The rendezvous was achieved despite an earlier loss of several guidance-control jet thrusters, some of them because of a helium propulsion leak, which Nasa and Boeing said should not compromise the mission.
The CST-100 Starliner, with veteran astronauts Barry “Butch” Wilmore and Sunita “Suni” Williams aboard, arrived at the orbiting platform after a flight of nearly 27 hours following its launch from Cape Canaveral Space Force Station in Florida.
The reusable, gumdrop-shaped capsule, dubbed “Calypso” by its crew, was lofted into space on Wednesday atop an Atlas V rocket furnished and flown by Boeing-Lockheed Martin’s United Launch Alliance joint venture.
It autonomously docked with the ISS while both were orbiting some 250 miles (400km) over the southern Indian Ocean, as the two vehicles soared around the globe in tandem at about 17,500 miles (28,160km) per hour.
The spacecraft’s final approach to the ISS and docking, following a brief interval when Wilmore manually controlled the capsule, was shown on a Nasa webcast.
“Nice to be attached to the big city in the sky,” Wilmore radioed to mission control in Houston shortly after docking.
On arrival, Wilmore, 58, and Williams, 61, spent about two hours conducting a series of standard procedures, such as checking for airlock leaks and pressurising the passage between the capsule and the ISS, before opening the entry hatches.
A live Nasa video feed showed the smiling new arrivals, wearing their blue flight suits, weightlessly floating headfirst through the padded passageway, one after the other, into the station. Williams was first.
They were greeted warmly with hugs and handshakes by the outpost’s current seven resident crew members: four fellow US astronauts and three Russian cosmonauts.
Plans call for Wilmore and Williams to remain aboard the station for about eight days, then depart on a return flight that will take Starliner on a fiery re-entry back through Earth’s atmosphere and end with a parachute and airbag-assisted landing in the US Desert Southwest, a first for a crewed Nasa mission.
The Starliner launch on Wednesday followed years of technical problems, various delays and a first successful 2022 test mission to the orbital laboratory without astronauts aboard.
Last-minute glitches had nixed the Starliner’s first two crewed launch attempts, including a helium leak found on the capsule’s propulsion system that officials later determined was not serious enough to warrant a mechanical fix.
Nasa and Boeing officials at the time pointed to a faulty seal on a thruster component that was failing to keep the helium inside.
Boeing built Starliner under contract with Nasa to compete with SpaceX’s Crew Dragon capsule, which since 2020 has been the US space agency’s only vehicle for sending ISS crew members to orbit from American soil. The current mission marks Starliner’s first test flight with astronauts aboard, a requirement before Nasa can certify the capsule for routine astronaut missions.
Selected as crew for the pivotal flight were two Nasa veterans who have previously logged 500 days in space between them: Wilmore, 61, a retired Navy captain and fighter pilot, and Williams, 58, a former Navy helicopter test pilot with experience flying more than 30 different aircraft.
Getting Starliner to this point has been a fraught process for Boeing under its US$4.2 billion, fixed-priced contract with Nasa, which wants the redundancy of two different US rides to the ISS.
The Starliner is several years late and more than US$1.5 billion over budget. Meanwhile, Boeing’s commercial aeroplane manufacturing operations have been rocked by a series of crises involving its 737 Max jetliners.