The beleaguered Crew Flight Test (CFT) of Boeing’s CST-100 Starliner has met with additional delay, as teams announced Thursday that Commander Barry “Butch” Wilmore and Pilot Suni Williams’ week-long mission to the International Space Station (ISS) will officially stand down from its No Earlier Than (NET) launch date of 21 July. Citing a pair of issues related to the spacecraft’s parachute lines and adhesive tape used on wiring harnesses, Boeing revealed that it remains “feasible” to launch later in 2023 and that teams are “trying to keep…on track” with Starliner’s first Post-Certification Mission (PCM)—its first operational long-duration flight to the space station—in late summer 2024.
On 25 May, NASA and Boeing conducted a joint CFT Checkpoint Review to assess various open work items, including several “emerging issues” that required “a path to closure” before the time-critical process of fueling the Starliner spacecraft in mid-June. It was noted that all In-Flight Anomalies (IFAs) from last year’s uncrewed Orbital Flight Test (OFT)-2 mission had been satisfactorily closed out and about 95 percent of CFT certification products—including approval of the Crew Module (CM) batteries and a proposed battery upgrade for future flights—were also complete.
At the time, NASA announced that Boeing engineers were also working to remove and replace a bypass valve in the active thermal control system on CFT’s Service Module (SM) that failed during preparations to load propellants aboard Starliner. This particular valve flows coolant into the system to cool the vehicle’s on-board avionics but was restricting flow to one of two redundant loops.
After running diagnostics to confirm the nature of this issue, Boeing expected the removal and replacement to take “about a week”. That replacement process is now complete, with broader analysis underway to consider any other affected systems.
Two other issues were noted in NASA’s 26 May Checkpoint Review update. The first was tape aboard the spacecraft that is meant to protect wiring from dust, chafing and circumvent the risk of electrical shorts.
The tape’s adhesive properties “could present a flammability risk under certain conditions” and teams were “evaluating…the system’s overall wiring protection” to verify its acceptability for flight. It was added that NASA and Boeing were working “to reassess” Starliner’s “certain joints” in the parachute system “based on new data reviews as part of the ongoing design certification process”.
According to Mark Nappi, Boeing’s vice president and program manager of the Commercial Crew Program, the parachute issue pertains to small fabric “soft-links” within the lines which recently underwent testing due to incorrect data recordings. This produced a lower failure load-limit than teams had previously understood and after testing these were found to fail at the lower limit, decreasing their safety factor “pretty significantly”.
Mr. Nappi added that the tape that wraps Starliner’s wiring harnesses and guards them against dust, chafing and the risk of electrical shorts had been “tested late in the process” and was “discovered to be flammable”. The issue had reached the top levels of Boeing leadership and it was “unanimously decided” to stand down from CFT in July.
In his remarks at yesterday’s media teleconference, NASA Commercial Crew Program Manager Steve Stich noted that teams were otherwise “on a good path” in terms of preparedness for CFT but stressed that there was “only a small window” available in July to fly the mission. Although none of the NASA representatives would be drawn on a new NET launch date, it was added that there exists a “window in the fall” to fly the mission, based on ISS visiting vehicle traffic demands.
Currently, SpaceX’s Dragon Endurance is scheduled to fly around mid-August to deliver Crew-7—NASA’s Jasmin Moghbeli and European Space Agency (ESA) astronaut Andreas Mogensen, together with Japan’s Satoshi Furukawa and Russian cosmonaut Konstantin Borisov—to the ISS for a six-month increment, with the return of Dragon Endeavour and her Crew-6 quartet of Steve Bowen, Warren “Woody” Hoburg, Sultan Al-Neyadi and Andrei Fedyayev anticipated before the end of that month, wrapping up their own half-year stay aboard the sprawling orbital complex.
September also looks busy, with Soyuz MS-24 scheduled to launch in mid-month with Russian cosmonauts Oleg Kononenko and Nikolai Chub, together with NASA’s Loral O’Hara, followed by the departure at month’s end of Soyuz MS-23 and its crew of Sergei Prokopyev, Dmitri Petelin and Frank Rubio after a year in orbit. The final two months of 2023 also are fully booked, with Northrop Grumman Corp.’s NG-20 Cygnus cargo ship and potentially AxiomSpace, Inc.’s Ax-3 all-private crewed mission targeting November launches and SpaceX’s CRS-29 Cargo Dragon and Sierra Nevada Corp.’s inaugural Dream Chaser penciled-in for December.
The CFT mission is currently baselined as an eight-day mission, during which Wilmore and Williams will conduct a complete shakedown of Starliner, from launch atop a United Launch Alliance (ULA) Atlas V out of storied Space Launch Complex (SLC)-41 at Cape Canaveral Space Force Station, Fla., through orbital operations to rendezvous, docking and undocking at the ISS and return to Earth, alighting on solid ground at White Sands Space Harbor (WSSH) in New Mexico. NASA previously stressed that there exists some scope to extend the astronauts’ stay aboard the space station if needed, but no definitive limit has been offered on exactly how long CFT might remain in orbit.
Wilmore previously served as pilot of shuttle Atlantis on the 11-day STS-129 mission in November 2009, before commanding Expedition 42 during a 167-day ISS increment from September 2014 through March 2015. For her part, Williams recorded the longest single mission ever undertaken by a woman when she spent 195 days in space during Expedition 14/15 between December 2006 and June 2007, then went on to command Expedition 33 during a 127-day ISS increment in July-November 2012.
All told, the duo have spent almost 500 days in space, completing 11 spacewalks and chalking up more than 76 EVA hours between them. And Williams also held the empirical record from September 2012 until March 2017 for the greatest number of spacewalking hours attained by a woman.