Boeing's Starliner successfully docks at ISS after helium leaks, thruster issue

Boeing's Starliner successfully docked at the International Space Station (ISS) Thursday afternoon, marking another milestone in the first astronaut-crewed test flight of the spacecraft.

NASA and Boeing confirmed Starliner docked at 1:34 p.m. ET. NASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams will soon enter the ISS's orbital laboratory, where they'll spend about a week, NASA said in a post on the social platform X

It comes after helium leaks and a thruster issue threatened to delay Starliner's docking.

Three helium leaks developed as Starliner made its way to the ISS, according to a post on X from the agency's Johnson Space Center late Wednesday.

One of the leaks "was previously discussed before flight along with a management plan. The other two are new since the spacecraft arrived on orbit," the post on X read.

The leaks are similar to those discovered during Starliner's launch attempt that was set for May 25. That launch was scrubbed after a small helium leak was found in the service module, which contains support systems and instruments for operating a spacecraft.

Helium is used to used to pressurize the spacecraft's thrusters, allowing them to fire, according to Boeing.

It's currently unclear how much helium is leaking or if it will affect Starliner's performance and ability to return to Earth in eight days.

However, two of the helium valves have been closed and the spacecraft is "stable," NASA said at the time.

Starliner was scheduled to dock at the ISS at 12:15 p.m. ET on Thursday but had to delay after mission control identified an issue with the reaction control system (RCS) jets that help the spacecraft's thruster maneuver.

The spacecraft was held out the so-called "keep out sphere," a boundary about 200 meters away from the ISS, until another docking window opened at 1:33 p.m. ET.

Williams and Wilmore are expected to spend one week aboard the ISS and will be evaluating Starliner and its systems. Upon re-entry, the spacecraft will deploy parachutes and an airbag system, landing the pair in the western U.S.

If the mission is successful, NASA could certify the spacecraft to perform routine missions to and from the ISS. NASA has primarily been using SpaceX's Dragon spacecraft to transport crew and cargo to the ISS.