WASHINGTON — NASA and Boeing said May 26 they are still working towards a July launch of the CST-100 Starliner on a crewed test flight despite “emerging issues” and concerns raised by a safety panel.

In a statement issued just before the close of business ahead of a holiday weekend, the two organizations said they completed a “checkpoint review” May 25 of preparations for the Crew Flight Test (CFT) mission, currently scheduled for no earlier than July 21. Two NASA astronauts, Butch Wilmore and Suni Williams, will fly on CFT to the International Space Station on the short test flight, the first crewed flight of the spacecraft.

NASA and Boeing said they have now completed 95% of the certification work needed for CFT. They have also addressed all the anomalies from the Orbital Flight Test (OFT) 2 mission, an uncrewed test flight of Starliner to the ISS one year ago.

“We are taking a methodical approach to the first crewed flight of Starliner incorporating all of the lessons learned from the various in-depth testing campaigns,” Steve Stich, NASA commercial crew program manager, said in a statement. “In addition to the closeout of ongoing work, the team remains vigilant on tracking new technical issues as we complete certification for crewed flight.”

That statement mentioned “emerging issues that need a path to closure” before NASA and Boeing decide to fuel the spacecraft in June for a July launch. Boeing officials said earlier this year they decided to fuel the spacecraft only within 60 days of launch as a measure to mitigate any fuel leaks that could corrode valves, an issue that delayed an August 2021 launch attempt for OFT-2.

Among the issues is swapping out a valve in the thermal control system in the spacecraft’s service module, which was reducing flow in one of two redundant loops that cool the vehicle’s avionics. The valve replacement will take about a week, NASA and Boeing said, and should not affect the CFT launch schedule.

Engineers are also evaluating whether tape used on wiring could pose a flammability risk. Although that tape is commonly used on other spacecraft, they are evaluating if it is acceptable for crewed flight. The organizations said that assessment should be done before the decision to fuel the spacecraft.

Another system being reviewed is Starliner’s parachutes. NASA and Boeing said they are reassessing margins in the parachutes, including the “overall efficiency” of joints in that system, to ensure they achieve the required safety factors for a crewed spacecraft.

The statement came a day after a public meeting of NASA’s Aerospace Safety Advisory Panel (ASAP) where the committee’s chair, Patricia Sanders, raised concerns about the ability to complete work, such as parachute certification, in time to meet the planned July 21 launch.

“It is imperative that NASA not succumb to pressure, even unconsciously, to get CFT launched without adequately addressing all the remaining impediments to certification,” she said, recommending that NASA bring in an independent group, such as the NASA Engineering and Safety Center, “to take a deep look at the items on the path to closure.”

The NASA/Boeing statement did not mention the ASAP meeting. However, it did address one issue Sanders raised about the spacecraft’s batteries. The organizations said they had approved the batteries for use on CFT “based on additional testing and analysis” with a proposal to upgrade the batteries on future missions.

Stich, in the statement, said the agency and company had made progress since late March, when they announced the certification work would push the CFT launch from April to July.

“If you look back two months ago at the work we had ahead of us, it’s almost all complete,” he said. “The combined team is resilient and resolute in their goal of flying crew on Starliner as soon as it is safe to do so.”

However, he did not rule out a slip from the current July launch date. “If a schedule adjustment needs to be made in the future, then we will certainly do that as we have done before. We will only fly when we are ready.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...