Plans to launch Boeing’s much-delayed Starliner spacecraft on its first crewed test flight Saturday were put on hold Tuesday evening to give managers more time to evaluate a small test flight. helium leak in the ship’s propulsion system. A new launch target was not announced.
The Starliner crew – Commander Barry “Butch” Wilmore and co-pilot Sunita Williams – remained at Johnson Space Center in Houston awaiting word on when to head to Kennedy Space Center to make final preparations for launch to the International Space Station.
United Launch Alliance
They had hoped to take off Saturday at 3:09 p.m. EDT, assuming NASA and Boeing executives agreed it would be safe to launch the spacecraft “as is,” with a small but persistent leak in the ship’s propulsion pressure system.
But multiple sources said earlier Tuesday that option was no longer on the table as additional meetings were planned to discuss the rationale for launching the spacecraft, assuming the leak would not worsen during the flight.
In a brief statement late Tuesday, NASA said: “The team has been in meetings for two consecutive days to review flight rationale, system performance and redundancy. Progress continues in these areas and the next possible launch opportunity continues to be discussed.”
NASA did not announce when the analysis might be completed or when another launch attempt might be made. Near-term launch options after Saturday and Sunday, based on the Starliner’s ability to match the station’s orbit, are May 28 and June 1, 2, 5 and 6.
The latest delay was a familiar setback for the hapless Starliner, which has suffered a steady stream of frustrating complications since an initial unmanned test flight was derailed in 2019 by software glitches and communications problems. A second unmanned test flight was launched and although it was generally successful, more problems were discovered after its return to Earth.
The helium leak was first discovered during a launch attempt on May 6. At the time, engineers concluded the leak was small enough to allow a launch, but the the countdown was canceled after engineers at Atlas builder United Launch Alliance noticed unusual behavior in an oxygen pressure relief valve in the rocket’s Centaur upper stage.
Managers ultimately decided to return the rocket to the company’s Vertical Integration Facility to replace the valve. That work was completed without incident and the new valve was cleared for flight.
Boeing engineers took advantage of the delay to conduct a more thorough assessment of the helium leak, which was traced to a specific thrust from the reaction control system in one of four “doghouse” structures surrounding the exterior of the aircraft’s drum-shaped service module the Starliner were mounted.
Each doghouse carries four orbital maneuver and attitude control (OMAC) thrusters and four smaller maneuver jets for the reaction control system. Pressurized helium gas is used to push propellants to the rocket engines in each doghouse, as well as four powerful launch abort engines that would only fire in the event of a catastrophic booster failure.
Engineers tightened the bolts around the flange where the leak was detected, pressurized the pipes, and then ran tests to determine if the leak was still present. In the meantime, the launch was rescheduled for May 21 and then, when tests showed the leak was still present, moved to Saturday to give engineers more time to review the data.
The flight is now on hold indefinitely, pending the results of the ongoing analysis.
