Tuesday evening’s launch of Boeing’s much-delayed Starliner spaceship on its first crewed test flight was postponed to provide managers additional time to assess a minor helium leak in the ship’s propulsion system. No new launch window was specified.
In order to finalize their preparations for launch to the International Space Station, commander Barry “Butch” Wilmore and co-pilot Sunita Williams of Starliner stayed at the Johnson Space Center in Houston until they received word on when to proceed to the Kennedy Space Center.
In the event that NASA and Boeing managers decided it would be safe to launch the spacecraft “as is,” with a little but persistent leak in the ship’s propulsion pressurization system, they had hoped to launch at 3:09 p.m. EDT on Saturday.
However, earlier on Tuesday, a number of sources stated that option was out of the question because more meetings were scheduled to talk about the justification for launching the spacecraft under the assumption that the leak would not get worse while in flight.
NASA said in a brief statement late on Tuesday that “the team has been in meetings for two consecutive days, assessing flight rationale, system performance and redundancy. There is still forward work in these areas, and the next possible launch opportunity is still being discussed.”
When the analysis might be finished or when a new launch attempt might be performed, neither was disclosed by NASA. Depending on the Starliner’s capacity to match the station’s orbit, there are other near-term launch options after Saturday and Sunday on May 28 and June 1, 2, 5, and 6.
The hard-luck Starliner has experienced a constant barrage of exasperating setbacks since an initial unpiloted test flight in 2019 was wrecked by software issues and communications hiccups. The most recent delay was a familiar one. Although the second unmanned test flight went mostly well, more issues were found after it returned to Earth.
First discovered on May 6, the helium leak occurred during a launch attempt. Engineers determined at the time that the leak rate was low enough to allow launch, but the countdown was canceled when United Launch Alliance engineers noticed anomalous behavior in an oxygen pressure relief valve in the Centaur upper stage of the rocket.
Ultimately, managers made the decision to tow the rocket back to the Vertical Integration Facility of the business in order to change the valve. The new valve was approved for flight once the work was finished without any problems.
During the delay, Boeing engineers conducted a more comprehensive investigation into the helium leak. They were able to identify the source of the leak as a particular reaction control system thruster located in one of four “doghouse” assemblies that were affixed to the outside of the service module that resembled a drum on the Starliner.
Four smaller response control system maneuvering jets and four orbital maneuvering and attitude control (OMAC) thrusters are included in each doghouse. Pressurized helium gas is used to drive propellants to four powerful launch abort engines, which are only meant to ignite in the case of a catastrophic booster failure, and to the rocket motors in each doghouse.
After pressurizing the pipes and tightening nuts around the flange where the leak was found, the engineers conducted tests to see if the leak persisted. To allow engineers extra time to review the data, the launch was postponed from May 21 to Saturday after tests showed the leak was still there.
Awaiting the outcome of the continuing analysis, the flight has been placed on indefinite pause.
