico to resolve that concern. Another sticking point has to do with yet-to-be-resolved issues with the Starliner’s forward heat shield.

The GAO report takes note of previously known snags associated with NASA’s heavy-lift Space Launch System rocket, or SLS, and the James Webb Space Telescope.

The SLS’ first uncrewed launch has been pushed back to somewhere between December 2019 and June 2020, due to a series of technical challenges including the completion of welding on its first stage. Meanwhile, the Webb telescope’s launch has been rescheduled for May 2020, due to setbacks experienced during integration and testing.

In both cases, further difficulties are likely to lead to additional delays and more cost overruns because the built-in budgetary and scheduling cushions have been depleted.

The GAO said the $11.3 billion Orion program is currently a big question mark. “NASA expects cost growth for the Orion crew capsule —one of the largest projects in the portfolio — but does not have a current cost estimate,” it said.

One of the big concerns is that further snags with the SLS will compound cost and schedule challenges for the Orion program. That, in turn, could have a big impact on the entire portfolio of NASA missions.

“Because the Orion program accounts for about 22 percent of all development costs, even a small percentage of

cost growth for the Orion program could significantly affect cost performance,” the GAO said.

Today’s report provides an encyclopedic rundown on 26 NASA projects with price tags that are greater than $250 million, including the Commercial Crew Program and 17 other missions that are currently in their implementation phase. The eight other missions — such as the Europa Clipper, the Low Boom Flight Demonstrator and the WFIRST space telescope — are still being formulated.

In general, the assessments argued for tighter cost controls and more realistic development schedules.

“NASA continues to face increased risk of cost and schedule growth in future years due to new, large and complex projects that will enter the portfolio and expensive projects remaining in the portfolio longer than expected,” the report said.

The GAO pointed up another challenge for the space agency: its aging workforce. About 56 percent of NASA’s 17,000 employees are 50 or older, which is a significant rise over the 49 percent reported five years ago. About 21 percent of the workforce is already eligible for retirement, the GAO said.

“Human capital officials noted that having an aging workforce is good for maintaining institutional knowledge due to experienced staff staying longer,” the report said, “but that having a low attrition rate makes it more difficult for the agency to make changes to its workforce skill mix as needed.”

In comparison, the median age for SpaceX’s 6,000 employees is said to be 31.