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The latest crewed launch attempt of the Boeing Starliner spacecraft is on track for Wednesday after a computer issue halted the countdown just minutes before liftoff on Saturday.
The historic mission, known as the Crew Test Flight, is scheduled to launch at 10:52 a.m. ET from the Cape Canaveral Space Force Station in Florida. The event will be broadcast live on NASA’s website, with coverage beginning at 6:45 a.m. ET.
Veteran NASA astronauts Butch Wilmore and Suni Williams will be the first crew aboard Starliner, propelled to orbit on an Atlas V rocket built by United Launch Alliance, a joint venture between Boeing and Lockheed Martin.
The much-anticipated flight was 3 minutes and 50 seconds from liftoff Saturday afternoon, when the ground launch sequencer, or the computer that launched the rocket, triggered an automatic hold. The crews safely removed the astronauts from the capsule, and Williams and Wilmore returned to crew quarters as fuel was drained from the rocket.
United Launch Alliance technicians and engineers assessed the ground support equipment over the weekend, examining three large computers housed inside a shelter at the base of the launch pad. All computers are identical, providing triple redundancy to ensure the safe launch of crewed missions.
“Imagine a big rack is a big computer where the functions of the computer as a controller are broken up separately into individual cards or printed circuit boards,” said Tory Bruno, president and CEO of United Launch Alliance, during a news conference Saturday. . “They’re all independent, but together, it’s an integrated controller.”
The cards inside the computers are responsible for various key systems that must be in place before launch, such as loosening bolts at the bottom of the rocket so that it can be lifted after ignition.
During the last four minutes before the launch, the three computers must communicate and agree with each other. But during Saturday’s countdown, a card on one of the computers was six seconds slower to respond than the other two computers, which indicated something wasn’t right and prompted its automatic hold, according to Bruno.
Over the weekend, engineers assessed the computers, their power supply and network communication between the computers. The team isolated the issue to a single ground power supply inside one of the computers, which provides power to the computer cards responsible for key countdown events – including the replenishment valves for the rocket’s upper stage, according to an update NASA is divided.
Starliner crews reported no signs of physical damage to the computer, which they removed and replaced with a spare. Meanwhile, mission specialists continue to analyze the faulty power unit to better understand what went wrong.
The other computers and their cards were also evaluated, and all are performing normally as expected, according to the ULA team.
The Starliner mission management team reviewed the computer replacement troubleshooting steps taken, and agreed that Starliner is “go” for Wednesday’s launch, according to an update from NASA.
“I appreciate all the work done by NASA, Boeing, and ULA teams over the past week,” Steve Stich, manager of NASA’s Commercial Crew Program, said in a statement. “The ULA team worked especially hard to quickly learn more about these issues, keep our NASA and Boeing teams informed, and protect the next effort. We will continue to take it one step at a time.”
Next try
Mission teams successfully worked through several other issues that arose earlier in the countdown to Saturday’s launch attempt. Among these problems was the loss of data from ground valves responsible for replenishing the liquid oxygen and hydrogen to the second stage, or upper stage, of the Atlas V rocket before liftoff.
Both the liquid oxygen and hydrogen, used to fuel the rocket, boil off as the rocket sits on the pad before launch, so refueling continues until liftoff. After assessing the issue, mission teams switched to a redundant system for valve data and were able to restart the process.
Weather conditions are 90% favorable for a Wednesday morning launch, with the only concern being cumulus clouds, according to the US Space Force’s 45th Weather Squadron. If the launch does not happen on Wednesday, there is another opportunity at 10:29 a.m. ET on Thursday, according to NASA.
If Starliner succeeds in taking off, the astronauts will spend just over 24 hours traveling to the International Space Station.
After getting close, Williams and Wilmore are set to spend eight days living in the orbital laboratory, joining the seven astronauts and cosmonauts already on board. Both will continue to test the functionality of the Starliner spacecraft while docked at the space station and then return home aboard the same capsule. He is expected to parachute to a landing at one of many designated locations throughout the southwestern United States.
Meanwhile, the two astronauts remain in quarantine to protect their health before launch, and are practicing procedures and simulations before the historic flight, according to NASA.
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