NASA astronauts will attempt another launch with Boeing Starliner.

• Boeing aims to launch its first Starliner flight with astronauts on Wednesday.
• The scheduled launch time is 10:52 a.m. ET from Cape Canaveral, Florida.
• NASA's Starliner crew has been delayed for years, while SpaceX's Dragon capsule has been flying astronauts for NASA since 2020.

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The Starliner spacecraft is set to launch its first flight with astronauts on Wednesday, marking the latest attempt to fly the long-delayed spacecraft.

The Starliner capsule, carrying two NASA astronauts, will be launched from Cape Canaveral, Florida, at 10:52 a.m. ET on an Atlas V rocket bound for the International Space Station.

The Boeing crew flight test mission has been attempted several times, with a launch attempt on Saturday being called off due to a problem with one of the computer's providing ground support to the rocket. An earlier attempt in early May was also called off due to an issue with the rocket itself.

If the launch is delayed again, Boeing has a backup opportunity scheduled for Thursday.

After the May attempt, ULA, a joint venture of Boeing and SpaceX, replaced the rocket's problematic valve. After Saturday's attempt, ULA replaced a faulty part in the ground infrastructure computer.

NASA and Boeing discovered a "minor" helium leak in Starliner between two previous launch attempts, prompting them to conduct another round of evaluations. After investigation, the source of the leak was traced to the spacecraft's helium propulsion system. However, officials stated that the leak is "controlled" and does not pose a "flight safety risk."

NASA's Starliner crew has not yet made their debut, while SpaceX's Dragon capsule has been regularly flying astronauts for NASA since 2020 under the Commercial Crew program. As a result, Boeing has incurred $1.5 billion in costs due to Starliner setbacks, and NASA has spent nearly $5 billion on development.

NASA has reassigned astronauts off the first Boeing crew flights in 2021, as the spacecraft was once seen as a competitor to SpaceX's Dragon but has since become a backup position due to setbacks and delays. Boeing is under contract to fly six operational Starliner missions to the ISS.

The final major step before obtaining NASA certification for regular missions is represented by Wednesday's crew flight test.

The astronauts

Starliner is being flown by Butch Wilmore, who is the commander, and Suni Williams, who is the pilot.

Prior to joining NASA in 2000, Wilmore was a U.S. Navy pilot and has previously flown to space twice, first on the Space Shuttle and later on Russia's Soyuz.

In 1998, NASA chose Williams, who had previously flown to space twice on the Space Shuttle and Soyuz, and like Wilmore, he was a Navy pilot before joining the space agency.

The rocket and capsule

The Starliner crew flight test marks the 100th launch of ULA's Atlas V rocket, which debuted in 2002.

The Starliner spacecraft is capable of carrying up to four NASA astronauts and over 200 pounds of research and cargo. It lands using a parachute and airbag system, and each capsule is designed for reuse, allowing for a maximum of 10 missions.

The mission

The Starliner system's certification as a NASA astronaut transport vehicle is the goal of Boeing's crew flight test.

On Wednesday, Starliner will launch and fly in space for approximately 25 hours before docking with the International Space Station at 12:15 p.m. on Thursday. Afterward, the astronauts will spend a week on the ISS, focusing on testing the spacecraft, before returning to Earth.