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#40
by
Jim
on 04 Dec, 2014 13:14
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Are the countdown steps of Delta-IV (or any other rocket) public? (at least for last 10-20 minutes)
not anymore. Propriety and ITAR information
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#41
by
newpylong
on 04 Dec, 2014 13:21
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Problems with port and core valve cycling. LOX valves are OK. The problems are with the LH2 valves.
'Sticky' valves from a long pre-launch cold soak?
Concur.
So is the valve not working to spec? Or the spec does not require the valve to work after a long hold? Either one seems odd to me - long holds are hardly an unusual occurance, so it should be covered by the spec. And on the valve side, surely some acceptance test requires it to work after a long cold soak.
You seem like the expert, don't you have the answers?
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#42
by
mcgyver
on 04 Dec, 2014 13:21
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When is next launch window?
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#43
by
enkarha
on 04 Dec, 2014 13:22
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Tomorrow same times I believe.
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#44
by
dl8zc
on 04 Dec, 2014 13:49
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Stupid Question: what are the causes of the limited launch window?
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#45
by
Hog
on 04 Dec, 2014 13:56
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When is next launch window?
Dec 5 12:05 GMT, its a 24 hour recycle.
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#46
by
eywflyer
on 04 Dec, 2014 13:58
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From what I've found online EFT-1 will be the 8th launch of the Delta IV-Heavy. How many scrubs have there been in the previous attempts?
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#47
by
Jim
on 04 Dec, 2014 13:59
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Stupid Question: what are the causes of the limited launch window?
lighting constraints at the launch site and landing area
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#48
by
Svetoslav
on 04 Dec, 2014 14:00
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I hate a very noobish question from earlier today.
Why isn't there strict security for boaters?
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#49
by
Jim
on 04 Dec, 2014 14:03
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I hate a very noobish question from earlier today.
Why isn't there strict security for boaters?
Because it is a large ocean, the US territorial waters are only out to 12 miles and we don't live in a police state
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#50
by
Lee Jay
on 04 Dec, 2014 14:10
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Will this valve problem cause trouble during detanking?
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#51
by
Jim
on 04 Dec, 2014 14:20
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Will this valve problem cause trouble during detanking?
It was a problem with closing, they are open for detanking
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#52
by
mheney
on 04 Dec, 2014 14:23
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I'd presume not - the problem is that it wouldn't fully close. You pump it dry, close other valves up the line, and then vent the tanks to clear out any residuals. Then get they guys with the WD-40 to fix the valves.
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#53
by
LouScheffer
on 04 Dec, 2014 15:24
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So is the valve not working to spec? Or the spec does not require the valve to work after a long hold? Either one seems odd to me - long holds are hardly an unusual occurance, so it should be covered by the spec. And on the valve side, surely some acceptance test requires it to work after a long cold soak.
Thinking about this some more. Surely the valve is designed to work even after a cold soak - it's a known operating condition. And so surely they took at least one valve, soaked it in liquid hydrogen for 6 hours (or whatever the longest cold soak might be) then verified it still worked.
But I guess they don't do this for each valve off the production line, since such a test is cumbersome and expensive. I'd guess they test it at room temperature, or maybe liquid nitrogen temps, and measure the margins. If they are within spec the valve is deemed good to go. (This is what they do for chips, like the ones in your cell phone. They are supposed to work from 0 deg C to 85 deg C, but they don't test every chip for this. Instead they test it at room temp, and if the margins are good enough, then assume it will work at the temperature extremes, based on full-temp-range testing of chips in the lab.)
So what they have now is some case where the valve can pass all tests, with appropriate margins, but still not work right after a long cold soak at liquid hydrogen temps.So in the long run they could test each valve after a cold soak (expensive) or figure out what they can do to reliably predict whether it will work after a long cold soak (could take longer).
But they can't do this by tomorrow. And swapping out the valves might not help, either, if 2 out of 3 valves show this problem. I'd doubt they can load the liquid hydrogen later - this seems like a huge change in procedure. So I suspect all they can do for tomorrow is have their valve-banging procedures at the ready, and hope for a short (if any) hold.
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#54
by
Coastal Ron
on 04 Dec, 2014 15:55
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Thinking about this some more. Surely the valve is designed to work even after a cold soak - it's a known operating condition. And so surely they took at least one valve, soaked it in liquid hydrogen for 6 hours (or whatever the longest cold soak might be) then verified it still worked.
But I guess they don't do this for each valve off the production line, since such a test is cumbersome and expensive.
And the need to replace a failed valve after a scrub is not expensive?
I'd be surprised if the valves are not tested multiple times over their operating ranges before leaving the factory. That said, just because they are tested doesn't mean they can't have issues later, but two at the same time is not a good sign. I'm sure ULA will have a chat with their valve supplier...
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#55
by
Coastal Ron
on 04 Dec, 2014 16:01
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A second article from Businessweek with an interesting claim:
Businessweek -
Why NASA's Orion Spacecraft Looks So Familiar"
Orion is roughly three times larger than the Apollo crew module, built to carry four astronauts as far as Mars, a 70-million mile round-trip journey that could take as much as 23 months."
It's amazing the pervasiveness of this meme.
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#56
by
Oberon_Command
on 04 Dec, 2014 16:16
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A second article from Businessweek with an interesting claim:
Businessweek - Why NASA's Orion Spacecraft Looks So Familiar
"Orion is roughly three times larger than the Apollo crew module, built to carry four astronauts as far as Mars, a 70-million mile round-trip journey that could take as much as 23 months."
It's amazing the pervasiveness of this meme.
LOL - that same article has a picture of the Orion mockup on a truck in front of the White House tagged as a picture of "the United Launch Alliance Delta 4 rocket". I didn't even bother reading the rest of the article.
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#57
by
I14R10
on 04 Dec, 2014 16:25
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What is the procedure now - are they going to replace the valve or try and make it work?
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#58
by
MattMason
on 04 Dec, 2014 16:30
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A second article from Businessweek with an interesting claim:
Businessweek - Why NASA's Orion Spacecraft Looks So Familiar
"Orion is roughly three times larger than the Apollo crew module, built to carry four astronauts as far as Mars, a 70-million mile round-trip journey that could take as much as 23 months."
It's amazing the pervasiveness of this meme.
The sadder part is that NASA itself perpetuates that meme, oversimplifying the fact that Orion is only the general command and reentry spacecraft, not the mission extended excursion mode.
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#59
by
Jim
on 04 Dec, 2014 16:36
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Valves aren't going to be replaced