May 20, 2022

— Starliner has arrived at the space station.

An achievement long in coming, Boeing's CST-100 Starliner spacecraft docked to the International Space Station for the first time on Friday (May 20).

The uncrewed capsule autonomously linked up with the Boeing-built international docking adapter on the forward-facing port of the space station's Harmony node at 8:28 p.m. EDT (0028 GMT on May 21), one day after lifting off on a United Launch Alliance (ULA) Atlas V rocket from Cape Canaveral, Florida, and two and a half years after the first Starliner orbital flight test was cut short by software problems.

"Hard mate is complete, ISS thrusters are enabled and we can welcome Starliner to the ISS," radioed capcom Rob Hayhurst from Mission Control.

"That's great news. Thank you to Rob and thank you to the entire ops team for some great work tonight," replied Expedition 67 flight engineer Bob Hines from aboard the International Space Station. "Today marks a great milestone toward providing additional commercial access to low Earth orbit, sustaining the ISS and enabling NASA's goal of returning humans to the moon and eventually to Mars."

"Great accomplishments in human spaceflight are long remembered by history and today will be no different. Starliner, its commander Rosie the Rockeeter and all the men and women who poured their hearts and souls into this vehicle for this mission, welcome to the International Space Station!" said Hines.

The accomplishment marks a major milestone toward Boeing flying astronauts to the station under a $4.2 billion contract with NASA's commercial crew program.

Boeing Starliner docks to space station. Click to enlarge video in new pop-up window. (Boeing)

The Starliner's journey to the space station began within 15 minutes of leaving Earth on Thursday. Despite two of its rear-facing orbital maneuvering and attitude control (OMAC) thrusters failing soon after firing, the result of a drop in chamber pressure, the Starliner entered a stable orbit. The capsule then conducted a series of burns to refine its approach to the station and demonstrate that it was able to safely maneuver.

NASA flight controllers working under contract for Boeing at the Johnson Space Center's Mission Control Center in Houston commanded the spacecraft to perform a simulated abort, showing that it could rapidly withdraw from an errant approach to the station. The capsule's reaction control system was also tested, ensuring the Starliner could make fine course corrections when in close proximity to the station.

The crew aboard the station showed they were able to communicate with the spacecraft by commanding the Starliner to turn on its docking lights. The capsule's navigation sensors were powered on for a far-field rendezvous demonstration.

Completing those trials, the Starliner continued on toward its destination, receiving the "go" for integrated operations with the space station. Entering the approach ellipsoid — the imaginary boundary surrounding the space station that is 2.5 miles long, 1.2 miles wide and 1.2 miles deep (4 by 2 by 2 km) — the Starliner entered a fly-around maneuver to reach the approach corridor for its docking.

Flying autonomously, the Starliner used its vision-based, electro-optical sensor tracking assembly, or VESTA, to navigate. The system uses a laser, visual cameras and an infrared camera to recognize the outline of the space station, or, when closer, markings on the station's exterior, to keep the Starliner on track and aligned during its approach and docking.

The station crew again demonstrated commanding the vehicle, this time directing the Starliner to briefly pause its approach. Flight controllers then commanded the capsule to demonstrate a retreat before entering the station's "keep out sphere" at 660 feet (200 m). The spacecraft then paused once more at 32 feet (10 m), during which some extra time was taken to ensure proper lighting and that the Starliner's docking ring was fully extended.

The docking marked the first time that two different companies' commercial crew spacecraft were connected to the station at the same time. The SpaceX Dragon Freedom, which brought the Crew-4 astronauts to the station in April, is docked to Harmony's zenith, or space-facing port.

With hooks and latches secured, the hatches separating the Starliner and station were set to be opened on Saturday morning.

The Starliner is packed with about 500 pounds (230 kg) of cargo, including food and other NASA-provided supplies for the Expedition 67 crew on the station. After being emptied of its cargo, the capsule will be repacked with nearly 600 pounds (270 kg) of equipment, including reusable Nitrogen Oxygen Recharge System (NORS) tanks that provide breathable air for the station's crew.

Pending weather conditions, the Starliner will spend about five days docked to the space station. It will then return, using parachutes and airbags to touchdown at the White Sands Missile Range in New Mexico.