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The CAIB has already begun work on the investigation in earnest. The following are major points of interest made public in the
course of their efforts:

Members arrived at KSC on 2/12/03 to tour the facilities that will be used in their efforts, including the Orbiter Processing Facility Bay 2, currently housing Endeavour, and Bay 3, where Discovery is undergoing maintenance. On the same day, the CAIB also visited the Vehicle Assembly Building where Atlantis, with its external tank and solid rocket boosters, is atop its mobile launch platform awaiting final checkout prior to rollout to one of the pad sites at Launch Complex 39. Afterwards, the CAIB met throughout the day with KSC officials to get an better overview of ground processing activities.

Over the next few days, the board visited the Solid Rocket Booster (SRB) Disassembly Facility, the SRB assembly and refurbishment facilities, the Launch Control Center, and Launch Pad 39A, where Columbia was launched. As the trip to KSC was essentially an orientation visit, the CAIB traveled to Huntsville, AB, and then to New Orleans, LA before returning to Houston where the board began working "seven- or six-day weeks".

• In it's first major finding announcement shortly after its formation, the NASA-appointed board put forth the hypothesis that superheated gases surrounding the spaceship during its descent through the atmosphere penetrated the left wing and fatally compromised its integrity. This was followed on 2/18/03 with the second major announcement confirming that ground observers had been correct, and that Columbia began fragmenting over the California coast well before the final disintegration over Texas. The conclusion was based on images taken by astronomers and amateur photographers on the West Coast. Using these images, the board concluded that Columbia was shedding pieces a full six minutes before it entered the airspace over the Dallas-Fort Worth Metroplex.
  
  Of note was the interest CAIB members expressed in the hope that searchers in Texas or farther west along the ground track will find droplets of melted aluminum among the debris. These particular bits of debris might offer answers to how quickly the Shuttle’s aluminum skin melted when superhot gases penetrated its left side. The board also clarified, however, that the search for the fragments that broke loose over California would probably have little, if any success. Per board
  member James Hallock, the fragments were "probably so small they burned up before reaching the ground."
   
• The CAIB also announced that it had split into three teams - materials, operations and technology - and began researching into what may have caused a breach in the Shuttle's left wing. With regards as to possible causes for the mishap, the board members also announced that at this time they were not convinced the debris that hit the left wing shortly after liftoff on 1/16/03 was in fact insulating foam from the External Tank. The CAIB is still strongly considering the possibility that the
  debris seen to have been impacting the leading edge and/or the underside of the orbiter was actually ice or a chunk of the heavier insulating material layered behind the foam.
   
• Meanwhile, the board announced that in addition to looking into the physical causes of the Columbia disaster, they would also be looking at the Shuttle program’s management practices, including the effects of recent cost-cutting. The board will now have more time as well: a 60-day deadline has been dropped.
   
• In response to criticism made by certain officials in Washington that the CAIB was too closely tied to NASA, the board announced plans to hold its first public hearing on or after 2/27/03. The hearing will be held in the Houston area, and non-NASA experts who have theories about what destroyed the Shuttle will be asked to speak before the board.
  
  Per board chairman Adm. Harold Gehman Jr. (USN RET) "We will invite experts who are not associated with any US government program who have theories or hypothesis, who have written to us or provided research documents, to express to us their opinions."
   
• On 2/18/03, the CAIB ordered an external fuel tank identical to the one used by Columbia be impounded at the Michoud Assembly Facility in New Orleans for testing. The board noted that as there is only one of these older revision tanks left in existence, if any destructive testing is to be performed, engineers need take extra precautions with regards to preserving the tank's condition as "we'll only get one shot at it," Adm. Gehman noted during the 2/18/03 announcements. The board also the board clarified that it would study the extensive library of tests already done on tiles and foam Before ordering NASA to perform new tests on either.  

• CAIB member Maj. Gen. John Barry (USAF) reported prior to the 2/18/03 briefing that he and other board members are reviewing NASA’s records on the reports of foam coming off the so-called bipod area - where a pair of struts holds the tank to the upper belly of the Shuttle - during previous launches. This is the same location where it is believed that one or more segments of External Tank Insulation Foam sheared loose from the External Tank and slammed into the left wing 81 seconds into Columbia's final ascent to orbit. Barry noted that four previous Shuttle flights had foam falling from this same bipod area:
   
  • Challenger (STS-7, 1/83)
     
  • Columbia (STS-32, 1/90)
     
  • Columbia (STS-50, 1/92)
     
  • Atlantis (STS-112, 10/02)

  Gen. Barry was quick to point out that a 10-year gap exists between the last instances of foam breakoff, which would require "some backtracking to do to be able to look at the history and make the analysis.”

  A diagram of the bipod assembly.

  The foam's purpose is to prevent ice buildup on the metal tank, which is filled with super-cold liquid hydrogen and oxygen during the final hours of the countdown, and also serves to protect the tank from engine and aerodynamic heating. Barry also stated that he had inquired with workers at Michoud as to whether moisture could have accumulated there and loosened the insulation, and that the board is "looking at that as maybe an option on why the foam came off and why we’ve had some problems in that area,”  
   

• As part of the investigation, The CAIB Advanced Sightings Team is working to pinpoint the location of hardware that may have separated from the Space Shuttle Columbia early in its final path over the western United States. in addition to collating data provided by NASA and the public, the Advanced Sightings Team is also collecting data from the Department of Defense (DOD), Department of Energy (DOE), the National Oceanic and Atmospheric Administration (NOAA), the US Geologic Survey (USGS) and all other sources of information relevant to the loss of Columbia that has become available. As of this writing, examples of the types of information provided by these various agencies are as follows:
   
  • On orbit photography and analysis - DOD
     
  • Radar searches - DOD
     
  • Infrasonic data - DOE, NOAA
     
  • Tracking of possible on orbit object from Columbia 1/17/03 and analysis - DOD
     
  • Launch Analysis - DOD
     
  • Identification of entry shedding events - DOD
     
  • Kirtland photo analysis - DOD
     
• The Advanced Sightings Team is also analyzing video footage turned in by space flight enthusiasts and other sources of information to document exactly when these events occurred. Analysts then calculate the exact time and angles of the observation by determining exactly where the videos were taken from and by identifying planets or star fields in the background. This allows the team to calculate trajectories to predict probabilities of where debris may have fallen to Earth by estimating properties of possible debris from the video and then incorporating known atmospheric and wind data. Radar data is then retrieved and investigated to search for specific signatures. This process serves to drastically reduce the area that must be searched.
  
  This analysis has already had one major finding. As mentioned previously in this section, the earliest shedding of Shuttle hardware was originally reported as appearing in videos taken near the California coast, and the CAIB has since confirmed that Columbia did in fact begin breaking up while over this area of the country.
   
• During the CAIB press briefing on 2/25/03, the board confirmed that one piece of Columbia debris found in far west Texas came from an upper section of one of the wings. However, the board chairman stressed that because of its damaged condition, they may never know which wing the piece came from.
  
  CAIB chairman Adm. Harold W. Gehman Jr. (USN, Ret.), said on 2/25/03 that the piece was a tile fragment. As the surface of the piece is black, leading investigators to think it came from the "leading edge," where the wing narrows to meet the fuselage. Adm. Gehman and the board hope the shard and other pieces of debris will shed light on what happened to the space Shuttle.
  
  "We're beginning to see some interesting trends in the evidence," he told reporters.
  
  The fragment was found about 3 miles north of Littlefield, Texas, which is 35 miles northwest of Lubbock and 40 miles from the New Mexico state line.
   

  The CAIB also presented two photos of a different recovered tile. The first photo is reportedly the inner surface of the tile, while the second is of the outer surface.
  The damage on the outer surface is said not to be typical of what has been seen on previous re-entries, and may have happened after the orbiter broke up. The brown specks are being analyzed and the board did not venture any speculation on what they may be other than to say that they might have even come from where the tile hit the ground.

  The photos are also available on the NASA Manned Spaceflight web server at: http://spaceflight.nasa.gov/Shuttle/investigation/caib/briefing_02252003.html

"I am told this is not typical of a re-entry tile," Gehman said. "This is very unusual. One of the riddles we have to sort out is whether or not this damage was done while the tile was still attached to the orbiter or whether this damage was done after the breakup and that's what it looks like when you try to re-enter the atmosphere in a non-aerodynamic state."

• During the 2/25/03 press briefing, CAIB member G. Scott Hubbard clarified some aspects of the board's search for answers into the loss of Columbia. He stated that engineers have not yet ruled out any "root cause" of the Columbia disaster, and that investigators are running computer simulations to virtually recreate breaches at various points on the wing to come up with locations that at might explain the series of sensor failures and rising temperatures that were radioed to Earth before the Shuttle disintegrated.

  But Hubbard stressed during the briefing that a simple answer might not be forthcoming. "It's well known that accidents in complex systems often involve a chain of events," said Hubbard. "It's not often one single thing caused the whole accident. So this complex series of events needs to be evaluated together. For example, eventually we would like to see if you can couple the external tank shedding event with TPS sensitivities with the calculations that are being done by the aerodynamics folks. So what we're doing right now is trying to bound the events in the orbiter, we're trying to go from the town to the ballpark to the seat."

  Hubbard then provided three examples to illustrate the difficulty of "bounding the event":
   

  1. "We did a hypothetical study of a 20-square-inch breach in the wing, 4 by 5 (inches), near the main landing gear door or the seal, that seems to account for the temperature rise," he said. "But this is a first cut with an initial set of assumptions. Figuring out what might happen to a plume going inside a wing is a very complex task. It's a good first step, but we don't have an answer there yet."
      
  2. "Secondly, the sensor data that we've all looked at, the rise in temperature, the sensors going off line, seems to be consistent with wires going through the wheel well being severed. But there is a sensor near the front of the spacecraft that also had an anomaly. How do you account for that? Again, it's a little early to conclude we have a complete story."
      
  3. "And finally, some initial aerodynamic analysis seems to indicate there was some disturbance going on in the vicinity of the left main landing gear wheel well, but eight different calculations all gave somewhat different answers."

  "So the story I'm trying to communicate to you is it's early yet to draw conclusions that we have boxed this story in, that we really have bounded the event. We're making good progress, we need to validate the data interpretations with analysis of debris, experimental tests and in selected cases with independent calculations and perhaps independent tests. We need to look at the system."
   

• In the last major finding reported during the 2/25/03 press conference, CAIB member Brig. Gen. Duane Deal (USAF) told reporters that investigators studying Air Force radar tracking tapes made during Columbia's mission clearly show a small object measuring about 1' square (30 by 40 centimeters) separated from the Shuttle on the second day of the flight. Columbia had just gone through a major maneuver in orbit on 1/17/03, about 24 hours into its flight, when the object popped out of nowhere. According to Deal, this suggests that the object could have broken loose from the Shuttle during the maneuver.
  
  Gen. Deal stated that the object did not have “the characteristics of being anything dense,” and that the radar reflectivity readings were still being studied in hopes of determining the object’s composition. The object re-entered the Earth's atmosphere three days later, and was tracked by military radar installations numerous times before its demise.
  
  Deal also stressed that it is still not known what the object might have been or whether it played any role in the ensuing catastrophe. "You or I could invent a dozen scenarios. It could have been something loose that separated, it could have been something inside the payload bay, it also could have been part of the left wing, where all the overheating and other troubles developed during re-entry."
  
  On a related note, NASA has tentatively ruled out the possibility that the object was a chunk of ice created by Columbia's waste water disposal system, which on a few previous missions had produced a buildup of flash-frozen waste water on the water dump outlet. This conclusion is based on data from the Shuttle which does not show any waste water dumps being performed prior to the object being detected that could have produced an object of the apparent size observed.
   
• In addition to the CAIB, NASA has launched its own series of internal investigations into the loss of Columbia. During a visit on 2/20/03 to Stennis Space Center in Mississippi, NASA chief Sean O’Keefe told reporters that the analysis into the possible problems from the external fuel tank alone fills an entire room at Michoud. "Everything is under consideration, though," O’Keefe stressed. “There is no favorite theory. There is no favorite approach to this. There is no preferred cause. There is nothing right now that would be argued as the most likely condition that I’ve seen yet, and that is also the view of the Columbia accident investigation board, I am advised.”
   
• On 2/28/03, sources close to the CAIB reported that the board intends to ask NASA to reassign certain NASA officials from the inquiry. According to the reports, Adm. Gehman will seek reassignments of Ron Dittemore, Linda Ham and Ralph R. Roe Jr. on the grounds of "possible conflicts of interest."
  
  Dittemore is the current program manager for the Shuttle program, and one of the more visible members of the NASA administration during the days following the loss of Columbia, while Ham and Roe are members of NASA's Mishap Response Team, which provides Gehman's panel with technical information about the disaster. Ham also is the agency's Shuttle-program integration manager and Roe, a former launch director, manages the Shuttle program's vehicle engineering. Both were instrumental in directing Columbia's final mission.
  
  The reassignments come following an appearance by Adm. Gehman before members of Congress. Gehman stressed that certain NASA managers would come under review during the investigation, and that while these managers are not under suspicion for wrongdoing Gehman did not want them in the position of investigating their own roles. Although these intentions were reportedly detailed in a letter Gehman recently sent NASA Administrator Sean O'Keefe regarding concerns about NASA's involvement in the investigation, sources close to the board have also stated that no specific individuals were named  in the letter. The CAIB has acknowledged the letter had been sent, but has not released the letter to the public as of the time of this writing.
   
• On 3/01/03, NASA Chief Administrator Sean O'Keefe officially denied the CAIB's request to reassign top Shuttle program officials now assisting the panel in order to ensure an independent investigation. In a letter posted on the CAIB's website, O'Keefe stated "I am convinced that this course of action will be viewed as prejudging the facts before the investigation is complete...Despite your assurances that no conclusions have been made arising from the facts of the investigation at this time, simply reassigning personnel  will not accomplish your stated goal. [In fact] replacement personnel could be subjected to the same appearance of conflict in the future, and I will not submit anyone to this treatment."
  
  O'Keefe however, acknowledged the need for changes in how NASA supports the board's mission. To that end, O'Keefe said NASA will assign professionals not connected to Shuttle management to work with board reviews of materials, operations and technology.
   
• On 3/4/03, the CAIB acknowledged during a press briefing that one major focus of the investigation involves examining burn patterns on debris from Columbia’s left side in an effort to “follow the heat.” These burn patterns include a spray of dark discoloration on tiles, believed to be congealed molten aluminum, as well as signs of extreme damage to the left-wing tires based on the remains recovered so far; of the landing gear, recovery teams have retrieved the complete nose landing gear and tires, the complete right landing gear, what are believed to be remains from all right and left tire sets, and what is strongly suspected to be parts of the left landing gear. In addition, the left elevon actuator was found to have a big hole - 4" x 2" - with indications of leaking hydraulic fluid.
  
  However, the board stressed that it was still not concluded whether the damage observed was an effect of the breakup or of heating occurring afterwards. Of major concern are the deposits of aluminum and steel slag on the inner surface of the U-shaped RCC panels on the leading edge of the left wing. CAIB member Roger Tetrault noted that engineers have not yet explained "how does (molten material) blow forward and how do you get stainless steel and aluminum up onto the back edge, if you will, of an RCC when in fact that stainless steel is behind the area?"
  
  Responding to this, CAIB member Rear Admiral Stephen A. Turcotte, noted that analysts are studying how convection from a plasma burn through could affect interior wing components, possibly causing the kind of back-flow seen in the RCC slag deposits. "While the board has not reached any conclusions, it is interesting to note that "the closer you get to the chine, or panel No. 9 where it nears the fuselage, you see more molten [deposits]. As you get farther away down the left edge of the wing, you see less molten spray," Turcotte said.
  
  Tetrault also expressed concerns with the initial findings of the distribution of the molten aluminum in relation to the telemetry from the wheel well, which showed a more gradual increase in temperature than one might expect from a direct burn through. "I'm having difficulty with some of the off-nominal timings," Tetrault said. "One of the reasons I'm having trouble is it's very simple, very simple physics," he said. "There was a temperature A brake line sensor), hydraulic fluid temperature A, that went up very early in the event, it was either the second or the third one that went off nominal. Temperature B, which sits about two inches away from it, did not rise until about a minute and a half later whereas temperature C, which is probably six feet away, and temperature D, which is four feet away, are all rising off nominal.
  
  "It doesn't make a lot of physical sense to me," Tetrault said. "What we found as we looked at these temperatures is that it appears to be a straight line up and at some point, NASA has called it off nominal. And there may be some variability on where that call is on where it is off nominal. So what I'm trying to tell you is if you're trying to put together a timeline, I think you can be fairly certain when (a sensor) went off line. But when it says it's off nominal, I think you're going to have to take that with a little bit of a grain of salt."
   
• When asked about the relationship between Columbia's attitude, or orientation, and telemetry indicating elevated temperatures, Tetrault said "it's interesting to note that all of them were going up off nominal but then they went up in a very, very sharp fashion as soon as it rolled into the left wing down attitude. I won't say anything more, but it's interesting to note that that occurred that way." Columbia had completed a right bank, or roll reversal, and was banking to the left when the ship broke apart.
  
  Adding yet another piece to the puzzle, Gehman said a closer analysis of the telemetry from Columbia shows the ship's flight computers began working to counteract atmospheric drag on the left wing earlier than investigators originally thought and that they applied quite a bit of muscle in the final seconds to keep the ship on course. "Even at the time of the final two seconds (of telemetry), the vehicle's attitude and position were correct," he said. "We do believe that the vehicle was fighting forces more strongly, the fight was getting a little more vigorous at that point and we also believe that the beginning of this, of some of the control measures that the vehicle was taking to maintain its attitude, started earlier than we previously thought."
   
• Telemetry still remains a point of confusion in some cases, as telemetry shows the tires were intact up until the final loss of signal, the possibility exists that the tires may have blown out after Columbia disintegrated, and may not have contributed to the breakup. CAIB chairman Adm. Harold Gehman Jr. reminded meeting attendees that while Columbia was still on course with its fuselage intact and its major systems still functioning in the final two seconds of telemetry, those two seconds contained no telemetry from any systems in the left wing, and showed the Shuttle's hydraulic reservoirs were empty. "We have telemetry from the wheel well up until the time of loss of signal that indicates those tires were intact," said Gehman. "They had the right air pressure and they had the right temperature. So whatever happened, happened after the loss of signal. By that point the left wing was either gone or so severely damaged the triply redundant hydraulic lines running into the wing had been severed.
  
  At the same time, the board further stressed that despite earlier reports by NASA officials regarding the narrowing of the focus to five specific RCC panels on the Shuttle's left wing, the investigation has yet identified the actual location of the breach. Said Tetrault: "I think it would be fair to say we have more questions than answers right now. But we're getting smarter fast and I believe there's a very good chance that we will, in fact, be able to localize the breach that occurred in the left wing. And we certainly need to do this in order to determine the cause of the accident. Until we have determined that location of the breach, every postulated cause of the accident is really just a theory."
   
• During the 3/4/03 press briefing, CAIB chairman Adm. Harold Gehman Jr. announced that public hearings would begin shortly, and the first was scheduled for 3/6/03. The hearings would allow the board to take testimony from non-NASA witnesses and also “read into the public record matters that we are investigating more privately,” Gehman said. Gehman also added that the board was still considering adding new members to the board, including a physicist and others who could provide perspective on “the history and culture and budgets and management at NASA.”
   
• On 3/5/03, while speaking to reporters regarding the status of the investigation, Adm. Gehman noted that the CAIB had officially concluded that telemetry does indeed show that Columbia's aerodynamic control surfaces were fighting drag earlier than it was previously estimated, which clearly indicated that Columbia was "wounded" earlier than previously thought. It's also clear, according to Gehman, that more than one heat-reflecting tile had to have been damaged to start the process that resulted in the loss of the Shuttle.
  
  "The analysis of some of the photography, the ground-based videography, we have now found shedding debris earlier than we previously thought," said Gehman. "We're pretty sure that the loss of one tile could not have caused the amount of heat that we're seeing inside the [left] wing. It's not enough, so a broken piece of tile by itself wouldn't have done this."
  
  Gehman confirmed officially what experts following the investigation have already suspected in that the board knows conclusively that Columbia's left wing had in fact failed. However, Gehman stressed there are "five or six processes that could have led to that outcome, and [we] are trying to find out which one caused it." Gehman also said investigators are looking for a significant clue that could lead them to find the answer to why the Shuttle broke up, and are frustrated that it hasn't been discovered after more than a month of searching.
  
  "Because it's a real puzzle. We don't have that golden nugget," Gehman said, although he expressed confidence the board would find the answer, and said they would know it when they saw it. It may be a piece of debris in the field. It may be a piece of analysis, it may be a piece of telemetry," he said. "In my opinion, not everything is on the table yet."
  
  However, Gehman said, his worst nightmare is that investigators would find out exactly what part of the Shuttle failed, but not why it failed.
  
  "I would be disappointed if that's the outcome," he said
   
• Also on 3/5/03, Adm. Gehman announced that three new members would be added to the CAIB. Those members are:
   
  • Dr. Sally Ride, the first American woman to fly in space, and former member of the Rogers Commission, the presidential board that investigated the 1986 Challenger disaster.
     
  • Dr. Douglas Osheroff, a Nobel laureate who chairs the physics department at Stanford University.
     
  • Dr. John Logsdon of George Washington University's Space Policy Institute.

In addition to the three new board members, Gehman also requested NASA Astronaut Michael J. Bloomfield (Lt. Col. USAF) be appointed as an Astronaut Advisor to the board. Bloomfield is a former chief of safety in NASA's Astronaut Office, and he currently serves as chief astronaut instructor. Bloomfield will assume the responsibilities currently performed by former Astronaut Bryan O'Connor, who will return to NASA Headquarters in his role as NASA Associate Administrator for Safety and Mission Assurance in Washington.

• On 3/07/03, the CAIB announced that it was forming a new team to look into NASA's internal communications, including e-mails and management directives. Board member Maj. Gen. Kenneth Hess, an aviation mishap expert stationed at Kirtland AFB, said the new team will aid three other groups previously established by the board that is already investigating the structural design, operations and technical aspects of the Shuttle itself, and how they related to the loss of Columbia on 2/01/03. The new team will also focus on the NASA "culture" itself, as well as some of the issues raised recently by former NASA official Henry McDonald during the CAIB's first public hearing in Houston on 3/06/03.
  
  During that first public hearing, McDonald, who headed a Shuttle study three years ago, told the board he and his panel found that top-level managers were not privy to all potential problems or the rate at which they were occurring. He blamed archaic database systems and said his recommendations for a more modern consolidated method - including better risk assessments - were never implemented. McDonald also noted that the same type of communication breakdown he claims to have warned about seems to have hindered engineers who evaluated damage to Columbia's wing and concluded the Shuttle and its Astronauts were safe.
   
• On 3/11/03, during a press conference packed with updates, the CAIB showed enhanced views of a previously-released video showing the underside of Columbia during ascent. The video, which indicated foam debris falling away from the ship's external fuel tank slammed into the lower leading edge of the orbiter's left wing within a few feet of where it merged with the fuselage, was contrast enhanced to show the debris and the suspected impact zones with a bit more clarity than previously seen.
  
  The video, however, does not appear to show any damage to the underside of the wing following the impact. It was hoped that the enhanced video might reveal a possible breach point. Damage seen in recovered debris suggests the plume exited the wheel well through seals around the landing gear door. At the same time, a vortex of hot air probably formed along the upper surface of the wing, ripping insulation tiles and blankets away as the disaster unfolded. This induced a dramatic increase in aerodynamic drag on the left wing, for which Columbia's flight control system attempted to compensate, first by adjusting the ship's roll trim and ultimately by firing right-side yaw jets in a futile bid to keep the ship's nose pointed in the right direction. Columbia eventually yawed out of control in a sort of tilted flat spin before breaking up high above Texas.
  
  "That piece of debris appears to hit on the leading edge, but on the lower half of the RCC," said CAIB Chairman Adm. Harold Gehman Jr. "In other words, the debris doesn't appear to go over the top and under the wing. All the debris appears to go under the wing. So it appears to hit the leading edge, but kind of on the underside of the leading edge and then all the debris follows the wind pattern. It appears to hit somewhere (at or near) RCC panel 6, 7 or 8, no closer than 6, no more than 8. As you see after the debris goes by, there's no missing tile. Nothing's missing, so once again we have these tantalizing little pieces of evidence that don't fit together."
   
• Adm. Gehman noted during the 3/11/03 press conference that the board is still very unsure as to what actually caused the mishap, as many of the clues uncovered so far tend to point to either more than one possible cause for the left wing breakup, or isn't enough of a damage threat to have been a major contributing factor to the breakup. In the case of the theory regarding RCC loss caused by the suspected foam strike, wind tunnel tests have shown the loss of a single RCC panel is simply not enough to explain the unusual and rapidly intensifying aerodynamic forces Columbia experienced during re-entry. Testing showed that at least three or four panels would have had to be missing to explain the re-entry data received, and no such damage can be seen in the launch footage, enhanced or otherwise.
  
  "Every time I think I've got it figured out, I get a piece of data that changes my mind," Gehman said. "If the aerodynamic surface were disturbed long before re-entry, that then leads you to believe there was some physical misarrangement of the wing that had nothing to do with entry. On the other hand, all of our photographic evidence indicates if there was a physical misarrangement on the wing it was so tiny it's not visible to anybody else, which would lead you (to believe) that it was some kind of a thermal event which was the triggering event which then started the unzippering process. And so, the fact that the orbiter was fighting an aerodynamic misarrangement earlier than we previously had thought makes my riddle very intriguing."
   
• During the 3/11/03 press conference, the CAIB also revealed that 20 seconds before the foam fell away from the so-called "bipod ramp" area of the tank just under the Shuttle's nose, Columbia rocketed through unusually high wind shear. The steering system in the Shuttle's left-side solid fuel booster swiveled the rocket's nozzle slightly to counteract the effects of the shear, putting some additional stress on the left side of the vehicle.
  
  This event occurred approximately three seconds after Columbia reached "Max Q," or maximum dynamic pressure. As this number varies from flight to flight, this time around it was measured at ~741 lbs/ft^2. Whether this had any effect on any damage to the wing caused by the foam strike and/or the higher than expected wind shear is not yet known, but investigators are taking all factors into account.
  
  "At 62 seconds on launch, we saw one of the larger transients we've seen on the solid rocket motor," said Maj. Gen. John Barry. "It was well within parameters, but interestingly enough, the two largest ones we've seen on ascent both happen to be Columbia, both happen to be going on 39-degree inclinations, both have lightweight tanks. So we're trying to identify if there's any commonality there as an additional stress load on the left-hand side of the orbiter, because it was with the left solid rocket motor that had this input."
   
• Adm. Gehman also noted during the 3/11/03 press conference that CAIB investigators and board members are scheduled to visit a Lockheed-Martin facility during the week of 3/17/03 to learn more about how RCC panels are repaired, serviced and mounted on the Shuttle. Investigators are particularly interested in how pockets, or voids, form in the layers making up the composite material due to oxidation. If Columbia had any RCC panels with similar voids, and if the panels were then hit by falling foam impacting at high speeds, a failure could result.
   
• 3/11/03 was obviously a busy day. One other point raised was that the "Starfire Photo" was still being analyzed to determine if any additional data could be recovered from the blurred infrared image. "Those photo experts are just now beginning their work in liaison with aerodynamics experts and plasma experts to try to see what the picture will really yield," said Maj. Gen. Kenneth Hess, a member of the CAIB. "But the important part right now is to enhance the photo as much as can be done without adjusting the facts behind the photo."
   
• In reference to another theory that has been discussed in recent weeks both by the CAIB and amongst some of the regulars on the sci.space.* groups who contribute to the FAQ efforts, the phenomenon known as asymmetric boundary layer transition was downplayed significantly by Board member Sheila Widnall, an aerodynamicist from MIT. This particular theory questioned whether this form of sudden onset of turbulence during hypersonic flight could have affected Columbia's left wing more than its right. Widnall noted that calculations performed based on show an asymmetric boundary layer transition, acting in the absence of any other problems, would have been too small by a factor of four to explain the unbalanced forces that led to Columbia's destruction. Widnall, in fact, sees "a heating event followed by a very rapidly developing aerodynamic event" as opposed to the mishap having been the result of turbulence.
   
• Adm. Gehman also stressed that odds are more likely that it may well have been a combination of factors that resulted in the loss of Columbia, and not any one specific failure. "What we're really looking at is a complex failure of a complex system," Gehman said. "It's possible, one of the scenarios we're looking at, it's possible the foam striking a healthy orbiter would not have done enough damage to cause the loss of this orbiter. But it's possible foam striking an unhealthy orbiter that had problems in it either due to stresses on launch - we talked about the wind shear, too much heating in transition of years before, aging of the orbiter, like the RCC faults we see, or a whole number of other complex issues - it's possible you could do some damage to this orbiter that ... she could have survived, maybe, at age 10, maybe she couldn't survive it at age 21."
   
• On 3/13/03, Adm. Gehman announced the results of the initial foam impact tests. A preliminary finding suggests that a striking blow from high-speed foam may harm the aluminum structure in the wing, but the thermal protection covering might not show any visible damage. One key piece of information the board is hoping that will shed additional light on the relevancy of the foam strike may come from photographic gear that was intended to record the jettisoning of the external tank from Columbia during ascent. This camera equipment was located on the underside of the orbiter, and if it survived the breakup any imagery that was taken may reveal more about what came off the large External Tank and from where on the tank it originated. This would be the only means of securing such evidence, as the External Tank is destroyed by aerodynamic stress as it tumbles towards its point of impact in the Atlantic Ocean.
  
  With regards to the impact testing, note that, investigators at the Southwest Research Institute verified on 3/13/03 that plans to begin additional foam impact tests would take place over "the next few weeks." Pieces of foam insulation roughly the same size as the chunks seen falling away from Columbia's external tank will be fired into various wing components with a powerful "chicken gun" normally used to shoot debris into jet engines and through aircraft cockpit glass. For more information, see Section V, under What's the best guess as to what caused the breakup?
   
• Also on 3/13/03, Maj. Gen. John Barry noted that work is still under way to identify an object detected by ground radar floating away from or near Columbia early in its 16-day mission. As Barry reported, experts at Wright Patterson Air Force Base in Ohio are studying radar signatures of test items that could have come off Columbia. Using several different radar systems, researchers are scanning a set of Shuttle parts approximating the size of the flotsam seen moving away from the orbiter on Day 2 of the mission in hopes of finding a match. In addition, reflectivity and luminosity tests are being conducted on the same set of suspect parts in an attempt to classify the nature of the object.
  
  Barry noted that spotting objects floating away from a Shuttle is not unusual. "Ice has come off, and screws, washers, thermal blankets and other items can be set free, much of this associated with an orbiter’s cargo doors being open," Barry said. “The question is, was that [object] something that was off the left wing? It was not sighted by the astronauts or reported. So we have to go back to the detective story on radar signatures that might help us find out what that object was.”
   
• On 3/17/03 during the CAIB's second public hearing in Clear Lake, TX, the board heard from Shuttle officials and a spacecraft re-entry expert, all of whom agreed that a crucial clue to understanding the cause of the loss of Columbia could be in a piece of debris yet to be discovered in the western United States.
  
  Speaking before the board, NASA flight director Paul Hill noted "If we can locate some of this (Western debris) ... that's going to make us immensely smarter on exactly how the failure started in the first place." Hill is currently leading debris recovery efforts in the Western US. While there have been reports of Columbia shedding debris as it flew across California to New Mexico, so far searchers have found not one single piece of debris west of Lubbock, TX. Finding debris in the Southwest "remains a top priority," Hill said.
  
  Also appearing at the hearing, Doug White, a NASA contractor employed by United Space Alliance, testified before the board that sensors in the left wing failed one by one as wiring burned or simply shorted. Columbia's onboard flight computers methodically adjusted the positions of the elevons to offset steadily increasing levels of aerodynamic drag acting to pull the ship's nose to one side.
  
  "The vehicle was in control and was responding to commands up to that point and after that point something changed, apparently," White told the CAIB. "It still continued to be in control and still continued to respond to commands, but the rates and the amount of muscle it needed to continue flying the vehicle the way it should be flown was continuing to increase. Something definitely happened at that point, again we don't know what, but something definitely happened at that point to cause the flight control system to need more muscle and start having to fight harder to control the vehicle."
  
  Although this caused unusual temperature and pressure readings and sensor dropouts, Columbia continued to fly "like a champ right up until the breakup," added Hill, who admitted he was "amazed" that Columbia was able to continue flying in relatively normal fashion for nearly 10 minutes while shedding multiple pieces of flaming debris as a plume of superheated air burned its way into the stricken ship's left wing.
  
  "We clearly had an external breach in the vehicle and had hot gas somewhere in the left wing for that significant period of time and the vehicle flew perfectly, no indication of what was going on in flight control and virtually no indication of what was going on in telemetry on the ground, other than we saw a few temperature, pressure indications that didn't make sense to us," he said. "But aside from that, the vehicle flew like a champ until right up until the breakup. So that did surprise us."
   
• What did not surprise Hill was that search teams have not recovered more wreckage than they already have. "Are we surprised that we only have 15 to 20 percent by weight of the orbiter? I don't think so," Hill observed. "I would think when you first see the debris count and you see how many individual pieces of debris [have been recovered], our first reaction was one of surprise, how could we have gotten that much of the orbiter down from 200,000 feet intact? I think you've all seen at KSC, what they have is a whole lot of little tiny pieces of what used to be an orbiter. And if you go look at it laying on the ground there in the high bay at KSC, you don't have a spacecraft laying there, you've got a whole lot of nothing. And I think that fits in with what our conventional wisdom was prior to this."
   
• During his testimony before the CAIB, Hill, who has been coordinating NASA's efforts to integrate amateur video into the agency's second-by-second entry timeline, also addressed how NASA has been helped in its effort to track down debris by the thousands of eyewitness reports and amateur videos shot by people who watched Columbia's breakup on 2/01/03. A short composite video was presented before the board by Hill, consisting of 15 to 20 amateur videos. Debris could be seen coming off 16 times, and on two occasions a flash preceded the falling debris, which may have been burning. "Without the public having taken these pictures on their own ... we wouldn't know any of this," Hill said. "These people are definitely our heroes."
  
  While the videos do not yet shed light on the nature of the debris, they clearly document a surprising number of events. Hill said engineers "continue to be shocked that we had debris coming off the orbiter as we crossed the California coast." Hill stressed the imagery as yet holds no clues as to exactly what was falling away from Columbia or even how large the pieces, whatever they were, might have been. In fact, only relative sizes can be inferred.
  
  "I am confident that many, if not all, of the things we label as 'debris shedding events' are, in fact, some object coming off of the orbiter," Hill said. "Can I tell you is it golf ball sized, or is it the size of this sheet of paper? I can't. It very well could be something as small as a marble in most of those videos and the ones we think are so significant and have gotten us so excited, those things could be golf ball sized. We really don't know. We know relative sizes, we know relative motions, but we don't know specifically what they are. But we are very confident, based on the way they behave after they separate from the orbiter, that they are, in fact, separate ballistic objects or objects that have mass in almost all cases. In the case of some of these flares, they could be something different like combustion products."
   
• Also appearing before the board was an expert in spacecraft re-entry, William Ailor of the Aerospace Corp., part of the contracting agencies working under United Space Alliance. Ailor told the board that the debris shed the earliest by Columbia would yield the best information about what happened. "That's going to be really the key here," Ailor said. "It certainly can be a big help, but you need to find the right stuff. The orbiter was controlled for a good period of the time and if evidence is found that could have occurred during that period and it indicates a particular flow pattern or something like that, I think that could be very useful. I think the early debris would be very critical to an analysis like that."
  
  Again, such debris, if it still exists, has been difficult to find. As of 3/18/03, no wreckage whatsoever has been found west of Texas despite the fact that Hill's debris recovery team has been able to determine the probable trajectories of several pieces of debris tracked as they fell off of Columbia as it passed over California. Using that data, researchers have found ground radar traces matching at least four debris shedding events - three of them in the debris 6 "footprint" - but again, no actual debris.
  
  "We think the brighter objects are more massive, are more significant, potentially higher ballistic numbers," Hill reiterated. "Certainly the [brightening of] the individual pieces of debris persists longer. We expect that those objects are more massive, higher ballistic number, because we think that the reason they persist longer is they are moving faster so they stay lit, they have their own plasma wake longer than, say, some lighter things, say an individual tile comes off versus some other heavier object. But I'll also say we cannot just look at these videos and determine what is it that's coming off the vehicle. Are we losing a tile here, are we losing some section of [the] thermal blanket that's on part of the external surface of the vehicle? We can't tell that. And until this day, with the good data we have on the ballistic analysis and the footprints, we still cannot say exactly what it is we see coming off. We are making some judgments on which of them are more significant or more massive than the others [such as] debris 6 and debris 14."
  
  Ailor added, "The work that's going on relative to finding the debris is really an important part and that really has to be emphasized. That's going to be a key to solving this puzzle, I believe."
   
• On 3/18/03 during its third public hearing, the board heard from engineers who are reconstructing the aerodynamics and thermodynamics of Columbia's reentry in an attempt to determine the nature of the suspected breach in the left wing and when it might have happened.
  
  "You've asked the $64,000 question," Steven Labbe, chief of the Applied Aeroscience and Computational Fluid Dynamics Branch at Johnson Space Center, told the board when asked what caused the loss of Columbia on 2/1/03. Labbe's team has been working on the initial wind tunnel tests on various possible types of damage, such as holes and missing RCC panels on the wing's leading edge, or a gouge in the main landing gear door. As of 3/18/03, testing involving a single failure of any one of these components of the Shuttle's Thermal Protection System has failed to result in any condition that would have resulted in any sort of catastrophic failure as experienced by Columbia during her last flight.
  
  Some investigators believe it is likely a damaged carrier panel or a broken/missing tile on a carrier panel just behind the RCC panels in question could have provided the entry point for the plume of hot air that ultimately destroyed the left wing. The day after launch, ground radars detected an object separating from Columbia that was roughly the same size as a carrier panel. Regardless of whether a carrier panel came off before or during entry, "it would be very easy to have damage occur and such that the RCC panels themselves would come off," said board member James Hallock. "They're only held on by, I believe, two bolts. Get this thing out, get some heat in there in the right place on those bolts and they could come loose and that's what could be happening, all this stuff is starting to open up into a larger area."
  
  "We're going to be looking at multiple panels missing, where our future work will focus on. We'll do a survey of the wing leading edge and look at other scenarios," Labbe added. "These are very preliminary results. It's premature to draw too many conclusions from these results. We're just getting started on this assessment."
   
• On 3/18/03 CAIB chairman Adm. Harold Gehman Jr. (USN ret.), speaking on behalf of the CAIB, said the board already is preparing to make some suggestions on how NASA can improve its operations. "There are a couple of [recommendations] that are percolating up to where we think they are benign enough, obvious enough that we don't need any further research. We're as anxious as everybody else is to get everything on the table so they can make the [return to flight] as quickly as they can."
  
  Although he declined to go into details regarding what recommendations were being discussed, Gehman did emphasize that one of the first recommendations the board could make would be for NASA to improve its communications with other governmental intelligence agencies. He wants the space agency to better coordinate how resources such as spy satellites and telescopes can be used to photograph Shuttles while in orbit to help detect problems. "It's not a security issue. It's a bureaucratic issue," Gehman stressed. "This is a system that broke. We think both sides of the house bear equal blame. Improvements in on-orbit photography that have come along, nobody from that part of the house has come down here (to NASA), knocked on their door and said, you know, things have changed since we made this agreement. And NASA doesn't have the right people cleared to receive the data. ... They made decisions without having the right information. The point is, this is a system that broke."
   
• Also on 3/18/03, board member and physicist James Hallock revealed that analysis on the debris recovered from Columbia's breakup indicated that atmospheric gases superheated at 3,000 F penetrated and completely filled Columbia's left wheel well, and melted a section of a titanium door mechanism. The plasma was eventually ejected from both sides of an exterior door. "Sometime during the event we had very, very hot temperatures in [the left wheel well]. What we're hoping to be able to do is home in on possibly where this breach actually occurred. We're not yet ready to turn around and say here is the story but we're getting many, many pieces of that puzzle."
   
• On a related note, Hallock also admitted he's doubtful that a micrometeoroid or piece of space junk was responsible for the breach that allowed the plasma stream to enter infrastructure of the left wing.
   
• On 3/21/03, NASA announced reorganization plans for its support of Shuttle accident related activities. These plans are intended to facilitate integration of NASA's efforts with the structure already implemented by the CAIB. NASA's own Mishap Response Team, formed immediately after the Columbia accident in accordance with established contingency plans, has officially completed its mission, and all NASA accident-related activities supporting the CAIB will transition to a newly-formed NASA Accident Investigation Team (NAIT). The NAIT has three subdivisions, which correspond with the major investigative elements of the CAIB, and will be headed as follows:
   
  • Randy Stone, deputy director of JSC, will chair the NAIT. Stone will also manage the subdivision related to flight operations, such as Mission Control, flight planning and crew training functions.
     
  • Frank Benz, director of engineering at JSC, will manage activities related to engineering and technology, such as debris, imagery and fault tree analyses.
     
  • Jim Kennedy, deputy director of the Kennedy Space Center, will manage activities related to materials, such as vendors, maintenance, internal processes and program management.

  The NAIT will also assume responsibility for other mishap response activities currently in progress, including the debris search and recovery efforts in east Texas and the efforts of NASA's Emergency Operations Center, which assisted in fielding calls and images from sources external to NASA. In addition, the NAIT will be assisted by NASA's Columbia Task Force, directed by Frank Buzzard, and will continue to facilitate the interface between the CAIB and NASA support activities.
   

• On 3/24/03, in a report by AvLeak, CAIB member Brig. Gen. Duane Deal (USAF) noted that the board will investigate whether Columbia could have been damaged by rainwater prior to arrival for overhaul at Boeing's Palmdale, CA facility in 1999, as well as whether any undetected water or corrosion damage could have contributed to the loss of Columbia. Deal noted that the board will investigate reports from NASA managers that latent effects from water penetration could possibly have degraded a left wing carrier panel or its smaller "gap seal" tiles that bridge the bottom side of the RCC panels on the leading edges of the wing with the larger black wing tiles.
   
• On 3/24/03, in a report by AvLeak, CAIB member Brig. Gen. Duane Deal (USAF) noted that the board will investigate whether Columbia could have been damaged by rainwater prior to arrival for overhaul at Boeing's Palmdale, CA facility in 1999, as well as whether any undetected water or corrosion damage could have contributed to the loss of Columbia. Deal noted that the board will investigate reports from NASA managers that latent effects from water penetration could possibly have degraded a left wing carrier panel or its smaller "gap seal" tiles that bridge the bottom side of the RCC panels on the leading edges of the wing with the larger black wing tiles. According to various sources both within NASA and from the news media, NASA managers have reportedly been raising concerns internally about the possibility of water damage to Columbia since shortly after the accident.
  
  While Shuttles are routinely exposed to rain and other adverse weather conditions while still on the launch pad, they're always in an upright vertical position that prevents rainwater from collecting and accumulating long enough to cause leakage or any sort of seepage. However, under normal circumstances Shuttles are never left sitting in the rain horizontally on their landing gear with the nose and wings angled downward as Columbia reportedly was prior to the 1999 overhaul. Both NASA and the CAIB are now showing interest into whether this could have somehow allowed water to seep into the RCC/carrier panel area and pool in such a way as to provide a source of corrosion to the RCC supports. According to some Shuttle experts, many of whom are former NASA, Boeing, Lockheed and USA employees, this sort of corrosion damage quite probably could have laid dormant and did not manifest itself until after the afflicted area was struck by External Tank debris during Columbia's ascent.
   
• Gen. Deal also noted on 3/24/03 that the CAIB plans to examine reports of whether a possible hypergolic propellant spill could have played a role in weakening RCC or tile bonds. At the same time, the board will also examine reports from within NASA of suspect tile-pull test data for Columbia.
   
• On 3/24/03, The CAIB released an new version of the Starfire image that was enhanced by the Center for Adaptive Optics at the University of California at Santa Cruz. According to Dr. John J. Bertin, professor of aeronautics at the Air Force Academy and an expert on hypersonics, at least part of the jagged feature on the forward part of the wing is actually a shock feature caused by the collision between the normal shock wave coming down the wing chine with an abnormal shock region generated by the damaged leading edge. The enhanced picture also appears to show a bit more clearly how the wing has been abnormally reshaped below the shock feature.
  
  Bertin believes a significant change in leading edge shape is most likely to be the source of the loss of lift in the left wing. By the time breakup occurred, the left yaw component had increased to a value of 160,000 ft-lb. of torque, which was overwhelming the flight control system at the same time the wing burned and/or sheared away from the fuselage. Aerodynamic and thermal analysis indicates that although reentry surface temperatures are supposed to be in the 2,500-3,000F design range, it is possible the wheel well and internal areas of the left wing were exposed to superhot gases in the 9,000F range that would cause instant burn through of the aluminum structure, which melts at only 1,000F.
   
• With regards to camcorder imagery taken by amateur photographers, Paul Hill, a Shuttle/station flight director helping to lead the analysis, noted during board testimony that "We can then measure how debris moves away from the orbiter. We know exactly where the orbiter is in space relative to the photographer, and we know exactly what the timing is, so we can then calculate the ballistic [coefficient] number of that object based on how it moves relative to the orbiter because we also know the orbiter's ballistic number. We then take that ballistic number for the object and build a vector so we can propagate that object forward all the way to the ground. Then we generate a series of footprints at 85,000 ft., 35,000 ft. and also for ground impact. By doing this, and coupling it with air traffic control radar data, NASA teams hope to aid searchers on where to look for specific debris."
  
  Adding to the observation was CAIB chairman Adm. Harold Gehman Jr. (USN ret.); "What is unfolding here is a scenario in which a particularly superheated plume of extraordinarily high temperatures above 3,000F could carve its way into the wheel well pretty rapidly," Gehman said.
  |
• With regards to the "mystery object" that separated from Columbia during its second day in orbit, researchers at the Air Force Research Laboratory's Advanced Compact Range for Radar Testing have completed initial radar reflectivity tests of 15 of at least 28 Shuttle components, including carrier panel, RCC and black tile and thermal blankets. The tests at the Wright-Patterson AFB, OH facility are intended to help define the object that radar detected separating from Columbia in orbit, and also to aid the assessment of the debris separated during reentry.
   
• On 3/26/03, the CAIB announced that NASA engineers expected to begin analyzing OEX data on the following weekend (3/29/03) in hopes of recovering readings taken from over 700 sensors located throughout Columbia's infrastructure. Analysts working with the CAIB expect the data will help them precisely map out the flow of plasma through the all-but-confirmed breach left wing to confirm, refine and/or modify current theories about where the initial breach occurred, and how the deadly plume then chewed through the interior of the wing.
  
  "In a perfect world, we will have 721 measurements, sensor outputs," said Scott Hubbard, a member of the Columbia Accident Investigation Board. "This covers the wings, the fuselage and the vertical tail surfaces. Of particular interest are going to be 182 pressure measurements, 53 temperature measurements and 447 loads, dynamics and stress measurements. Among these will include a series of measurements - [that is] if we get all the data back - on the left wing: strains, stresses and strains, temperature and pressures."
  
  Hubbard also cautioned that while data was found on the tape, it's condition was still an unknown factor. "Now we have to note, this has been through a very severe ]environment," Hubbard cautioned. "We don't know if the tape has been demagnetized, we don't know yet the quality of the data in there. But if the tape is, in fact, readable, this would be a gold mine of information that could lead us to a much, much better understanding of what happened throughout the vehicle and particularly on the left wing."

While speaking to the press following the CAIB Public Hearing on 3/26/03, Hubbard verified that additional studies of enhanced photography of foam debris slamming into Columbia's left wing appears to show the material hit the underside of the left wing's leading edge in a roughly two-square-foot region centered on a specific panel of protective carbon composite material just forward of the left main landing gear wheel well.

• During the 3/26/03 Public Hearing, more evidence was presented to support the theory of a burn through at a breach point located at or near RCC Panel #6. In testimony before the board, two CAIB investigators revealed that a partially melted RCC support strut from just behind RCC Panel #11 - located outboard of Panel #6 - that shows clear signs that plasma entered a cavity enclosed by the wing's RCC panels and then moved outboard, as one would expect from a breach located closer inboard to the fuselage.

"There's actually an open space inside the leading edge," said Gregory Kovacs, a professor at Stanford University. "So it's possible if there was a breach, something could have flowed down that open space and then eroded the components in there. So on that score, I think we are thinking about flows down there, where they're concentrated maybe closer to the breach. That's the kind of thinking we're going through." It's this possible breach location that has investigators in anticipation of the OEX data. Two temperature sensors monitored by the OEX were mounted underneath insulation on the wing spar behind RCC Panels #9 & #10. If a breach did in fact occur inboard of these two panels, near RCC Panel #6, those sensors most likely survived long enough to record the initial intrusion of superheated plasma before it proceeded to work its way into the infrastructure of the left wing. In addition to the partially melted support strut, analysis of other fragments of recovered debris from the left wing show that concentration of metallic slag splattered on the inner surface of the leading edge panels actually increases towards the area of the leading edge and underside where the foam impact was observed. When combined, these two independent lines of evidence are consistent with a breach at or near RCC Panel # 6 and/or an adjacent closeout panel.

• With regards to the deposits of metallic slag, NASA and CAIB investigators are continuing detailed chemical and metallurgical analysis of recovered debris to decipher complex damage patterns in hopes of pinning down the breach location and plume propagation path. On 3/26/03, Mark Tanner, an expert in failure and forensic analysis with Mechanical and Materials Engineering, said "what we're trying to do is get an idea from the flow patterns, the splatter patterns and the deposits, where was the breach, where was the origin this whole thing started from. Or origins."
   

  Complicating the picture is the ever present problem of determining when the observed damage occurred. As noted by Dr. Gregory Kovacs during his 3/26/03 testimony, "A key question when we're looking at these pieces is with the damage we see, was it caused by something that happened on ascent, on descent, breakup or ground impact. A lot of these pieces, you look at them and there's pine needles embedded in them. So clearly that did not happen in space and we're taking great care to understand the relationships of those issues [...] there's a lot of jigsaw puzzling going on out there. It is like putting together a multi-thousand piece 3D jigsaw puzzle on a 2D surface." Engineers believe between 35 percent and 50 percent of the Shuttle actually made it to the ground. The rest presumably burned up in the atmosphere following breakup, including virtually all of the aluminum skin structure of the wings. "A lot of the parts have come through an aluminum molten rain cloud if you will, where they have aluminum splatter over much of the debris," NASA test director Steve Altemus said of the wreckage recovered to date. "We see that molten aluminum on almost everything we have back. It may also speak to why we don't have upper wing surface on the left wing in that that's very thin aluminum. So yes, we expect a great deal of the aluminum not to have made it to the ground."

  When asked by CAIB members if "anything unusual leaps out under casual inspection," Altemus observed "what did strike me as odd, first of all, is the size of the pieces, how small they actually are, and also there's very little left wing lower surface structure and very little left wing upper surface structure. When you walk the grid, that's what you notice, what is not present as opposed to what is there."
   

• On 3/28/03, NASA Administrator Sean O'Keefe announced that the US military had agreed to a request by NASA to regularly capture detailed satellite images of Shuttles while in orbit. In an apparent response to the persistent questioning by the CAIB, the US Congress, the press, and the American people about why no such pictures were taken of Columbia in light of possible damage to the left wing, O'Keefe noted that the agreement with the US National Imagery and Mapping Agency (NIMA) called for the agency to use their reconnaissance satellites to image "targets of opportunity" during Shuttle flights without NASA having to make specific requests for such images.
  
  The agreement was formalized in a letter sent a few days earlier from O'Keefe to Lt. Gen. James R. Clapper, the director of NIMA, and will make available to NASA detailed pictures of the Shuttle during future missions, even though it remains unclear how useful such images might be. Each of the Shuttle's delicate insulating tiles is about 3 inches wide, and the level of useful detail the current series of reconsats are capable of resolving is a closely guarded secret. O'Keefe himself would not discuss these capabilities due to security reasons, but did acknowledged there were some "opportunities that would have been certainly greater than zero" to capture images of Columbia and that these "would have been very convenient."
  
  O'Keefe did, however, suggested that America's capability "isn't anything like what a Clancy novel would have you believe," and made it clear he was not making a decision about whether any NIMA-supplied images might actually have helped determine the extent of damage to Columbia. "I'm not ever engaging in shoulda, coulda, woulda's," O'Keefe said. "I want to see all the facts in before I ever make a determination on this or make a judgment about somebody else's judgment."
  
  At the time of this writing, NASA is still working out details about which of its employees will have adequate security clearances to view the images received from these reconsats. O'Keefe himself noted that the number of employees during Columbia's final flight who could have viewed such images was "no more than single digits, and you've got a lot of fingers left over on one hand."
  
  During the same announcement, O'Keefe indicated NASA was pursuing similar agreements with the US Air Force to take pictures of Shuttles with the powerful, ground-based telescopes such as those located at the Starfire Optical Range at Kirtland AFB, located outside of Albuquerque, NM. It is theorized that had these telescopes been used to image Columbia during reentry instead of the 3½-inch "experimenter's" version that snapped the "Starfire Photo", enough detail could have been resolved to have answered the question as how badly the left wing was damaged, and possibly given clues as to the true nature of the breach in the leading edge.
   
• On 3/31/03, the CAIB announced the initial findings from the analysis of the data tape that survived along with the OEX recorder recovered by debris a search team on 3/19/03. According to a CAIB spokesman, the data clearly indicates that superheated plasma entered the leading edge of Columbia's left wing ~16 seconds after entering the region of maximum aerodynamic heating during reentry. The two sensors and their corresponding RCC panels that provided the data were both located just outboard of the point where NASA and CAIB engineers have become more convinced that a deadly breach occurred along the leading edge of Columbia's left wing.
  
  According CAIB spokeswoman Laura Brown, temperature sensors located behind RCC panels #9 and #10, showed a sudden rapid spike, or increase, in temperatures before the sensors failed and dropped off line. One of the sensors was located on the front surface of the wing spar, underneath a layer of insulation, while the other was located behind the spar within the infrastructure of the wing itself. Based on the timestamps for the readings, the spikes occurred a minute and eight seconds earlier than previous signs of trouble were noted in data downlinked thru TDRS from Columbia, and strongly suggest that Columbia almost certainly began reentry with a compromised Thermal Protection System - a breach of some sort that quite probably and quite suddenly worsened as the Shuttle entered maximum aerodynamic heating.
  
  "[The readings] go way up and then they go to zero," said Brown. "I think what it also indicates is the mechanism of failure was already in place."
  
  The sudden temperature spikes, which initial timestamp analysis places at having begun at 7:51:09am, appear to be highly consistent with what would have been seen as the result of entry of reentry plasma through a pre-existing breach in the leading edge. In what has become the leading scenario for the orbiter's breakup, the superheated gasses would have entered through an opening in or between the U-shaped leading edge panels. Had this occurred, this would have triggered the observed temperature spikes in the sensors behind RCC Panels #9 & #10, before continuing into the wing's infrastructure.
  
  Following the preliminary review of the OEX recorder, it was determined that the tape recorded good data from approximately 420 of the 721 sensors feeding data to the OEX, including the two particular sensors in question. Brown noted, however, that while good data was received that concurs with the current "best guess" scenario, the timing of how the leading edge sensors responded to the spikes is still unclear. One sensor failed and went off line ~20 seconds after its counterpart, but both clearly showed the sharp increases in temperature that, according to NASA specifications, were significantly above what sensors would ever detect during a normal reentry.
  
  Following this release of initial analysis, NASA engineers will begin the process of weaving the new information into NASA's entry timeline. They also plan to continue work to recover OEX data recorded during Columbia's ascent to determine if any readings might be indicative of external tank foam striking the left wing 82 seconds or so after liftoff. A preliminary look at the OEX data gathered during ascent reportedly shows what was described as "a potentially interesting signature," but NASA and CAIB officials cautioned that the readings may have been the result of a sensor failure or a wiring defect totally unrelated to the suspected foam strike along the leading edge of Columbia's left wing.
   
• Following Brown's initial statements regarding the OEX data, CAIB chairman Adm. "Hal" Gehman waxed positive on the condition of the data as being "a treasure trove of data." Prior to the retrieval of the intact OEX recorder, the initial loss of contact with Columbia occurred at 8:59:32am, followed by a a final two-second burst of telemetry thirty seconds later that indicated Columbia was in the process of yawing out of control to the left. Gehman confirmed that the OEX recorder ran for an additional eight seconds after final loss of signal, although he stressed that this particular set of data had not yet been recovered, but was expected to give significant insight on how much of Columbia was still intact at that point and when final breakup most likely began.
  
  Gehman then noted that the timing of these events recorded by the OEX recorder suggested that Columbia did in fact began its re-entry with a breach of some sort that allowed superheated plasma to penetrate behind the leading edge panels, and then continued to burn its way into the interior of the wing. From there, the plasma are believed to have entered the wheel well through a vent on its forward face, which in turn triggered the brake line temperature increase.
  
  According to Gehman, five minutes after Columbia began entry interface at 8:44:09am, a sensor mounted on a brace behind RCC panel #9 began responding to a "very sharp temperature increase" at 8:49:09am, approximately two minutes before the Shuttle entered the region of maximum heating. Exactly three minutes after this initial temperature rise, the sensor failed and dropped off line after detecting a temperature of 450°F. Eight seconds later, at 8:52:17am, a sensor mounted on a brake line in the left main landing gear wheel well recorded the start of an unusual temperature rise. At 8:52:49 a.m., a sensor mounted on the forward interior edge of the wing -  just behind the failed sensor in the leading edge cavity -  began registering a rapid increase as superheated plasma began to penetrate through the interior. Approximately seven seconds after that, data from sensors mounted toward the back of the wing also began dropping off line as the plume burned its way through a wire bundle routed around the outside of the landing gear wheel well.
  
  "Now interestingly enough, the first temperature rise we see inside the wheel well occurs at 52:17," Gehman observed. "Just about the time the sensor outside the wing spar fails, the temperature inside the wing spar starts to go up. So this is interesting to us [...] The sensor mounted on the inner surface of the wing spar roughly behind [RCC Panel] number 9 starts to rise 520 seconds after [Entry Interface], which is something like eight minutes and 40 seconds, which would make it something like 52:49. The temperature sensor inside the wing starts to rise almost coincidentally with the time the temperature sensor outside the spar goes off line, which leads you to believe there was a whole lot of heat outside the spar which finally ate its way into the wing. Remembering the melting temperature of aluminum is something like 900 degrees, it got really hot outside the spar, ate its way through and the temperature sensor outside the spar goes off line. It probably got destroyed."
  
  According to Gehman, the temperature data recovered from the OEX recorder does not rule out or confirm an initial breach at or near RCC panel #6. He emphasized that engineers "will be making calculations over the next few days to determine what sort of breach would be required near [RCC] panel #6 to produce a temperature increase like the one seen on the sensor behind RCC #9." At such an extreme altitude as what Columbia experienced during entry interface, heat transfer was low due to the lower dynamic air pressure. As to whether or not the aluminum structure of the wing spars behind the RCC panels could have conducted that much heat, or whether a breach occurred outboard of RCC 6, Gehman pointed out that this had not yet been determined.
  
  "At the altitude and the speed the orbiter was going at the time the new temperature rise was seen, the aerodynamic pressures are extraordinarily low," Gehman pointed out. "So you could conclude the orbiter began it's entry with a pre-existing fault. In other words, it wasn't air pressure that knocked this thing off, it wasn't some kind of a weakness in which some part of the orbiter was ripped off when it entered the atmosphere, this looks to us like it probably had a pre-existing condition."
  
  Gehman also strongly urged those representing the news media not to jump to any conclusions about the possible location of the initial breach; "Where the temperature sensor is does not suggest where the breach is," Gehman said. "We are still pulling all the data together to attempt to indicate where the breach is. But this certainly leads us away from things like tile and landing gear doors and things like that."
   
• On a related note, Gehman stated that CAIB and NASA investigation teams were "working to extract data about the forces acting on Columbia during launch." NASA has confirmed that Columbia encountered high wind shear during launch, prompting more extreme booster steering movements than normal. Whether those forces contributed to stresses that, when aggravated by the debris strike, could have led to an RCC failure or a carrier panel problem is not yet known. But Gehman said OEX data from ascent will be factored into upcoming tests in which foam will be fired at leading edge components to determine what sort of damage they might have suffered.
   
• On 4/1/03, CAIB chairman Gehman and Maj. Gen. Barry announced that the board was also focusing the investigation on the possibility that paint primer from the Shuttle launch towers may have combined with rainwater that splashed onto Columbia and formed pinholes in the leading edge of the left wing that may have contributed to the disaster. Such corrosion over the two decades Columbia was in service could have weakened the RCC panels along the edge, possibly enough to break when struck
  by a chunk of foam during liftoff.
  
  According to Barry, pinholes in the 1/4"-thick protective carbon lining the edge may have allowed air pockets to form. This in turn could have allowed air to penetrate the inner surface of the RCC panels and deteriorate the carbon via oxidation. While the pinholes - which were first discovered on Columbia in 1992 after 12 flights - have appeared on all four Shuttles, according to NASA and the CAIB, patched the larger holes were patched. Neither NASA nor Shuttle support contractors Boeing and United Space Alliance inspected the orbiter fleet thoroughly for any underlying air pockets that may have formed.
  
  Based on post-flight analyses, as many as 20 to 40 pinholes formed on each RCC panel over the years. The current theory being studied by the CAIB points to the source of the pinholes being the result of zinc leaching out of the paint primer on the metal tower that swings around the Shuttle and protects it on each of the two seaside launch pads. Because the structure was not repainted and refurbished, more primer was exposed and when it rained corrosive zinc oxide washed onto the Shuttles.
  
  "This dates back to Apollo days, and a lot of that infrastructure has not been replaced because they had made a decision they were going to go" with next-generation spaceships that have yet to materialize, Barry said. "Infrastructure is definitely going to be part of our investigation...NASA is aware of the leaching problem, but I don't think it quite got the attention maybe that it has now, obviously, with the mishap."
  
  At this point, both Barry and Gehman stressed that while the leaching paint primer is a leading potential explanation for the pinholes. But it's also possible salt spray from the Atlantic formed the holes. Gehman then noted in addition that NASA had somewhat addressed the problem of zinc oxide sprays by slathering the leading edges with sealant and other material, but stressed that a different question needed to be addressed. "The question is, once again, just like everything at NASA: Who knew it high up? Was it a serious consideration? Did they have anybody looking at aging as a weakening? We don't know that yet."
   
• Also on 4/1/03, the board announced that investigators had reported finding additional defects in last remaining Lightweight-model External Tank, including evidence of a bonding problem with the insulating foam. The Lightweight-model fuel tank - identical to the one Columbia was launched with on its final mission - has been undergoing analysis at the Michoud Assembly Facility in New Orleans. According to Barry, the report to the CAIB noted that this spare tank was found to have 32 air pockets in the foam on the bipod area.
  
  The bipod area, a connection point between the tank and the forward underside of the Shuttle, is where a 2-pound, 25x15x5" thick piece of External Tank insulation foam broke off Columbia during liftoff. Based on previous NASA analysis, air pockets like those found on the tank under scrutiny, mostly 2 inches to 3 inches in size, could cause the foam to pop off when the tank encounters high levels of atmospheric drag. According to the same report, some foam in this location was also found to be improperly bonded to the tank and to the bipod itself.
   
• Finally, the board addressed the so-called "Mystery Object" that floated from Columbia just one day into its flight. Following analysis of data both from the orbiter's course correction logs, and from radar data taken by tracking stations operated by the Air Force Space Command, the board is now convinced the object was "almost certainly was a so-called carrier panel from the underside of the wing's leading edge," one of the 2-to-3' (60-to-90-cm) long strips of metal that connect the carbon on the leading edges to the thermal tiles that cover the rest of the wings.
  
  The "Mystery Object" that drifted away from Columbia was detected in extensive post-accident studies of about 3,100 radar images that Space Command trackers took of orbiting objects during the mission, prompting fleeting speculation that a piece of "space junk" or a micrometeoroid had struck the orbiter. The object was first spotted floating near Columbia. It began to tumble and eventually fell out of orbit. The object could have originated from Shuttle hardware that had been weakened or loosened by the impact of foam debris that flew off the Shuttle's external tank during launch. In one scenario proposed by NASA engineers, the same hardware a day later could have gotten jarred free by an OMS or RCS burn.
  
  Following extensive analysis of 29 samples of various Shuttle materials sent to Wright-Patterson AFB in Ohio, where analysts have been studying the samples' radar signatures in an attempt to match one with the object seen in orbit, only the carrier panel gave off a signature that provided a close enough match to be considered. "we've concluded that, right now, only the carrier panel remains a viable candidate for the Day Two object," said CAIB member Maj. Gen. John L. Barry.  According to Barry, the board's report states that shortly before the "Mystery Object" appeared out of nowhere on the Space Command radar screens, columbia had performed an attitude adjustment maneuver in orbit that most likely shook the carrier panel loose.
  
  A single missing carrier panel would, according to board member Roger Tetrault, cause a gap in the leading edge of the wing sufficient enough to allow re-entry plasma to penetrate and burn through the wing. Tetrault also noted that, while a missing carrier panel was still a prime suspect, he also stressed that the breach could have involved the RCC panels, seals, stainless steel support structures or even the connecting bolts that hold most of the wing infrastructure together. Barry added that additional tests are planned to see if, for example, a partial section of a leading-edge carbon fiber panel would produce a similar signature. while other tests will be done on carrier panels with varying numbers of ceramic tiles and other hardware attached, Barry added.
  
  “We have to sort our way through all of those and make a determination of which one” failed, Tetrault emphasized. “If we fail to do that properly and we get the wrong one, then we could have a future accident.”
  
  Ironically, Tetrault's comments were made prior to reports that RCC Panel #6 - the panel from the area where the board believes the breach occurred — was identified in wreckage at KSC earlier in the day. According to the initial reports, the panel appears to be intact and in relatively good shape. Experts following the investigation have noted that the condition of this particular panel could prompt the CAIB to reconsider as to where the actual breach in the left wing occurred.
  
  "That means that not a whole lot burned around it," Barry said in response to the RCC finding. "It probably means the carrier panels on either side didn't burn...this is a detective story. Now we have one more part of the puzzle. It's a long, long process."
  
  The debris recovery team at KSC had previously identified 10 other carrier panels and is still looking for panels number 5, 8, 9 and 12.
   
• On 4/7/03, the CAIB heard testimony regarding the External Tank foam impact issue and NASA's plans for investigating and solving the problem. Speaking before the board, Col. James D. Halsell Jr. (USAF) opined that NASA had failed to see a trend in the shedding of insulating foam from the outside of the Shuttle's External Tanks, despite reports of a similar incident involving the Shuttle Atlantis on STS-112 several months prior to the Columbia accident, because the agency thought that it had solved the problem years earlier. In addition, the prior incident in October of 2002 was not considered by NASA officials as related to incidents in the prior 20 years, primarily due to the fact that the design of the tanks had been overhauled and upgraded.
  
  Halsell, who has flown on five flights and was previously in line to command a mission to the International Space Station, explained that standard NASA procedures called for any problem categorized as "criticality 1" - one that threatened the loss of the crew or the vehicle - to be treated with the utmost importance and seriousness. Risks to the Thermal Protection System automatically in that category as the TPS has no backup. Action was deferred, according to Halsell, because in analyzing the Atlantis mission, "they felt comfortable at that point in time that they had no generic issue that indicted follow-on, future tanks that they were going to fly."
  
  The issue was also discussed at length at Endeavour's  - the orbiter which flew following the Atlantis flight in question - flight review November 2002, and according to Halsell everyone at NASA felt comfortable there was nothing new or generic about the problem and that no changes or weaknesses in the application or manufacturing of the polyurethane foam were made that would have introduced errors. "[The review board] felt comfortable the risks were sufficiently understood and the Shuttle safe to fly," said Halsell, "Whether it was appropriate or not, I think there was a consideration that this was a new occurrence."
  
  Although no large foam pieces in fact came off Endeavour's fuel tank, and appeared to have confirmed the review board's conclusions,  Halsell stressed that had Columbia had returned home safely, the foam loss at Columbia's liftoff would have been recognized as having been almost identical to that seen on the previous Atlantis mission, and both incidents together would have been a sign of a "generic" problem requiring a top-priority investigation into cause, effect and repair.
  
  Halsell also went to great lengths to defend the analysis following the foam impact during the launch of Atlantis on mission STS-112:  "It's well known that we did liberate a piece of foam on STS-112," Halsell emphasized. "The process by which we went through understanding what had happened, how that related to our previously accepted hazards...and what was the appropriate course of action from that point on, all followed the processes we had in place to try to ensure the right decision and right tradeoffs and risks got made.  For example, the in flight anomaly situation for STS-112, that did come to a program requirements change board, it was decided there that an in-flight anomaly designation was not required for this particular item because the previously accepted and documented hazards, and if I remember correctly there were two integrated hazards which were violated, or which were called into question by this particular instance, two of them dealing with the external tank liberating foam and creating a hazard to some other vehicle component, there was nothing about that particular instance which invalidated the rationale for the previously accepted risk.
  
  "In other words," Halsell said, "we didn't move up into the right on the risk matrix according to what we knew at that point in time. So the action that was levied at that program requirements change board was to the external tank project, to go back and fully understand what had happened, why it had happened and what we were going to do to keep it from happening in the future. Also another action was levied to bring that item forward at the flight readiness review to make sure it was discussed fully prior to STS-113. So using that as my example, I would say that that's an example of how the process worked properly and the item was brought forward to the flight readiness review and it was discussed at some considerable length there."
  
  When asked as to who had the ultimate responsibility for accepting or rejecting analyses of this nature, Halsell replied "the short answer is that it's the [Space Shuttle] program manager's job to organize the appropriate response to any and all issues when it comes to making the final determination if we can recommend to the associate administrator that we're ready to go fly safely. So if Ron Dittemore was sitting here in front of me, he would say it's my in box because he's the one who controls the resources and the application of those resources."
   
• On a related note, after Halsell's testimony on 4/7/03, Robert Castle Jr., chief engineer of the Mission Operations Directorate, stated during testimony regarding the foam issues that "although there were extensive rules for various failures, there were none for damage to the thermal-protection system, because there was no procedure to deal with it." Castle did stress, however, that NASA has not hesitated to delay or halt flights or make major changes when it recognizes problems.
   
• Following Halsell & Castle's testimonies, Lee D. Foster, a foam expert from NASA's Marshall Space Flight Center, testified before the board on the engineering standpoint regarding the foam loss. Foster also acknowledge NASA's diligence for halting flights when problems are found, but also noted that the shedding of foam from the External Tank has always been addressed differently. Despite related problems that stretch from the first Shuttle launching, NASA has treated the problem as one of upkeep rather than of safety. "Everything was judged as a maintenance item," said Foster, "and not a safety-of-flight issue."
  
  Foster's testimony, according to several experts on sci.space.Shuttle who're following the board meetings, demonstrated that there is considerable uncertainty as to how much foam overall had been shed and from where. The main method for measuring shed debris, according to Foster, has been counting the number of "dings" and "divots" found in the tiles during post-flight checkout. However, it was not clear what fraction of all foam impacts would be recorded on the tiles.
  
  Appearing with Foster was another foam expert, J. Scott Sparks, department lead for external tank issues at NASA. Scott also noted that NASA researchers were unaware of any records that listed counts of debris strikes on the RCC panels. A similar lack of data also exists for the areas of the External Tank where shedding has occurred in the past. Three orbiters - Atlantis, Endeavour and Discovery - have cameras that photograph the bipod ramp area of the tank as it separates from the orbiter, but actual observations of shedding foam hitting the Shuttle during ascent have been few and poor in quality. Foster then acknowledged that cameras did not always show where the foam came off and, over the years, engineers sometimes had to rely on "guesswork." In those instances, no major damage was caused by debris, but he added: "I'm not sure if there's any comfort in that." In addition, Scott noted, some launchings are in darkness, which renders the photographic record poorer.
  
  Sparks and Foster also testified that despite more than twenty years of research into reducing and eliminating foam loss from the Shuttle's External Tank, enough debris is still produced from shedding during each ascent to cause between 30 to 40 "hits" on the Shuttle's underside that produce blemishes and even dents larger than one inch across. According to NASA records, the majority of these shedding events occur in the intertank region of the External Tank, the section that separates the ET's liquid oxygen and hydrogen tanks. The intertank is noted for its ribbed structural members - also called "ribbing" and/or "stringers" - and provides the surface to which other components are mounted to allow the solid-fuel boosters and the bipod assembly struts that hold the nose of the orbiter in place to be attached. It is the bipod region that is of significant interest, as in at least five cases, foam broke away from this area.
  
  These components - including the "ribbing/stringers", a series of retaining bolts in the flange area where the top of the hydrogen tank connects to the intertank, the bipod components themselves, and a plethora of other components - must all be insulated by foam using a manual spray applicator. How this foam is applied and how it bonds with these irregularly shaped surfaces is theorized by NASA engineers to play a major role in debris shedding. One effect, known as "popcorning", results when air bubbles trapped underneath and/or within  the foam liquefy when the External Tank is loaded with the Shuttle's required supercold propellants. During launch and ascent, the liquefied air trapped in these voids can warm up and evaporate in an explosive manner and cause pieces of insulation to blow out and away from the tank..
  
  "You've got a foam that has to be applied over a certain type of underlying structure and making that so that it is free from shedding seems to be, over the last 20 years, a tough thing to do," observed board member Scott Hubbard.
  
  "Yes sir. And generally, you've really got to go back to the beginning as far as the design of the tank," Sparks replied. "I'm not so sure the TPS (thermal protection system) processors were in the same room when they designed the tank. Because it was designed structurally to be optimized. It's not designed for the TPS to be processed on there. If you were to redesign completely a tank, you would make the exterior a bit smoother, you know, you'd have those people in the same room."
  
  Despite the effort to resolve the shedding problems, statistical analysis of the actual impact damages eventually produced a baseline that allowed the foam loss to become accepted as a "routine occurrence."
  
  "This is a very impressive list of all the things that have been done over the past 22 years to address the shedding of external tank debris," Hubbard said. "Nevertheless ... the line is pretty much a flat line there, whether it's 10 or 15 or 20 or whatever. So do you see any way to drive that line down to zero or near zero?"
  
  "We're always trying to improve the product," Sparks said. "But we don't want to change the product unless we're justifiably sure that's going to improve the product. ... There have been several improvements that I think the program has been proactive in pursuing. But indeed, there's still a level (of debris) and generally they're coming from those closeouts in that intertank region that seem to be problematic. So we try to improve our processing to the extent possible but thus far, it's staying in that (average) range."
  
  Finally, Foster discussed 17 changes that NASA had made in the foam since the first Shuttle flight in 1981. One was to stop using what NASA referred to as "two-tone foam," - two different types of foam mixed together - , in the area of the bipod ramp. This area, where the tank attaches to the orbiter, is inherently hard to insulate because it has bolts and other mechanical parts that are difficult to cover completely. As analysis had not detected any shedding from the bipod ramp area for quite a few years, the problem was considered solved, and contributed to the failure to identify the foam shedding experienced during the previous Atlantis launching as a sign of a deeper problem.
   
• During the CAIB hearings on 4/8/03, board chairman Adm. Harold Gehman revealed that NASA had relied on a flawed analysis of debris damage on Columbia, and in turn resulted in miscommunications that prevented engineers from securing photos of the Shuttle in orbit.
  
  Considered by observers as some of the sharpest criticism voiced by the board to date, Gehman referred to the computer modeling used to assess foam impact damage to the Shuttle's thermal protection system as “rudimentary” and not meant to predict safety. Gehman described the model as being merely a "spreadsheet" and not an actual computational design, and emphasized that it was based on testing of much smaller debris - significantly smaller than the 2 lb (1 Kg) piece that slammed into Columbia's leading edge at 500mph ~81 seconds after liftoff. Using this model, the analysis led by engineers working for NASA contractor Boeing, reached the conclusion that "little harm was done." This in turn became a major bolster to the belief by NASA that Columbia was in no danger and would return safely.
  
  Speaking with Gehman, board member and former Astronaut Sally Ride noted that the major problem with this analytical model was that it had never been used before during an actual Shuttle flight. Video taken by ground tracking cameras of the debris striking the wing was of poor quality due in part to difficulties with the focusing mechanisms on one specific camera. NASA engineers needed to know more about the speed and location of where the falling foam hit on the wing, as well as the size of the foam itself in order to properly assess the potential damage. NASA engineers who followed up on the Boeing analysis realized they needed more data, Ride said, and then asked NASA officials to request pictures of the orbiting Shuttle, but none was ever taken. The resulting failed request for military photos “looks as though it was literally a miscommunication," said Ride.
  
  Ride told reporters “If you had given them good information to start with, they could have given you an answer,” referring to the analytical program used by engineers to assess damage. “But there wasn’t enough information. So you’re asking them to predict where something’s going to hit but you can’t tell them how it started. [This] led this whole group to say, ‘Get us more data, get us some photos.”’
  
  With regards to the miscommunications between NASA engineers and higher-ranking officials, Ride opined that it appeared that “one group was saying, ‘Let’s wait until the analysis is complete to see whether we need photos’ and then that was interpreted as, ‘There will be no photos.’ In other cases, it was for different reasons. It’s a pretty complex story. It’s a real web of interpersonal communications.” This web, according to Ride, apparently stretched even up to the Astronauts aboard Columbia, who accepted the engineers’ conclusion that they would be in no danger during their reentry.