SpaceX Falcon 9 set for comeback after upper-stage failure SpaceX aims to resume launching the Falcon 9 rocket tomorrow after the Federal Aviation Administration (FAA) agreed to let the company return to flight operations. An FAA spokesperson told The Register: "After a comprehensive review, the FAA determined no public safety issues were involved in the anomaly that occurred during …
“This particular line failed, so we remove it because we don’t need this one”. Idiot. The line failed because it hadn’t been secured properly, and metal fatigued. That’s a failure of process and inspection. *Any* of the lines could have been forgotten, just happened to be this one. Removing one line, fixes nothing.
It’s exactly as bad as Ariane 6 “the APU failed on the second re-light, so missions that only require the APU to light once are unaffected”. Or Boeing Starliner “it’s fine to launch with one failed power unit, because there’s a redundant one which would have taken over had this occurred after launch”
It seems the stupid is really infectious this month.
> Yeah they could be inspecting all the other lines and clips after this event
They did. From https://www.spacex.com/updates/#falcon-9-returns-to-flight :
> An additional qualification review, inspection, and scrub of all sense lines and clamps on the active booster fleet led to a proactive replacement in select locations.
The more complex a system gets, the more possible points of failure are introduced. If a review shows that a sensor is not needed, then removing this sensor is absolutely a valid solution to removing not only the failure that has occured, but also to various other possible failures involving the same hardware.
In the automotive business, there is a drive to replace sensors with digital models running in the software. If it is not there, then it can not fail.
"Simplify, then add lightness"
"For near term Falcon launches, the failed sense line and sensor on the second stage engine will be removed. The sensor is not used by the flight safety system and can be covered by alternate sensors already present on the engine."
So, why was it installed in the first place? What (probably bleeding obvious to everyone else) have I missed?
I think it's like Musk's decision to remove all sensors from Tesla's except the cameras.
You don't need radar to tell you you're coming up fast on an obstacle when you have cameras. Well, not unless it is foggy. Or it's night you're on an unlit motorway and there's a black velvet sofa bed sitting in the road (happened to my wife, saved by radar).
Your car probably has a rev counter, a speedometer, and a sensor for the current gear. Any one of those sensors is mostly redundant, you could usually figure out the reading by looking at the other two sensor readings. There are times when having all three sensors is helpful. However, if a car manufacturer discovered that one of those sensors was randomly making the car explode, then they could remove that sensor and just calculate the value in software from the other two readings.
[Car speed] = [engine speed] x [gear ratio for current gear]; or [engine speed] = [Car speed] / [gear ratio for current gear]; or [gear ratio for current gear] = [Car speed] / [engine speed].
(Pre-emptive nitpick: There are laws saying that there has to be a speedometer. I'm ignoring that for this example).
> So, why was it installed in the first place? What (probably bleeding obvious to everyone else) have I missed?
"During a news briefing Thursday, SpaceX director Sarah Walker said this sense line was installed based on a customer requirement for another mission. The only difference between this component and other commonly flown sense lines is that it has two connections rather than one, she said. This may have made it a bit more susceptible to vibration, leading to a small crack."
- https://arstechnica.com/space/2024/07/spacex-roars-back-to-orbit-barely-two-weeks-after-in-flight-anomaly/
From what I gather the speed of identification of the problem held no magic; "Was there any difference between this one and all the others?" - Yeah, we had put an extra line in this one for a prior customer specification "Show me the plan... yeah, right there, it also deviates from the primary line in its fixings"
So, that's all fair enough if I have defined it correctly, however, as noted elsewhere, that does still leave a QC/QA problem for SpaceX that was overlooked.
Not unique of course, accomodating customer specs beyond standard, is the bane of every industry I've ever been involved in - of course one can offer to custom build, but of course each custom build is in essence a new build.
Part of the additional cost for customisation should be for additional QA/QC - and customers do pay a premium for customised rocket payloads for sure.
Which makes me ponder certification in general. How far can a Falcon 9 (or any other rocket system) deviate from its certification before it requires re-certification?
A line here, a fastener there, a customer specifies a change of paint job, when does it become a rocket of Theseus?
Just an idle pondering, doubt I'll ever find out, but certainly we know what the outcome can be if you take it to extremes in an aircraft...
"So, we changed the upholstery fabric, and the design of the drinks trays... "Yeah sure, sure fine" Lets see, we have a new logo on the tail, new engine, avionics and change of flight characteristics, complimentary hot-towels and new uniforms for the stewardesses. "Yeah, sure, sure....no, wait, what?"
"Which makes me ponder certification in general. How far can a Falcon 9 (or any other rocket system) deviate from its certification before it requires re-certification?"
If Boeing's 737MAX is anything to go by, it can deviate a *lot* from the original design and still be classed as "certified" :-)
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