Author Topic: Shuttle Q&A Part 5  (Read 1542529 times)

Offline Danny Dot

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Re: Shuttle Q&A Part 5
« Reply #440 on: 08/25/2009 07:43 am »
Is this what you're looking for?

9:41 pm     Countdown resumes at the T-3 hour mark
12:21 am     Countdown enters a 10-minute hold at the T-20 minute mark
12:31 am     Countdown resumes at the T-20 minute mark
12:42 am     Countdown enters an ~45-min. hold at the T-9 minute mark
1:27:05 am     Countdown resumes at the T-9 minute mark

Yes, thank you.  10 minute hold at T minus 20, 45 minutes at T-9.  How about the T minus 3 hour hold?  How long is it?

Danny
Danny Deger

Online AnalogMan

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Re: Shuttle Q&A Part 5
« Reply #441 on: 08/25/2009 07:47 am »
Is this what you're looking for?

9:41 pm     Countdown resumes at the T-3 hour mark
12:21 am     Countdown enters a 10-minute hold at the T-20 minute mark
12:31 am     Countdown resumes at the T-20 minute mark
12:42 am     Countdown enters an ~45-min. hold at the T-9 minute mark
1:27:05 am     Countdown resumes at the T-9 minute mark

Yes, thank you.  10 minute hold at T minus 20, 45 minutes at T-9.  How about the T minus 3 hour hold?  How long is it?

Danny

2hr 30mins hold at T minus 3 hours.
2hr hold at T minus 6 hours (normally)

Edit: 1 hour hold at T minus 6 hours for this STS-128 24-hour scrub
« Last Edit: 08/25/2009 05:52 pm by AnalogMan »

Offline Hobbs

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Re: Shuttle Q&A Part 5
« Reply #442 on: 08/25/2009 05:34 pm »
During tanking/replenish is the LO2 pumped through the SSMEs and then into the tank or is it sent straight up into the tank with a "trickle" sent through the engines, if its option 2 what percentage of the total flow is sent to the engines?

Offline ChrisGebhardt

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Re: Shuttle Q&A Part 5
« Reply #443 on: 08/25/2009 08:08 pm »
LH2 and LOX are loaded through the T0 umbilicals into the aft of the Orbiter, then up through the porpellant lines and into the respective tanks of the ET.

Offline mkirk

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Re: Shuttle Q&A Part 5
« Reply #444 on: 08/25/2009 08:33 pm »
During tanking/replenish is the LO2 pumped through the SSMEs and then into the tank or is it sent straight up into the tank with a "trickle" sent through the engines, if its option 2 what percentage of the total flow is sent to the engines?

As the oxygen comes in from the Tail Service Mast via the Fill & Drain Lines, it flows into the common LO2 Manifold (that all 3 engines feed from) and through the prevalves and into the engines - while it can flow through the turbo pumps it CAN NOT flow into the cumbustion chamber because the main oxidizer valves are closed at this point.  From the LO2 Manifold the flow of oxygen also goes out through the ET Feedline Disconnect and up the Downcomer (this is the 17 inch feedline you see running up the outside of the ET) and into the bottom of the oxygen portion of the external tank.

Mark Kirkman
« Last Edit: 08/26/2009 03:23 pm by mkirk »
Mark Kirkman

Offline ceepdublu

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Re: Shuttle Q&A Part 5
« Reply #445 on: 08/26/2009 03:45 am »
What does the scrub scenario look like if one of the LH2 fill/drain valves were to get stuck in the closed position?  Wait a week for boiloff via flarestack?

Offline ChrisGebhardt

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Re: Shuttle Q&A Part 5
« Reply #446 on: 08/26/2009 03:54 am »
They said in the presser that they can drain the tank through the PV13 valve... it would just take hours long than usual.

Online butters

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Re: Shuttle Q&A Part 5
« Reply #447 on: 08/26/2009 04:24 am »
If the fill/drain valve issue is an instrumentation problem, what instrumentation would be involved?  Is there any instrumentation within the valve assembly that indicates position, or is valve position derived from pressure transducers in the feedline manifold, external tank, tail service mast, etc.?

Seems to me that if they know the pressures in the LH2 tank and T-0 umbilical, then they should be able to determine the position of the fill/drain valve unless there is an off-nominal leak in the circuit.  So if there's a problem with the valve instrumentation itself (if applicable) or the feedline manifold pressure transducer, then there should be alternative methods of monitoring the valve position.

Offline brahmanknight

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Re: Shuttle Q&A Part 5
« Reply #448 on: 08/26/2009 11:19 am »
Is there a list of the all the Criticality 1 systesms on the space shuttle? 

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #449 on: 08/26/2009 11:23 am »
then there should be alternative methods of monitoring the valve position.

Not viable.  How would position be know with no flow?

Offline joncz

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Re: Shuttle Q&A Part 5
« Reply #450 on: 08/26/2009 03:00 pm »
What does the scrub scenario look like if one of the LH2 fill/drain valves were to get stuck in the closed position?  Wait a week for boiloff via flarestack?

There's an 8-1/2 minute rapid-drain procedure - but it's likely a one-shot deal  :o

Offline ceepdublu

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Re: Shuttle Q&A Part 5
« Reply #451 on: 08/26/2009 03:38 pm »


There's an 8-1/2 minute rapid-drain procedure - but it's likely a one-shot deal  :o
[/quote]

That was actually my initial thought before asking the question... ;)

Offline cabbage

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Re: Shuttle Q&A Part 5
« Reply #452 on: 08/26/2009 09:17 pm »
I notice on another thread that after boiloff they have inerted the tank with helium. Is there a reason for using helium for this rather than (say) nitrogen? Is it a concern that the tank is too cold for nitrogen?

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #453 on: 08/26/2009 09:21 pm »
I notice on another thread that after boiloff they have inerted the tank with helium. Is there a reason for using helium for this rather than (say) nitrogen? Is it a concern that the tank is too cold for nitrogen?

LH2 would condense the N2

Offline ginahoy

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Re: Shuttle Q&A Part 5
« Reply #454 on: 08/27/2009 02:11 am »
My apologies if this has been asked before...

After a 24-hr weather scrub, I'm trying to understand the specific reasons why the vehicle can't remain fueled and then topped off prior to crew arrival the following day. Is it due to the volatility of the liquid hydrogen? Or would it waste too much fuel via boil-off? Or would the ET turn into a huge icicle due as the insulation and tank mass loses all its embodied heat? Are there other factors?

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #455 on: 08/27/2009 04:35 am »
Is it due to the volatility of the liquid hydrogen? Or would it waste too much fuel via boil-off?

Bingo

Offline glen4cindy

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Re: Shuttle Q&A Part 5
« Reply #456 on: 08/27/2009 04:39 am »
What does the scrub scenario look like if one of the LH2 fill/drain valves were to get stuck in the closed position?  Wait a week for boiloff via flarestack?

There's an 8-1/2 minute rapid-drain procedure - but it's likely a one-shot deal  :o

This "8-1/2 minute rapid drain sounds like a "launch" without lighting the SRB's.  But, that is not even a consideration right? Wouldn't that require replacement of the SSME's?

Offline glen4cindy

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Re: Shuttle Q&A Part 5
« Reply #457 on: 08/27/2009 04:42 am »
LH2 and LOX are loaded through the T0 umbilicals into the aft of the Orbiter, then up through the porpellant lines and into the respective tanks of the ET.

Are the T0 umbilicals those grey things that stand up from the MLP behind the wings?

If not, where are they located?

Thanks.

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #458 on: 08/27/2009 04:45 am »
LH2 and LOX are loaded through the T0 umbilicals into the aft of the Orbiter, then up through the porpellant lines and into the respective tanks of the ET.

Are the T0 umbilicals those grey things that stand up from the MLP behind the wings?

If not, where are they located?


Those are the tail service masts, in which the T-0 umbilicals are located

Offline ChrisGebhardt

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Re: Shuttle Q&A Part 5
« Reply #459 on: 08/27/2009 05:00 am »
What does the scrub scenario look like if one of the LH2 fill/drain valves were to get stuck in the closed position?  Wait a week for boiloff via flarestack?

There's an 8-1/2 minute rapid-drain procedure - but it's likely a one-shot deal  :o

This "8-1/2 minute rapid drain sounds like a "launch" without lighting the SRB's.  But, that is not even a consideration right? Wouldn't that require replacement of the SSME's?


He was being facetious.

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