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Two ideas Shuttle return to flight -- Do they hold up?
I thought of posting this as a followup. There are several threads where
it would fit. But then I thought it might get lost -- like my post about the effect of atomic oxygen on RCC did, a few months back. Anyway, I want to run these ideas past some of the professionals here, to get some feedback on their merits. Idea 1 -- inspecting shuttle TPS integrity. All the discussion I've seen on this topic focuses on using some sort of camera (or in-person EVA) to inspect the tiles, RCC panels, etc from the outside for damage. It just occurred to me that if there are any cracks in the RCC such as were seen in earlier foam impact tests at SWRI, they would let significant light enter the wing structure. That is even more true for the hole produced in the latest test. My idea rests on the assumption that no light enters the wing if its TPS is intact. If that is true, I think that placing some photodetectors at certain places inside would give a reliable indication of a breach. This should not add much weight or greatly increase the sensor data load. I leave to those more familiar with the wing structure the questions of how many photodetectors would be needed, and where they should be placed. What I'm after is a go/no-go indication. Idea 2 -- repair of an RCC breach. This one seems more dubious. Suppose the shuttle carried a spare set of RCC panels. (They might be nested so as to take up relatively little volume.) If a breach were found, an EVA would be done to place a matching panel over the broken one. It could be glued or bolted in place, or both. Potential problems with this idea are whether the attachment methods would hold well enough, and the likelihood of step-height changes at the edges of the replacement panel causing a premature airflow transition. OK, those are my ideas. Have at them now. g Chris W. |
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Two ideas Shuttle return to flight -- Do they hold up?
Christopher P. Winter wrote in
: My idea rests on the assumption that no light enters the wing if its TPS is intact. Unfortunately, it's not. The critical damage threshold for the wing leading edge RCC is 0.25 in, not full penetration. Idea 2 -- repair of an RCC breach. This one seems more dubious. Suppose the shuttle carried a spare set of RCC panels. (They might be nested so as to take up relatively little volume.) I'm not sure you can nest them due to the very gradual size changes from panel to panel. In either case, the mass penalty would be prohibitive. Potential problems with this idea are whether the attachment methods would hold well enough, and the likelihood of step-height changes at the edges of the replacement panel causing a premature airflow transition. The step-height tolerance is around 0.1 inches for the RCC. Pretty tight. OK, those are my ideas. Have at them now. g Good thinking, though. Keep 'em coming! -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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Two ideas Shuttle return to flight -- Do they hold up?
Christopher P. Winter wrote:
I can accept the mass-penalty objection. Of course, it probably would not be necessary to carry a complete set of replacement panels. Maybe just a few flat patches, and some with various curvatures. Is RCC at all flexible? If so, it might be possible to force a patch to conform to a curvature mismatch without inducing too much stress. A question: Once the orbiter got out of the high temperature phase of re-entry, how critical is the integrity of the leading edge for maintaining flight control ability? Assuming you had some way of applying a patch that would last through just one re-entry and it was very poorly shaped, could the shuttle still fly and land? It seems to me that the biggest problem with re-entry is the high-temperature plasma getting into the aluminum structure and burning it away. If you could devise some way to keep the plasma out of the wing just long enough to get past that part of re-entry, you'd go a long way to getting the orbiter back in one piece. JazzMan -- *************************************** Please reply to jsavage"at"airmail.net. Curse those darned bulk e-mailers! *************************************** |
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Two ideas Shuttle return to flight -- Do they hold up?
Christopher P. Winter wrote in
: On 11 Jul 2003 00:38:51 GMT, "Jorge R. Frank" wrote: Christopher P. Winter wrote in m: My idea rests on the assumption that no light enters the wing if its TPS is intact. Unfortunately, it's not. The critical damage threshold for the wing leading edge RCC is 0.25 in, not full penetration. I needed some time to think about this. If I understand you correctly, the photodetector solution fails because a) a normal wing is not light-tight, and b) an RCC panel could be critically damaged and still not admit sunlight. I'm not 100% sure about a), but it sounds reasonable. b) is definitely true; RCC panels are around a third of an inch think. OK, how about this: Consider an RCC panel with 0.25 inch removed at one spot. Would that spot have significantly different thermal characteristics than the rest of the panel? If exposed to direct sunlight in space (1350W/sq. meter), would the panel behind the spot warm up more than elsewhere? Would the difference be detected with a simple (i.e. short-wave, non-cooled) IR sensor? I have no idea. I can accept the mass-penalty objection. Of course, it probably would not be necessary to carry a complete set of replacement panels. Maybe just a few flat patches, and some with various curvatures. Is RCC at all flexible? If so, it might be possible to force a patch to conform to a curvature mismatch without inducing too much stress. RCC is not terribly flexible. As for the 0.1-inch step-height problem, I imagine the edges of the replacements could be beveled. The current thinking is to open an "umbrella"-like support behind the hole. You'd put a flat patch over that, and a spray-on ablator to fill the gaps. Finally, trowel the ablator to smooth out the step-height. But RCC repair capability is very much a work-in-progress; there are a lot of different ideas being considered. The *hope* is that the ET bipod ramp fix (along with a couple of other ET foam fixes) will mitigate the risk of *large* pieces of foam to the extent that you no longer have to worry about large holes in the RCC, just small holes and divots. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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Two ideas Shuttle return to flight -- Do they hold up?
Rusty Barton wrote in
: Would it be possible to fit some type of boost protective covers over the RCC areas of the Shuttle? These could possibly be ejected after the External Tank is jettisoned to prevent the covers from following the Shuttle into orbit. This might preclude the need for on orbit inspection of the RCC areas after each launch. Generally I'm not in favor of adding a cover that would require active ejection. That's one more crit-1 failure mode, and should be avoided if possible. However, an ET aerodynamic fairing could accomplish the same purpose and would be passively separated with the ET. It would add weight to the ET, but it would "pay for itself" because the reduction in drag would result in zero net performance loss. See p. 189 of Jenkins, 3rd ed, for some illustrations of ET aerodynamic fairing concepts that were considered during early shuttle development. I do not think such a concept could be, or should be, a return-to-flight constraint, but it should be considered for extended shuttle service life. Gemini and Apollo each used some type of boost covers during launch. You sure about Gemini? I know Apollo did, and it was jettisoned with the escape tower, but Gemini had no escape tower. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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Two ideas Shuttle return to flight -- Do they hold up?
On 13 Jul 2003 03:11:53 GMT, "Jorge R. Frank"
wrote: Gemini and Apollo each used some type of boost covers during launch. You sure about Gemini? I know Apollo did, and it was jettisoned with the escape tower, but Gemini had no escape tower. I believe that Gemini had a white fiberglass? cover over the end of the nose of the spacecraft during launch. It protected the spacecraft rendezvous radar hardware during ascent. Here are several pictures showing Gemini with and without it. Gemini with nose fairing before or during launch: http://images.jsc.nasa.gov/iams/imag...0/10074429.htm http://images.jsc.nasa.gov/iams/imag...0/10074429.jpg http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-000612.html http://grin.hq.nasa.gov/IMAGES/LARGE...000-000612.jpg Gemini without nose fairing after reaching orbit: http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001495.html http://grin.hq.nasa.gov/IMAGES/MEDIU...000-001495.jpg http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001049.html http://grin.hq.nasa.gov/IMAGES/MEDIU...000-001049.jpg -- Rusty Barton - Antelope, California | "When I die, I'm leaving my Visit my Titan I ICBM website at: | body to science fiction." http://www.geocities.com/titan_1_missile | - Steven Wright |
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Two ideas Shuttle return to flight -- Do they hold up?
Rusty Barton wrote in
: On 13 Jul 2003 03:11:53 GMT, "Jorge R. Frank" wrote: Gemini and Apollo each used some type of boost covers during launch. You sure about Gemini? I know Apollo did, and it was jettisoned with the escape tower, but Gemini had no escape tower. I believe that Gemini had a white fiberglass? cover over the end of the nose of the spacecraft during launch. It protected the spacecraft rendezvous radar hardware during ascent. Here are several pictures showing Gemini with and without it. Thanks, Rusty! -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
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Orbiter boost protective covers (was: Two ideas Shuttle return to flight -- Do they hold up?)
OK -- it's been suggested to provide boost protective covers for the wing
leading edges and possibly the nose cap. It occurs to me that you'd have to have a pretty robust BPC, since RCC supposedly has pretty decent tensile strength and it failed pretty obviously when a briefcase-sized chunk of foam hit it. What's more, if a BPC is designed to allow the orbiter to survive an impact of the force with which Columbia's wing was struck, it would have to be able to absorb and transmit a good deal of kinetic energy into the orbiter structure without damaging or compromising its own mountings and without damaging the more fragile RCC below it. And without damaging any other portion of the vehicle. Finally, it would have to be jettisonable in such a way as to leave an aerodynamically smooth surface at the separation planes. And cannot allow any recontact between the BPC segments and the vehicle. When you consider all the factors, it doesn't sound like the simple fix you might think it is... -- It's not the pace of life I mind; | Doug Van Dorn it's the sudden stop at the end... | |
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Orbiter boost protective covers (was: Two ideas Shuttle return to flight -- Do they hold up?)
Doug Van Dorn wrote:
OK -- it's been suggested to provide boost protective covers for the wing leading edges and possibly the nose cap. It occurs to me that you'd have to have a pretty robust BPC, since RCC supposedly has pretty decent tensile strength and it failed pretty obviously when a briefcase-sized chunk of foam hit it. What's more, if a BPC is designed to allow the orbiter to survive an impact of the force with which Columbia's wing was struck, it would have to be able to absorb and transmit a good deal of kinetic energy into the orbiter structure without damaging or compromising its own mountings and without damaging the more fragile RCC below it. And without damaging any other portion of the vehicle. Finally, it would have to be jettisonable in such a way as to leave an aerodynamically smooth surface at the separation planes. And cannot allow any recontact between the BPC segments and the vehicle. When you consider all the factors, it doesn't sound like the simple fix you might think it is... I do not see the practicality of it either. First, let's compare with Apollo CM BPC’s. Those were not all THAT protective, not like a shuttle would need. The forward half of the Apollo BPC was called the hard BPC, it was a relatively strong and hard conical assembly from the top down to just a bit below the LES tower legs. The remaining lower half was called the “soft” BPC. It was made out of multiple segments of fiberglass spliced together radially in 7 places. It didn’t seem to give that much protection other than to keep the highly reflective mylar (?) surface of the CM clean while on the pad and for the early launch phase, till the LES was jettisoned. IIRC, when the tower jettisoned, the lower BPC collapsed inwards on itself since it had no real strength, there was enough dynamic pressure on it to collapse it. The forward “hard” BPC might be considered armor, but in relative terms the lower “soft” BPC was more like a raincoat than armor. Now, a shuttle type BPC for the leading edges would have to be “hard” for its full length, and hard means not only strong (armor), but heavy. Since it would need to avoid hitting the orbiter when it was released, it probably would have to ride a long way till the atmosphere was virtually non-existent. Given the strength it would need by itself, the technical problems of attaching it, and the technical problems of separating it, I would think it would be more practical to introduce the... RRCC: Reinforced-Reinforced Carbon-Carbon Yes, it would add more weight, but the weight penalty would probably not be as bad as carrying a BPC that weighed twice as much (or more) and introduced all the complicated other problems. How much reinforcement and how? I do not know. It would be great if Kevlar could be added to the fabrication of the RCC, but I have a gut feeling that Kevlar is incompatible due to the extreme heat. If the RCC panels could have some sort of lightweight “filler” material inside of portions of them to help give some internal stiffness, rather than being as thin-walled hollow as they are now? If this was a composite aircraft, the answer might be as simple as filling the cavity with foam....(ironic to say that), but I can’t think of any foam that could take the heat. Possibly, just possibly, using silica tile type material, cut to match the inside contour of the RCC segments. Although that still might not be robust enough to support the RCC from cracking/fracturing. And I know it might not be practical to do that and still have the internal access needed to actually attach and service the RCC segments. So, any practical solution to trying to improve ability to withstand impact probably would be more along the lines of just making the panels thicker, plus making the attachment brackets stronger as well, since IIRC last week’s test also did a number on at least one bracket assembly. I won’t be surprised if nothing is done, and the attention goes towards preventing Bipod foam from ever coming off again (IIRC there won’t be any more bipod ramps, period). Which is great unless some other significant piece of foam or something else comes off the ET (or SRB). - George Gassaway |
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Two ideas Shuttle return to flight -- Do they hold up?
On Sun, 13 Jul 2003 12:22:15 -0400, "Terrell Miller"
wrote: "Christopher P. Winter" wrote in message .. . Anyway, I want to run these ideas past some of the professionals here, to get some feedback on their merits. My idea rests on the assumption that no light enters the wing if its TPS is intact. If that is true, I think that placing some photodetectors at certain places inside would give a reliable indication of a breach. This should not add much weight or greatly increase the sensor data load. I leave to those more familiar with the wing structure the questions of how many photodetectors would be needed, and where they should be placed. What I'm after is a go/no-go indication. IOW, you want credit for the idea, but you have no intention of doing the research to determine whether your idea would actually work, and you're not gonna lift a finger to do any of the actual gruntwork if it does. You are the Pointy Haired Boss and I claim my $5 Interesting analysis. I wrote a sarcastic reply. Then I discarded it, because I want to keep this conversation serious. Yes, I would love to get credit for the idea. I'd also be happy to do the research to fix any problems it has (which, as JRF pointed out, are many) and the "gruntwork", as you call it, to implement a real solution. Would that I were in a position to do so. As things stand, I could have either put the idea(s) out for discussion here, sent them to the CAIB in a letter, or sat on them. I chose the former because it seemed the quickest way to get something going. If I had sent them to the CAIB, it would have been weeks before anyone saw the letter, and who knows how long before those ideas were evaluated (if they ever were). However, I'll also note that this would be a better route to keeping whatever credit my ideas might earn for myself alone. If I had sat on them... But you can figure that one out. Chris W. |
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