A draft of a US Congressional report into NASA's commercial crew program has found technical problems with both SpaceX's and Boeing's efforts to provide transport to the International Space Station. However, according to The Wall Street Journal, the forthcoming report from the US Government Accountability Office focuses most closely on issues with turbopumps in SpaceX's Falcon 9 rocket.

The newspaper says the report has found a "pattern of problems" with the turbine blades within the turbopumps, which deliver rocket fuel into the combustion chamber of the Merlin rocket engine. Some of the components used in the turbopumps are prone to cracks, the government investigators say, and may require a redesign before NASA allows the Falcon 9 booster to be used for crewed flights. NASA has been briefed on the report's findings, and the agency's acting administrator, Robert Lightfoot, told the newspaper that he thinks “we know how to fix them.”

A spokesman for SpaceX, John Taylor, said the company already has a plan in place to fix the potential cracking issue. "We have qualified our engines to be robust to turbine wheel cracks," Taylor said. "However, we are modifying the design to avoid them altogether. This will be part of the final design iteration on Falcon 9." This final variant of the Falcon 9 booster, named Block 5, is being designed for optimal safety and easier return for potential reuse. According to company founder Elon Musk, it could fly by the end of this year.

The new report also cites other problems with the commercial crew development efforts by SpaceX and Boeing. The latter company, for example, may be having difficulty with ensuring the reliability of its parachute systems to bring crews safely back to a land-based landing.

Both companies are also struggling to meet NASA's mission requirement for a loss-of-crew probability of 1-in-270. NASA has previously acknowledged this issue, citing the challenge of dealing with micrometeoroid and orbital debris. During a NASA Advisory Council meeting late in 2016, the director of the commercial crew program, Kathy Leuders, said the companies were looking at options such as an on-orbit inspection to ensure the spacecraft was safe to fly back through Earth's atmosphere. "There’s really not anything more from a design perspective that will make it better," she said. "At some point you have to fly, there’s only so much shielding will accomplish."

Boeing has set a “no earlier than” date of August 2018 for its first crewed test flight as part of the commercial crew program, and SpaceX has targeted May 2018. The new GAO report is consistent with schedule concerns raised previously about the viability of those dates. According to an unofficial Ars analysis published in late January, even a single crewed test flight in 2018 by either company appears unlikely. Operational flights appear unlikely before mid-2019.