Observation on TPS damage on Orbiter

NASA photos | 2-3-03 | BoneMccoy

[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.

[small_l_libertarian]

On Fox News during Cavuto's repeat show last night, they had a very clear video of the insulation/ice falling off of the tank and hitting the wing. At the end of the video when the plume sprays out, you can very clearly see that the original "chunk" also comes out from under the wing.

The plume appears to be tile dust to me, too, but I'm basing it on the fact that I saw the chunk come out from under the wing, pretty much the same size/shape it went in, not the color of the plume (looking at the color was a very good idea, though).

(Now, I was viewing this video at midnight, so it may just be my eyes...)

[snopercod]

Thanks. Those are the best photos I've yet seen of the "debris". Here are my thoughts:

1. It looks like ice to me, too, not ET TPS. My guess is that it came from the ET LH2 repress line, the 2" line that runs up the left side of the tank which is used to repressurize the ET LH2 tank as the LH2 is sucked out of it during ascent. IIRC, the ET LH2 Repress Line is at ambient temps pre-launch, but pressurized with hot gasses from the engines on ascent. That could have melted off a chunk of ice.

2. Take a second look at the launch video and you will see frost actually growing on the intertank during ascent. Atmospheric conditions must have been right for ice built up on that line or it's attachments during pre-launch or ascent.

3. The impact area looks to me to be very close to where the LMG door was located. The white "vertical" line you see in the "enhanced" areas is the "bond line" between the wing and the fuselage. (It's not really a line, but just a change in curvature in the tiles which appears as a line in reflected light.)

4. The hinges of the 4'x12' +/- gear doors are along the bond line, and the door swings outboard upon closing. The front-outboard corner of the gear door is ligned up with the point of the leading edge where the chine sweeps outward. In picture #3, you can see that plume on the right side of the enhanced circle sweeping directly over the leading edge of the LMG door area. The front-outboard corner of the door is less than 3' away from the leading edge of the wing! (The main impact in the photos seems to be inboard of the bond line.)

5. The landing gear door area is one of the hottest areas of the shuttle on re-entry (second or third only to the nose cap and leading edges, I believe)

(I have the shuttle tile drawings in front of me as I type this. I haven't found my ET drawings yet. We boxed everything up when we left KSC...)

[snopercod]

The SILTS pod is still there (that bulb on the top leading edge of the vertical stabilizer). But to the best of my knowldege, they haven't flown the camera for ten years or so.

[lysol@whitehouse]

Observing Monday's news conference, Ron Dettemore's composure appeared to dramatically change when asked about the possibility of ice on the insulating foam, and how that would change estimates of damage to the tiles. His voice hardened and became loud as he appeared to obfuscate and hide behind "intelligent men assessed all possibilities and decided there was not a problem". None of the reporters challenged him at this point, following up with a marshmallow question of "what about the future of space flight?" Reminds me of the Challenger news conferences. Bless the heroes of Columbia.

[exnavy]

On Sat. afternoon I heard a nasa spokesman say "there was a midcourse autopilot correction due to extreme high level buffeting and turbulance". Do you suppose that turbulance could have caused the loss of more loosened tiles than would have normally occured?

[OldFriend]

Your analysis is the very best to date. Thanks for making it simple to understand and sounding so logical.

[snopercod]

I just saw the same stop-frame video on Fox. What looks like a plume in pic #3 wasn't moving, so disregard what I said about it in my paragraph #4.

[OldFriend]

There may not have been sensors where the event originated.

[snopercod]

Turbulence is a concern, but I think it might have caused ice to fall off, not tiles. The tiles are stuck on there real good.

[michigander]

A piece of what is believed to be the underside and rear of the left wing of the space shuttle Columbia lies
against a fence near Nacadoches, Texas, February 3, 2003. During liftoff a piece of insulation hit Columbia's
left wing and NASA officials said Monday that it could have smashed into the some of the more than 20,000
thermal tiles covering the craft. REUTERS/Rick Wilking









A closeup view of tiles on what is believed to be the underside and rear of the left wing of the space shuttle
Columbia near Nacadoches, Texas February 3, 2003. During liftoff a piece of insulation hit Columbia's left
wing and NASA officials said Monday that it could have smashed into the some of the more than 20,000
thermal tiles covering the craft to protect it from burning up on reentry. REUTERS/Rick Wilking

[Budge]

Good, Bones. That plume has had me intrigued from the first. Whatever the object is/was, insulation from the ET, ice, or a combination of the two, it was large before the impact.

As far as the plume, I wonder if the size would be consistant with only the object being shattered. Personally I don't think so, but that is only MHO.

[small_l_libertarian]

I think I see the chunk in this series of stills, as well.

Debris Stills

In the last two frames, I can see the "chunk" (when the plume sprays out) come out from under the wing, and pass in front of the SRB (down toward the bottom of the SRB, near the small orange bit showing).

Does anyone else see this?

[bert]

.....ET insulation is orange/brown in color......

..... The interior of the tile is a white.....

It seems to me these statements are contradictory. Based on long ago upclose observations of the material, I thought it was white throughout with a black exterior surface.

If a tile sheared off as opposed to becoming unstuck, the exposed sheer surface would be white. If on impact the fragment disintegrated into a powdery cloud, the appearance would be light colored, in, fact would be reflective, and would be visable as a plume.

Similar visable phenomena would result from an ice blob so I can reach no conclusion.

[sam_paine]

So if it was a plume of smashed tile, then there should be some evidence near the launch site, or perhaps residue on the SRBs? I assume it was fairly far downrange when this occured, thus over water? Oh well.

[Budge]

I keep going back to the slo-mo pictures on Florida Today's site. I noticed that in about frame 10 and 11 (if I am counting correctly) that there is a small plume that appears under the wing immediately before the large plume in appears in frames 12 & 13.

Am I seeing correctly? Is that an additional small plume or perhaps something in the background?

[Revelation 911]

yeah I saw it - I also noticed there was enough material (be it ice, foam or tile) to swirl behind in the turbulence

[Budge]

I can see the "chunk" (when the plume sprays out) come out from under the wing,...

I see that also, S1L. It appears the plume actually "splits," so to speak, and the chunk is to the left side of the 'split.'

Does anyone else see the small "plume" in frames 10 & 11?

[okie01]

"This information will increase understanding of leeside aeroheating phenomena and will be used to design a less conservative thermal protection system."

I read this as suggesting that they weren't experiencing recurrent overheating on the upper left wing and fuselage. Instead, they believed that they were "over-insulated" and could potentially implement a "less conservative thermal protection system". In other words, save a couple of pounds...

[ijcr]

Firstly the chemical composition of the foam insulation was changed recently due to the ban on the use of freon. The "new" foam doesn't maintain integrity quite as well under high heating conditions and some pieces have been coming off, so NASA sands the foam still thinner to design "minimums" to still protect the aluminum skin, yet decrease the amount of foam that potentially could come off.

Secondly, All the tanks come in from the factory a light tan in color, and can eventually reach a chocolate brown depending on how long it sits on the pad in the sun. Any orange tinting should be very subtle. Actually, the orange influence is attributed more to what the sunlight is contributing that day whether it be close to sunrise or sunset than anything else.

Thirdly,The super-lightweight ET's, which first flew in 1998, have an even lighter color.

Finally, public affairs now shoots a lot of their images with digital cameras and these cameras sometimes have trouble reproducing reds, yellows, and tans.Often in filming a rapid event will go to white,eg fill a balloon with a dark powder and film it being burst...the result is often a white cloud.

[RippleFire]

Something else of interest from http://brian.carnell.com/articles/2003/02/000003.html

More on Shuttle Foam Damage from STS-87

By Brian Carnell

Monday, February 3, 2003

This NASA page has notes by a NASA worker from 1997 about the "significant damage" done to STS-87 from the reformulated, Freon-free foam insulation flaking off during the Shuttle's ascent (emphasis added),

 

During the STS-87 mission, there was a change made on the external tank. Because of NASA's goal to use environmentally friendly products, a new method of "foaming" the external tank had been used for this mission and the STS-86 mission. It is suspected that large amounts of foam separated from the external tank and impacted the orbiter. This caused significant damage to the protective tiles of the orbiter. Foam cause damage to a ceramic tile?! That seems unlikly, however, when that foam is combined with a flight velocity between speeds of MACH two to MACH four, it becomes a projectile with incredible damage potential. The big question? At what phase of the flight did it happen and what changes need to be made to correct this for future missions? I will explain the entire process.

And intriguing comments about similar issues during STS-86,

 

The STS-86 mission revealed a similar damage pattern but to a much lesser degree than STS-87. The STS-86 tile damage was accepted ruled as an unexplained anomaly because it was a night launch and did not provide the opportunity for the photographic evidence the STS-87 mission did. A review of the records of the STS-86 records revealed that a change to the type of foam was used on the external tank. This event is significant because the pattern of damage on this flight was similar to STS-87 but to a much lesser degree. The reason for the change in the type of foam is due to the desire of NASA to use "environmentally friendly" materials in the space program. Freon was used in the production of the previous foam. This method was eliminated in favor of foam that did not require freon for its production. MSFC is investigating the consideration that some characteristics of the new foam may not be known for the ascent environment.