Today we give a look into yesterday's Boeing Starliner Launch, which didn't happen, yet, due to a mechanical issue on a fuel valve on the launch itself.
So if you were going to blame Boeing for a glitch on the spacecraft, this is not the case.
The long awaited launch of the Starliner capsule had to be scheduled due to a different problem and today we give a look at the cause thanks to the words of Tory Bruno, President and CEO of United Launch Alliance (ULA).
Boeing Starliner Spacecraft
As you may already know, the Starliner Spacecraft has been developed and built by Boeing as a Crewed Spacecraft to serve Low Earth Orbit destinations, among which we find the International Space Station (ISS). Limited to this characteristic you can see it as a competitor, or a substitute, of the SpaceX Crew Dragon. Being a crewed spacecraft is a crucial detail to understand the reason behind the scrubbed launch of yesterday.
An aviation analogy
If you are familiar with the aviation world, the following design idea will be familiar to you. Without going too much into details, when you have a tank mounted on an aircraft you'll have to consider pressure variation when going up and down (yes, some rockets get down to the surface while still working... read: SpaceX). Actually, no fuel tank should be designed as completely sealed, if not for very particular applications, but this is specifically true if the atmospheric pressure around that tank is changing. Abrupt variations in that sense could cause overpressure inside the tank with potential explosion after structural collapse.
Considering a much more tragic example, think about fuselage rapid decompression of some old Boeing 737 planes (Aloha Airlines Flight 243): in this case the root cause of the tragedy was a structural damage which propagated and caused the whole fuselage to collapse, but the principle of pressure difference is applicable for the scope of this example.
Well, as a design mitigation to this, all tanks onboard are vented through one or more venting valves. Due to the critical importance of these components, their standard position is 'open', which means that those valves are always in their open position, without the need for any mechanical or electrical input. Under some circumstances they can be actuated, controlled by a specific algorithm, and closed. Due to some external factors, such as fuel loading, vibrations or temperature differences, just to make an example, the closing mechanism of the valve can be indadvertedly actuated, even with some frequency, which could cause the valve to cycle between the open and close position also more than once every second!
The investigation
This sort of resonance condition is still to be investigated by ULA, since no instrumentation is directly mounted on that valve, but they acquired data in a indirect way, thanks to accelerometers mounted close to the device, probably on the launcher structure.
Safety First!
Now, the circle closes: is this enough to scrub an entire launch? As Tory bruno said during yesterday's press conference, if a satellite was inside the rocket it would already be in orbit. However, being the Starliner Spacecraft a crewed one, when you are flying people the safety precautions are lifted a little up. Additionally to the valve itself, also fuel loading and unloading procedures have to consider the presence of people onboard due to, just to make an example, toxic gasses that could release in the vicinity of the crew; thus they couldn't modify the propellant loading procedure to further check the valve.
Conclusion
In conclusion, the launch was scrubbed due to a venting valve glitch which caused the actuation of strong safety procedures.
Next attempt is now scheduled for Friday 17th of May - next week.
Stay tuned with the SpaceInfo Club for any update.
We also released a YouTube video further discussing this topic: you can find it here.
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