Many space fans have been following the successful launch of the Boeing Starliner, another commercial organisation aiming to make space more accessible. It successfully reached the International Space Station, delivering Butch Wilmore and Suni Williams into orbit but it wasn’t without a hitch. Three of its thrusters experienced problems and there were ‘five small leaks on the service module.’ The crew and ground teams are working through safety checks of power and habitability. To ensure a safe return of the astronauts NASA has extended the mission by four days to 18th June.
Boeing Starliner is a reusable (partly) spacecraft designed to transport crews to low Earth orbit. NASA is the lead customer so, once certification has been achieved, will be used to deliver astronauts regularly to the ISS. It consists of a crew capsule that can be used ten times and an expendable service module. Measuring 4.6 metres in diameter it is slightly larger than the Apollo Command module that was a part of the historic Armstrong, Aldrin and Collins mission to the Moon.
The Boeing Starliner launch marked its first crewed trip into orbit, with the objective of data collection for certification by NASA for regular crewed missions to ISS. The tests are numerous and include; running the spacecraft in minimal power mode (for when docked to ISS), checking suitability to support crew on its own in the event of an emergency, performing habitability studies for a four person crew and a multitude of other system checks. The module has been docked to ISS since 6th June.
Teething problems for any new module are always expected but when the word ‘leak’ pops up it is most definitely a cause for concern. In the case of Starliner, five small leaks have been detected in the service module helium manifolds. When Starliner launched, the ground team already knew there was one leak in the propulsion system but now, four more have been detected! The flight engineers initially suspected a flaw in a manifold seal or possibly even faulty installation but now, with the four additional leaks they’re trying to understand if there is a common problem.
The leaks are not the only problem that has been experienced. As Starliner approached ISS, it relied upon precise pulses from the 28 reaction control thrusters. During this critical phase of the docking process, five of them failed. More accurately, the spacecraft control software deduced they were not working and deselected them. The first docking window was missed as a result but the crew were able to test and restart four of the five engines allowing them to safely dock. Engineers are still looking into the thruster problem but are confidence it will allow the safe return of the astronauts.
As for the helium leak, flight engineers have examined the leak rate and confirmed that Starliner has sufficient margin to support a return trip to Earth. With Starliner docked to the ISS the manifolds are all closed preventing any helium loss until the return trip which takes just seven hours. Even with the manifolds open and the rate of leak there is sufficient helium to support 70 hours of flight time.
Ground support teams are continuing to work through the problems and the return plan. They will explore tolerances and possible operational mitigations for the remainder of the mission. As the team depart from the ISS, no earlier than 18th June they will slowly adjust orbit away from the Space Station. A deorbit burn will be completed before entering the atmosphere and landing in south-western United States.
Source : NASA, Boeing Progress on Testing Starliner with Crew at Space Station
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