Posted on 02/04/2003 1:34:19 AM PST by bonesmccoy
In recent days the popular media has been focusing their attention on an impact event during the launch of STS-107. The impact of External Tank insulation and/or ice with the Orbiter during ascent was initially judged by NASA to be unlikely to cause loss of the vehicle. Obviously, loss of the integrity of the orbiter Thermal Protection System occured in some manner. When Freepers posted the reports of these impacts on the site, I initially discounted the hypothesis. Orbiters had sustained multiple impacts in the past. However, the size of the plume in the last photo gives me pause.
I'd like to offer to FR a few observations on the photos.
1. In this image an object approximately 2-3 feet appears to be between the orbiter and the ET.
2. In this image the object appears to have rotated relative to both the camera and the orbiter. The change in image luminosity could also be due to a change in reflected light from the object. Nevertheless, it suggests that the object is tumbling and nearing the orbiter's leading edge.
It occurs to me that one may be able to estimate the size of the object and make an educated guess regarding the possible mass of the object. Using the data in the video, one can calculate the relative velocity of the object to the orbiter wing. Creating a test scenario is then possible. One can manufacture a test article and fire ET insulation at the right velocity to evaluate impact damage on the test article.
OV-101's port wing could be used as a test stand with RCC and tile attached to mimic the OV-102 design.
The color of the object seems inconsistent with ET insulation. One can judge the ET color by looking at the ET in the still frame. The color of the object seems more consistent with ice or ice covered ET insulation. Even when accounting for variant color hue/saturation in the video, the object clearly has a different color characteristic from ET insulation. If it is ice laden insulation, the mass of the object would be significantly different from ET insulation alone. Since the velocity of the object is constant in a comparison equation, estimating the mass of the object becomes paramount to understanding the kinetic energy involved in the impact with the TPS.
3. In this image the debris impact creates a plume. My observation is that if the plume was composed primarily of ET insulation, the plume should have the color characteristics of ET insulation. This plume has a white color.
Unfortunately, ET insulation is orange/brown in color.
In addition, if the relative density of the ET insulation is known, one can quantify the colorimetric properties of the plume to disintegrating ET insulation upon impact.
Using the test article experiment model, engineers should fire at the same velocity an estimated mass of ET insulation (similar to the object seen in the still frame) at the test article. The plume should be measured colorimetrically. By comparing this experimental plume to the photographic evidence from the launch, one may be able to quantify the amount of ET insulation in the photograph above.
4. In this photo, the plume spreads from the aft of the orbiter's port wing. This plume does not appear to be the color of ET insulation. It appears to be white.
This white color could be the color of ice particles at high altitude.
On the other hand, the composition of TPS tiles under the orbiter wings is primarily a low-density silica.
In the photo above, you can see a cross section of orbiter TPS tile. The black color of the tile is merely a coating. The interior of the tile is a white, low-density, silica ceramic.
For the first time, the Columbia Accident Investigation Board has endorsed a detailed failure scenario developed by NASA and contractor engineers that traces the shuttle's destruction to a breach in the ship's left wing at or near leading edge panels 8 and 9. That scenario, first reported by CBS News on April 20, assumes Columbia began its ill-fated Feb. 1 descent to Earth with a breach in the leading edge and that hot gas ate its way into the interior of the wing less than eight minutes after the orbiter fell into the discernible atmosphere 76 miles above the Pacific Ocean.How large the initial breach might have been is not yet known. But the day after Columbia's launching, military radars tracked an object separating from the orbiter. Investigators believe the "flight day 2 mystery object" left an opening of some sort that provided a direct path for hot air to enter a cavity behind the U-shaped reinforced carbon carbon panels making up the leading edge of the left wing. More than two dozen shuttle components have been tested to find the best match with the radar data and today, experts testified before the CAIB that only two candidates are still on the table (a third has yet to be tested).
One is a large section of an RCC panel measuring up to 120 square inches. The other is a T-seal, one of 22 such fasteners used to lock the RCC panels together. Under the scenario developed by NASA and the CAIB, the mystery object could be either the T-seal between RCC panels 8 and 9 or a large section of the lower portions of the RCC panels themselves.
"From all the testing and analysis we've done, we feel RCC T-seals as a class cannot be excluded and RCC, what we call acreage, or pieces of the panel, cannot be excluded," said Steve Rickman, chief of the thermal design branch at the Johnson Space Center. "But there is another point to be made there, that the panel acreage itself would have to be on the order of 0.33 inches thick for it to have the correct ballistics. ... It turns out that on the lower panel acreage in the panel 8-to-9 region you do have RCC panel acreage that is of this thickness."
The loss of a T-seal would have left a slot-like gap between panels 8 and 9 just a few inches across as opposed to the much larger hole represented by the loss of a section of RCC panel measuring between 90 and 120 square inches. Engineers currently are trying to determine how big the actual breach must have been to permit the entrance of enough heat to explain the timing of sensor readings and dozens of subsequent sensor failures.
"My understanding is that NASA is, in fact, doing specific analyses for those different shapes, sort of two-dimensional analysis," said board member Sheila Widnall. "My understanding is the hole sizes they've been using to date are quite a bit smaller than the RCC panel that was suggested in the Wright Patterson radar tests. So I think more analysis is clearly required."
Board chairman Harold Gehman said "this is one of the key areas we're going to continue to focus on."
"The way I like to describe it is that the breach that was there at the time of entry has to be big enough to cause the heat scenario that we saw but it also has to be small enough to permit the orbiter to get all the way to Texas. Keeping in mind that we've got some bounds in there and we've got a very, very rich timeline, I believe we've got a good chance of achieving the analysis it's going to take to be more specific about this. We're talking about weeks of work here. It's just plain hard work."
But it is critical work and it will play a major role in how NASA and CAIB investigators design upcoming tests at the Southwest Research Institute in San Antonia, Texas, to fire external tank foam insulation into leading edge components in a bid to simulate what went wrong in the first place.
As is well known by now, just 82 seconds after liftoff Jan. 16, a large piece of foam broke away from Columbia's external fuel tank. The debris originated at or near the left bipod ramp, an aerodynamically shaped area of foam just in front of a strut that helps hold the nose of the shuttle to the tank. At least three distinct pieces can be seen falling away from the bipod area in enhanced footage from ground cameras. But only one - the largest - actually hit the left wing. Experts testified today the large piece measured 24 inches by 15 inches with an uncertainty of 3 inches. The thickness of the debris has not been determined but it is believed to be relatively thin. The impact velocity was somewhere between 610 feet per second and 840 feet per second, or between 416 mph and 573 mph.
The debris hit the left wing in a "footprint" centered on the lower side of RCC panels 6 through 9. It's possible the impact damaged the T-seal between panels 8 and 9 - or cracked one of the RCC panels - and that the damaged component finally shook free the day after launch, leaving an opening into the cavity behind the leading edge. Investigators have not yet come up with a credible mechanism to explain how the damaged component was able to remain in place for a full day and then separated on flight day two.
But for their part, Gehman said the board has deliberately excluded the foam impact as a direct cause of the disaster in its working hypothesis of what went wrong.
"We were careful not to say the foam knocked a hole in the leading edge of the orbiter because we can't prove it," he said. "Now that's not to say we don't believe that's what happened, but we were careful here to base our working scenario on agreed facts and right now, we aren't willing to make that kind of a statement."
Whatever caused the breach in the leading edge, the pathway for hot air was large enough to trigger a remarkably rapid series of events. The shuttle entered the atmosphere at 8:44:09 a.m. Less than eight minutes later, at 8:52:05 a.m., the shuttle began responding to unusual aerodynamic forces. At some point between that moment and 8:52:16 a.m. - 11 seconds later - the hot air had burned its way through the wing spar and into the wing's interior. One minute later, by 8:53:10 a.m., 120 sensors had dropped off line as the super-heated air burned through wiring inside the wing just behind the spar.
That data was recorded on board and not transmitted to the ground. The first realtime indication of a possible problem in the left wing came at just about that same moment - 8:53:10 a.m. - showing up on a computer display monitored by the mechanical systems officer in mission control. By that point, the wing was in severe distress and complete failure was just seven minutes away.
The upcoming tests at the Southwest Research Institute, scheduled to begin in early June, "will demonstrate to us whether or not we have a plausible scenario," Gehman said. "But it doesn't seem to me that it will prove anything one way or the other."
Gehman said the board hopes to begin writing its report later this month. No more hearings are currently scheduled for Houston but the board plans to relocate in Washington next month and one or more hearings may be held there to flesh out questions about NASA's management and operating philosophy. Gehman said it will not matter in the long run whether investigators ever conclusively link the foam impact with the leading edge breach.
"We can make fairly good case of what we think the return-to-flight criteria should be with or without any positive knowledge or positive proof that the foam caused the accident," he said. "Because we're going to make return-to-flight recommendations that are designed to enhance the safety of the orbiter in every way we find that it needs to be enhanced.
"Just fixing the foam alone won't do it. So I'm not the least bit concerned that our inability to make a positive statement with proof that the foam knocked a hole in the leading edge of the orbiter in any way slows us up or in any way restricts what we need to do in order to come up with a criteria for return to flight. Most of our work on return-to-flight issues has to do with the fact that the safety margins have been changed over the years and we're going to try to restore those safety margins back to at least as far as we're comfortable with."
Lest there be any doubt Gehman is serious about addressing a wide-range of issues in the board's final report, he stressed again today that "we're looking at this program and these shuttles in a very, very broad way. We have to, because we don't have a single point failure like the O-rings (that caused the Challenger disaster). And therefore we're going to come up with a broad range of recommendations, which taken together, we believe, will make the program safer. The fact that we don't have a single causal event doesn't bother me in the least. ... It may not be quite so easy to explain, but practice wise and function wise, it doesn't bother me in the least."
He also said the board plans to address the overall risk of flying the shuttle to stimulate public debate.
"The board is going to attempt to characterize the true risk in our own words," Gehman said. "Whether or not we put a number on that, the board hasn't decided. But we are going to attempt to describe for our constituents - the Congress, the administration, the astronauts and the people of the United States - what the risk is in this enterprise. It's not zero, it's not anywhere near zero.
"I don't know that the board would be interested in putting a number on it. ... Whether or not we pass judgment on any number that NASA uses remains to be seen. But we will attempt to characterize the risk in our own terms and if it differs from NASA's, so be it. But that will be one of our goals, to restate the risks in terms that there can be a good public policy debate on whether or not we should be doing this or not."
Readers are encouraged to review the April 20 CBS News status report below for details about NASA's failure scenario. Here is the text of a CAIB news release today summarizing the board's conclusions to date:
Columbia Accident Investigation Board Releases Working Scenario"By building a working hypothesis, it really enables us to focus the testing, it enables us to much more narrowly direct the analysis, it really produces a very synergistic effect on different disciplines," Gehman said.Houston, Texas -- The Columbia Accident Investigation Board (CAIB) today released their working scenario.
After three months of intense investigation including thorough reviews of hardware forensic analysis, orbiter telemetry, Modular Auxiliary Data System (MADS) recorder measurements, general public still and video photography, hypersonic wind tunnel testing, and aerodynamic and thermal analysis, the Columbia Accident Investigation Board, with the assistance of the NASA Accident Investigation Team (NAIT), has reached the following preliminary conclusions.
Launch:
Approximately 81 seconds after a 10:39 EST launch on January 16, 2003, post launch photographic analysis determined that foam from the External Tank (ET) left bipod ramp area impacted Columbia in the vicinity of the lower left wing RCC panels 5-9.Orbit:
While Columbia was on orbit for 16 days, there was no indication of damage based on orbiter telemetry, crew downlinked video, still photography or crew reports.An Air Force Space Command post flight evaluation of radar tracking data indicated an object in the vicinity of the orbiter on flight day two, remained on orbit for approximately two and a half days, then reentered the atmosphere. Radar testing and ballistics analysis of various thermal protection system items and thermal blankets, along with careful inspection of downlinked orbiter payload bay video, has been used in an attempt to identify that object. Testing and analysis to date have eliminated from consideration all but a piece of an RCC T-seal or RCC panel with a rib. However, there is no conclusive evidence that either of these items was the object that departed the orbiter.
Entry:
The de-orbit burn and entry targeting were accomplished using well-established Mission Control Center procedures. There were no problems identified with this process.On the morning of February 1, Columbia entered with unknown damage to an RCC panel or T-seal in the left wing RCC panel 5-9 area. Hardware forensic analysis and a review of MADS temperature and strain measurements on the left wing leading edge structure point to the RCC panel 8/9 area as the most likely area of damage. The forensic evidence indicated the RCC panel 8/9 area was subjected to extreme entry heating over a long period of time, leading to RCC rib erosion, severely slumped carrier panel tiles, and substantial metallic slag deposition on the RCC panels nearest the damaged area.
MADS data indicated the RCC cavity temperature and the temperature behind the wing leading edge spar began to rise at approximately 8:49:00 EST. This indicates that hot gas flowed into the RCC cavity between entry interface 8:44:09 EST and 8:49:00 EST. Three minutes later, at 8:52:00 EST, temperature and strain measurements indicated that hot gas penetrated the internal part of the wing via a breach in the wing leading edge spar. Immediately, the hot gas inside the wing began to heat wire bundles containing real-time telemetry and MADS data. A MADS upper left wing pressure measurement was the first to fail at approximately 8:52:16 EST. Over the next four minutes, 164 other measurements fail, with the last failure at approximately 8:56:24 EST. Most measurements failed very quickly, within the first two minutes of the breach.
Columbia's flight control system began to sense increased drag on the left wing due to the damage at 8:52:05 EST. The vehicle easily compensated for the initial aerodynamic disturbance. A significant change in the vehicle aerodynamics was observed at 8:54:20 EST, indicating a change in the damage to the left wing. At the same time several very bright debris events were seen in ground-based videos.
Soon after the hot gas entered the left wing multiple debris events were captured on video by observers on the ground. These video images begin at 8:53:46 EST (20 seconds after California coastal crossing) and end with Columbia's final break-up. The exact source of the debris may never be fully understood. However, upper wing skin and Thermal Protection System (TPS) parts are possible candidates. Damage to the internal aluminum wing structure was most probable during this timeframe as well. These debris events appeared to affect orbiter communication. There were 13 unexplained communication dropouts in this timeframe.
By 8:56:16 EST hot gas had penetrated the wheel well wall as indicated by an off-nominal rise in hydraulic line temperatures. Another significant change in Columbia's aerodynamics occurred at 8:58:09 EST, accompanied by several more debris events. The vehicle responded to this event with a sharp change in its aileron trim. Additionally, by 8:58:56 EST all left main gear tire pressure and temperature measurements were lost, indicating a rapid progression of damage inside the wheel well. A continual progression of left wing damage caused another abrupt change in the vehicle's aerodynamics at 8:59:29 EST. Columbia attempted to compensate by firing all four right yaw jets. By 8:59:32 EST the Mission Control Center had lost all telemetry data. MADS recorder data was lost at 9:00:14 EST. Based on video imagery, main vehicle aerodynamic break-up occurred at 9:00:23 EST.
Analysis and Testing Underway to Support the Working Scenario:
Although there is an abundance of existing evidence supporting the Working Scenario described above, the CAIB and NAIT have the following analyses and testing underway to refine the details of the scenario:
The CAIB has not reached any final conclusions and has not determined the cause of the loss of the shuttle and crew. The board's final report will be issued later this summer.
- Completion of RCC and tile impact testing at Southwest Research Institute.
- Aerothermal analyses to correlate off nominal heating trends in left fuselage sidewall and left Orbiter Maneuvering System (OMS) pod heating that were observed in the MADS data.
- Instrumentation wire burn-through arc jet tests and thermal analyses to support the timing of observed instrumentation failures.
- Instrumentation circuit analyses or testing to confirm the failure signatures observed in the data.
- Hypersonic wind tunnel testing and aerodynamic analyses to explain aerodynamic roll and yaw moments observed in flight data.
- Thermal analysis of RCC panel 9 clevis and spar temperature sensor responses to support or refute flight data.
- Gas flow and heat transfer calculations internal to the wing to support the MADS sensor readings in and around the wheel well.
- Arc jet testing and/or analysis of previous arc jet testing to determine feasibility of RCC erosion observed in several key pieces of RCC panel 8/9 debris.
- Continued forensic testing and analysis of significant recovered debris.
- ET dissection and cryopumping tests.
"The real value of this is that it tells us what to do now and where to go next," he said. "The foam impact testing is very important to us, we have to continue the very, very hard work on the aerothermal analyses to correlate some of these events that we have really good data on but yet we can't quite fully understand everything that's happening, like how long does it take to burn through Kapton wiring, how long does it take to create a knife edge (burn pattern) in a piece of RCC that's a third of an inch thick, how long does it take to burn through aluminum skin and those kinds of things."
[If you want off or on my Columbia ping list, let me know. FReegards.]
They are still saying a large block of foam broke off -- ignoring the impact and position of the smaller preceding foam chunk.
The fixation on the RCC assembly, and ignoring a carrier panel (either upper or [to my mind less likely] lower) loss that would meet the approximate entry hole determination. I think that a lower panel would have allowed a quicker cutting into the wing in a shorter time than an upper panel and the turbulent entry.
Crap! They saw it with their own damn eyes.
So now they are going to make debris proof RCC panels??????? They will end up in a total re-design and this bird will never fly again.
But......This is what I expected.
This is not what should be done.
Fix the foam, fly the bird is too damn simple of an explanation.
Screw it! (or screw them)
Tile Damage Seen As Key in Shuttle Breach
HOUSTON -
Columbia accident investigators announced Tuesday they have concluded that damaged thermal tiles allowed superheated gases inside the space shuttle's left wing as it re-entered the atmosphere, leading to its destruction.
"We have a very good understanding of what happened," investigation board chairman Harold Gehman said at a news conference. "The orbiter (space shuttle) was returning with a pre-existing flaw in the wing.... The wing got heated from the inside."
However, Gehman said how the wing was damaged remains unproven, although a collision with foam insulation from the shuttle's external fuel tank during launch remains the most likely cause.
The shuttle came apart over Texas on Feb. 1 while streaking toward a planned landing at the Kennedy Space Center (news - web sites) in Florida. Seven astronauts were killed and the shuttle fleet was grounded while investigators looked for the cause of the accident.
The board for weeks was unwilling to take a firm position on what happened even as evidence mounted that a hole in the left wing was at the heart of the disaster. Even Tuesday, the board called its conclusions a "working scenario."
But Gehman said "we made sure that there were no facts that contradicted our scenario."
"We now know enough," he said. "We're at the point where we should focus our efforts."
He said the board will be able to make a broad range of recommendations this summer to make the shuttle program safer.
Gehman said the board may never be able to prove the wing was damaged by the foam insulation, though technicians next month will test that idea by firing chunks of the material at thermal tiles. But Gehman said NASA (news - web sites) already knows peeling insulation is a problem that must be fixed before the shuttle fleet flies again.
Also among the board's conclusions:
_As Columbia was launched Jan. 16, photos showed that the leading edge of the left wing was struck by a large piece of foam insulation. There was no indication while the craft was in orbit that the wing had sustained serious damage.
_On the shuttle's second day in orbit, Air Force radar detected an object drifting free of Columbia. Later analysis suggests, but does not prove, that the object was either a piece of reinforced carbon tile or a seal from the leading edge of the wing. It could have been broken by the foam during launch and then shaken free during a maneuver by Columbia.
_When Columbia re-entered the atmosphere on Feb. 1, gases heated to several thousand degrees entered a hole in the wing and melted metal struts and wiring.
_Sensors inside the wing detected rising temperatures within five minutes after the craft began its descent. Within six minutes, the sensors stopped sending data, suggesting wires were melting. In 15 minutes, all communication with Columbia ceased. Observers on the ground, from California to Texas, reported seeing burning debris falling.
_Reinforced carbon panels from the leading edge of left wing, numbers 8 and 9, were eroded by extreme heat. Other pieces from the wing were splashed with molten aluminum, copper, nickel and other metals, indicating extreme heat.
Gehman said there is a "high level of agreement" on the scenario among board members, but that "we reserve the right to change any part of it" if new facts surface.
Under the scenario developed by NASA and the CAIB, the mystery object could be either the T-seal between RCC panels 8 and 9 or a large section of the lower portions of the RCC panels themselves.
Curious, since at last week's CAIB press conference they indicated that the breach had to be inboard of that particular T-Seal based upon sensor failure times.
The maroons are trying to make the scenario fit the floating piece of unknown crap.
What if the unknown crap is just that! (unknown crap)
I love it when a plan comes together. By the time they get done with this, there will be a slew of impossible recommendations and as X-bob said earlier, the foam problem will be addressed by stressing the adhesion importance.
But, I differ with him about the fact that the shuttle will not be touched and returned to flight. I see a total redesign on the RCC coming out of this. (You could shoot the thing with a high powered rifle before, how much better can it get)
That's why we need to know what kind of modification was done to Columbia's leading edge at Palmdale in 1999, and more importantly, why it needed to be done. What is NASA covering up?
As to the floater, they are not following the rules of systematic troubleshooting. The floater is an anomaly that may or may not factor into the demise of the shuttle. It should not be given much weight in the scenario due to the total lack of identification of the item.
It could just as well be a scrap piece of construction material that a tech was using to kneel on during the installation of the lab. That expanded metal grating is a real pain on the knees. Lets say he went to lunch and slid it under a wire bundle. let's say he got re-assigned and never returned to the area to retrieve it. Let's say that during the rough turbulence the item moved out of the hiding place and floated out sometime after the cargo doors were opened.
They have weighted it as connected to the scenario when it may not be at all related.
I was actually being sarcastic when I said that.
I don't think the RCC is in any way a problem, except for the silicon dioxide coating. I believe they can improve on that a bit.
No, the reason I said that was that they appear to be finding fault with things that are not directly related. things that perhaps could be improved but at great cost in time.
Time...........................There is none to spare and they appear to be taking a shotgun approach that will not get the shuttle flying in time.
I am so disappointed with the progress of the program. If it is not money, then it is lengthy accident investigations that really are not getting to the root of the problems. (like the 0 ring thing) So, much time lost for such a small change. They could have shaved many months off that layover.
This time, they already knew they had a foam problem, but the big one did not happen and now it has. They should be done with this and recommending a total revamp at Michoud.
No, these shuttles will not be flying unless someone steps in and sets them a goal and a deadline. (which will not happen)
I don't know how this will turn out, but I have little faith in the process. I fear the shuttle may not fly for a year or perhaps more. This is what I fear.
Sure does seem that way!
Last week it was very clear that Panel 8-9 was too far outboard to be the site of the initial breech.
This week, the CAIB has returned to Panel 8-9 and is making sounds like they're getting tired and want to end the investigation PRIOR TO explaining the delamination of the ET insulation.
This is GD stupid!
Regretably, I'm losing confidence in the CAIB. After spending about three hours a week participating in this historic thread, I am reaching the conclusion that the chairman of the CAIB is no engineer and does not belong in charge of a major engineering effort like the CAIB investigation.
While the Admiral may have the bars to investigate the USS Cole attack, he is showing signs of lacking the experience required to fully evaluate the science and engineering involved with the Columbia loss.
The men in this thread with experience in the program are AHEAD OF CAIB and have consistently demonstrated their expertise in ADVANCE OF CAIB activity.
While the Admiral may not comprehend the utility of impact testing, the FAA has done impact testing on aircraft components for decades. Perhaps the US NAVY might consider similar tests with their aircraft.
If Gehman makes such a ludicrous report that our team can rip it to shreds, he didn't do anyone a favor and just wasted millions of tax dollars and six months of time.
Someone at CAIB needs to report the following:
1. NASA IS TO FIX THE FOAM
2. NASA IS TO IMPACT TEST THE RCC AND LEADING EDGE SYSTEMS IN THE CONFIGURATION OF THE REMAINING THREE ORBITERS
3. THE US CONGRESS NEEDS TO FUND A REPLACEMENT FOR THE STS
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.