PickyPerkins

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.

sir

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.

DrSyn

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!

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.

PickyPerkins

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,

DrSyn

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:

Further thoughts, anyone?

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

PickyPerkins

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,

DrSyn

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

DrSyn

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.

BOAC

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

OVERTALK

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).

PickyPerkins

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.


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.


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?

OVERTALK

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).

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.

PickyPerkins

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,

DrSyn

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.

OVERTALK

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).

PickyPerkins

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.

ORAC

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.....

DrSyn

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

ORAC

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.

UNCTUOUS

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.