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."

From the Albuquerque Journal a picture of the system used by the "Starfire geeks":

http://www.abqjournal.com/pix/020903...pe02-13-03.jpg

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 !

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!

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.

When in doubt, launch another project:


www.denverpost.com/Stories/0,1413,36%257E33%257E1185329,00.html

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.

http://ourworld.compuserve.co.uk/DrS...ges/RCC-XS.jpg
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."

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

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.

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.

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.

From space.com article


On what basis ?!

Strikes me as really odd

--alex

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 --------

http://home.infi.net/~blueblue/_uimages/pi.gif

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

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?

http://home.infi.net/~blueblue/_uimages/pi.gif

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."

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. http://home.infi.net/~blueblue/_uimages/pi.gif

Picky

Isn't that picture dated 1979 ? - there's a caption in the folder above.

Presumably that picutre was taken during construction or something ??

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.

http://home.infi.net/~blueblue/_uimages/pi.gif

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
_

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.

This photo of the left wing has been published. Sorry, I can't remember where I saw it. I think it was taken on about the 4th day of the flight. The photo seems to show no visible damage.

Note added on March 5, 2003
The photo referred to above was taken during orbit 5 on flight day 1 and is the 8th photo here.
http://home.infi.net/~blueblue/_uimages/pi.gif

hmmm.....

cheers Picky,

I was also looking for a pic which shows the leading edge root extension / fillet section - the part where the wing leading edge sweep angle changes. I guess this is probably not visible from inside the orbiter.

I am glad that a few continue to show concern for this historic accident. Some interesting points raised by OT. I remain convinced, however, that the foam alone (now officially 3 pieces) was capable of doing the necessary damage, with or without added ice. I also believe that any ice involved was no more than subliminal but could indeed have precipitated debonding of the foam, for reasons already stated. sir, there are no known pics of that section of the LE, sadly.

There have been many previous significant hits on the TPS from foam, and well documented. I am inclined to believe that Columbia's TPS took at least two hits which damaged different sections of the heat shield, thus making the "back-tracking" of the break up sequence more difficult for the investigators. The RCC area still makes by far the most disasterous likelihood, with the possibility that any tile damage alone might have been survivable. But where was the RCC breached?

The original theories are holding up uncannily well. NASA provides a comprehensive tile pattern diagram here (PDF 337kb), which can be expanded in good detail. I am told it is quite accurate by those in the know. They also released a significant photo of a recovered portion of the left wing. Whilst I have no doubt that someone already knows exactly where it came from, I have found no official reference (OK, tell me I missed it).

Anyway, having mucked about with it for a while, it seems to me that it is from just inboard of the forward edge of the left wheel well. The blue outlines represent my efforts, whilst the yellow segment is an alternative theory doing the rounds elsewhere. If anyone can spot an elongated trapezoid like the one centre left (lower pics), with similar surrounding patterns, feel free to contradict - I'm not proud!
http://ourworld.compuserve.co.uk/DrS...ages/WL107.jpg
Note that the bare metal at the bottom of the picture has a smooth edge, as if it were cut by a torch. Not symptomatic of a break, or split.

So the questions are, just how many breaches in the TPS were there? Did the "spray" evident in the launch photos include significant "tile dust"? Answers on a post . . . please.

DrSyn Your analysis agrees exactly with the caption here of the photo, which reads:
--- Start quote ----
Piece of STS-107 left wing underside, forward and inboard of the corner of the left main landing gear door. Delivered to Barksdale Air Force Base on February 7, 2003.
--- End of quote ----

Cheers, http://home.infi.net/~blueblue/_uimages/pi.gif

Thanks for that, Picky, I must have walked right past that caption on my way to the big picture (duh, on my part!). Anyway it adds an interesting dimension, as the "smooth edge" is actually inboard of the wing bulkhead and under the lower fuselage. Was there a burn-through from the wheel-well, or down the inboard RCC "tunnel", or was the TPS also damaged further inboard than just the wing area? It does tend to support the multiple-damage theory, in my view.

Here are a couple of views highlighting the location of that section:
http://ourworld.compuserve.co.uk/DrS...mages/WW3D.jpghttp://ourworld.compuserve.co.uk/DrS...images/WWA.jpg
Further thoughts, anyone?

Addendum: This article in today's Houston Chronicle is worth a read. Must dash - another early start coming up :(

A question just so that I can be sure that I understand your left-hand drawing and to avoid confusion.

Shouldn't the center of the red ellipse be placed about one minor diameter lower than shown, so as to to be positioned around the corner where the front in-board lower edges of the wheel well meet?

Cheers, http://home.infi.net/~blueblue/_uimages/pi.gif

Yes, it was a bit "off", Picky. Now revised to be more illustrative!

There is a plethora of information on the web relating to the cause of this accident, some of it rather poor. As is usual, the official sources tend to be rather slow in updating. Some of the most erudite and current info is being supplied by a few of the US press sites, presumably "close to sources". I thought it would be helpful to those interested if I posted links to the ones that appear to have an educated grasp of the disaster.

Houston Chronicle

This site seems to pick up on the latest developments rather well and in good detail. Further to my earlier post, they published an update (ex- LA Times!) on the possible RCC theory yesterday evening, which places possible damage right up at sections 1/2.

Orlando Sentinel

Not quite as prolific as the Hou Chron but well informed. In particular, they published some excellent graphics in the first weeks, which provide some splendid pictures of the structures that have been discussed on this thread. A must for pilots who find text descriptions tedious to fathom! Some talented artists there, among which the name Ingrid Pecca seems to feature often.

An interesting article relates to safety recommendations that are already being looked at. Relevant to OVERTALK's earlier post.

CBS News

This site contains some excellent articles and seems to be on the ball all the way. Worth monitoring.
--------------------------------------------------------------

I won't mention those that might have been expected to be at the front, but have rather lost their impetus recently. There is a surprising lack of currency at certain sites which are normally as close to the action as it gets :(

I hope this is helpful to Space-PPRuNers. Please post any others you think useful.

UK television (Channel 4 - yuk!) are broadcasting something like 'Should it have launched?' this Saturday - 2000Z I think.

It would appear that the much earlier speculation on these pages about the cause and effect is now being borne out by CAIB conclusions. However there are still some areas that they've yet to reach:

a. A sacrificial silicone-based elastomeric wedge-shaped leading edge for the inboard areas of the Orbiter's wings that would protect the easily shatterable RCC sections from launch debris strikes. This covering would burn off in the early stages of re-entry and being a simple wedge-shape, would not unduly affect shuttle performance during an in atmosphere launch abort.

b. The solution to in situ in orbit repairs. The two long-handled over-centre locking clamps for mounting a (say) 15ft cable along the leading edge and enabling an EVA astronaut to apply a two part exothermic one-time repair patch.

c. The projection ahead of the inboard left wing leading edge shown in the Starfire Photo is obviously due to the super-heated plasma and the flat-plate effect (and here). This is something that NASA is yet to come to terms with. (quote: "The theory is also supported by a photograph taken by astronomers in Albuquerque, N.M., showing what appears to be a damaged, jagged area of the left wing.")

d. It is only a short step from here (this quote) to relating the super-heated plasma to the flat-plate effect.
"The leading edge theory is supported by several other pieces of evidence. Recovered leading edge panels now at Kennedy Space Center in Florida show that the attachment points were melted, rather than broken." and
"The wing was being eaten from the inside out," board member Roger Tetrault said. Similarly, investigators cannot explain why a piece of the left wing that adjoined the wheel well shows signs that a stream of hot gas had spewed out of the wing. Obviously the superheated plasma was entering forcefully at the leading edge RCC breach. Entry elsewhere would not explain the jagged projection ahead of the inboard L.E. or the "eating out" of the wheel-well interior....or the molten aluminium that was latterly being sprayed over the Shuttle's exterior by the plasma cloud (and embedded in the leading edges of non RCC tiles)

e. From the Washington Post Sunday 23 Feb 03 [page A20] "A worst-case analysis by Boeing Co engineers of the potential damage caused by the tank insulation estimated that the material could have hit the wing at more than 400mph and could have included pieces of ice which would have done more damage than the foam alone. A NASA engineer calculated that if the material was iced, it could have hit the shuttle with a force equivalent to that of a 500lb safe hitting the wing at 365mph."

Columbia moved to launch-pad 39a on 9 Dec 02. Columbia launched 17 Jan 03. By my reckoning it spent 39 days in the coldest temperatures Florida has had on offer in the last 100 years. The fact that, over many temperature cycles, the ET foam "worked" (and then cracked to its substrate due to ingress of moisture) should surprise no-one. Once the tank was filled with liquid hydrogen any trapped water would become adhesive ice and hold the ET foam in place (although cracked) until two things happened - aerodynamic heating and the drop [below the level of the foam's cracks] of the hydrogen fuel (as it was being used up during the launch). At that point (approaching about 400 kts) any weakened area of foam substrate (still stiffened by its water content in the form of ice) would lose its icy adhesion, detach and head for the Orbiter. The aerodynamics of the combo unfortunately had it hitting at what would prove to be the Orbiter's weakest point (the easily shatterable leading edge RCC tiles just forward of the wheel well's outer forward corner).

I have been looking again at the re-entry image taken by the USAF in New Mexico and first posted by DrSyn on 8th Feb 2003.

I posted several processed images the next day, a and b. The last figure shows the right wing superimposed over the left wing, and what I assumed (and still do) was ablated material ahead of and behind the left wing.

http://home.earthlink.net/~pickyperk.../wingcuff3.gif
The images above are the original image on the left, followed by the same image limited to 3- and 2- levels of gray respectively (all seen from below), and a photo of STS-107 on the launch ramp (seen from above).

It looks to me as though much of the leading edge of the left wing cuff may be missing, and if ablated material is present perhaps more structure may be missing than appears to be the case in this figure.

Missing material was not evident in my first post because the right wing cuff was superimposed over the left wing cuff hiding the latter. If I had done the superposition both ways the missing areas would have been evident.

http://home.earthlink.net/~pickyperk.../wingcuff4.gif
This figure shows the 2-level image and its mirror image, and the two superimposed. In superimposing these two images I have made the nose and wingtips coincide. The LH half of the superposition shows the ablated material ahead of and behind the left wing, while the RH half again suggests to me that much of the leading edge of the left wing-cuff may be missing.

So I am inclined to think now (as suggested by DrSyn for different reasons) that burn-through may have been INITIALLY far ahead of the wing and in particular much further forward than where the sweep back of the leading edge changes, and subsequently into the wheel well possibly from inside the wing cuff or fuselage.

If this is so perhaps the Boeing and NASA assessment that the damage to the underwing wing tiles was tolerable may have been correct, and that other damage further forward on the cuff was fatal. The tile hit map in the article titled, “From the beginning, foam was a concern for NASA” in the Orlando Sentinel linked to by DrSyn shows that most of the hits to STS-87 (more than 300) were on the wing cuff areas and not on the lower wing surface or leading edge. There might have been hits on STS-107 not visible to video cameras on the ground..

What do other people think? http://home.infi.net/~blueblue/_uimages/pi.gif

Hyper-Heated Plasma - Served on a Flat Plate
 

Picky
Not really following your argument here. But caution, I may just be being dense.
I gather from this that you disagree with the proposition that the jagged projection ahead of the left wing might be the hyper-heated plasma bow-wave (many orders of magnitude hotter than anything ever seen before) associated with a failed and shattered RCC section 6 or 7 (see below). A knowledgeable friend of mine says that "Yes, it would be opaque as far as a camera is concerned, just like the heat off the desert sands creates mirages and heat-haze - but only much more so" That's where I got the idea of the "flat-plate" effect. Consider that the reason why the Orbiter's wing leading edges are so relatively blunt is because the designer's choice was to absorb high mach re-entry heat in the bow-wave created ahead of a blunt wing section. Once you take away just one of those curved LE RCC sections, you are left with the inconel support brackets and an oblique flat plate of the aluminium wing. An erosion process quickly starts courtesy of the hyper-heated plasma and this is now being referred to as the "zipper effect" (which causes adjacent RCC tiles to be shed progressively out along the wing).
http://www.iasa.com.au/folders/Safet...files/ww3d.jpg
The trail behind (in that photo) is the detritus of that process. So as well as the inside of the wing being"eaten from the inside out" (once the gap between the flat-plate LE and wheel-well was broached), the LE flat-plate effect would have grown in length, creating greater adverse yaw and roll effects. Evidence for this has been found in the fact that the Orbiter parts recovered have had a fine coating of black aluminium oxide and the leading edges of ceramic tiles have sprinkled into them the once molten orange beads of one of the alloy metals found in Inconel 718 and 600 (the melted RCC support brackets). Hope you're following this line of thought. I'd be interested in why it might be invalid.

Basically it comes down to what I've said before. Give one of those solid RCC sections a square-on icy hit and shatter it and then there's really nothing retaining the pieces in situ (in addition to the all-important RCC anti-oxidant coating being pierced). After a few hot/cold cycles facing towards or away from the sun in orbit and the mildest manoeuvre would throw a large chunk of that shattered RCC tile (which is exactly what apparently happened from the manoeuvre logs - as recorded by Radar). The scene was then set for the erosion, wheel-well broaching and L.E. unzippering process. The early pre-dawn pyrotechnics over California would have been those section 6 RCC carbon fragments hyper-heating to a white glow and detaching.

A wedge-shaped elastomeric sacrificial Leading edge protective launch shield (for half a wing-span each side) is what the NASA Doctor is likely to order. That should adequately protect the RCC and burn away promptly without drama on re-entry, but without compromising its "in atmosphere" abort glide performance. In addition I cannot see NASA ever again foregoing in-orbit inspections of critical areas. Two-part exothermic mix "once only" overlays could be applied to any areas thought dicy. With the right composition goo, they just shrink into position and would protect against the sort of development that, with Columbia, started right at the entry interface and continued for 10-15 minutes.

OVERTALK I am not disagreeing with anything you are saying. I assume all the “flat-plate”, zipping, and other processes you refer to went on, and that we do see ablated materials ahead of and behind the left wing.

To summarize, there seem to be 3 possible areas of INITIAL damage:

(1) Under the wing, studied by Boeing and concluded to be tolerable.
(2) Leading edge, now under study by the CAIB.
(3) Wing cuff almost as far forward as the cockpit.

I am just suggesting that there is a hint of evidence for (3).

But I don't see any evidence as to whether (2) preceded (3), or the other way around.

But I do suggest that (3) could have initiated (2), but that (2) was unlikely to have initiated (3).

Cheers, http://home.infi.net/~blueblue/_uimages/pi.gif

I wish I had time to stop and discuss the above in more detail, but I am seriously busy at present and not just with flying! I agree with you, OT and PP, on the substance of what you guys are saying. As far as I can tell, a primary line of thought on the Board revolves around a breach at RCC 1/2 starting the "chain".

Do remember that the Kirtland shot was taken barely a minute before the total and highly visible disintegration started. Prior to that, whilst still in darkness, several "flashes" had been well observed as she passed across the dark sky. If, as is now being suggested, these were the evidence of zippering from the glove (cuff) rearwards, by the time they snapped her from Kirtland, the leading edge would have been well strippped back.

Tech note: Inconel melts at around 1350ºC, so not too quickly in that plasma. Any exposed Al surfaces, however, would be melting like cheese. Hence the complexity of the probable heat paths and patterns.

Therefore, that pic, with any additional heat effects described in above posts, would be quite accurate. However, it is not showing the initial cause/source, but merely the final state of Columbia just before she was overwhelmed. Hope that makes sense.

Also, I would just repeat what I have said previously: bear in mind that there was probably more than one damage point (as per previous flights ad infinitum). This time, unfortunately, it involved the RCC sections. Any one of them would be fatal. Thus, what did which first is largely academic. The issue remains to stop bits coming off in the first place.

Check out the 1999 Annual Report (sorry - 3.6mb PDF!), and see what they were saying about possible on-orbit damage to the RCC and the proposed fix (search "Inconel"). They were thinking in terms of micro-meteorite damage of up to 0.25" and its catastrophic effect in the wrong place. Not a hunk of debris "the size of a briefcase". You'll see what I'm getting at. The lower area of the RCC was considered most critical.

Of the three pieces of debris that detach from the ET in the crappy launch video, one which makes a fleeting appearance may have been well inboard, and one appears to strike the underside near RCC 7-9, IMHO.

Really must dash, but will chip in as time permits. God bless pioneers, all.

Glancing Blows and Ricochets
 

Dr Syn and Picky

Yes we are agreed except about the initial damage being that far forward on the wing cuff. It would appear to me to be so very tangential to the airflow that any telling blow would have had to be a ricochet forward (unrealistic).

The yellow highlit section in the diagram above (and anywhere further outboard) would be my guess for the position of the initial damaging blow by the ET's icy foam. The damage wouldn't necessarily be visually apparent - but once shattered, the positional (retention) integrity of an RCC section would be compromised (as would its anti-oxidation preventive coating).

The in-fuselage sensor record of overheating should be able to be explained away by conductive heat along a metal structural member. Like Dr Syn, I'm very busy and may have missed the basic reason as to why the forward wing cuff now figures (apart from the very "open to interpretation" graphic transpositions and superimpositions).

This is a 2 line summary of what I was trying to say above:

The USAF photo reduced to 2 levels of gray shows a narrower left wing cuff compared with that on the right wing.

IF the left wing cuff is actually narrower, then some of the left wing cuff may be missing.

That's all.

I have no other reason to suggest damage to the cuff.

Note added on March 13th, 2003

Except, of course, that most (by a large margin) of the debris hits are on the underside of the wing cuffs.

http://home.earthlink.net/~pickyperkins/_uimages/pi.gif

LA Times - 12 March:

Shuttle Investigators Look at Possibility of Weakened Wing.
Damage resembling pinholes is found on Columbia's left leading edge. Area may have been more vulnerable to a collision with debris.

HOUSTON -- Columbia accident investigators said Tuesday that they have found most of the leading edge of the shuttle's left wing and have discovered extensive damage that may help explain how the orbiter broke up on Feb. 1.

Investigators are looking at the possibility that the leading edge, which sustains some of the hottest temperatures on the shuttle skin as it flies back to Earth, was weakened through years of wear and tear that left pinholes and voids, investigators said.

The damage was similar to what termites cause in wood, said Harold W. Gehman Jr., chairman of the Columbia Accident Investigation Board. In this case, the voids occurred in reinforced carbon material just a quarter-inch thick that shields the aluminum wing from temperatures of nearly 3,000 degrees.

The voids and pinholes by themselves probably did not cause a failure in the leading edge, but they could have made the wing more vulnerable to a collision with debris, Gehman said. The board is still trying to assess whether the shuttle was damaged on liftoff by foam debris falling from the shuttle's external tank or by a collision with something in space.

"It is possible that the foam striking a healthy orbiter might not have done enough damage to cause the loss of the orbiter," Gehman said. "But it is possible that foam striking an unhealthy orbiter that had problems ... could do some damage. Is it an event she could have survived at age 10 but that she couldn't survive at 21?"

The Columbia was on its 28th flight when it broke apart, killing all seven astronauts aboard. It flew its first mission in 1981.

The concerns about the leading edge panels are not new. NASA has commissioned or conducted at least a dozen studies in the last decade looking at the panels. The studies examined damage by orbital debris, such as micrometeoroids, and pinholes that were first discovered on the Columbia in 1992.

The leading edge is constructed of a thin layer of material known as reinforced carbon carbon, sandwiched between two coatings of silicon material. The pinholes penetrate the exterior coating, allowing contaminants to eat away the interior carbon and leave voids, the investigators said...............

The investigators have some of the pieces from almost all of the 22 leading edge panels that line each wing. Notably, the panels from the left side show significantly more damage than the ones from the right side, Gehman said.

Investigators want to know how NASA and its contractors inspected and maintained those leading edges and whether the procedures were adequate, said Maj. Gen. John Barry, a board member. A team of investigators next week will visit the Lockheed Martin Corp. plant that provides the panels, he said. On six prior shuttle flights, orbiters returned with their leading edges damaged by debris, micrometeoroids or other causes, Barry said.

A Boeing official said Tuesday that "several of the wing leading edge RCC panels were reinforced to resist penetration or damage" when the Columbia went through a 17-month overhaul in Palmdale from 1999-2001. The official declined to provide details, saying the company needed approval from NASA to release the information.......

Other studies during the late 1990s raised the possibility that hot gases during reentry could enlarge pinholes that were appearing on the panels but concluded that the problem was unlikely to endanger the spacecraft or its crew. The microscopic holes were discovered in 1992 as NASA officials inspected the Columbia shuttle after its 12th flight. Inspections found the pinholes in other orbiters and NASA officials concluded that the holes generally developed after 10 to 15 flights, although the Columbia seemed to have the worst experience with them.....

There are links to the RCC "erosion" problems on the main sites (see previous posts), including detailed pictures. The article posted by ORAC contains some prime BS from Boeing in the line, "The [Boeing] official declined to provide details, saying the company needed approval from NASA to release the information...". I suspect that the line translates " . . and as an official spokesman for Boeing, I haven't a clue what I am talking about, so I'll pretend that it's a state secret to fob-off you journos . . ."

The 1999 Annual Report (3.6mb PDF, as per my previous) stated it quite openly and clearly. I'll quote it directly as some of you may not have beeen able / had time to view it.

"Another safety improvement the SSP implemented was additional thermal wing leading edge protection to prevent wing structure over temperature/failure and potential loss of vehicle due to a hole in the wing leading edge. Current wing leading edge capabilities permit a 1in. hole on the upper surface of any panel. But on the lower surface, no penetrations are allowed on the lower surface of panels 5-13. In these locations, a hole generated by orbital debris would allow heat from the plasma flow during entry to quickly erode the 0.004-in. thick Inconel foil of the “Incoflex” insulators. This will cause a loss of insulating properties and exposing the leading edge attach fittings and wing front spar to direct “blast” from the hot plasma.

"The upgrade to include additional insulation would allow single entry with a penetration of up to 0.25 in. diameter in the lower surface of reinforced carbon-carbon panels 9 through 12 and up to one inch on panels 5 through 8 and panel 13. The design team evaluated requirements for meeting the 0.25 in. requirement.

"A variety of design requirements also considered during the evaluation including minimum weight with no additional post-flight inspections. The implemented design solution after analysis and testing were complete was to add high-temperature Nextel 440 fabric to the Incoflex insulators with one layer for panels 5 through 7 and 11 through 13 and two fabric layers for panels 8, 9 and10 (highest heating environments).

"Overall weight increase to the orbiter was 53 lb. This hardware is currently implemented on OV-103, OV-104 and OV-105 and OV-102 during the maintenance down period ['99-01]." (My emphases)

It may or may not be relevant, but note that panels 1-4 were not included. Also, 107 launch-debris impact is believed to be on the lower surface of the LE, and only orbital, not launch, debris is considered in the above scenario despite earlier experience. No intention of insulting anyone's intelligence here but, just to clarify, due to high alpha (40º) during max re-entry heating, the lower surfaces bear the brunt.

Off to bed :(

CNN - 17 March - Shuttle lost a 'steady stream' of debris.

HOUSTON, Texas (AP) -- Columbia lost "a steady stream" of pieces from California all the way to its final breakup over Texas, as wires in its left wing burned and shorted out, shuttle officials told the accident investigation board Monday.

"We continue to be shocked that we had debris coming off the orbiter as we crossed the California coastline," said NASA flight director Paul Hill. He is leading debris recovery efforts in the West, which so far have yielded no wreckage.

Later, to illustrate his point, Hill showed a video that was a composite of 15 to 20 amateur videos sent in by citizens.

Hill expressed amazement that during much of the time debris was falling and sensors were going haywire -- probably from hot atmospheric gases that had entered a hole in the left wing -- "the vehicle flew perfectly, no indication of what was going on in flight control."

Aside from unusual temperature and pressure readings and sensor dropouts, "the vehicle flew like a champ right up until the breakup, so that did surprise us," he said, testifying in the second hearing of experts before the investigation board. Another hearing is set for Tuesday morning.

He and another shuttle official, Doug White of the NASA contractor United Space Alliance, said the sensors probably started blinking out one by one as the wires burned inside the left wing and, in some cases, simply shorted during Columbia's doomed re-entry on February 1.

The investigation board suspects the left wing was breached possibly by launch debris 16 days earlier. At least three pieces of insulating foam or other material on the external fuel tank snapped off and hit the wing.

In the videotape Hill showed, the shuttle is seen as a bright, white object against the dark sky; 15 times, a piece big enough to be seen came off. Twice, a flash accompanied the shedding object, perhaps the result of combustion -- in other words, the pieces may have been burning when they came off.

Hill told the seven board members present that without the videos, "We wouldn't know any of this. These people are definitely our heroes."

An expert in spacecraft re-entry, William Ailor of the Aerospace Corp., said 10 percent to 40 percent of the pieces that typically fall from a returning spacecraft usually survive atmospheric re-entry. Most of that falls in the ocean and is never recovered, however, he noted.

He advised the board to focus the debris search on the early wreckage and on parts of the shuttle of particular interest, like the left wing.

He said it is critical to the investigation to find some of shuttle pieces that fell out West. So far, that hasn't happened.

The Westerly Debris
 

The reason why those coast-crossing sources of brilliant light detaching from the Columbia won't be found is that they were almost certainly highly incandescent particles of carbon from the shattered portion of the left wing's RCC leading edge breaking away (see previous OVERTALK posts from a few weeks ago).

In the pre-dawn darkness they would have appeared very bright but soon burnt up almost completely. Anyone familiar with the carbon arc searchlight as used on Maritime Patrol P2's and P3's will explain to you why the carbon feed-rod burns up but punches out over 200 million candle-power in the process. The RCC is made from the same stuff.

So looking for carbon particles that are likely to have been latterly very small would be a vain quest. I would be very surprised if anything is ever found West of Ft Worth.