New Starliner launch target identified after setback

The mission, which has suffered a series of setbacks since an initial launch attempt failed on May 6, is now scheduled for 10:52 a.m. EDT on Wednesday, with a backup launch window available on Thursday.

The Starliner CFT is intended to be the spacecraft's final test flight before NASA certifies it for service missions to the ISS, the first of which could occur next year. To date, all eight commercial crew rotation missions to the orbiting laboratory have been flown by SpaceX's Crew Dragon.

The company signed its own multibillion-dollar contract with the space agency at the same time as Boeing, but has already established itself as an invaluable partner. The same cannot be said of the aerospace giant, which has only sent Starliner to the ISS once.

Attempts to launch CFT have been delayed or canceled due to a litany of problems. First, it involved a faulty pressure control valve on United Launch Alliance's (ULA) Atlas V launch vehicle, which will carry Starliner into orbit. Then crews discovered a small helium leak on Starliner itself, involving one of the 28 thrusters in its service module's reaction control system. These small engines use helium to perform minor maneuvers and keep Starliner in orbit.

NASA and Boeing have since described the leak as stable but opted not to repair it, which would require unstacking the Starliner from Atlas V and could take months. However, while investigating the root cause of the leak, crews discovered what the space agency described as a “design vulnerability” in the capsule's propulsion system.

In a scenario that NASA estimates has a probability of about 0.77 percent, the original leak could combine with an adjacent leak to prevent Starliner from performing a deorbit burn. It is the maneuver that returns a spacecraft to the Earth's atmosphere after its mission.

All this risk identification and assessment work pushed the CFT back to Saturday. But another problem forced the launch to be canceled just minutes before liftoff and made a second go-around impossible on Sunday.

According to the Starliner team, the problem is once again on the ULA side.

During the countdown, ground support equipment on the Space Launch Complex-41 platform at the Cape Canaveral space station in Florida experienced problems, which crews attributed to a power supply unit on one of the three chassis of the Atlas V Centaur upper stage. The power pack indirectly powers the Centaur's shutdown valves during the launch sequence, and all three chassis must be functioning for the countdown is finished.

According to ULA CEO Tory Bruno, the chassis with the faulty powertrain was quickly replaced. The new equipment was tested again and was functioning normally on Sunday. NASA and Boeing added that they had not observed any physical damage to Starliner or Atlas V, and that crews would conduct a “full failure analysis” to determine what went wrong.

NASA astronauts Butch Wilmore and Suni Williams, the Starliner's first human passengers, remain in quarantine at the Kennedy Space Center. If all goes according to plan, Wilmore and Williams will dock with the ISS later this week. There, they will spend about a week testing Starliner's systems as NASA prepares for the next step in the program: certification.

After that, Starliner would begin alternating six-month commercial crew rotation missions with SpaceX's Dragon.