Justin Wheat - 18/12/2007 9:53 PM
Lots of speculation questions being asked
And Hale is close to losing his patience! Though smiling at the same time.
Vent arm now away from the tank
Chris Bergin - 18/12/2007 11:24 AM
L2 sources note initial TDR data point to the problem being with the LH2 Feedthrough Connector.
This - at this stage - would confirm the engineering thought process on this prior to the tanking test:
http://www.nasaspaceflight.com/content/?cid=5309
Check the time Chris posted this.
Other sites now just starting to publish the same thing over four hours later.
This is why this site is the best and L2 is where you are on the frontline, as there's mbs of presentation and images on there days ago!
I love this site.
Thanks Rob. All thanks to the sources, who are excellent.
Major cross agency/cross contractor meeting concluded.
Info and presentations arriving into L2, with lots of options.
All appear to point at R&R, all allow for Jan 10 launch date. Will collate and write up tomorrow when it's all in.
So that's R&R at the pad? given that roll-back/repair/roll-out/pad flow wouldn't normally be possible in that timeframe?
ichilton - 19/12/2007 2:18 AM
Hi,
What's R&R?
To help with abbreviations - click the "acronyms" link above...
Eight mitigation options on the connector have been created by the ET folks, as per L2 slides, etc.
Three allow for Jan 10 launch - possibly option 4 too.
The rest range to delaying to to around mid Feb.
PRCB to decide on which forward plan to take (so around 24/48 hours until we know for sure). We cover PRCB extensively on L2, so: Two articles, one on the options, one on which they take to come this week.
Was the tanking test nominal?
I just woke up right now...
Let's hope we launch on schedule...
Transcript from yesterday's presser:
Participant
Wayne Hale – Manager, SSP
Opening
Today did a tanking test with special instrumentation to look at the wiring on the liquid hydrogen low level fuel circuits – I was quite worried that everything would work perfectly and we’d be unable to find where the problem lies, but fortunately we had some problems
-- saw three separate problems – there are five sensors, four at one level and one slightly higher – today we had problems on three of the sensors and captured the data, which indicates we have a problem at the feed-through – open circuits are occurring at the very cold temperatures
We had ECO sensors 2 and 3 fail open circuits very briefly, for two to four seconds each – then sensor 2 remained find for the rest of the test, and sensor 3 had problems again when we started to drain the test – sensor 1 indicated an open circuit and stayed that way until well after the tank was dry – all three have returned to working now
-- some of the data is still being collected – they’re looking at the recorded voltages, the TDR information, literally gigabytes of information – the preliminary indication, though, is that we have a problem at this connector
-- we’ve seen all five of the sensors misbehave now in one way or another, and the pass-through connector is the only thing they have common
-- the plan tomorrow is to come in and talk to program management in a formal way with recommendations for forward work – there are a number of options they may recommend, but we’re going to do this very systematically
"We probably owe an apology to the folks that make the sensors. Today the sensors themselves were exonerated. This is clearly a problem with the wiring upstream as it comes out of the tank."
-- I don’t know how this will affect the launch date yet – we need to get to the bottom of this, fix it and fly safely through the rest of the program.
Q&A
Q: How old is this equipment? Might that be a factor? And what is the availability of replacement hardware?
we’ve been very concerned about aging – the equipment is less than 10 years old, which is young by shuttle standards, but we have a team looking at that
-- everything on the shuttle is custom made – I don’t have a timeline on replacing it, but there are certain things we might be able to do to make the connection more robust – and it could be an installation problem – we could be pulling a vacuum with the cold temperatures and pulling on the connections
-- we’ve got more work to do before we can tell you exactly what’s at the bottom of the problem and what we need to do, but manufacturing of these parts can be turned around in very short order
Q: What do you mean by an open circuit? It’s a place where you’re not getting a contact?
yes – in some of these circuits we’ve lost conductivity for brief periods of time and sometimes for longer periods – and it happens when it’s at these very low temperatures, so we know it has something to do with temperature
-- and an open circuit is just like it works in your light bulb – if the circuit’s not closed, it won’t light up
Q: is this outside or inside the tank?
by the nature of it, it goes through the tank – that’s why we call it a pass-through connector, part of it is inside and part of it is outside
-- it would take a week to 10 days to get to the part outside for a change out – the part inside would mean you have to go inside the tank through the man hole, and that would take longer
-- exactly what we have to do and where we need to do it is work ahead, but I’m just pleased as punch to know that we can narrow it down to this area
Q: How big is the connector?
if you think about a big electrical plug like you might see in industrial lighting or the lights you might have in a television studio – there are three major parts: the sockets on the inside, the sockets on the outside and the pass through part which is a metal, glass and pin arrangement
Q: Can you make this repair at the pad? And is this a new phenomenon or is this what caused the earlier problems?
I don’t know the answer to either of those
Q: Do you think another cryo test will be required at some point? Or will your launch attempt work for a fueling test? And are you still optimistic of getting to your three out of four criteria for launch?
we’ve stood down for the near-term tanking, which we’d planned if we’d had a problem not related to the ECO sensors – whether we think about this for 48 hours and want to come back and do another test is work ahead of us – there are cryogenic tests going on as we speak, though, at Marshall and Kennedy, and they’ll continue
-- I suspect part of the way to get to the bottom of this is take apart what we have on the vehicle, take a close look at it and decide how to go forward
Q: Is there a way to fix it without a tanking test?
yes, it’s possible, hypothetically – what I need for the team to do is go home and think about it – we’ll come back tomorrow and talk about options, then there will be more tests in the future
"I’d like to fly as soon as possible, but above that we need to fix this problem."
-- we won’t be driven by a particular launch date, but by the data
-- the good thing is that we know exactly what we need to work on now – this is a problem that’s solvable – I don’t know how long it will take, but I’m confident that the team can now come up with a good solution
Q: Are the parts installed at KSC or in New Orleans?
in New Orleans – but let me hasten to say that we don’t know that there was anything wrong with how it was installed – we’ve tried to improve the way we install these, and perhaps in that process we somehow made it worse – we need to do the investigative work to find out what caused these problems
Q: Was there anything in the data that would influence the rationale for wanting four of four for launch or three of four?
that’s putting the cart before the horse – we need to fix the problem, and then depending on how good we feel about that fix, we’ll address what the launch criteria should be – you might want to require more to work than you really need if you don’t feel very confident in the fix – if you do feel confident, you might be willing to go back to the old requirement of three of four
Q: Is it practical to think this problem can be fixed in time for a launch of Jan. 10?
the program has been asked to assemble the space station – we’d like to do that as quickly as we can, so long as it’s safe – we’ll follow this trail where it leads it and we’ll fix it and then we’ll go fly
"I’m not worried about that. What we need to do is take it one step at a time."
Q: Did the time-domain reflectometer pulse generator help you determine the source of the problem?
I’m not the technical expert, but my understanding is it sends a small electrical pulse down the line and based on when the reflection comes back, it tells you where the resistance in the line changes – based on the time, it knows how far down the wire you have your open circuit
-- unfortunately the resolution is not good enough to tell you whether it’s in the inside or outside part of the connector
Q: Are these pieces made in lots?
the ET is the only part of the shuttle that we don’t get back – every other part, we tear down and examine every streak and smudge, which contributes to safety – so all you’ve got is the data that came down the telemetry stream and the pictures you get back, so you have to make a lot of inferences
"So we’ve probably been chasing some rabbit trails. Now we have a different way of looking inside this tank, electrically, and now we have some more information that’s been very helpful."
Chris Bergin - 19/12/2007 8:50 AM
Transcript from yesterday's presser:
Thanks Chris... This was very helpful as John's site is still down and some folks couldn't catch it live
Thanks for the transcript Chris, good work, especially if you had to type it up. After I read your post, I listened to it at
http://www.space-multimedia.nl.eu.org/index.php?option=com_content&task=view&id=3202&Itemid=1 . You earlier mentioned that Hale got frustrated, but I didn't sense that in the video, except for the quip that the feed through connector is a feed through, i.e. both in and outside the tank!
One question I would like to see posted: What were the original requirements for the feed-through connector with regard to cryogenic environment and cycling, and what are the features in the design that meet these requirements? For example, is there a preload required in the sockets, both for room temp and for cryo? Surely there aren't wipers or springs in the pins, but I would think the designers included some feature to deal with thermal contraction of the pins, and also the possibility for the air trapped inside to freeze? Are there o-rings or wipers or silicone on each pin, or are they bonded to the glass? Are they installed in a vacuum or does air just sit down inside all the time? I've tried to find a drawing, but can't.
Rainer has a great post on the ECO system at
http://spacelaunch.gerhards.net/2007/12/space-shuttle-eco-sonsors-in-depth-view.html but admits that he couldn't find drawings of the connectors.
Oh, those pics! Guess I'll go get my wallet. Thanks for the pointer. BTW, could you make the picture captions searchable?
Still, I'd like to know what the original designers thought of this possibility at the time.
mwfair - 19/12/2007 4:49 PM
BTW, could you make the picture captions searchable?
Yeah, I'll see if I can add key words into the body of the article that would make such a search easier. Good call! For the interim, Searching LH2 and Connector in the news site search box should bring up all articles we've done on it (and thus the images associated).