Image of Columbia from Air Force. Photo: NASA TV
Posted on 02/07/2003 4:08:42 PM PST by Lokibob
Image of Columbia from Air Force. Photo: NASA TV |
According to sources close to the investigation, the images, under analysis at the Johnson Space Center in Houston, show a jagged edge on the left inboard wing structure near where the wing begins to intersect the fuselage. They also show the orbiter's right aft yaw thrusters firing, trying to correct the vehicle's attitude that was being adversely affected by the left wing damage. Columbia's fuselage and right wing appear normal. Unlike the damaged and jagged left wing section, the right wing appears smooth along its entire length. The imagery is consistent with telemetry.
The ragged edge on the left leading edge, indicates that either a small structural breach -- such as a crack -- occurred, allowing the 2,500F reentry heating to erode additional structure there, or that a small portion of the leading edge fell off at that location.
Either way, the damage affected the vehicle's flying qualities as well as allowed hot gases to flow into critical wing structure -- a fatal combination.
It is possible, but yet not confirmed, that the impact of foam debris from the shuttle's external tank during launch could have played a role in damage to the wing leading edge, where the deformity appears in USAF imagery.
If that is confirmed by the independent investigation team, it would mean that, contrary to initial shuttle program analysis, the tank debris event at launch played a key role in the root cause of the accident.
Another key factor is that the leading edge of the shuttle wing where the jagged shape was photographed transitions from black thermal protection tiles to a much different mechanical system made of reinforced carbon-carbon material that is bolted on, rather than glued on as the tiles are.
This means that in addition to the possible failure of black tile at the point where the wing joins the fuselage, a failure involving the attachment mechanisms for the leading edge sections could also be a factor, either related or not to the debris impact. The actual front structure of a shuttle wing is flat. To provide aerodynamic shape and heat protection, each wing is fitted with 22 U-shaped reinforced carbon-carbon (RCC) leading-edge structures. The carbon material in the leading edge, as well as the orbiter nose cap, is designed to protect the shuttle from temperatures above 2,300F during reentry. Any breach of this leading-edge material would have catastrophic consequences.
The U-shaped RCC sections are attached to the wing "with a series of floating joints to reduce loading on the panels due to wing deflections," according to Boeing data on the attachment mechanism.
"The [critical heat protection] seal between each wing leading-edge panel is referred to as a 'tee' seal," according to Boeing, and are also made of a carbon material.
The tee seals allow lateral motion and thermal expansion differences between the carbon sections and sections of the orbiter wing that remain much cooler during reentry.
In addition to debris impact issues, investigators will likely examine whether any structural bending between the cooler wing structure and the more-than-2,000F leading edge sections could have played a role in the accident. There is insulation packed between the cooler wing structure and the bowl-shaped cavity formed by the carbon leading-edge sections.
The RCC leading-edge structures are bolted to the wing using Inconel fittings that attach to aluminum flanges on the front of the wing.
The initial NASA Mission Management Team (MMT) assessment of the debris impact made Jan. 18, two days after launch, noted "The strike appears to have occurred on or relatively close to the "wing glove" near the orbiter fuselage.
The term "wing glove" generally refers to the area where the RCC bolt-on material is closest to the fuselage. This is also the general area where USAF imagery shows structural damage.
The second MMT summary analyzing the debris hit was made on Jan. 20 and had no mention of the leading-edge wing glove area. That report was more focused on orbiter black tiles on the vehicle's belly. The third and final summary issued on Jan. 27 discusses the black tiles again, but also specifically says "Damage to the RCC [wing leading edge] should be limited to [its] coating only and have no mission impact." Investigators in Houston are trying to match the location of the debris impact with the jagged edge shown in the Air Force imagery.
Columbia reentry accident investigators are also trying to determine if, as in the case of the case of Challenger's accident 17 years ago, an undesirable materials characteristic noted on previous flights -- in this case the STS-112 separation of external tank insulation foam debris -- was misjudged by engineers as to its potential for harm, possibly by using analytical tools and information inadequate to truly identify and quantify the threat to the shuttle. As of late last week, NASA strongly asserted this was not the case, but intense analysis on that possibility continues.
The shuttle is now grounded indefinitely and the impact on major crew resupply and assembly flights to the International Space Station remain under intense review.
Killed in the accident were STS-107 Mission Commander USAF Col. Rick Husband; copilot Navy Cdr. William McCool; flight engineer, Kalpana Chawla; payload commander, USAF Lt. Col. Michael Anderson; mission specialist physician astronauts Navy Capt. Laurel Clark and Navy Capt. David Brown and Israeli Air Force Col. Ilan Ramon.
"We continue to recover crew remains and we are handling that process with the utmost care, the utmost respect and dignity," said Ronald Dittemore, shuttle program manager.
No matter what the investigations show, there are no apparent credible crew survival options for the failure Columbia experienced. With the ISS out of reach in a far different orbit, there were no credible rescue options if even if wing damage had been apparent before reentry -- which it was not.
If, in the midst of its 16-day flight, wing damage had been found to be dire, the only potential -- but still unlikely -- option would have been the formulation over several days by Mission Control of a profile that could have, perhaps, reduced heating on the damaged wing at the expense of the other wing for an unguided reentry, with scant hope the vehicle would remain controllable to about 40,000 ft., allowing for crew bailout over an ocean.
Reentry is a starkly unforgiving environment where three out of the four fatal manned space flight accidents over the last 35 years have occurred.
These include the Soyuz 1 reentry accident that killed cosmonaut Vladimir Komarov in 1967 and the 1971 Soyuz 11 reentry accident that killed three cosmonauts returning after the first long-duration stay on the Salyut 1 space station.
The only fatal launch accident has been Challenger in 1986, although Apollo astronauts Gus Grissom, Ed White and Roger Chaffee were killed when fire developed in their spacecraft during a launch pad test not involving launch.
No other accident in aviation history has been seen by so many eyewitnesses than the loss of Columbia -- visible in five states.
Telemetry and photographic analysis indicate the breakup of the historic orbiter took place as she slowed from Mach 20-to-18 across California, Nevada, Arizona and New Mexico with the loss of structural integrity 205,000 ft. over north central Texas where most of the debris fell.
The science-driven STS-107 crew was completing 16 days of complex work in their Spacehab Research Double module and were 16 min. from landing at Kennedy when lost. Landing was scheduled for 8:16 a.m. CST.
Abnormal telemetry events in the reentry began at 7:52 a.m. CST as the vehicle was crossing the coast north of San Francisco at 43 mi. alt., about Mach 20.
The orbiter at this time was in a 43-deg. right bank completing its initial bank maneuver to the south for initial energy dissipation and ranging toward the Kennedy runway still nearly 3,000 mi. away.
That initial bank had been as steep as about 80 deg. between Hawaii and the California coast, a normal flight path angle for the early part of the reentry. The abnormal events seen on orbiter telemetry in Houston indicate a slow penetration of reentry heat into the orbiter and damage on the wing, overpowering the flight control system. Key events were:
But the rate of left roll was beginning to overpower the elevons, so the control system fired two 870-lb. thrust right yaw thrusters to help maintain the proper flight path angle. The firing lasted 1.5 sec. and, along with the tire pressure data and elevon data, would have been noted by the pilots.
At about this time, the pilots made a short transmission that was clipped and essentially unintelligible
In Mission Control, astronaut Marine Lt. Col. Charles Hobaugh, the spacecraft communicator on reentry flight director Leroy Cain's team, radioed "Columbia we see your tire pressure [telemetry[ messages and we did not copy your last transmission."
One of the pilots then radioed "Roger," but appeared to be cut off in mid transmission by static. For a moment there was additional static and sounds similar to an open microphone on Columbia but no transmissions from the crew.
All data from the orbiter then stopped and the position plot display in Mission Control froze over Texas, although an additional 30 sec. of poor data may have been captured.
Controllers in Mission Control thought they were experiencing an unusual but non-critical data drop out. But they had also taken notice of the unusual buildup of sensor telemetry in the preceding few minutes.
About 3 min. after all data flow stopped, Hobaugh in mission control began transmitting in the blind to Columbia on the UHF backup radio system. "Columbia, Houston, UHF comm. check" he repeated every 15-30 sec., but to no avail. In central Texas, thousands of people at that moment were observing the orbiter break up at Mach 18.3 and 207,000 ft.
Milt Heflin, Chief of the Flight Director's office said he looked at the frozen data plots. "I and others stared at that for a long time because the tracking ended over Texas. It just stopped. It was was then that I reflected back on what I saw [in Mission Control] with Challenger."
The loss of Challenger occurred 17 years and four days before the loss of Columbia.
"Our landscape has changed," Heflin said. "The space flight business today is going to be much different than yesterday.
"It was different after the Apollo fire, it was different after Challenger."
Columbia, the first winged reusable manned spacecraft first launched in April 1981, was lost on her 28th mission on the 113th shuttle flight.
Many thanks for those; it also shows a larger 'plume' off the rear left wing.
Anyone got any thoughts on the speculation given by musicman in his post at #152? Looking at the series of slides and the depictions of the sensor dropouts, it seems to me that the 'orange' wire bundle was impacted and cut by plasma leakage. The rear sensors on the blue bundle stayed nominal, those tied into the orange bundle just dropped. That, to my mind, indicated that the leading edge RC/C was compromised.
As I understand the situation, Columbia was just completing their first s-turn to the right when the problems began to manifest themselves. The picture in my mind is 40 degrees nose up, with the right wing pointing at the earth...initially 80 degrees, then 43 degrees. Similar to a "camera pass" at an air show, only more extreme. They were slicing thru the thin air to lose altitude.
From the following description of the Digital Auto Pilot [DAP], it appears that the pitch and roll thrusters were inhibited at the point in the descent when the breakup started, but the yaw thrusters were still enabled. I assume that the rudder was ineffective at this point because it was being blanked by the high pitch attitude. Any comments? Do I have this right that the right wing (not the left) was pointing into the wind pretty much?
I must have something backwards because the picture in this thread shows the left wing down, not the right.
(BTW, the shuttles determine the dynamic pressure by measuring the deceleration.)
The aft RCS jets maneuver the spacecraft until a dynamic pressure of 10 pounds per square foot is sensed; at this point, the orbiter's ailerons become effective, and the aft RCS roll jets are deactivated. At a dynamic pressure of 20 pounds per square foot, the orbiter's elevators become effective, and the aft RCS pitch jets are deactivated. The orbiter's speed brake is used below Mach 10 to induce a more positive downward elevator trim deflection. At Mach 3.5, the rudder become activated, and the aft RCS yaw jets are deactivated (approximately 45,000 feet).Entry flight control is maintained with the aerojet DAP, which generates effector and RCS jet commands to control and stabilize the vehicle during its descent from orbit. The aerojet DAP is a three-axis rate command feedback control system that uses commands from guidance in automatic or from the flight crew's RHC in control stick steering. Depending on the type of command and the flight phase, these result in fire commands to the RCS or deflection commands to the aerosurfaces.
In the automatic mode, the orbiter is essentially a missile, and the flight crew monitors the instruments to verify that the vehicle is following the correct trajectory. The onboard computers execute the flight control laws (equations). If the vehicle diverges from the trajectory, the crew can take over at any time by switching to CSS. The orbiter can fly to a landing in the automatic mode (only landing gear extension and braking action on the runway are required by the flight crew). The autoland mode capability of the orbiter is used by the crew usually to a predetermined point in flying around the heading alignment cylinder. In flights to date, the crew has switched to CSS when the orbiter is subsonic. However, autoland provides information to the crew displays during the landing sequence.
So the adverse yaw must have come from drag. And any roll must have been inertial. But according to NASA, the flight attitude of the vehicle was within nominal parameters up to the point where comm was lost.
From the briefing I heard yesterday, it appears that a number of sensors in the left wheel well and on the left trailing edge either dropped offline in the two minutes before the loss of comm, or registered out-of-norm temperature increases, some as high as 14 degrees/minute. That would indicate some kind of thermal event in that vicinity, although there are certainly other explanations.
I wonder if anyone has ruled out the possibility of fire, maybe of electrical origin.
I realized that, but decided not to comment on it. The actual distance is not significantly different from that to have great bearing on your analysis. I believe somewhere in this thread someone estimated that at the time of this picture the Shuttle was 200-300 miles from the camera, but I'm not going to look for it. I've no reason to doubt that ball park estimate, especially given the 4miles/sec speed the Shuttle was travelling at the time. Sounds reasonable to me.
That leads me to wonder just what kind of cameras the conspiracy theorists have, by the way. I figure that in a thousandth of a second exposure the Shuttle would have travelled around 15-20 feet. Wreaks havoc on the clarity you can get... to say nothing about the kind of lensing and tracking required to get anywhere near that kind of film speed capability even ignoring the plasma effects ... Oh, but we know NASA and the AF are hiding loads of info, so they must be able to do it... just snap their fingers...
Don't be so sure. I saw pictures of a Titan ascent after it had shed the boosters, and the resolution was remarkable. They were classified as secret. Six months later the same photos were published in an aerospace calandar for public consumption. The investigation is not done yet.
Could be.
In this flight regime, the yaw thrusters were enabled, as they should have been. I am pretty sure that the rudder was blanked by the body of the orbiter at the high pitch angle at the time.
--Check Six my friend...
Musicman has a good idea, I would suspect that the NASA and contractor engineers would be looking for any differences in the shuttle systems data available from telemetry prior to and after the external tank insulation debris even.
brityank, my first impression of the NASA sensor timeline graphics brought me to the same preliminary conclusion you did concerning damage to the "orange" wire bundle - the failure mode of ALL of the temperature sensors in that bundle failed offline, there were no temperature changes noted. I do not know the type of temperature sensors used, thermocouples, RTDs, thermistors, or likely a mix, but it does not matter in this instance - its clear in the data then that there was no heating of these particular sensors to the point of failure. Exactly how the sensor wiring failed is not so clear, but certainly open to various theories at this point. If the sensors are indeed routed as per the NASA graphic, any damage near the wing cove/wheel well area could have caused this, whether the damage was exteme heat due to a wing breach, or physical damage due to debris. If I had to guess at this point, I would go with the leading edge RCC damage you postulate, or maybe even a significant loss of tiles on the wheel well area leading to a breach.
Of course, the precursor to all of this were the first sensor anomolies, which were increases in temperature of the brake lines. This was well noted in one of Ron Dittemore's early press conferences (Feb. 3?): http://www.newsday.com/news/health/orl-ss-nasa-transcript020303,0,5690321.story?coll=ny-health-utility
Hopefully, we will get more detailed techncial data from NASA, I don't expect it from the news media!
By the way, there is an excellent 3D cutaway graphic of the orbiter's left wing at the Orlando Sentinel:
http://www.orlandosentinel.com/news/custom/space/orl-asec-ssphoto020803,0,7510410.graphic
NASA must go through every branch of the fault trees, must not assume anything, in order to find the root cause. That is the essence of a good root cause analysis. I trust these guys, they will do a good job. But hey, what can I say- in the end, it will be the foam.
(Take your left hand, turn it 3/4th of the way palm in toward your face while pointing your fingers up, and you'll have a pretty good representation of the angle you're viewing the shuttle from in this photo.)
Now look at the edge of the left wing, which is on the bottom in this perspective. Notice how, beginning where the wing meets the middle of the fuselage, there is a sharp right angle and something pointing out from the edge. Then there is a kind of curve inward, leading to another less prominent portion sticking out, then a longer, more gradual curve inward before the normal outward curvature of the wing resumes.
This photo was shot only 1 minute before the breakup over Texas. If it does, indeed, show what it appears to, that means large pieces of that wing came off in the preceding 5 or 6 minutes of re-entry. This is consistent with what the videos of the shuttle over California show: large pieces breaking off. This is not just some tiles coming off, but actual pieces of the wing structure.
I don't think there's any question that left wing started coming apart as it met resistance from earth's atmosphere. The only reason the shuttle didn't fall straight out of the sky immediately upon the breakup of the wing, as a plane would, was its velocity.
Now as to what the root cause of the structural failure of the wing was, it's going to be exceedingly difficult to determine. The foam debris may or may not be the root cause. Could be just a coincidence. If it is the root cause, it must have done a heck of a lot more than just damage a few tiles on liftoff.
That indeed is my gut feel at this point. In case you missed it, the following thread has a lot of good info and informed FReep-Expert speculation on the breakup:
Observation on TPS damage on Orbiter [opens in new window]
I think this is significant, since if the leading edge of the left wing had been damaged (either during launch, or by ice from the urine-dump port), it would have been out of the wind during the initial roll to the right.
As the shuttle reversed and rolled to the left, the left wing would be poining at the ground and toward the forward path of the Columbia - IOW, into the wind.
I found this at a NASA website and thought it was concise [Link]:
Deorbit burn occured at 8:15 a.m. EST (1315 GMT) for a planned landing on KSC Runway 33. At approximately 8:52 a.m. EST, Columbia was crossing over the coast of California and entering Roll Reversal #1. Columbia was traveling at Mach 20.9 and 224,390 ft (MET 15 days 22 hours 17 min 50 seconds)At 8:52:20 EST, Columbia's Left Main Gear Brake Line Temp D in the left wheel well showed an off nominal temperature rise (2 degrees/min) followed by an off nominal temperature rise in Brake Line Temp A (6 degrees/min) at 8:52:39 (13:52:39 GMT) and Temp C (5 degrees/min) at 8:52:48. At 13:52:59 GMT, flight controllers saw a loss of sensor data (offscale low) from the Left Inbord Elevon Lower Skin Temp followed by a loss of sensor data from the Hydraulic System 3 Left Outboard Elevon Actuator Return Line Temp (13:53:10), Hydraulic System 1 Left Inboard Elevon Actuator Return Line Temp (13:53:11), Hydraulic system 1 Left Outboard Elevon Actuator Return Line Temp (13:53:31), Hydraulic System 2 Left Inboard Elevon Actuator Return Line Temp (8:53:36). Wires from these sensors are routed inside the wing from the orbiter midbody, in front of the main landing gear towards the leading edge and then back to the sensor locations near the trailing edge of the wing.
At 8:54 a.m. EST, while the orbiter was crossing over Eastern California, sensors indicated there was an increase in temperature in the left wheel well and Mid Fuselage. The Left Main Gear Brake Line Temp B showed an off nominal temperature rise (6 degrees/min) (8:54:13) followed by an off nominal rise (6 degrees/min) of the Mid Fuselage Left Body Line (X-axis=1215) Temperature (8:54:22), Left Main Gear Strut Actuator Temp (7 degrees/min) (8:54:27), Left Main Gear Uplock Actuator Unlock Line Temp (4 degrees/min) (13:54:36) and the System 3 Left Hand Forward Brake Switch valve Return line Temp (5 degrees/min) (13:55:23). Over a 5 minute period, Columbia's left side increased 60 degrees F while the right side increased only 15 degrees F during the same time. During this time, the inside of the Payload Bay was normal.
Shortly before 8:58 a.m. EST, while the orbiter was over New Mexico, sensors indicated an increase in drag on the left side and the flight control systems were automatically compensating. Then the Main Landing Gear Left Outboard Wheel Temperature Sensor went offline (13:55:35) followed by the Left Upper and Lower Wing Skin Temp Sensor (13:56:20). At 13:57:54, the System 2 Left Hand Aft Brake Switch Valve Return Temp increased in temperature (14 degrees/min) and the Main Landing Gear Left Hand Outboard and Inboard Tire Pressure 1&2 (13:58:33/13:58:39) and Wheel Temperature (13:58:35) goes offline (offscale low).
At 8:59 a.m. the Tire pressure sensor caused an onboard alert that was acknowledged by the crew. Communication with the crew and loss of data occured shortly after while Columbia was at a Mission Elapsed Time (MET) of 15 days 22 hours 20 minutes 22 seconds. The vehicle broke up while traveling at 12,500 mph (Mach 18.3) at an altitude of 207,135ft over East Central Texas resulting in the loss of both vehicle and crew. (Reference: JSC Ron Dittemore Post flight Technical News Conference 2/1/03, 2/2/03 and 2/7/03 3:30 pm CST).
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