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#2640
by
sivodave
on 20 Jun, 2012 08:34
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Hi all.
a question regarding the HAC. Why at the beginning the HAC was a cylinder and and not a cone? and also why for the OFT missions the HAC (which was a cylinder) was flown following a straight-in approach and not an overhead approach?
Thanks very much
Davide
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#2641
by
JayP
on 22 Jun, 2012 21:24
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Hi all.
a question regarding the HAC. Why at the beginning the HAC was a cylinder and and not a cone? and also why for the OFT missions the HAC (which was a cylinder) was flown following a straight-in approach and not an overhead approach?
Thanks very much
Davide
Probably to make it easier for the crew if they lost stearing commands on the HSI needles and had to manually navigate the approach using the TACANs. A cylindrical HAC is functionaly similar to a DME arc approach.
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#2642
by
sdsds
on 07 Jul, 2012 02:10
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(Apologies in advance if this has been asked and answered previously.)
What were the planned and actual maximum values of dynamic pressure during any Shuttle launch? What was the design limit? How does that compare to the planned, max, and design limit for Apollo?
EDITs: The graph at
http://www.aerospaceweb.org/question/aerodynamics/q0025.shtml seems to show Shuttle max Q values of approx. 700 lb/ft
2.
"Apollo by the numbers" gives max-q values also in lb/ft
2 of
Apollo 7 665.60
Apollo 8 776.938
Apollo 9 630.73
Apollo 10 694.232
Apollo 11 735.17
Apollo 12 682.95
Apollo 13 651.63
Apollo 14 655.80
Apollo 15 768.58
Apollo 16 726.81
Apollo 17 701.75
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#2643
by
Kyra's kosmos
on 13 Jul, 2012 18:38
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Could anyone please positively identify the purpose of the unusual lockers MF710 and MF71M on the STS-27, 30, 32, 34, and 36 missions ?
Ive attached a collage from the mission videos.
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#2644
by
sivodave
on 14 Jul, 2012 09:14
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Hi all.
A question regarding TPS on Columbia. Why throughtout the program up to the last mission the LRSI tiles on the nose and upper wing surface where not replaced by the AFRSI as in the other Orbiters?
And also why were the black tiles kept in place on the glove area of the wings?
Thanks very much
Davide
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#2645
by
Jim
on 14 Jul, 2012 12:28
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Hi all.
A question regarding TPS on Columbia. Why throughtout the program up to the last mission the LRSI tiles on the nose and upper wing surface where not replaced by the AFRSI as in the other Orbiters?
And also why were the black tiles kept in place on the glove area of the wings?
Thanks very much
Davide
No need to. Was just cheaper to leave as is.
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#2646
by
Ronsmytheiii
on 14 Jul, 2012 15:24
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And also why were the black tiles kept in place on the glove area of the wings?
From pg 169 of this thread:
The black chine areas on Columbia were to minimize on-orbit thermal stresses on the underlying structure; later vehicles incorporated structural changes that made the extra thermal absorption unnecessary.
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#2647
by
mgfitter
on 14 Jul, 2012 20:42
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Can anyone tell me what the technical reason(s) were for the Shuttle External Tank to have a limit of 13 cryo/pressure cycles?
I guess it has to do with crack behavior in the Al and Al-Li materials used for the primary tank skins, but I can't find any reference (even in the SLWT handbook) to which specific element on the tank was responsible for the limitation. Can anyone here shed some light? Jim?
-MG.
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#2648
by
Fequalsma
on 15 Jul, 2012 12:30
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al-li fracture mechanics
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#2649
by
sdsds
on 16 Jul, 2012 03:39
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I speculate the External Tank cycle limit, and maybe other limits, were fundamentally due to the disposal without recovery of the ET for each flight. Without the ability to examine the tanks after recovery it was never possible to say, "Oh, we have plenty of margin here" or, "Ooh, we've just been getting lucky there!"
Take for example the STS-133 stringer issue. In a sense we got lucky the foam cracked, leading to the investigation which showed the trouble with the underlying stringers. But did anyone ever estimate how many prior tanks were launched with cracked stringers which were never noticed because there were no cracks in the covering foam?
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023677_2011024985.pdf
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#2650
by
mgfitter
on 16 Jul, 2012 12:03
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So that suggests that somewhere in their archives NASA has some detailed test data that shows Al-2219 and Al-Li 2195 in a given thickness develops a certain amount of crack behavior when subjected to n cycles of pressure/cryo exposure.
Assuming you have access to that sort of data, what is the typical solution if you need to increase the number of safe cycles? Is it mostly a question of thickening the material up and just taking the weight penalty?
-MG.
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#2651
by
vulture4
on 16 Jul, 2012 12:28
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So that suggests that somewhere in their archives NASA has some detailed test data that shows Al-2219 and Al-Li 2195 in a given thickness develops a certain amount of crack behavior when subjected to n cycles of pressure/cryo exposure.
Assuming you have access to that sort of data, what is the typical solution if you need to increase the number of safe cycles? Is it mostly a question of thickening the material up and just taking the weight penalty?
-MG.
Aluminum alloys always tend to have a fatigue limit based on the number of cycles they are exposed to a given level of cyclic stress. If a crack develops stress is concentrated at its tip and the crack propagates. Increasing thickness in high-stress areas and/or checking carefully for cracks are the only general countermeasures I am aware of, though careful avoidance of corrosion and crack-initiating stress concentrations can help.
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#2652
by
Fequalsma
on 19 Jul, 2012 23:38
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Fracture Control Methodology for the Space Shuttle Aluminum-Lithium External Tank
Wells, Douglas N., NASA Marshall Space Flight Center, USA; McGill, Preston B., NASA Marshall Space Flight Center, USA; Elfer, Norman C., Lockheed Martin Michoud Assembly Facility, USA; Faile, Gwyn C., NASA Marshall Space Flight Center, USA
ASTM 33rd National Symposium on Fatigue and Fracture Mechanics, 26 Jun. 2001, Moran, WY, USA; Sponsored by American Society for Testing and Materials, USA
The Space Shuttle External Tank (ET) serves as the structural centerpiece of the Space Shuttle system, connecting the Solid Rocket Boosters and the Orbiter while carrying 730 000 kg of propellants for the main engines. Due to the size and criticality of the structure, the ET presents a tremendous challenge for implementing a complete fracture control program. Typical approaches to pressure vessel fracture control are inadequate for the structure due to a combination of low attainable proof factor, extremely short cyclic mission life and nonlinear material behavior. Fracture control for the ET is empirically based and established via mission-specific testing, proof test, nondestructive evaluation, and process control. A recent redesign of the tank incorporating aluminum-lithium alloys has presented unique challenges to the established ET fracture control methodology. This paper describes the fracture control approach for the ET and the adaptation of methodologies for the aluminum-lithium redesign. The described approach can be applied to any fracture critical structure with short mission life and operational stresses which approach the capability of the material.
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#2653
by
STS-85
on 24 Jul, 2012 19:33
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Correct me if I'm wrong.. but was STS-41G the only flight to make a LEFT overhead turn around the HAC to runway 33 at KSC? And STS-79 the only flight to make a RIGHT overhead turn to runway 15?
Or were the others that had the unusual approach?
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#2654
by
wolfpack
on 26 Jul, 2012 17:29
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I'm not enough of a rocket scientist to crunch the numbers, so I'll ask.
How much of a payload increase to ISS orbit would an STS with 3 SSME's at 109% bring?
Then, add 5-seg SRB's to the 109% SSMEs, and how much does it increase (assuming the stack can take those loads)?
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#2655
by
alk3997
on 27 Jul, 2012 03:55
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I'm not enough of a rocket scientist to crunch the numbers, so I'll ask.
How much of a payload increase to ISS orbit would an STS with 3 SSME's at 109% bring?
Then, add 5-seg SRB's to the 109% SSMEs, and how much does it increase (assuming the stack can take those loads)?
I seem to remember that 3 engine 109% with a superlightweight tank would have been beyond the attach point's capabilities. You might be able to extrapolate if someone remembers the STS-61F/G increase for Centaur at 109%. Of course the Centaur flights would have used a lightweight tank, so that answer really isn't accurate and they didn't fly to 51.6 degrees or carry that particular amount of OMS prop or insert to as high of an apogee...
5-seg SRBs would have been a new outer-moldline for the stack. It would have had to been analyzed to determine how much dynamic pressure would have been allowed and therefore it isn't really possible to say how much of a payload increase. It isn't just making the structure lighter that is needed to increase payload weight. You really have to do the engineering to determine it.
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#2656
by
DaveS
on 12 Aug, 2012 20:13
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I have read somewhere that during Approach&Landing the speedbrake closed setting is fixed at 15%. Is this correct and why 15% and not fully closed (0%)?.
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#2657
by
mkirk
on 12 Aug, 2012 20:20
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Hey Dave S
The space shuttle approach landing and rollout flight procedures handbook has a great run down of the spread brake logic. Do you have access to that? Also I think I covered it as well in an earlier q&a. If those don't help let me know and I will try and cover it again.
Mark Kirkman
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#2658
by
DaveS
on 12 Aug, 2012 20:40
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Hey Dave S
The space shuttle approach landing and rollout flight procedures handbook has a great run down of the spread brake logic. Do you have access to that? Also I think I covered it as well in an earlier q&a. If those don't help let me know and I will try and cover it again.
Mark Kirkman
Thanks for the tip on the handbook, it covers it nicely there.
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#2659
by
jeff122670
on 12 Aug, 2012 23:06
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Do we have this handbook posted anywhere? If so, perhaps a link??
Thanks!!