Tuesday, May 14, 2024

Starliner Slips Another Four Days

The scheduled date for the Crewed Flight Test of Boeing's Starliner has slipped out again, due to Boeing troubleshooting a small helium leak in the Starliner spacecraft itself. The last date we had was this coming Friday, the 17th; that has now been rescheduled for Tuesday, May 21 at 4:43 pm EDT (2043 UTC).

Boeing's ground team traced the leak to a flange on a single reaction control system thruster on the spacecraft's service module.

There are 28 reaction control system thrusters—essentially small rocket engines—on the Starliner service module. In orbit, these thrusters are used for minor course corrections and pointing the spacecraft in the proper direction. The service module has two sets of more powerful engines for larger orbital adjustments and launch-abort maneuvers.

Like many other spacecraft, the thrusters are fueled by the toxic combination of hydrazine (N2H4) and nitrogen tetroxide (N2O4) using the helium just to pressurize the system. The leak is important because the Starliner is to stay docked at the ISS for the week of the CFT-1 mission and the pressure must be maintained. This is a common fuel/oxidizer system for small thrusters; the Crew Dragon currently docked to the ISS for the Crew 8 mission and the previous ones that have flown other missions have stayed docked for the months those missions stayed docked to the ISS.

According to NASA, engineers plan to address the helium leak using "spacecraft testing and operational solutions." In other words, managers don't anticipate any need to physically repair the leak.

The original cause of the launch scrub back on Monday, May 2nd, was due to a valve problem. ULA rolled the Atlas V back to their Vertical Integration Facility (VIF) to swap out the faulty pressure regulation valve on the Atlas V's Centaur upper stage. Once installed on the rocket, the new valve performed normally in tests inside the VIF. ULA will roll the rocket back to the launch pad before the next launch attempt; I think the last attempt at this mission rolled out two days before the launch date.

A view looking down onto the Starliner capsule atop its Atlas V launch vehicle inside the VIF at Cape Canaveral Space Force Station, Florida. Image credi: ULA

My first reaction to this picture was that I'd like to know what those two black streaks are, about 60 degrees apart on one side (top of the frame) and 120 degrees apart on the other side. They kinda look like burn marks. Then I thought maybe I don't really want to know that. "Ignorance is bliss" and all that.


  1. Those burn marks are obviously from testing something. You'd think, after all the time the darned thing has been in the shop, someone would have washed them away or painted them.

    As you said, not really inspiring, unless it's inspiring the crew to use the escape system to get far away from that thing.

  2. Used helium for leak testing, just remarkable how tiny an atom it is compared to other gases, would find leaks you would think where impossible. You must have superb sealing and mating surfaces. The gas can seep along a grain line or abrasive/polish defect on metal to metal sealing faces, so tiny most times you can not see it without a high power loop.And even then you could say no way its getting thru right there. Funny stuff that gas.
    Then again, other gases and liquids could not get thru, their molecules are tool large comparatively.

    1. Only Hydrogen - that's a leak that is downright dangerous. Glad it's Heliuml!