STS-107, Chronicle Of A Disaster Foretold?
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It is becoming apparent that the genesis of this Shuttle accident was not unlike that of the Challenger....too many people (who should have known better) disregarding the environmentals pre-launch.
It has been admitted that the Columbia sat on its launch pad much longer than any other Shuttle before it (39 days) and that the weather was the coldest Florida weather for over 50 years. I recall seeing deep snow on the TV at the time. That's a lot of freeze/melt/re-freeze cycles for the foam insulation - which undoubtedly as a result was rain-soaked, freeze-cracked and was ready to separate in large icy spear-like stalactites under the stresses of max Q (81 secs into launch). Of course, once the liquid hydrogen was loaded, the foam was then frozen in place. It took the post-launch thermodynamic heating to thaw it and it then separated along its cyclic fault-lines. If you look here (link) you will see that it has happened before and damaged the RCC leading edge in a similar fashion to what is here suggested may have happened to STS-107.Once you read into the NASA specifications for the RCC leading edge, it becomes apparent that it was "toughened" - but only against high temperatures (as part of the TPS) - and never against IMPACT. They never took the required precautions against launch debris impact - probably because the spec for its "raison d'etre" was always to revolve around its resistance to re-entry heating.
A likely fix would be to affix a vulcanized sacrificial strip along the RCC Leading Edge (even a non-aerodynamic and deflective one). That reasonably practical fix would provide launch debris impact protection yet quickly burn away on re-entry. A pointy impact of an icy stalactite on that RCC L.E. probably did what you would expect any pointy impact to do to what's essentially nothing more than a toughened graphite, i.e. shatter it. Because it is only "bolted on" (via inconel attachments), loss of its structural integrity (by shattering) would have led to it being rapidly eroded away. But how?
If you read the NASA blurb here, they describe it as being critically coating-protected against oxidization. Once an RCC section was shattered on launch, that section’s oxidization destruction on re-entry was assured. Unfortunately that section was right ahead of the port wheel-well’s outboard forward corner. Superheated white-hot RCC pieces detaching was what the Owens Valley Astronomer would have seen in the pre-dawn darkness. The underlying aluminium wing surface is only rated to 175 odd degrees. No wonder the wheel-well was pierced and the events in there set in train (see ]here and here.
Further Reading on the Thermal Protection System is here.
This is an excerpt from the most recent set of modifications made to the Shuttle Fleet. I obtained these documents just prior to NASA pulling all information about the shuttle from the net on that fateful Saturday. Read carefully.
" The area aft of the reinforced carbon-carbon nose cap to the nose landing gear doors has sustained damage (tile slumping) during flight operations from impact during ascent and overheating during re-entry. This area, which previously was covered with high-temperature reusable surface insulation tiles, will now be covered with reinforced carbon-carbon.
The low-temperature thermal protection system tiles on Columbia's midbody, payload bay doors and vertical tail were replaced with advanced flexible reusable surface insulation blankets.
Because of evidence of plasma flow on the lower wing trailing edge and elevon leading edge tiles (wing/elevon cove) at the outboard elevon tip and inboard elevon, the low-temperature tiles are being replaced with fibrous refractory composite insulation (FRCI-12) and high-temperature (HRSI-22) tiles along with gap fillers on Discovery and Atlantis. On Columbia only gap fillers are installed in this area."
It has been admitted that the Columbia sat on its launch pad much longer than any other Shuttle before it (39 days) and that the weather was the coldest Florida weather for over 50 years. I recall seeing deep snow on the TV at the time. That's a lot of freeze/melt/re-freeze cycles for the foam insulation - which undoubtedly as a result was rain-soaked, freeze-cracked and was ready to separate in large icy spear-like stalactites under the stresses of max Q (81 secs into launch). Of course, once the liquid hydrogen was loaded, the foam was then frozen in place. It took the post-launch thermodynamic heating to thaw it and it then separated along its cyclic fault-lines. If you look here (link) you will see that it has happened before and damaged the RCC leading edge in a similar fashion to what is here suggested may have happened to STS-107.Once you read into the NASA specifications for the RCC leading edge, it becomes apparent that it was "toughened" - but only against high temperatures (as part of the TPS) - and never against IMPACT. They never took the required precautions against launch debris impact - probably because the spec for its "raison d'etre" was always to revolve around its resistance to re-entry heating.
A likely fix would be to affix a vulcanized sacrificial strip along the RCC Leading Edge (even a non-aerodynamic and deflective one). That reasonably practical fix would provide launch debris impact protection yet quickly burn away on re-entry. A pointy impact of an icy stalactite on that RCC L.E. probably did what you would expect any pointy impact to do to what's essentially nothing more than a toughened graphite, i.e. shatter it. Because it is only "bolted on" (via inconel attachments), loss of its structural integrity (by shattering) would have led to it being rapidly eroded away. But how?
If you read the NASA blurb here, they describe it as being critically coating-protected against oxidization. Once an RCC section was shattered on launch, that section’s oxidization destruction on re-entry was assured. Unfortunately that section was right ahead of the port wheel-well’s outboard forward corner. Superheated white-hot RCC pieces detaching was what the Owens Valley Astronomer would have seen in the pre-dawn darkness. The underlying aluminium wing surface is only rated to 175 odd degrees. No wonder the wheel-well was pierced and the events in there set in train (see ]here and here.
Further Reading on the Thermal Protection System is here.
This is an excerpt from the most recent set of modifications made to the Shuttle Fleet. I obtained these documents just prior to NASA pulling all information about the shuttle from the net on that fateful Saturday. Read carefully.
" The area aft of the reinforced carbon-carbon nose cap to the nose landing gear doors has sustained damage (tile slumping) during flight operations from impact during ascent and overheating during re-entry. This area, which previously was covered with high-temperature reusable surface insulation tiles, will now be covered with reinforced carbon-carbon.
The low-temperature thermal protection system tiles on Columbia's midbody, payload bay doors and vertical tail were replaced with advanced flexible reusable surface insulation blankets.
Because of evidence of plasma flow on the lower wing trailing edge and elevon leading edge tiles (wing/elevon cove) at the outboard elevon tip and inboard elevon, the low-temperature tiles are being replaced with fibrous refractory composite insulation (FRCI-12) and high-temperature (HRSI-22) tiles along with gap fillers on Discovery and Atlantis. On Columbia only gap fillers are installed in this area."
From the Albuquerque Journal a picture of the system used by the "Starfire geeks":
and a close-up from AP:
Not quite sure to understand what we are looking at.
The camera or whatever was attached to the scope is definitely not consumer
grade , no camcorder or webcam . There are other gizmos in the image which
look professional. Does anyone know any of these pieces of equipment?
Edited to remove that huge picture that ruins all the formatting of the thread. If you want to use a picture that is larger than the normal screen size the just post a link to the page with the picture instead of the picture itself!
Sorry about that - won't happen again !
and a close-up from AP:
They used a Questar 3.5" telescope on a fixed tripod and the tracking
mirror (which is a flat mirror and a high-precision pointing stage) to
point. They started putting things together the evening before, just
on a lark.
"They mounted [the Questar] in front of a set of larger movable
satellite-tracking mirrors that had been salvaged from White Sands
Missile Range two decades ago.
"Old but still reliable, the mirrors tracked the shuttle, reflecting
its image back to an instrument room where the telescope was mounted."
...emerged from clouds...to clouds...24 seconds...only time to snap one
picture...36 degrees above the western horizon, nearly 70 miles away at
the time.
mirror (which is a flat mirror and a high-precision pointing stage) to
point. They started putting things together the evening before, just
on a lark.
"They mounted [the Questar] in front of a set of larger movable
satellite-tracking mirrors that had been salvaged from White Sands
Missile Range two decades ago.
"Old but still reliable, the mirrors tracked the shuttle, reflecting
its image back to an instrument room where the telescope was mounted."
...emerged from clouds...to clouds...24 seconds...only time to snap one
picture...36 degrees above the western horizon, nearly 70 miles away at
the time.
The camera or whatever was attached to the scope is definitely not consumer
grade , no camcorder or webcam . There are other gizmos in the image which
look professional. Does anyone know any of these pieces of equipment?
Edited to remove that huge picture that ruins all the formatting of the thread. If you want to use a picture that is larger than the normal screen size the just post a link to the page with the picture instead of the picture itself!
Sorry about that - won't happen again !
Last edited by atakacs; 17th Feb 2003 at 14:17.
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atakacs, mate. I think they've established that Starfire isn't going to provide any great answers.
Any chance of doing something about that darned great photo? It's a bit of a screenful!
Any chance of doing something about that darned great photo? It's a bit of a screenful!
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A protective leading edge material designed to burn away on re-entry is an excellent idea but there must be a way of jettisoning the non-aerodynamic protective material in the event that orbit is not achieved and the shuttle either does a return to KFC or lands at one of the contingency strips in Rota, Spain or Dakar, Senegal.
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When in doubt, launch another project:
www.denverpost.com/Stories/0,1413,36%257E33%257E1185329,00.html
www.denverpost.com/Stories/0,1413,36%257E33%257E1185329,00.html
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arcniz, someone at the top is finally waking up to reality, just like they did after Challenger. Then, they realised that the ELV program was almost non-existent and took steps to rectify it. Now, they find that only three Orbiters remain to look after the ISS/HST and other great investments. Aviation is not isolated from the rest of history in repeating itself every so often. The politicians see to that!
OVERTALK's sacrificial strip is an interesting concept. I feel, however, that preventing bits falling off the ET during launch might have first priority, as the TPS has worked satisfactorily on 111 occasions and has been upgraded in the light of operational experience.
On the question of ET ice, I remain doubtful. It was not a cold day and those who were around the stack prior to launch say that there was no visible ice present on the tank. Also, OT, the ET coating is weatherproof and, theoretically cannot soak up water. I understand that there were no signs of cracked foam on launch day. However, the thermal cycles you mention are valid. What if micro-cracks evolved that were not easily visible but let in some moisture?
Ice has always been an issue on the ET, but large chunks of foam falling off has not, until STS-112/107. There may be other issues here, perhaps the earlier redesign of the foam to eliminate CFCs, for example. I hate to raise it, but QC has to be considered too. As I said on an earlier post, without the ice, one 2.5lb mass (or two!) striking at just the wrong angle, at that speed, is quite a whack.
With all the descriptives flying around about the RCC sections (my favoured theory) I thought it might help to post a diagram which illustrates the RCC attachment system. This is from the Curry/Johnson presentation (pdf 900kb) at the Future Space Shuttle Conference 1999. The enlargement also shows the later mod and a T-seal. To my mind, the (flexible) T-seals are one feature that would not enjoy being whacked and could let in a lot of plasma, initially in a metered manner.
Enlargement
As mentioned elsewhere, if plasma gets past, or through, an RCC panel, how long would it take to reach past the secondary protection and on to the alluminium attach points? Where it goes thence is largely academic - but surely a "bad day."
OVERTALK's sacrificial strip is an interesting concept. I feel, however, that preventing bits falling off the ET during launch might have first priority, as the TPS has worked satisfactorily on 111 occasions and has been upgraded in the light of operational experience.
On the question of ET ice, I remain doubtful. It was not a cold day and those who were around the stack prior to launch say that there was no visible ice present on the tank. Also, OT, the ET coating is weatherproof and, theoretically cannot soak up water. I understand that there were no signs of cracked foam on launch day. However, the thermal cycles you mention are valid. What if micro-cracks evolved that were not easily visible but let in some moisture?
Ice has always been an issue on the ET, but large chunks of foam falling off has not, until STS-112/107. There may be other issues here, perhaps the earlier redesign of the foam to eliminate CFCs, for example. I hate to raise it, but QC has to be considered too. As I said on an earlier post, without the ice, one 2.5lb mass (or two!) striking at just the wrong angle, at that speed, is quite a whack.
With all the descriptives flying around about the RCC sections (my favoured theory) I thought it might help to post a diagram which illustrates the RCC attachment system. This is from the Curry/Johnson presentation (pdf 900kb) at the Future Space Shuttle Conference 1999. The enlargement also shows the later mod and a T-seal. To my mind, the (flexible) T-seals are one feature that would not enjoy being whacked and could let in a lot of plasma, initially in a metered manner.
Enlargement
As mentioned elsewhere, if plasma gets past, or through, an RCC panel, how long would it take to reach past the secondary protection and on to the alluminium attach points? Where it goes thence is largely academic - but surely a "bad day."
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DrSyn
It may be the case that the ET foam is water-proof but it would only take a minor imperfection to allow water to infiltrate and affect the adhesive over 39 days of rainy freeze/thaw/re-freeze (mechanism for that described below). A large section of iced foam might detach not only because of degraded adhesive but because of the weight of water behind it. But there is a further factor - when you're talking about a cryogenic fuel-load.
"It was not a cold day and those who were around the stack prior to launch say that there was no visible ice present on the tank." Any poorly adherent foam section would look like any other but once the External Tank is fuelled with liquid hydrogen (at minus 250deg F), I understand that it is one large icicle. But you have to further consider that any water infiltrating behind the foam is not just ice, it is super-cooled and will contract quickly and mightily. That almighty contraction would suck in the surrounding foam - forming a circumferential crack (albeit one that may not be visible and may be initially only in the adhesive substrate - but that's where it counts). That crack then delineates the piece that will/could later detach. At max Q I would guess that there are areas of lower pressure around the ET (i.e. where the airflow sucks). Once thermodynamic heating reduces the adhesive quality of the ice itself behind that flawed section of increased weight foam (like hand-warming an ice-tray) that flawed section is free to detach (but it's still an icicle in stalactite form).
Even though the external tank's cladding may be tested waterproof where it's made, transportation, erection and attachment stresses on the empty vehicle may well compromise the water-proofing of the foam cladding on that flimsy, empty (and therefore flexible) tank. The solution may be to simply give it a good ScotchGuarding spray top-to-bottom once it is in the launch position.
But as further insurance, a sacrificial rubbery L.E. wedge (aka false leading-edge) on the Orbiter's wing would easily deflect any such stalactite and burn away early on re-entry. I will be surprised if they don't go for this as a fix.
OVERTALK
It may be the case that the ET foam is water-proof but it would only take a minor imperfection to allow water to infiltrate and affect the adhesive over 39 days of rainy freeze/thaw/re-freeze (mechanism for that described below). A large section of iced foam might detach not only because of degraded adhesive but because of the weight of water behind it. But there is a further factor - when you're talking about a cryogenic fuel-load.
"It was not a cold day and those who were around the stack prior to launch say that there was no visible ice present on the tank." Any poorly adherent foam section would look like any other but once the External Tank is fuelled with liquid hydrogen (at minus 250deg F), I understand that it is one large icicle. But you have to further consider that any water infiltrating behind the foam is not just ice, it is super-cooled and will contract quickly and mightily. That almighty contraction would suck in the surrounding foam - forming a circumferential crack (albeit one that may not be visible and may be initially only in the adhesive substrate - but that's where it counts). That crack then delineates the piece that will/could later detach. At max Q I would guess that there are areas of lower pressure around the ET (i.e. where the airflow sucks). Once thermodynamic heating reduces the adhesive quality of the ice itself behind that flawed section of increased weight foam (like hand-warming an ice-tray) that flawed section is free to detach (but it's still an icicle in stalactite form).
Even though the external tank's cladding may be tested waterproof where it's made, transportation, erection and attachment stresses on the empty vehicle may well compromise the water-proofing of the foam cladding on that flimsy, empty (and therefore flexible) tank. The solution may be to simply give it a good ScotchGuarding spray top-to-bottom once it is in the launch position.
But as further insurance, a sacrificial rubbery L.E. wedge (aka false leading-edge) on the Orbiter's wing would easily deflect any such stalactite and burn away early on re-entry. I will be surprised if they don't go for this as a fix.
OVERTALK
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I don't dispute the idea of moisture getting behind the scenes, OT - that was behind my point about possible "micro"-cracks. You've expanded the point quite well, however 
The scenario has been revisited by the Board over the past few days, and I am sure you've been following it as closely as I.
The subject is being eruditely discussed elsewhere, and by some who are or were actively involved in the program. As there has been no further interest in this thread in past days, there seems little point in continuing it here. I'll conclude with a couple of recent quotes which I thought were interesting:
"NASA believes the piece of insulating foam detached from a section of the external fuel tank called the bipod. In addition to sprayed-on polyurethane foam, portions of the bipod and other parts of the tank exposed to the highest temperatures also are treated with a silicon-based substance called Super Lightweight Ablator. The concern is whether that material under the foam also broke lose from the giant aluminum tank, which might have added considerable heft to a piece of foam originally calculated to weigh 2.67 pounds."
". . . . Was it ablative material behind the foam? Was it metal behind the foam or was it ice?"
As it should, the investigation is maintaining a wide perspective.
The scenario has been revisited by the Board over the past few days, and I am sure you've been following it as closely as I.The subject is being eruditely discussed elsewhere, and by some who are or were actively involved in the program. As there has been no further interest in this thread in past days, there seems little point in continuing it here. I'll conclude with a couple of recent quotes which I thought were interesting:
"NASA believes the piece of insulating foam detached from a section of the external fuel tank called the bipod. In addition to sprayed-on polyurethane foam, portions of the bipod and other parts of the tank exposed to the highest temperatures also are treated with a silicon-based substance called Super Lightweight Ablator. The concern is whether that material under the foam also broke lose from the giant aluminum tank, which might have added considerable heft to a piece of foam originally calculated to weigh 2.67 pounds."
". . . . Was it ablative material behind the foam? Was it metal behind the foam or was it ice?"
As it should, the investigation is maintaining a wide perspective.
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Addendum
Indeed, this article highlights just how a potential weak link in the chain of the otherwise well-sealed ET TPS might allow moisture into the system - especially with prolonged weathering. Interesting reading.
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Jettisonable Leading Edge Material or Fillet?
RobertS975
You have to work out a risk-management philosophy that's weighted toward the the greater threat (launch debris damage or launch abort).
a. Engine failure aborts, if some engine power/thrust remained, the Orbiter's aerodynamics wouldn't be degraded unrealistically by a wedge-shaped protective inboard leading edge. Many jet aircraft sport those for improved spin-stall characteristics. You'd probably only need about two metres per side in order to protect the very vulnerable areas of the wheel-well in particular. The remaining outboard span's protective sacrificial overlay could be a conformal section (not wedge-shaped deflective).
b. Alternatively, for the highly vulnerable inboard areas, a jettisonable false section similar to a fillet could be fitted. An in-atmosphere emergency jettison of that could be as simple as an explosive bolt each side at its leading fuselage attachment point. In the event of an abort they'd peel away with the ET and SRB's. For re-entry, it would be pre-jettisoned (or it could simply depart by design with the ET or SRB's, its protective role being superfluous by then).
It's not really rocket science, it's just a matter of protecting what demonstrably post-Columbia needs to be protected / needed to restore confidence / is required to avoid the necessity for complex in-orbit inspections.
You have to work out a risk-management philosophy that's weighted toward the the greater threat (launch debris damage or launch abort).
a. Engine failure aborts, if some engine power/thrust remained, the Orbiter's aerodynamics wouldn't be degraded unrealistically by a wedge-shaped protective inboard leading edge. Many jet aircraft sport those for improved spin-stall characteristics. You'd probably only need about two metres per side in order to protect the very vulnerable areas of the wheel-well in particular. The remaining outboard span's protective sacrificial overlay could be a conformal section (not wedge-shaped deflective).
b. Alternatively, for the highly vulnerable inboard areas, a jettisonable false section similar to a fillet could be fitted. An in-atmosphere emergency jettison of that could be as simple as an explosive bolt each side at its leading fuselage attachment point. In the event of an abort they'd peel away with the ET and SRB's. For re-entry, it would be pre-jettisoned (or it could simply depart by design with the ET or SRB's, its protective role being superfluous by then).
It's not really rocket science, it's just a matter of protecting what demonstrably post-Columbia needs to be protected / needed to restore confidence / is required to avoid the necessity for complex in-orbit inspections.
From space.com article
On what basis ?!
Strikes me as really odd
--alex
A NASA official told searchers that the hilly desert and knee-high sagebrush near the Nevada-Utah state line may contain a six-foot chunk of landing gear, said Bob Williams, a Lincoln County sheriff's volunteer and a spokesman for the Nevada search effort.
Strikes me as really odd
--alex
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I imagine the searches on the Nevada-Utah state line are being made on the basis of radar returns, and that some guesses about what to look for have been made based on the trajectories of the debris. Maybe they are looking for a main gear door rather than for the main gear itself. The door could be about six feet long and might have fluttered down.
Seems that some people who should know are still not entirely happy with the composition of the inquiry board and its reporting responsibilities:
---- Start quote -------
.... "It would put their independence beyond a doubt if they were to report to the president," said David C. Acheson, a member of the Challenger board. Acheson, 81, a retired attorney living in Washington, was one of the 13 members of the Rogers Commission, named after its chairman, the late William P. Rogers, the former Secretary of State. ......The Rogers Commission was made up of engineers, an astronomer, a lawyer, a space journalist, Nobel Prize-winning physicist Richard Feynman, former astronauts Neil Armstrong and Sally Ride and legendary test pilot Chuck Yeager. Its unsparing 1986 report on the Challenger accident pushed NASA to make significant safety and management changes to the space shuttle program. .... "I think one of the big differences is we had several serious scientists on the board," said Eugene Covert, 77, an engineering professor at MIT and Rogers Commission member. "I don't think there are any serious scientists right now." .......
---- End quote -------
http://customwire.ap.org/dynamic/sto...MPLATE=DEFAULT
Note added Feb 25 2003
From: http://www.spaceflightnow.com/shuttl...30220pinpoint/
------- Start quote ---------
Video imagery of Columbia's entry provided to NASA was analyzed by imagery, trajectory and ballistics experts," the release said. "The results of that analysis were then provided to National Transportation Safety Board officials who reviewed air traffic control radar imagery in that area during the time of Columbia's descent.
"The review resulted in what is believed to be a significant radar track of a piece of debris as it fell to Earth. As a result, a search of the Caliente area near the Nevada-Utah border is under way using Civil Air Patrol assets. A search using additional means also may be forthcoming."
--------- End quote --------
Seems that some people who should know are still not entirely happy with the composition of the inquiry board and its reporting responsibilities:
---- Start quote -------
.... "It would put their independence beyond a doubt if they were to report to the president," said David C. Acheson, a member of the Challenger board. Acheson, 81, a retired attorney living in Washington, was one of the 13 members of the Rogers Commission, named after its chairman, the late William P. Rogers, the former Secretary of State. ......The Rogers Commission was made up of engineers, an astronomer, a lawyer, a space journalist, Nobel Prize-winning physicist Richard Feynman, former astronauts Neil Armstrong and Sally Ride and legendary test pilot Chuck Yeager. Its unsparing 1986 report on the Challenger accident pushed NASA to make significant safety and management changes to the space shuttle program. .... "I think one of the big differences is we had several serious scientists on the board," said Eugene Covert, 77, an engineering professor at MIT and Rogers Commission member. "I don't think there are any serious scientists right now." .......
---- End quote -------
http://customwire.ap.org/dynamic/sto...MPLATE=DEFAULT
Note added Feb 25 2003
From: http://www.spaceflightnow.com/shuttl...30220pinpoint/
------- Start quote ---------
Video imagery of Columbia's entry provided to NASA was analyzed by imagery, trajectory and ballistics experts," the release said. "The results of that analysis were then provided to National Transportation Safety Board officials who reviewed air traffic control radar imagery in that area during the time of Columbia's descent.
"The review resulted in what is believed to be a significant radar track of a piece of debris as it fell to Earth. As a result, a search of the Caliente area near the Nevada-Utah border is under way using Civil Air Patrol assets. A search using additional means also may be forthcoming."
--------- End quote --------
Last edited by PickyPerkins; 25th Feb 2003 at 17:53.
Ecce Homo! Loquitur...
An upper wing heat shield tile has been recovered in west Texas. It shows extreme heat damage, much more than can normally be expected during re-entry.
CNN
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Can someone please explain to me about the wing roughness of the Columbia?
I have seen a roughness of 0.1-0.2 inches is being talked about.
Is this a waviness in the wing surface, or what?
The metal wing itself is presumably accurate and made according to drawings to within a few thousandths of an inch, so was not rough (in the sense of deviating from the intended contour) at all.
The tiles are computer designed and cut (is this right?) so that they are also presumably accurate in shape and thickness, and also made according to drawings to within a few thousandths of an inch.
I take it that the tiles themselves are not rough, and that the problem is not in the tiles themselves, since all Shuttles have tiles but only Columbia has been said to suffer from excessive wing roughness.
So how does roughness arise, what does it consist of, and what causes it?
Is it something which could have been worked on during one of Columbia’s three 12 mth long re-fits at Palmdale?
Did these re-fits include complete re-tiling?
I have seen a roughness of 0.1-0.2 inches is being talked about.
Is this a waviness in the wing surface, or what?
The metal wing itself is presumably accurate and made according to drawings to within a few thousandths of an inch, so was not rough (in the sense of deviating from the intended contour) at all.
The tiles are computer designed and cut (is this right?) so that they are also presumably accurate in shape and thickness, and also made according to drawings to within a few thousandths of an inch.
I take it that the tiles themselves are not rough, and that the problem is not in the tiles themselves, since all Shuttles have tiles but only Columbia has been said to suffer from excessive wing roughness.
So how does roughness arise, what does it consist of, and what causes it?
Is it something which could have been worked on during one of Columbia’s three 12 mth long re-fits at Palmdale?
Did these re-fits include complete re-tiling?
Ecce Homo! Loquitur...
Wing Roughness.
The comments about turbulent flow are interesting when put together with the state of the upper wing tile found in west Texas.
"Normally the shuttle's wings transition from laminar to turbulent flow at 1,200 seconds into re-entry, Gibson said. "On STS-28, on Columbia, that transition happened at 900 seconds -- 300 seconds early. As you might expect, the left wing saw a significantly higher heating environment than the rest of the orbiter."
The comments about turbulent flow are interesting when put together with the state of the upper wing tile found in west Texas.
"Normally the shuttle's wings transition from laminar to turbulent flow at 1,200 seconds into re-entry, Gibson said. "On STS-28, on Columbia, that transition happened at 900 seconds -- 300 seconds early. As you might expect, the left wing saw a significantly higher heating environment than the rest of the orbiter."
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Thanks for the link, ORAC
The article you link to says:
-------- Start quote ---------
… Even with replacements over the years, 70 percent of Columbia's tiles were the originals… Surface roughness ……. has to do with the gaps between the shuttle tiles and the "step," or difference in height, between one tile and its neighbor. …….The roughness of the wing is indicated by a measurement called the K equivalent, derived by combining data on the gaps and steps with information on the airflow …
-------- End quote ---------
The impression I get now is that the roughness is a left-over of the tile-installation learning curve from 20+ years ago. In that case, there may be nothing wrong with either the tiles or the wing, just that the installation methods had not yet been developed sufficiently when the first Shuttle was built. I wonder if the left wing was built first?
One might guess that if tiles projected various distances due to imperfect installation, then the adhesion in some cases might not have been too good either.
The article you link to says:
-------- Start quote ---------
… Even with replacements over the years, 70 percent of Columbia's tiles were the originals… Surface roughness ……. has to do with the gaps between the shuttle tiles and the "step," or difference in height, between one tile and its neighbor. …….The roughness of the wing is indicated by a measurement called the K equivalent, derived by combining data on the gaps and steps with information on the airflow …
-------- End quote ---------
The impression I get now is that the roughness is a left-over of the tile-installation learning curve from 20+ years ago. In that case, there may be nothing wrong with either the tiles or the wing, just that the installation methods had not yet been developed sufficiently when the first Shuttle was built. I wonder if the left wing was built first?
One might guess that if tiles projected various distances due to imperfect installation, then the adhesion in some cases might not have been too good either.
Last edited by PickyPerkins; 27th Feb 2003 at 12:49.
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sir
Thanks for the correction. The Columbia was not launched until 1981, so if the photo was made in 1979 it must show it in its “as made” condition. I will edit my post above to delete the photo.
------------------------------------------
03/12/79 Overland transport from Palmdale to Edwards
03/20/79 SCA Ferry Flight from DFRF to Bigs AFB, Texas
03/22/79 SCA Ferry flight from Bigs AFB to Kelly AFB, Texas
03/24/79 SCA Ferry flight from Kelly AFB to Eglin AFB, Florida
03/24/79 SCA Ferry flight from Eglin, AFB to KSC
11/03/79 Auxiliary Power Unit hot fire tests, OPF KSC
12/16/79 Orbiter integrated test start, KSC
01/14/80 Orbiter integrated test complete, KSC
02/20/81 Flight Readiness Firing
04/12/81 First Flight (STS-1)
-----------------------------------------------
Note added later
After some further digging I find that the photo was taken on March 25, 1979, the day after Columbia arrived at KSC for the first time after its delivery flight from California.
Thanks for the correction. The Columbia was not launched until 1981, so if the photo was made in 1979 it must show it in its “as made” condition. I will edit my post above to delete the photo.
------------------------------------------
03/12/79 Overland transport from Palmdale to Edwards
03/20/79 SCA Ferry Flight from DFRF to Bigs AFB, Texas
03/22/79 SCA Ferry flight from Bigs AFB to Kelly AFB, Texas
03/24/79 SCA Ferry flight from Kelly AFB to Eglin AFB, Florida
03/24/79 SCA Ferry flight from Eglin, AFB to KSC
11/03/79 Auxiliary Power Unit hot fire tests, OPF KSC
12/16/79 Orbiter integrated test start, KSC
01/14/80 Orbiter integrated test complete, KSC
02/20/81 Flight Readiness Firing
04/12/81 First Flight (STS-1)
-----------------------------------------------
Note added later
After some further digging I find that the photo was taken on March 25, 1979, the day after Columbia arrived at KSC for the first time after its delivery flight from California.
Last edited by PickyPerkins; 28th Feb 2003 at 03:02.
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A Reasonable Explanation
>JBS said:
>"I read today they say it
>localized to four panels on the leading edge of left wing."
>
>JBS
Haven't been able to find this anywhere. Do you have a URL??
However, in response, my theory about the "flat-plate effect" of losing a section of the RCC leading edge is so far supported by all that's been declared or noted (and borne out well by the info in the links below):
_
a. The reinforced carbon-carbon (RCC) is vulnerable to impact-shattering - by (say) the pointy impact of an icy stalactite from the detached tank foam and its two underlays (the substrate that supposedly has no purpose and above which is the ablative layer, more adhesive and foam). Why did the foam (and its sub-layers) separate and why would it be hard and icy? Well supposedly the Columbia was on launch-pad 39A for 38 days, longer than any other shuttle before it. It sat through some of the coldest sub-zero weather in Florida's recorded history. All the freeze/thaw/refreeze cycles would have allowed water to get beneath the external tank's foam adhesive and loosen it (as well as cracking sections circumferentially – it’s called cryo-pumping – see Link 3 below). At launch the water beneath the foam would have been adhesive ice (because of the liquid hydrogen) – but later, at that 81 second point it would have had enough aerodynamic heating and lift-suction to have melted that ice (and the ET's icy hydrogen fuel would have been emptying quickly to well below that high-up point anyway).
_
b._ Once impacted (by a hard pointy object) the RCC on the Orbiter’s Wing Leading Edge would shatter and then (no longer being a solid integral mass) lose its retention by that section’s inconel bracket and also lose the integrity of its impermeable top layer of silicon carbide and tetraethyl orthosilicate (that protects it against oxidization on re-entry).
_
c._ Reportedly a small object was radar-detected in orbit floating near the Shuttle. My theory has this as a sizeable segment of that RCC section that was shattered (and located just forward of the outboard corner of the wheelwell). Why would it have separated? As the Shuttle orbits it is subjected to intense heat and then cold and eventually all those expansion/contraction cycles would allow a shattered segment to work free and float off under any light manoeuvre.
_
d._______ Upon re-entry, because of the loss of solidity in that RCC section (plus a sizeable missing segment) the remaining shattered RCC pieces would have been quickly oxidized and detached. That was the pre-dawn fiery sparking seen by the Owens Valley astronomers (and others). At that point there remains only the Inconel 718 bracket and the flat-plate aluminium leading edge – before the wheelwell is broached. Because of the flat-plate effect, localized extremely high plasma temperatures, far in excess of those ever before seen on re-entry, would be generated and that superheated plasma bubble would create the distinctive extension well ahead of that inboard wing [as seen in the Air Force telephoto as a protuberance]. Of course at the same time that aluminium flat-plate would be melting and allowing ever-increasing amounts of that superheated plasma into the wheel-well. Evidence for this?
_
e._______ Dittmore said that some recovered left wing tiles exhibited heat damage “that was not caused by re-entry heating”. In addition there were embedded orange beads within the over-heated areas of those tiles. My theory is that those beads will prove to be an oxide of one of the constituent metals in the Inconel RCC support bracket.
______ _
Solutions?
1._ Shuttle crews have already flight-tested miniature robot cameras for in orbit inspection. See link here
_
2._ A two-part mix layer of an Araldite-like epoxy-based ablative substance could be overlaid across a damaged section (including the LE) and exothermically set itself in place. If thick enough, it should last out a "once off" re-entry (and be within the controllability of the lateral controls – or a similar patch applied to the other wing for symmetry). Once damage is evident, to achieve this “patching” an EVA astronaut would require a couple of LE overcentre-locking clamps (i.e. with long handles to get back above and below the LE) and an LE cable between them (for his positioning and leverage and to hold the 2 clamps together). The clamps would be affixed and later removed whilst he is tethered and manoeuvring with a jet-pack. This is not rocket-science.
_3. It might be possible to affix a sacrificial wedge-shaped launch leading-edge that would protect those inboard areas near the wheel-wells, in a protective profile that would be acceptable aerodynamically for a launch abort - and yet quickly burn away on re-entry. Silicon rubber springs to mind as a suitable protective medium.
A._ Link__ What is RCC?
_
B._ Link__ A Leading edge breach is chief candidate.
_
C._ Link__ The External Tank and its Foam
_
>"I read today they say it
>localized to four panels on the leading edge of left wing."
>
>JBS
Haven't been able to find this anywhere. Do you have a URL??
However, in response, my theory about the "flat-plate effect" of losing a section of the RCC leading edge is so far supported by all that's been declared or noted (and borne out well by the info in the links below):
_
a. The reinforced carbon-carbon (RCC) is vulnerable to impact-shattering - by (say) the pointy impact of an icy stalactite from the detached tank foam and its two underlays (the substrate that supposedly has no purpose and above which is the ablative layer, more adhesive and foam). Why did the foam (and its sub-layers) separate and why would it be hard and icy? Well supposedly the Columbia was on launch-pad 39A for 38 days, longer than any other shuttle before it. It sat through some of the coldest sub-zero weather in Florida's recorded history. All the freeze/thaw/refreeze cycles would have allowed water to get beneath the external tank's foam adhesive and loosen it (as well as cracking sections circumferentially – it’s called cryo-pumping – see Link 3 below). At launch the water beneath the foam would have been adhesive ice (because of the liquid hydrogen) – but later, at that 81 second point it would have had enough aerodynamic heating and lift-suction to have melted that ice (and the ET's icy hydrogen fuel would have been emptying quickly to well below that high-up point anyway).
_
b._ Once impacted (by a hard pointy object) the RCC on the Orbiter’s Wing Leading Edge would shatter and then (no longer being a solid integral mass) lose its retention by that section’s inconel bracket and also lose the integrity of its impermeable top layer of silicon carbide and tetraethyl orthosilicate (that protects it against oxidization on re-entry).
_
c._ Reportedly a small object was radar-detected in orbit floating near the Shuttle. My theory has this as a sizeable segment of that RCC section that was shattered (and located just forward of the outboard corner of the wheelwell). Why would it have separated? As the Shuttle orbits it is subjected to intense heat and then cold and eventually all those expansion/contraction cycles would allow a shattered segment to work free and float off under any light manoeuvre.
_
d._______ Upon re-entry, because of the loss of solidity in that RCC section (plus a sizeable missing segment) the remaining shattered RCC pieces would have been quickly oxidized and detached. That was the pre-dawn fiery sparking seen by the Owens Valley astronomers (and others). At that point there remains only the Inconel 718 bracket and the flat-plate aluminium leading edge – before the wheelwell is broached. Because of the flat-plate effect, localized extremely high plasma temperatures, far in excess of those ever before seen on re-entry, would be generated and that superheated plasma bubble would create the distinctive extension well ahead of that inboard wing [as seen in the Air Force telephoto as a protuberance]. Of course at the same time that aluminium flat-plate would be melting and allowing ever-increasing amounts of that superheated plasma into the wheel-well. Evidence for this?
_
e._______ Dittmore said that some recovered left wing tiles exhibited heat damage “that was not caused by re-entry heating”. In addition there were embedded orange beads within the over-heated areas of those tiles. My theory is that those beads will prove to be an oxide of one of the constituent metals in the Inconel RCC support bracket.
______ _
Solutions?
1._ Shuttle crews have already flight-tested miniature robot cameras for in orbit inspection. See link here
_
2._ A two-part mix layer of an Araldite-like epoxy-based ablative substance could be overlaid across a damaged section (including the LE) and exothermically set itself in place. If thick enough, it should last out a "once off" re-entry (and be within the controllability of the lateral controls – or a similar patch applied to the other wing for symmetry). Once damage is evident, to achieve this “patching” an EVA astronaut would require a couple of LE overcentre-locking clamps (i.e. with long handles to get back above and below the LE) and an LE cable between them (for his positioning and leverage and to hold the 2 clamps together). The clamps would be affixed and later removed whilst he is tethered and manoeuvring with a jet-pack. This is not rocket-science.
_3. It might be possible to affix a sacrificial wedge-shaped launch leading-edge that would protect those inboard areas near the wheel-wells, in a protective profile that would be acceptable aerodynamically for a launch abort - and yet quickly burn away on re-entry. Silicon rubber springs to mind as a suitable protective medium.
A._ Link__ What is RCC?
_
B._ Link__ A Leading edge breach is chief candidate.
_
C._ Link__ The External Tank and its Foam
_
NASA have released a 13 minute video shot inside the orbiter by the crew, during re-entry of Columbia, and ending 11 minutes before the loss of communication with the orbiter.
Video (Real Media)
and some images of Columbia in orbit, 4 days into the mission, photographed from the AMOS system in Hawaii.
None of these pictures show the left wing leading edge area, although the right wing leading edge is clearly visible.
Surely some images showing the left wing were captured too ? I wonder if they will be released.
Video (Real Media)
and some images of Columbia in orbit, 4 days into the mission, photographed from the AMOS system in Hawaii.
None of these pictures show the left wing leading edge area, although the right wing leading edge is clearly visible.
Surely some images showing the left wing were captured too ? I wonder if they will be released.