NASA and Boeing have decided to delay the return of the CST-100 Starliner spacecraft from the International Space Station (ISS) until early July. The postponement allows for continued investigation into propulsion system issues.
Initial Plans Postponed
On June 21, NASA announced the halt of previously scheduled plans for Starliner to depart the ISS on June 25 and land at White Sands, New Mexico, on June 26. This mission, known as the Crew Flight Test (CFT), includes NASA astronauts Butch Wilmore and Suni Williams.
Unlike earlier delays, NASA has not provided a new departure date. Instead, they stated that future return opportunities will be evaluated after a scheduled spacewalk on July 2, the second of two planned spacewalks at the ISS.
Focus on Data-Driven Decisions
“We are taking our time and following our standard mission management team process,” stated Steve Stich, NASA’s commercial crew program manager. “We are letting the data drive our decision-making relative to managing the small helium system leaks and thruster performance observed during rendezvous and docking.”
Stich added that an agency-level review of Starliner would be conducted before its departure due to the extended duration of the mission. Initially intended to last eight days, the spacecraft will now remain at the ISS for almost a month.
Confidence in Readiness
During a June 18 briefing, Stich and other officials expressed confidence in Starliner’s readiness for the June 26 return. Testing showed all but one reaction control system thruster functioning well, and helium leaks in the propulsion system had decreased.
“We really like the opportunity on the 26th because it’s a great opportunity into the White Sands Space Harbor,” Stich mentioned, highlighting favorable pre-dawn landing conditions.
Strategic Use of Extra Time
Stich noted that the additional time would facilitate more data collection and coordination around the two planned spacewalks. “We are strategically using the extra time to clear a path for critical station activities while preparing for Butch and Suni’s return and gaining valuable insight into the system upgrades for post-certification missions,” he said.
Avoiding Schedule Conflicts
NASA officials had previously scheduled the spacewalks to avoid conflicts with Starliner’s potential departure dates. Dana Weigel, NASA ISS program manager, mentioned that if the first spacewalk, scheduled for June 24, were delayed, the Starliner’s then-planned June 25 undocking would take priority.
Opportunity for Extended Analysis
Mark Nappi, Boeing vice president and commercial crew program manager, emphasized the benefit of extending the mission. “This is an opportunity to fully understand the system’s performance without the pressure of schedule or time,” he said. “We have the time. We’ll let the data drive our decision-making.”
Flexible Return Schedule
The NASA statement did not specify how long Starliner might stay at the ISS, only noting that the crew is well-supplied and not pressed for time. Stich indicated that Starliner could remain at the station for up to 45 days.
At the June 18 briefing, NASA flight director Mike Lammers mentioned that landing opportunities follow an “every four day” pattern, influenced by the ISS’s orbit and landing site locations in the southwestern United States. This suggests the next landing window after the spacewalks would be around July 4.
Assured Crew Safety
Both in the latest statement and the June 18 briefing, NASA assured that Starliner could safely return Wilmore and Williams if an emergency arose. “So far, we don’t see any scenario where Starliner is not going to be able to bring Butch and Suni home,” Stich said. “We’re just taking a little more extra time to resolve the data and also learn as much as we can while we have the service module in orbit.”