Due to delays stemming from manufacturing and safety certification issues, the new manned spacecraft being developed by Boeing and SpaceX may not be ready to ferry U.S. astronauts to the International Space Station before NASA’s contract with Russia’s Soyuz program in November of 2019 runs out, meaning that beginning in late 2019, the ISS may not have an American presence onboard for the better part of a year — and possibly longer.

This troubling news comes from a report prepared by the U.S. Government Accountability Office (ACO) that assesses the impact of the delays in the development of Boeing’s CST-100 Starliner and SpaceX’s Dragon 2 spacecraft, both part of the broader Commercial Crew Development (CCDev) program, would have on the delivery of American astronauts to the ISS. Initiated in 2010, CCDev awarded Boeing and SpaceX $6.8 billion to develop their respective spacecraft, with the Dragon capsule expected to be ready for early 2017, and the Starliner for later the same year.

But numerous problems in the development and manufacture of the spacecraft have caused the two companies to delay their delivery dates, with Boeing now due to be ready in January 2019, and SpaceX the following month. The spacecraft will then undergo NASA’s safety certification process, necessary to determine whether or not the craft are safe to launch astronauts into space: unfortunately, the nature of this certification process is a concern, as NASA "doesn’t have a consistent approach for calculating this [safety] metric," according to the GAO report, meaning that "results can vary based on who within NASA is conducting the analysis."

The safety metric, called "Loss of Crew" by NASA, is a score based on the likelihood of a crewmember being injured or killed during any given flight. The margins for the Dragon and Starliner capsules are being set at three times higher than that of the Space Shuttle, allowing for a 1-in-270 chance of an incident for the modern craft, as opposed to the Shuttle’s 1-in-90. Unfortunately, there appears to be no agreement between NASA, CCDev, its safety officer, and Boeing/SpaceX on how to determine this metric.

This uncertainty regarding this safety metric may cause further delays in delivering a viable spacecraft, as the GAO’s "Commercial Crew Program’s schedule risk analysis shows that the certification milestone is likely to slip." If the crafts’ respective certifications do end up being pushed back, this means a manned launch may be delayed until the end of 2019.

NASA, along with all contributors to the ISS, currently delivers its astronauts to the station via the Russian Soyuz program, and has done so since the retirement of the Space Shuttle program in 2011. But NASA’s contract with Roscomos, Russia’s official space agency, runs out in late 2019 and hasn’t been renewed, meaning that hitching a ride with Russian Cosmonauts might not be an option. "The process for manufacturing the [Soyuz] spacecraft and contracting for those seats typically takes three years—meaning additional seats would not be available before 2021," according to the GAO report.

This could make for a 9-month gap in the presence of U.S. crewmembers on the ISS, and if Boeing and SpaceX’s certification milestones aren’t met on time — and that is highly likely, given NASA’s lack of certainty — that gap could very well widen. The GAO report calls on NASA to come up with contingency plans in case this scenario comes to pass, and to launch a review of the certification process after it has been completed for the new craft, to "document lessons learned [relating to the potential] loss of crew as a safety threshold for future crewed spaceflight missions, given the complexity of the metric."