Author Topic: Shuttle Q&A Part 5  (Read 836871 times)

Offline oxford750

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Re: Shuttle Q&A Part 5
« Reply #40 on: 06/16/2009 01:18 AM »
 With regard to OMS assist, I thought I read some where that the OMS engine could only work in the vaccum(spel) of space, or am I getting RCS thusters and OMS engine mixed up?

Oxford750

Online Jorge

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Re: Shuttle Q&A Part 5
« Reply #41 on: 06/16/2009 01:56 AM »
With regard to OMS assist, I thought I read some where that the OMS engine could only work in the vaccum(spel) of space, or am I getting RCS thusters and OMS engine mixed up?

The OMS does have a minimum altitude, but IIRC it's 70,000 ft. OMS assist occurs after staging, which is around 150,000 ft.

The question does come up a lot but usually in the context of "can you fire the OMS on the ground"...
JRF

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Re: Shuttle Q&A Part 5
« Reply #42 on: 06/16/2009 01:58 AM »
I guess what I'm wondering is what gives the greater benefit, loading those OMS tanks with fuel and then burning them, or not filling the amount that would be burned.

I assume from your answer that it's the former.

That is correct, and that is why OMS assist is done.

IIRC, the OMS tanks have to be filled completely (or as close to full as possible) because there is no sensor gage to tell you how much prop is in them.  They have to fill OMS tanks completely to know with a high degree of certainty how much prop is in them at launch.  Then, you burn what you don't need for the miss during ascent -- OMS assists -- and use calculations once on orbit to approximate how much OMS prop is left in the tanks after each firing of the OMS engines.

Am I remember incorrectly?

You're remembering incorrectly. While I don't know the details of OMS fill on the ground, I do know that the OMS tanks do have quantity gauges. The gauges require the propellant to be "settled" at the rear of the tanks in order to work - which is true on the ground, or during powered flight.
JRF

Offline oxford750

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Re: Shuttle Q&A Part 5
« Reply #43 on: 06/16/2009 03:14 AM »
Thanks Jorge.


Oxford750

Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #44 on: 06/16/2009 07:02 AM »
They're all helium, no?  The Air Liquide GN2 line is kept at 6-7 ksi.  No real need for a plenum.

It's been a while since I was out there, but my foggy memory is that the tanks contain, not just helium, but also nitrogen and breathing air (for SCAPE operations and possibly crew cabin supply). But I could be wrong (happened once or twice before)......

Thanks for the replies, guys.
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Offline ChrisGebhardt

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Re: Shuttle Q&A Part 5
« Reply #45 on: 06/16/2009 08:12 AM »
Thanks Philip and Jorge.  I think Philip is correct, I'm thinking PRSD.

After some many days of dealing with GUCP and range schedules I guess my Orbiter propellant tank knowledge slipped a little.

Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #46 on: 06/16/2009 01:45 PM »
Padrat, you got to be up close and personal with it the last couple days or so. What is the large black rectangle to the left of the GUCP? It looks to be about 5 ft high, maybe 6 ft across?

(not exactly singling you out. anyone can answer :) )

thanks
« Last Edit: 06/16/2009 01:45 PM by usn_skwerl »
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Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #47 on: 06/16/2009 02:06 PM »
Nice. Thanks for the quick replies. Struck me odd to see a garage door (or hiding spot for lesser motivated employees) up so high.
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Offline Mach25

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Re: Shuttle Q&A Part 5
« Reply #48 on: 06/16/2009 05:34 PM »
Banjul, also no longer used, is Yundum International Airport. NASA built a dedicated building at each of those locations.

STS-125 was told "negative Moron, select Banjul." Wouldn't that imply it's still used?

Selecting Banjul onboard would cause onboard guidance to steer toward that site in the event a TAL abort were declared.  The more likely actual landing site in that case would be Amilcar, Cape Verde, which is a little "short" of the Gambian coast but along the same trajectory.

Online rdale

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Re: Shuttle Q&A Part 5
« Reply #49 on: 06/16/2009 06:18 PM »
Thanks for clarifying - that makes more sense.

Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #50 on: 06/17/2009 12:31 AM »
Can the shuttle launch in rain (not thunderstorms)? And does it go through mach 5 before 60,000 ft or above it?
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Offline psloss

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Re: Shuttle Q&A Part 5
« Reply #51 on: 06/17/2009 12:35 AM »
Can the shuttle launch in rain (not thunderstorms)?
No.  Flight through precip is a violation of weather rules.  (In fact, they won't even ferry an orbiter through rain if they can avoid it.)
« Last Edit: 06/17/2009 12:36 AM by psloss »

Offline Lee Jay

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Re: Shuttle Q&A Part 5
« Reply #52 on: 06/17/2009 12:35 AM »
Can the shuttle launch in rain (not thunderstorms)? And does it go through mach 5 before 60,000 ft or above it?

No.  Way above.

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #53 on: 06/17/2009 12:40 AM »
Can the shuttle launch in rain (not thunderstorms)? And does it go through mach 5 before 60,000 ft or above it?

rain on tiles is like water on sugar cubes

Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #54 on: 06/17/2009 12:41 AM »
I wasn't sure about rain during launch, due to the weatherproofing on the tiles. Thanks gentlemen.
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Offline Lee Jay

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Re: Shuttle Q&A Part 5
« Reply #55 on: 06/17/2009 12:42 AM »
Can the shuttle launch in rain (not thunderstorms)? And does it go through mach 5 before 60,000 ft or above it?

rain on tiles is like water on sugar cubes

I thought the orbiter regularly gets soaked at the pad and the tiles are waterproofed during each OPF flow.  I also thought the issue was *high velocity* rain drops causing mechanical (as opposed to chemical like water dissolving sugar) damage to the TPS.  Am I wrong?

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #56 on: 06/17/2009 12:44 AM »
I wasn't sure about rain during launch, due to the weatherproofing on the tiles. Thanks gentlemen.

Waterproofing is to keep them from absorbing water while on the ground.  The internal water would turn to steam during ascent and entry and pop off parts of the tiles

Offline usn_skwerl

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Re: Shuttle Q&A Part 5
« Reply #57 on: 06/17/2009 01:17 AM »
Thanks for the explanation Jim. I didn't think the heat got between the tiles enough to cause steam.
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Offline oxford750

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Re: Shuttle Q&A Part 5
« Reply #58 on: 06/17/2009 02:02 AM »
Hi folks:

I am sitting sitting here in Vancouver, Canada watching launch prep for STS-127 -hope she goes- and some questions came to mind.

1) How do they chill the lines for tanking (I didn't think you could put anything in the lines prior to tanking as they go to the LH2, LOX tanks)?
2) Why does the GUPC vent line come off at ignition and not when the "beanie cap" comes off as I assume both tanks need to be repressurized?
3)  What is the difference between fast fill and slow fill?
4) Why are the LH2 tank and LOX tank filled at different times?

Thanks
Oxford750

Offline Jim

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Re: Shuttle Q&A Part 5
« Reply #59 on: 06/17/2009 02:07 AM »
Hi folks:

I am sitting sitting here in Vancouver, Canada watching launch prep for STS-127 -hope she goes- and some questions came to mind.

1) How do they chill the lines for tanking (I didn't think you could put anything in the lines prior to tanking as they go to the LH2, LOX tanks)?
2) Why does the GUPC vent line come off at ignition and not when the "beanie cap" comes off as I assume both tanks need to be repressurized?
3)  What is the difference between fast fill and slow fill?
4) Why are the LH2 tank and LOX tank filled at different times?

1.  by slowly running the propellants through them
2.  GH2 is flammable and you don't want it venting around the pad.  If there is a scrub, the vent line still needs to be in place
3.  Flow rates
4.  Safety.  Just keeping the hazard level as low as possible

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