The first Crewed Test Flight was scrubbed last night around two hours before the scheduled launch and has been rescheduled for this Friday at 6:16 PM EDT.
... But mission teams called the attempt off about two hours before Monday's planned liftoff, after identifying a faulty "oxygen relief valve" on the upper stage of Starliner's rocket ride, a United Launch Alliance (ULA) Atlas V. The valve was "buzzing," opening and closing rapidly, during the launch countdown, forcing the delay, ULA officials said.
Admittedly, I didn't work with relays very much in my design years; they're just not used very often in the kind of work I did (radio frequency (RF) applications). The only times I've seen relays buzzing it was caused by the voltage driving the relay's coils being too low, which implies that the issue here isn't the relay but the circuit driving it - possibly including the wiring.
Originally, everyone involved was saying they should be able to try to launch again tonight. That lasted until some time this morning when they gave the date of the next try as Friday evening. Since it's a fairly good rule of thumb that, "in Space 1.0 nothing happens quickly - and manned flight isn't even that fast" I'll just keep an eye on it. Should they need to roll the Atlas V and Starliner stack back to their assembly area, that probably adds a couple of days on to the delay.
The CFT-1 Starliner Capsule on top of its Atlas V ride at the SLC-41 launch pad. Image Credit: ULA on Flickr
SiG, don't equate relay buzzing with valve buzzing. I've encountered both.
ReplyDeleteThe valve has gas flowing past the valve seat, then the return spring pushes it closed, then the pressure pushes past the seat, and so on (rinse, repeat). It *can* be mitigated or even stopped by cycling the valve plunger by electrically pulsing the valve, causing the valve to reopen and shut again and the plunger reseating itself. Hopefully closing it for good this time. Valves in rockets and other critical systems are rated for so many cycles (10,000 is a typical figure) before wear is considered to downcheck the valve. If it's "buzzing", that's considered a "cycle" (per buzz), BTW. Cautious lot, they are...
Relay buzzing? the relay driver circuit is malfunctioning, or in the case of an AC relay, the D-ring fell off. I actually had that happen, ONCE. Or, like me, you made a programming error and are cycling the relay as fast as it can be driven. Also, if it's an AC relay a low-voltage condition will make it buzz as well. I've seen that condition as well.
Experience, baby!
Agree with Igor. I worked with LOTS of electrically actuated valves back when I was doing Industrial Controls. And I've seen the shading ring pop off poorly made AC relays, too. They tend to go kind of nuts when that happens....
ReplyDeleteDrjim, the ones that mostly dropped the D-ring were poorly crimped and were only held on by the varnish they coated the coils in. After many hot/cold cycles, and if the relay was vertical or upside-down, off fell the D-ring. Sure buzzed/chattered loudly!!
DeleteThe little electronics place I worked at in high-school made relays, both AC and DC. The assemblers would stake the ring on the core after the coil bobbin was on, and then put some epoxy on it. I thought the epoxy was overkill due to how securely it was staked on, but the Engineer told me it was there to mitigate any buzzing that might develop with use.
DeleteSo, in legacy aerospace, a legacy item still has stupid issues. First launched (for Atlas V) in 2001 and they're having this issue?
ReplyDeleteValve was probably Made in China...
DeleteIf so, then you can count on prosecution like LE bolts!
DeletePossible if its a spring loaded valve, say a tiny bit of liquid gas seeps past, even clusters of molecules along the polish grain surfaces, or say the seat finish was damaged, even a scratch will create a leak path sometimes, everything leans towards entropy and path of least resistance, the liquid warms up and expands to a gas at the seal surfaces, a frequency might develop which creates rapid open close cycle, don't need much movement it simply finds its own natural frequency and there you have it, begins a pulse which winds up making it buzz.
ReplyDeleteThe spring rate is least at full closure, could then be a defective spring, its weak or the heat treat is defective. Combination of things.
Thanks for the detail, Anon - Drjim and I know this, but "assumed" most readers would figured that out. My bad.
DeleteYou guys see the short stubby vacuum bell SpaceX used on a second stage to save on costs? Guess the copper bells are one of the highest cost parts, and they decided if they are throw aways better in the long run to go short. Good thinking good idea. No part is a good part, or part of a no part.
ReplyDeleteSpaceX hires some scary smart Engineers!
DeleteCompany I worked at, we built rigid tube sets for Pratt-Florida RL-10 engines, every tube for a given engine, shipped in a large crate, ready to bolt on. One of the final inspections was we had this young lady whose specialty was ball checking, each tube had to pass a precision inspection single bearing ball, check for ID and any blockages. The RL-10 uses some rather long 1/4 inch tubes with many bends to get from here to there around all the other componants. The young lady used a cardboard box with all the corners and flaps on the inside taped so when she dropped these tuny balls she would not loose them, for 1/4 in tube the ball was .083" OD, even woth the catch box sometimes itwould get away, if you camn not find the ball you have to check the tube with another ball and or have it radiographic checked, make sure its not lodge stuck in the tube assembly. Well somehow that tiny ball ended up being missed in the tube, passed final inspection, shipped, mounted on an engine, and when they went to test fire that engine that tiny ball got stuck in a shut off valve of all places, and they had a runaway RL-10 only way to turn it off was cutting off the main fuel feeds from the test stand to the engine, something else fudged up on that, and it took awhile to shut the engine down.
ReplyDeleteWhat our guy who was down at the tests for the tube setas told us, the engine ran so long it caused the pond along/below the exhaust path to be sucked dry, they found a deer and a mess of smaller critters, frogs, fish, dead stuck to trees and branches down range. Guess everyone had a good laugh over it. That nice young lady was so embarrassed, rather upset with herself, as she was most conscientious and excellent employee, we all got together got her a card some flowers and a pizza so she felt a little better about it all.
I have copyrighted "If it's Boeing, you ain't going."©
ReplyDeleteI expect to retire on royalties from t-shirt sales alone.
You'll end up being so rich you can buy a ride - on a Dragon Capsule...
Delete