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#3460
by
eric z
on 26 Aug, 2017 12:58
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Hi Dosobo, Welcome and have fun here! You ask a great question...sometimes we can get so lost in the trees, we don't see the forest, or vice-versa! There are many reasons we are where we are today, and you are about to be flooded with a lot of well-informed opinions, and maybe even some not-so well informed. Let's see what you think a few pages into this thread after getting hopefully thoughtful and diverse views. Keep an open mind, I've certainly had my eyes opened here, and have changed my mind on some things, but also have renewed strength in other things I believe in. Also, if you can, and maybe you already have, join L2 for even more extensive FUN!
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#3461
by
Weasel Pilot
on 15 Sep, 2017 22:38
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Both the LOX tank and the LH2 tank had four sensors at the 100% level - a low sensor, two (assumedly) median sensors and a high sensor (plus other sensors at the 98% and overfill levels). Does anybody know how much space there was between the 100% low sensor and the 100% high sensor? In other words how much vertical space did 1% of propellant take up in the tank? Obviously due to the tank shapes this would vary with location in the tank, but at the top (100% level) does anyone know what this was?
Dave
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#3462
by
brickmack
on 15 Sep, 2017 23:23
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6 inches for the LOX tank, 8 for the LH2 tank
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#3463
by
Weasel Pilot
on 20 Sep, 2017 00:16
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Thanks! Awesome response!!
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#3464
by
Weasel Pilot
on 20 Sep, 2017 17:58
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Which begets another question...or actually five -
1. The tank fill schedule (as I understand it) was low flow to 2% then high flow (5,000 gal/min) til 98% then low flow again to 100%
a. What was the low flow rate?
b. How do it know? No 2% sensor...
2. The feed lines openings were offset (as I measure it, 10 degrees for LOX and 6 degrees for LH2).
a. I ASSUME that this was to make up for gravity effect, si or no?
b. Why are these not the same? (density delta twix LO2 & LH2?)
c. Was the offset towards or away from the orbiter?
Dave
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#3465
by
mkirk
on 20 Sep, 2017 18:52
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Which begets another question...or actually five -
1. The tank fill schedule (as I understand it) was low flow to 2% then high flow (5,000 gal/min) til 98% then low flow again to 100%
a. What was the low flow rate?
b. How do it know? No 2% sensor...
Dave
There is a lot packed into those questions, so let me take the first one since I can answer that pretty quickly and easily. If someone else doesn't beat me to it, I will try and come back with a good answer to the second question later.
Slow Fill for LO2 to 2% level was based on time (about 11 minutes) at a flow rate of about 270 gallons per minute.
Fast Fill for LO2 to 98% level sensor was at around 1300+ gallons per minute.
LO2 Topping occurred at approximately 800 gallons per minute.
LO2 Replenish was in the neighborhood of 100 gallons per minute.
The launch vehicle was "designed to accept" 5000 gallons of LO2 per minute. This was from a DOD requirement for so called "rapid response" launching of the shuttle. However, the facility at KSC was only capable of delivering about 1400 gpm.
Slow Fill for LH2 to 5% occurred at a flow rate of 1200 gallons per minute until the 5% sensor was wet.
Fast Fill commenced at around 6900 gallons per minute until about the 85% level, then switched to "Reduce Fast Fill" until the 98% sensors were wet.
LH2 Topping to the 100% sensor occurred at about 600 gallons per minute.
LH2 Replenish was approximately 200 gallons per minute.
Mark Kirkman
Space Shuttle Hugger and NASA Geek
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#3466
by
Jim
on 20 Sep, 2017 19:58
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2. The feed lines openings were offset (as I measure it, 10 degrees for LOX and 6 degrees for LH2).
a. I ASSUME that this was to make up for gravity effect, si or no?
b. Why are these not the same? (density delta twix LO2 & LH2?)
c. Was the offset towards or away from the orbiter?
Dave
No, they were offset due to orbiter hanging off the side of the ET and creating an offset CG and hence, the centerline of thrust was not parallel to the centerline of the ET
Towards the orbiter
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#3467
by
Weasel Pilot
on 21 Sep, 2017 20:01
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Thanks again! Excellent response/info.
I'm trying to get my (very) limited grey matter wrapped around the offset CG thing - I realize why the CG was offset, but did the offset cause/require a pitch that in turn caused the feed ports to be "canted"?
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#3468
by
wolfpack
on 21 Sep, 2017 20:16
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Thanks again! Excellent response/info.
I'm trying to get my (very) limited grey matter wrapped around the offset CG thing - I realize why the CG was offset, but did the offset cause/require a pitch that in turn caused the feed ports to be "canted"?
Thrust (acceleration) vector. It's not "straight up" through the ET.
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#3469
by
Jim
on 22 Sep, 2017 13:22
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Thanks again! Excellent response/info.
I'm trying to get my (very) limited grey matter wrapped around the offset CG thing - I realize why the CG was offset, but did the offset cause/require a pitch that in turn caused the feed ports to be "canted"?
If the thrust vector does not go through the CG, then there is a moment and the vehicle rotates.
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#3470
by
DaveS
on 28 Sep, 2017 03:21
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For the first few shuttle flights, the CDR executed a +Y translation following the normal +Z translation away from the ET. My question is, when did the +Y translation morph into the +X translation maneuver we’re familiar with?
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#3471
by
Archibald
on 30 Sep, 2017 15:21
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Why didn't the shuttle external tank have LOX/LH2 common bulkhead - unlike Saturn S-II ? they were of similar sizes and volumes.
I thought it could have made the E.T lighter, helping the shuttle performance a little ? by 1979 the Air Force was considering strapping Titan engines or solid rocket motors to improve performance.
Could a common bulkhead external tank have been fitted to shuttles as an upgrade ?
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#3472
by
Welsh Dragon
on 30 Sep, 2017 16:58
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SRB thrust beam needed to go between the tanks, didn't it? Guess you could have made a circumferential thrust ring of some description, but that would probably wipe out the weight saving of the common bulkhead.
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#3473
by
Jim
on 30 Sep, 2017 23:03
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Why didn't the shuttle external tank have LOX/LH2 common bulkhead - unlike Saturn S-II ? they were of similar sizes and volumes.
I thought it could have made the E.T lighter, helping the shuttle performance a little ? by 1979 the Air Force was considering strapping Titan engines or solid rocket motors to improve performance.
Could a common bulkhead external tank have been fitted to shuttles as an upgrade ?
Those were NASA studies
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#3474
by
penguin44
on 01 Oct, 2017 07:45
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Recently was looking at old mission pictures and the images of Challenger post landing and actually in the preflare on 61a gave me a start! The browned burn from nose cap up to the cabin window was striking. I've never seen the shuttle look like that in that area. Was is a different reentry plan? High inclined orbit?
My other question was regarding I believe sts 8 or maybe 9. I read that there was tile slumping. I don't know what that is and what would cause it?
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#3475
by
Jim
on 02 Oct, 2017 00:26
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Recently was looking at old mission pictures and the images of Challenger post landing and actually in the preflare on 61a gave me a start! The browned burn from nose cap up to the cabin window was striking. I've never seen the shuttle look like that in that area. Was is a different reentry plan? High inclined orbit?
No, just waterproofing material burning off. no different entry
My other question was regarding I believe sts 8 or maybe 9. I read that there was tile slumping. I don't know what that is and what would cause it?
I believe it was in the elevon area. Slumping is melting.
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#3476
by
DaveS
on 02 Oct, 2017 01:06
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Recently was looking at old mission pictures and the images of Challenger post landing and actually in the preflare on 61a gave me a start! The browned burn from nose cap up to the cabin window was striking. I've never seen the shuttle look like that in that area. Was is a different reentry plan? High inclined orbit?
No, just waterproofing material burning off. no different entry
Yes. What they used pre-Challenger was stock 3M ScotchGuard that was sprayed directly onto the orbiter. It was later found that the ScotchGuard wasn’t working too well with the adhesive used to bond the tiles to the orbiter. This caused alot tiles to debond and was what was really behind the “TPS issues” with Challenger that forced her substitution with Discovery for STS-51C. In fact the problems were so severe that they removed Challenger’s original body flap and used the one intended for Atlantis. The body flaps were never changed back prior to the loss of Challenger so even to this day, Atlantis still have the refurbished body flap from Challenger.
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#3477
by
penguin44
on 02 Oct, 2017 07:20
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Great, thanks for the quick response gang! I knew someone here had the answer. I love this site.
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#3478
by
brickmack
on 02 Oct, 2017 16:03
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Neat. Was there any other major hardware from Challenger/Columbia that made it to the end of the program? I seem to recall something about a custom payload mounting structure actually being recovered from Columbia's debris and studied for use on a later mission, don't think it happened though
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#3479
by
Fequalsma
on 03 Oct, 2017 00:39
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Here is a link to an AIAA paper on the Orbiter TPS:
https://arc.aiaa.org/doi/abs/10.2514/6.2011-7308that Wayne Hale also mentioned in his L2 post:
https://forum.nasaspaceflight.com/index.php?topic=29231.msg1611589#msg1611589Yes. What they used pre-Challenger was stock 3M ScotchGuard that was sprayed directly onto the orbiter. It was later found that the ScotchGuard wasn’t working too well with the adhesive used to bond the tiles to the orbiter. This caused alot tiles to debond and was what was really behind the “TPS issues” with Challenger that forced her substitution with Discovery for STS-51C. In fact the problems were so severe that they removed Challenger’s original body flap and used the one intended for Atlantis. The body flaps were never changed back prior to the loss of Challenger so even to this day, Atlantis still have the refurbished body flap from Challenger.
