Picky Perkins--
The NY Times of Feb. 5 ran an article summarizing the paper you cite, under the title NASA Was Told in 1990 About Vulnerable Protective Tiles Here's the URL: http://www.nytimes.com/2003/02/05/na...t&position=top

The article, which is well worth reading, focuses on the wheel wells, pointing out why they are potential trouble areas, but it also explains by implication why the diagram of danger areas is asymmetrical. (By the way--the Times article has a similar but simplified diagram of the shuttle, but the paper it cites, by the authors you name, is dated 1990. A minor mystery, probably not worth puzzling over.)

The Times authors say,
"Tile damage in the wheel areas was relatively high, as it was along the whole right side of the underbelly. That, they found, was because foam insulation had flown off two long pipes that run alongside the external fuel tank."

In addition,"To the data on tile damage, the scientists added temperature readings of where the shuttle tiles became hottest and were most likely to burn through. Dr. Paté-Cornell said the wheel areas got unusually hot during re-entry because their doors created a 'discontinuity' in the tiles that would disrupt the smooth flow of air over the shuttle's belly."

The authors of the cited paper then correlated the tile-damaged and high-heat areas with vulnerable parts of the shuttle: places where hydraulic lines ran underneath, as well as sites of hydrogen and oxygen tanks.

vaneyck

Thanks for the interesting NY Times article. The reason for the seeming discrepancy in the dates is given in the article: “They did their study for NASA in 1990 and published three academic papers on their work in 1993 and 1994.”

The diagram seems to have been omitted from the on-line version you linked to.

The NY Times article seemed to me to be somewhat misleading in that it did not specifically say that improvements were made to the doors as a result of the study:
--- Start quote from the 1994 paper ------
… tiles in some particularly hot areas had to be redesigned. For example, the tiles in the elevon cove (the gap between the rear flaps) and on the edges of the main landing doors had to be reinforced. After these adjustments, normal heat loads were not considered a problem for well-bonded tiles. This is why our analysis focuses mostly on the possibility of tile debonding because of a weak bond or the impact of controllable debris. …
--- End quote -----------------------------------

One of the surprising findings in the 1994 paper was that a few (e.g. 12) tiles were found installed with no bond at all. They were only kept in place by friction with adjacent components. Also, workers were given a quota of tiles to install in each shift. They found they could speed up the cure of the adhesive by spitting on the adhesive, and this aided them in meeting the quota. However, once in space, resin which had been spat on reverted back to a liquid! The paper implied that all these aspects were taken care of long ago as a result of the study.

Another interesting NY Times article says that roughness can trigger turbulence at much higher speeds than normal (e.g. Mach 18) and lead to much higher than normal heating, and that this had happened to Columbia before. Apparently a much-studied phenomenon. It can happen on one or both sides of the a/c. http://home.infi.net/~blueblue/_uimages/pi.gif

There has been a lot of speculation about the tiles since the investigation started, and Ron Dittemore, for whom I have the utmost respect, has been reluctant to identify them as the culprit. Having followed this mission, and most others, from start to finish (and this time into the sad beyond), I sympathise with his caution.

It is undoubtedly one of the most critical features of the Orbiter and is only put to the test during re-entry when the craft is exposed to the greatest thermal and aerodynamic stress. The max q occurs at around the altitude and velocity at which Columbia was observed to have failed (re: previous questions). However, from the earliest flights, Shuttles have returned safely to Earth with some remarkable tile damage without suffering nail-biting damage to the underlying "conventional" structure. Many improvements to tile bonding, and related issues, have been implemented over the years.

The Tile Papers

Just to clear up a couple of points raised by PickyPerkins & vaneyck in respect of the (superb) Paté-Cornell/Fischbeck paper Risk Management For The Tiles Of The Space Shuttle (et al):

Caution: Please note that the following links may require long download times on slow modems.

1. The original was first published in 1990. The (shorter) "RIsk Management" paper appeared in 1994 and also won an award. I think it gained further awards in later years (not relevant to this thread, however). These documents are not "proper" PDFs in that they are effectively photocopies on Acrobat. Not exactly leading-edge technology :(

2. The apparent asymmetry in the diagram on Picky's post is explained by, "We found that 15 percent of the tiles account for about 85 percent of the risk and that some of the most critical tiles are not in the hottest areas of the orbiter's surface" in the above papers. . . . . IE: It depends on what's underneath the tile (hope that helps).

Whilst this excellent audit did result in significant changes to tile processing and inspection, it did not (and may not have been intended to) discuss loss of the Reinforced Carbon-Carbon (RCC) sections of the heat shield in depth.

KE=½MV² . . . or not ?

And here lies the rub (sic). What really happened when that "2.2 lbs (1kg)" chunk of ET insulation struck the RCC leading edge of the left wing at a relative speed of [±]1090 ft/sec (330 m/sec) ? That's a KE of 40,200 ft lb (54,500 j). Where did it all go ? Did it simply fragment on impact thus dissipating the KE, or did its MV² weaken or fracture part of that most critical component ? Quite a punch, though. Imagine the effect on your head at such velocity. Ouch ?

Unlike the tiles, the rigid RCC leading-edge sections are bolted to the wing with more flexible separators between each section. Behind them is further thermal protection, eventually leading to the flat front of the leading-edge aluminium wing box. Forget the razor-like profile of the old F-104 Starfighter wing, this STS baby is 5 ft thick at max chord. That's one heck of a speed brake if even one RCC fairing is removed at Mach 20 . . . . near the time that Max q was achieved and the anomolies began to appear.

Focus! . . . Focus!

In many aviation-related accidents there have always been "Godarnit" impairments to otherwise vital evidence. What a shame that the critical hi-res cameras, that could have produced photo qualities that we have marvelled at on most post 51-L launches, were out of focus on this particular launch. Is this simply complacent lack of attention to QC, at the relevant sites ?

Equally unfortunate is the much-circulated picture of Columbia from the Starfire Optical Range (SOR, Kirtland AFB, NM) which, according to the publicity, is allegedly capable of resolving a 1 ft object at 600 miles (OK, I know there are two optical devices). The picture of Columbia at a mere 40 miles-up is unimpressive. It was released to the press as a negative and, either way, is inconclusive but significant. It just appears to show an anomaly on the left wing leading edge where RCC sections should be. It also shows a more pronounced trail from the left wing immediately aft of that anomaly. It is of course presently a coincidence that drag was observed to be building up on that side at the time.

http://ourworld.compuserve.co.uk/DrS...s/Kirt-107.jpg

Dittemore is now (with great relief, no doubt) handing over to an "independent" BOI. I am sure it will do its job well. Be patient. I doubt it was the tiles. The truth will out.

Syn and other knowledgeable people
 

Very interesting stuff. For a space laymen such as myself, are the flight controls on the Shuttle already in use during the exit phase? The point being - would a left yaw tendency already have been noticeable during the climb at any point?

My understanding is that this is a degraded image. The original, forwarded to the investigation team, should have an order of magnitude better resolution.

Sorry, can't quote any source...

--alex

Relative velocity of foam chunk?
 

DrSyn, Could you explain further the 330m/s you give as the relative velocity of the chunk that came off the ET.

I would expect the relative value to be somewhere between the shuttle velocity and zero depending on how long it would take the chunk to accelerate to its falling velocity.

Drag and the thin air density at that altitude would be factors in this acceleration and I don't have the mathematics to work this one out.

atakacs, you forgot to add at the end, ". . . or they'll shoot me!" You are quite right. I should have put a ;) after that little dig! As they boldly advertise Starfire's "1ft @ 600 miles" capability, the public release of an ultra lo-res blur seemed slightly bizarre to me. It would be sad indeed if that expensive bit of kit were unable to provide the investigators with such potentially vital evidence.

RBF, useful question - the relative velocity was not my calculation. ½MV² is about the limit of my practical Physics these days! It was based on the Jan 17 routine post-launch debris review which (I think) estimated that the debris had reached 744 mph / 1090 ft/s at the time of impact. I now note that in the Jan 21 report, that estimate had been reduced to "730 ft/s" (222 m/s) which would make the KE about 29,570 j (40,090 ft lb). Notwithstanding any math error on my part (!), those Jan estimates are a tad "ball-park" and may not have had total unanimity in their conclusions. Still, in the wrong place - quite a whack methinks. Enough to weaken a RCC panel or its attachments?

I am sure they'll work it out and have the remaining fleet up and running before too long. Good luck Admiral Gehman and team.

Sorry, FC, I didn't mean to ignore you! Yes, the aerosurfaces do carry out various functions during the very early part of launch and then position to provide wing load relief. Otherwise all "steering" is effected by thrust vectoring.

Like all space rockets, the shuttle stack climbs initially at a steep angle to get it into the less dense upper atmosphere ASAP, before accelerating rapidly down range. If any abnormal drag had occurred during ascent, the necessary corrections should be evident from the telemetry. I guess by now they have looked through that in great detail.

Any missing tiles or weakened RCC component would probably not be a major factor until the high stresses of re-entry. Whatever first detached over California most likely holds the clue.

Question for those who know, 'cos I don't.

About ten years ago I found myself spending some time in Russia looking at Spacecraft systems, we covered re-entry technology.

The semi-spherical capsules built by the Russians (most notably Resurs and Soyuz) use a single piece moulded composite heat shield which ablates. and in the course of re-entry loses 10-20mm of thickness (for the unmanned Resurs capsules they actually re-use these once). Buran on the other hand, uses a form of thermal quilt, I believe using substances not chemically all that dissimilar to asbestos.

An obvious feature of both of these is that neither has or critical local attachments, which seem from most discussion to be the weak point on the Orbiter's system. So why did NASA go for this particular solution - is it because it's an obvious derivative of the system used on the Apollo capsules? NIH syndrome? Or were they genuinely convinced that it was the best solution available - in which case what are the faults in the Russian systems that I can't see?

G

Apollo had an ablative heat sheild, not the tiles like the shuttle.

The tiles were to be reusable quickly and it can be argued have worked quite well for 100+ missions.

Asbestos is very tough to use in the USA now with current regulations.

Furthermore the Buran only flew once so it is not really a good comparison as far as reusability is concerned. It would be intersting how many flights it would have flown before it blew up.

Cheers
Wino

According to this site the Soviet Buran shuttle used similar materials and methods to the US Shuttle.

------- Start quote ---------
The gliding descent from the orbit through dense layers of atmosphere has stipulated the necessity to use a principally new reusable thermal protection system designed to sustain 100 flights. For the BURAN orbiter three kinds of thermal protection have been developed:

• "carbon-carbon" material with maximum operating temperature up to 1650 degrees C for the components with the highest thermal load -the fuselage nose and wing leading edge,
  
• ceramic tiles for parts heating up to 1250 degrees C,
  
• flexible material for surface parts with the temperature not higher than 379 degrees C.

All of them surpassed by strength the materials used in the USA Space Shuttle construction.
------- End quote ---------

Question: How were the spherical spacecraft prevented from spinning on reentry initiated by random protrusions on their surfaces?

The unevenness might be there initially or develop as ablation proceeded. http://home.infi.net/~blueblue/_uimages/pi.gif

DrSyn posted a photo above which has been said (not by DrSyn) to show a “bite out of the wing”.

I may be trying to squeeze more out of this fuzzy photo than there is to be squeezed, but my impression is that it shows something projecting forward of the wing rather than something bitten out of it.

To make this easier to talk about, I took the image of the left-hand side of the a/c and flipped top-to-bottom, and drew in some vertical guide lines. I accept that the photo does not show a truly plan view. However, I think its near enough.

I think I see something projecting forward of the leading edge of the left wing in the flipped image. What do other people see?

The next two images are copies of the first two, but with more contrast. The last image is a superposition of images 2 and 3.

What could the projection be (if it is really there at all)? Is it a solid part of the orbiter? I assume not, but it might be. Could it be material being ablated off the wing? The atmosphere was very thin where it was photographed over New Mexico, at maybe 200,000 ft. Could ablated material move up-wind at all on a vehicle moving at more than Mach 20 in a VERY thin atmosphere? I have no idea.

Anybody have any relevant information or opinions?

http://home.infi.net/~blueblue/_uimages/compd.gif
http://home.infi.net/~blueblue/_uimages/compdd.gif

Note added 10th Feb. 2003
Looking at the video shot in Texas it seems obvious that ablated or burning material can and does move ahead of the solid material. So personally I now tend to believe the photo may show ablating material both ahead of and trailing behind the left wing.

This material seems to be in line or outboard of the undercarriage door area. As far as I can tell fron photos, the hinge of the doors are about in line with the change in angle of the leading edge of the wing, with the undercarriage well being inboard of the hinges.

Looking at the original photo posted above by DrSyn, the pixel size seems to me to be appreciably smaller that the size of the features under discussion. http://home.infi.net/~blueblue/_uimages/pi.gif

Some of the physics

Neither the mass nor the density of the object that fell off affect the total energy delivered to the structure. The relevant quantities are the area of the fragment presented to the slipstream, the dynamic unit pressure at the prevailing flight conditions and the distance between the point of detachment and the point of impact. From this must be subtracted the energy remaining in the fragments immediately after impact.

Assessing the potential for damage is far more difficult as it involves the area of impact and the strength and rigidity of both the fragment and the structure.

Just catched this one:

Atlantis Adjusted Re-entry Fearing Damage

Really wondering if it might have made a difference...

--alex

I heard (on the Batchelor and Alexander show) last night that the ex-Orlando Sentinel NASA beat reporter said after Challenger the whole nasa staff knew their was only a 12% that any shuttle would come down safely. If I find the link I'll post it.

Has anyone access to any similar pictures of previous shuttle re entries? These could make it easier to judge what is a genuine anomaly and what is an artifact of the photograph.

The asymetry between wings in the photos probably indicates that the wing is ragged or damaged.

However the detail can not be ascertained in a jpeg photo with low resolution such that the pixels are far bigger than the defect. with accompanied bleed over of black information into white pixels.

The good pictures available to NASA have not been published.

You might try this link: STS96

Which raises an interesting question: is the Starfire's image IR ? If so there should be some sort significant temperature gradations visible ?
If the Starfire's telescope is IR and caught the shuttle exposing previously unheated material, we would see
a different shade of black/gray or bright white/lesser white. :confused:

BTW: another picture worth mentioning (I guess): Average ascent picture

--alex

(Quote)
I heard (on the Batchelor and Alexander show) last night that the ex-Orlando Sentinel NASA beat reporter said after Challenger the whole nasa staff knew their was only a 12% that any shuttle would come down safely. If I find the link I'll post it.

Whilst I've no doubt that you're quoting correctly, I think this is a rather libelous thing for anybody to say about a group of highly trained aerospace professionals. I don't for a moment believe that it is true - who in such a case would send people up. Also, the statistics simply don't bear out the point.



Re: Russian capsules. The apparently spherical shape is an illusion, the bottom is actually about the same shape as the Apollo capsules, it's just that the top continues round in something rather more resembling a sphere than NASA's preferred cone. I suspect the Russian system is rather more structurally elegant, but otherwise very similar. Small corrections were aerodynamic through built in combination of shape and CG (a bit like a weeble). Large corrections were via small motors in the apex I think - but this was really only for the earliest stage of re-entry.


Thanks for the correction about Buran heatshield. My work in Russia was mainly on Resurs with a bit of Soyuz so I'm probably just remembering the quilting as an example of alternative methods.

G

Rather than post again, I have added a note to my post of 9th February 2003. http://home.infi.net/~blueblue/_uimages/pi.gif

PickyP

I have also had a play with this image. I traced the outline of the right (intact looking) wing, and flipped the outline onto the left (damaged looking) wing.

Then I wondered why it looks asymmetric - now could that be because this photo was taken when Columbia was making the left turn - at that point it was rolled 57' left, hence left wing down.

This does 2 things - it makes the fin (and any associated plasma trail) visible to the camera - which I believe is the trailing edge artefact, and may also make visible any plasma / hot flow above the wing to some extent.

Anyone know if there is a significant (ie visible) 'cloud' of plasma or material above the wing in normal re-entry ?



http://www.grafsnowboards.com/shuttle.jpg

The orange line is a symmetrical outline of the right wing (for reference).

Anyone got an opinion ?

An Answer to Picky P's Question??
 

Picky Perkins

Re the question you asked in your 09 Feb post:

"I think I see something projecting forward of the leading edge of the left wing in the flipped image. What do other people see?"

"Anybody have any relevant information or opinions?"




You may find the answer here at this link (as supported by various emerging facts and the Pate-Cornell/Fishbeck 1994 Paper)

I do NOT think that it was anything to do with a "not quite overhead shot" or a banked attitude. In fact the damage discussed in the link may have propagated ALONG the LH leading edge by the time this shot was taken (60 secs prior to break-up)

TheShadow

I looked at the re-entry image of STS-96 which was linked to by atakacs.

It is remarkably symmetrical compared with the one image available for STS-107 Columbia, and has almost no trailing material. http://home.infi.net/~blueblue/_uimages/pi.gif

http://home.infi.net/~blueblue/_uimages/STS96.gif

sir,
 

In your image, with the centre line, the Shuttle looks asymetric from the tip of the nose to the end of the fuselage. That indicates to me that the shuttle was one wing high at the time.

Smackdown of the Shuttle Program written in 1980!

Little did the author know he was being an optimist.

Regards.

Yet another interresting picture

Not really conclusive, though...

--alex

atakacs
---------
This diagram from the same web site you linked to has the same illustration but also has some words with it which seem to make a lot of sense out of what we have been hearing about the ablation pattern and the sequence in which the sensors failed.

--- Quote from words on the diagram ----
... Wiring diagram shown is for the left wing. Scanners attached to the orange lines failed first, and six sensors on the main gear failed last.
----- End of quote -----------------------------

The orange wires take a 90º bend directly behind the leading edge of the wing where the sweep-back angle changes, shown in the NASA photo below of Columbia on the pad before launch of STS-107.

Of course, we should also remember the NASA warnings against jumping to conclusions which may turn out later to be wrong. http://home.infi.net/~blueblue/_uimages/pi.gif

http://home.infi.net/~blueblue/_uimages/wing.jpg

One of the press releases covering the sequence of events says something like.... the onboard systems fired the thrusters when the elevons were unable to correct for the asymetric drag.

Out of interest, have the thrusters ever been fired before during this phase of flight or is this just a sign of how bad the situation really was?

Some very interresting picts here:

http://www.eclipsetours.com/sat/index

The net is an amazing place...

--alex

Engineering?
 

CNN this morning showed exerpts from a NASA engineering memorandum suggesting that there would be a problem if the shuttle undercarriage didn't deploy when needed. In contained phrases like "Totally screwed up" and "World of hurt". Are these NASA engineering terms? Most engineering memoranda I have seen are a bit more technical. Are these the terms NASA engineers think in?

It was an internal email apparently hence the informal language, see this story: Email warned of catastrophic failure.

Regrettably, it now seems that the lo-res picture that has triggered so much debate in recent days really is all they took at Kirtland on that fateful morning - with a 3½" telescope and an "old" computer . . "in their free-time." Evidently, the precision elements of Starfire were not employed nor, indeed, requested. No comment.

Just to consolidate some of the plethora of references on this thread (please note download size before clicking!) here are links to the pdf (Acrobat) docs referred to - the big ones are for seriously interested folks only! (Shift+Left Click to view in a separate window) :

The emails mentioned by rehkram can be found here (192kb).
The original Paté-Cornell/Fishbeck paper - 1990 (4.8mb).
The later Paté-Cornell/Fishbeck paper - 1994 (2.9mb).

Ms Paté-Cornell has been reported as saying that she agrees with Ron Dittemore's remark about a "missing link" at an earlier briefing following the accident. It is also now being suggested that one sensor indicated "improper" left gear deployment, just before breakup, although two other sensors did not. Gear extension at that speed, if so, would undoubtedly be catastrophic and does not, in my personal opinion only, explain the progressive drag increase observed prior to the main event.

Below is a diagram of the left wing structure, which I hope helps to visualise the layout and what it all looks like under the Thermal Protection System (TPS). Note the short distance between the LE and the wheel well, around the point where the wing-sweep changes.
http://ourworld.compuserve.co.uk/DrS...images/LWs.jpg
Enlargement .

This is taken from the earlier Ko-Fields Report Oct 1987 (1.3mb)

I remain inclined to believe that there may have been (also) a RCC LE panel contributing to the scenario. This would indeed be a formidable missing link. Picky's link of Columbia's LE (Page 10) clearly shows the grey RCC panels for those unfamiliar with the subject. Likewise, the video appears to show two separate pieces of debris falll from the ET at the 81-sec point during launch ---- two bits = two possible damage sites.

I read the whole email. 40 psi overpressure my foot!! What about the kinetic energy of the wheel fragments? I remember on an introductory course to the F101 that we were told that the most dangerous thing on the aircraft was not the nuclear weapons, but the tyres. It was phrased thus: Each wheel contains enough stored energy in compressed air and stretched nylon to put a golf ball into geosynchronous orbit.

Further to my last, this statement has been recently released:
----------------------------------------------------------------------------
Steve Nesbitt
Columbia Accident Investigation Board Feb. 13, 2003
(Phone: 713/301-9571)

RELEASE: 03-072

STATEMENT BY THE COLUMBIA ACCIDENT INVESTIGATION BOARD (Feb. 13, 2003)

Note: The CAIB has asked NASA for administrative support to release information to the public and the media. The following statement was provided by the CAIB for release.

Thermal Analysis Shows Hot Plasma Possible in Columbia Left Wheel Well Area

Preliminary analysis by a NASA working group this week indicates that the temperature indications seen in Columbia's left wheel well during entry would require the presence of plasma (super heated gas surrounding the orbiter during re-entry).

Heat transfer through the structure as from a missing tile would not be sufficient to cause the temperature indications seen in the last minutes of flight. Additional analysis is underway, looking at various scenarios in which a breach of some type, allowing plasma into the wheel well area or elsewhere in the wing, could occur.

Other flight data including gear position indicators and drag information does not support the scenario of an early deployment of the left gear.

The search continues for possible debris from Columbia in the western U.S., but as of early Thursday, no debris further west than Ft. Worth, Texas has been confirmed as Shuttle-related.
------------------------------------------------------------------------------
I refer to my (and others') earlier remarks on RCC sections.

RCC; chronology
 

Here is a NASA plain english overview of RCC (reinforced carbon-carbon) panel manufacture, fixings and usage on the wing leading edge:
http://spaceflight.nasa.gov/shuttle/...ps/carbon.html
Plus some coherent reporting on the exact sequence of events, contains some information I'd not seen before:
http://sfgate.com/cgi-bin/article.cg...4/MN226524.DTL

atakacs wrote: Some very interresting picts here: http://www.eclipsetours.com/sat/index The net is an amzing place...
-----------------------------------------------------------------------

Apparently too interesting. The picts have been removed. http://home.infi.net/~blueblue/_uimages/pi.gif

Search for Shuttle Pieces
 

Foot search continues in Albuquerque, New Mexico today for a desk sized pice of shuttle that was tracked by radar as it fell into the Sandia Mountains East of Albuquerque. USAF helicopter search of the area on Thurs yielded nothing, but the search was instigated after a local woman found a confirmed piece of the shuttle on Thurs morning.

Albuquerque is some distance away from the main crash area in Texas, and the shuttle was viewed as it passed overhead to be reasonably intact (ie no distinct trails in the sky).

A report says that early analysis of low-frequency infrasound data sound-wave recordings suggests that the space shuttle Columbia depressurized and blew apart in a single explosion near Lubbock, Texas.

The report says that a preliminary analysis was posted earlier this week on a Southern Methodist University (SMU) web site and then removed. NASA has impounded the information, along with similar recordings from other infrasound stations in the western United States.

Infrasound is low-frequency sound, waves at 20 hertz or lower – just below the threshold of human hearing. The report said that it took about 30 minutes for the sound waves to travel the distance from the shuttle to the infrasound array near Lajitas in the Big Bend region, and to another in Nevada.

I believe the main purpose of the infrsound network is to plot lightning strikes over the entire USA. http://home.infi.net/~blueblue/_uimages/pi.gif

Picky

TRY
this link

Associated Press
HOUSTON -- The board investigating the space shuttle Columbia disaster Saturday toured the Louisiana plant where the orbiter's external fuel tank was built, while searchers scouring the mountains of New Mexico -- west of where any debris has been found -- were coming up empty.

Investigators also revealed that two more Columbia control jets, making at least four in all, continued to fire in a desperate attempt to stabilize the shuttle during its final minutes.

The jets fire automatically when flaps on the shuttle's wings and tail are inadequate to control abnormal motions encountered at supersonic speeds. The information was coaxed from the final 32 seconds of ragged data sent from Columbia as it was breaking apart, investigators said.

The last voice communication from the shuttle's seven astronauts came as Columbia streaked across New Mexico during reentry Feb. 1 before breaking apart about two minutes later.

People near New Mexico's Sandia Mountains, east of Albuquerque, reported hearing a whooshing sound, said Peter Olson, a spokesman for the New Mexico Department of Public Safety. He said there also was radar evidence that debris could have fallen in the state, but he didn't have details.

About 140 searchers concentrated Saturday on a rugged 2-square-mile area of Embudito Canyon, walking a few feet apart. Nothing was found as teams began wrapping up by afternoon; one searcher picked up a small disc of melted metal that was later identified as part of a beer can. Two helicopters from White Sands Missile Range that criss-crossed the area also came up empty.

The Embudito Canyon search was expected to last only a day, but NASA could search elsewhere in the state, officials said.........