A new report provides some insight into the challenges that SpaceX and Boeing are facing when it comes to flying commercial crew missions, and it also suggests both companies may be nearly two years away from reaching operational status for NASA.

The assessment of large projects at NASA, published on Tuesday by the US Government Accountability Office, found that certification of the private spacecraft for flying astronauts to the International Space Station may be delayed to December 2019 for SpaceX and February 2020 for Boeing.

"Both of the Commercial Crew Program's contractors have made progress developing their crew transportation systems, but delays persist as the contractors have had difficulty executing aggressive schedules," the report states.

Both SpaceX, with its Dragon spacecraft, and Boeing, with its Starliner vehicle, are engaged in intense development, testing, and assembly programs in preparation for critical flight tests. To become certified for operational missions, each company must complete one uncrewed flight and one crewed mission.

NASA officially updated the schedule for these flights in January of this year. Under the new timeline, Boeing is slated to fly an uncrewed test flight of Starliner in August 2018 and a second flight with astronauts in November. SpaceX is scheduled to fly a demonstration flight of its Dragon in August, followed by a crewed mission in December. However, the certification dates referenced in the GAO report indicate that NASA's recently published schedules may be too optimistic.

Technical challenges

The GAO report also provides some clarification on the major technical issues each company is working on as it gets closer to test flights into space.

For SpaceX, the top risks identified in the report are fairly well-known and concern the Falcon 9 rocket used to launch Dragon. NASA has concerns about the composite overwrap pressure vessels that led to a catastrophic accident during fueling of the Falcon 9 rocket in 2016. NASA engineers are also tracking the company's changes to the Merlin engines to be used in the Block 5 design of the Merlin rocket.

"NASA program officials told us that they had informed SpaceX that the cracks were an unacceptable risk for human spaceflight," the report states. "SpaceX officials told us that they have made design changes, captured in this Block 5 upgrade, that did not result in any cracking during initial life testing. However, this risk will not be closed until SpaceX successfully completes qualification testing in accordance with NASA's standards without any cracks."

The report also cited two significant issues that Boeing is working regarding the Starliner. In some abort scenarios the company has simulated, the Starliner spacecraft has tumbled. Boeing hopes to put these concerns to rest with a pad abort flight test, which should occur soon.

NASA also has concerns about Starliner's forward heat shield, which protects the parachutes during re-entry but may damage the parachutes as it is pulled away from the spacecraft. "If the (commercial crew) program determines this risk is unacceptable, Boeing would need to redesign the parachute system, which the program estimates could result in at least a six-month delay," the new report states.

On the positive side, the report notes that unlike some of NASA's other large programs also experiencing significant delays, the space agency will not directly bear the cost of these delays. Because the commercial crew program operates under a fixed-price contracting system, its costs are within one to two percent of earlier estimates.