The rendezvous of the CST-100 Starliner with the orbital research outpost, currently home to a seven-member crew, occurred nearly 26 hours after the capsule was launched from Cape Canaveral US Space Force Base in Florida.

Starliner lifted off on Thursday and reached its intended preliminary orbit 31 minutes later despite the failure of two onboard thrusters.

Boeing said the two defective thrusters posed no risk to the rest of the spaceflight, which comes after more than two years of delays and costly engineering setbacks in a program designed to give NASA another vehicle for sending its astronauts to and from orbit.

Docking with ISS took place as the two vehicles flew 436 km over the south Indian Ocean, according to commentators on a live NASA webcast of the linkup.

Much was riding on the outcome, after an ill-fated first test flight in late 2019 nearly ended with the vehicle's loss following a software glitch that effectively foiled the spacecraft's ability to reach the space station.

Subsequent problems with Starliner's propulsion system, supplied by Aerojet Rocketdyne, led Boeing to scrub a second attempt to launch the capsule last summer.

Starliner remained grounded for nine more months while the two companies sparred over what caused fuel valves to stick shut and which firm was responsible for fixing them, as Reuters reported last week.

Boeing said it ultimately resolved the issue with a temporary workaround and plans a redesign after this week's flight.

Besides seeking a cause of two failed thrusters shortly after Thursday's launch, Boeing said it was monitoring some unexpected behaviour detected with Starliner's thermal-control system, but that the capsule's temperatures remained stable.

"This is all part of the learning process for operating Starliner in orbit," Boeing's mission commentator Steve Siceloff said during the NASA webcast.

The capsule is scheduled to depart the space station on Wednesday for a return-flight to Earth, ending with a airbag-softened parachute landing in the New Mexico desert.

A success is seen as pivotal to Boeing as the Chicago-based company scrambles to climb out of successive crises in its jetliner business and its space defence unit. The Starliner program alone has cost nearly $600 million in engineering setbacks since the 2019 mishap.

If all goes well with the current mission, Starliner could fly its first team of astronauts to the space station as early as the autumn.

For now, the only passenger was a research dummy, whimsically named Rosie the Rocketeer and dressed in a blue flight suit, strapped into the commander's seat collecting data on crew cabin conditions during the journey, plus 363 kg of cargo to deliver to the space station.

The orbital platform is currently occupied by a crew of three NASA astronauts, a European Space Agency astronaut from Italy and three Russian cosmonauts.

Since resuming crewed flights to orbit from American soil in 2020, nine years after the space shuttle program ended, the US space agency has had to rely solely on the Falcon 9 rockets and Crew Dragon capsules from Elon Musk's company SpaceX to fly NASA astronauts.

Australian Associated Press