On Thursday, Boeing may have a second likelihood at a do-over for the area taxi it has constructed for NASA.

The Starliner capsule will take astronauts to and from the Worldwide House Station, however first it has to finish a check flight with out astronauts to confirm that its methods all work correctly. Its two earlier makes an attempt to hold out that preparatory journey — the primary in December 2019 and the second in August 2021 — have been each marred by critical technical issues. The setbacks have additionally value Boeing hundreds of millions of dollars.

However now, lastly, Starliner is once more on the launching pad. Right here’s what you could find out about its flight.

Liftoff is scheduled for six:54 p.m. Jap time on Thursday from Cape Canaveral House Pressure Station in Florida. NASA Television will begin streaming protection of the launch at 6 p.m.

Climate forecasters give an 90 p.c likelihood of circumstances favorable for launch. There’s a backup launch window on Friday at 6:32 p.m., however the climate may be much less promising, at solely 30 p.c, due to anticipated thunderstorms within the space.

Boeing performed an uncrewed check flight of Starliner in December 2019. The problems started almost as soon as it reached orbit.

A software program error precipitated the Starliner’s clock to be set to the flawed time. That precipitated the onboard laptop to attempt to transfer the spacecraft to the place it thought the vessel needs to be. The firing of the thrusters used up a lot of the propellant, and plans for Starliner to dock on the area station have been referred to as off.

Whereas troubleshooting that drawback, Boeing engineers found a second flaw that will have precipitated the flawed thrusters to fireside because the capsule ready for re-entry, doubtlessly resulting in the destruction of the spacecraft. They mounted that software program flaw whereas Starliner orbited the Earth, and the capsule landed safely at White Sands, N.M.

These issues put a maintain on what would have been the following step: an indication flight with astronauts aboard. NASA advised Boeing that it wanted to repeat the uncrewed check flight, at Boeing’s value.

Boeing spent greater than a yr revamping and retesting the software program, and in August final yr, Starliner was again on the launching pad at Cape Canaveral House Pressure Station in Florida, on high of a second Atlas 5 rocket.

The countdown began, however needed to be halted. Flight managers found that 13 valves in Starliner’s propulsion system had failed to open.

Boeing then spent about eight months investigating the corrosion that had precipitated the valves to stay shut. Boeing swapped out the service module — the piece of Starliner under the capsule that homes the propulsion system — with one which had been deliberate for the following mission.

Now, it’s prepared for that second do-over.

Though this mission isn’t carrying any astronauts, one in all Starliner’s seats might be stuffed by a model named Rosie the Rocketeer. Rosie additionally flew on the primary orbital check in 2019, outfitted with sensors to measure circumstances throughout the capsule.

There’s additionally greater than 800 kilos of cargo aboard, principally meals and provides for the area station crew, but in addition some memorabilia. The spacecraft is to carry again to Earth nearly 600 kilos of cargo from the area station.

NASA and Boeing officers say they’ve methodically analyzed and glued the software program flaws that lower quick the 2019 check flight. An issue with the communications system has additionally been mounted.

In addition they say they perceive how the valves turned caught. Moisture within the air reacted with the thruster propellant, nitrogen tetroxide, producing nitric acid that corroded the valves.

“The trick for this flight was to get rid of that moisture and ensure that it doesn’t trigger these nitrates to type,” Mark Nappi, vp and program supervisor at Boeing for the industrial crew program, mentioned throughout a information convention on Tuesday. “We went to nice extent to ensure that the valve is correctly sealed off so there’s no potential for moisture intrusion into the valve.”

Dry nitrogen was despatched by the valves to assist take away moisture.

Throughout preparations, the valves have been opened and closed plenty of occasions with none issues, Mr. Nappi mentioned.

Boeing can be contemplating longer-term options together with a redesign of the valves, he mentioned.

After the area shuttles have been retired, america needed to depend on Russia’s Soyuz rockets for journeys to and from the Worldwide House Station. NASA then employed two firms to take astronauts to and from the station: SpaceX and Boeing. On the time of Boeing’s check flight in 2019, it appeared that Starliner would beat out SpaceX’s Crew Dragon capsule for the primary mission with astronauts.

However with issues grounding Starliner, SpaceX has since launched seven Crew Dragon missions with astronauts. 5 have been for NASA. Two others carried private citizens to orbit.

SpaceX’s missions additionally look like considerably cheaper than Boeing’s. When NASA introduced the contracts in 2014, Boeing was set to obtain $4.2 billion whereas SpaceX was to obtain $2.6 billion. (The area company didn’t launch particulars of the contracts, making it tough to precisely evaluate the price of a seat on Starliner with one on Crew Dragon. In 2019, the NASA inspector common estimated that every seat on a Crew Dragon prices $55 million, whereas a seat on Starliner prices $90 million.)