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.

[Rightwing Conspiratr1]

Firstly the chemical composition of the foam insulation was changed recently due to the ban on the use of freon.

It's absolutely moronic that NASA would have to use substandard materials because of environmental wackoism. It wouldn't have bothered me in the least if they had decided the best material for the job was spraying asbestos over everything. Freon? Freon? Freon? I have no words for the stupidity of banning a material that isn't dangerous at all to anything in the amounts used.

[XBob]

the best comparison I can easily think of is to that of an old box of baking soda, (only much lighter) rather cohesive, and will hold it's shape outside the box, until you drop or impact it, then it comes apart into fine granuals.

there are a couple of photo's of tiles in texas that landed on a road and were run over and crushed, at relatively low speed.

[Cold Heat]

The loss of the tile should not impact the relative readings of anything

I do not think it did.

This first indication of trouble was the increased temps("shot up fast") in the brake lines on the left wheel. This occured as they were approching California.

It was then that the computer sensed they were going too fast. The s-turns began. Then the temp sensors in the wing dropped off line.(over Nevada)

I think temps in the brake lines could only increase if plazma entered the wheel well. This happened very early in the re-entry. Almost as if the well was open to space or the door was ajar. The drag problem did not start until after the sensors crapped out. I think the wing began melting out at this time. About a minute and a half later they lost contact over texas.

This tells me the well cover came off some how. They have said that this is not likely because of the checks and rechecks.

Could this be a simple case of human error? There does not seem to be enough time to burn through the door before the brake line temps showed big increases. The wiring for the sensors likely goes through the wheel well as does the tire pressure sensor. The plasma needed a bit of time to burn through this high temp protected wiring.

This all happened so early on. It began on initial re-entry, when temps would be relatively low on the underside of the craft. They started shedding tiles and pieces at well over 225,000 feet.

Almost as if a section of the wing had no tiles at all. Yet we know from photo evidence after the foam dropped the there was no large area of damage. In fact it showed none. (low res photo)

The only way that I can see this happening, is if the well cover was gone. It would fit the senario.

[XBob]

we do a lot of moronic things in this country, (and especially in the government and NASA) because of moronic regulations. Did you ever see the 1 3/4" thick regulation from OSHA on how to design a toilet seat, which all government procurement departments had to comply with?

I was on the freon transition team, where we in the early 90's started programs to totally stop using freon in the space program by 1995 (implementation of the Monteral anti-freon convention the US had signed in about 1988 or 89). We used freon to clean all the parts before assembly. We replaced it by using de-mineralized water, with no cleaners/surfactants, or anything, just plain water.

[bonesmccoy]

Regarding photos of LH wing structure after impact, does anyone have a link?

I missed the press conf today and would like to believe that this is not the cause of the accident. However, let's look at some estimates of impact energy for ice on the wing area.


"The videos that NASA has are much clearer"

Yes, I posted those links in the thread a bit later.

It sounds like you want to discuss the momentum of the object. Regardless of whether or not the object is 10 kg or 100 kg, the velocity at separation from the stack is identical.

The force of impact changes depending upon the mass.

p=mv

f = ma

assume
foam mass = 4 kg
ice mass = 20 kg
v = relative velocity of impact
p(ice) = 20kg * v
p(foam) = 4 kg * v

Note mass ratio between ice vs. foam determines the ratio of the momentum of the two objects.

You are correct regarding the momentum of the object.

since force of impact = mass of object x acceleration of object into wing

f(ice)=20kg x a
f(foam)=4kg x a

The force of impact is also dependent on the same variable.

---

If the object is primarily ice and is a circular object about 50 cm in diameter and 5 cm thick...
the volume of that cylinder would be pi x r^2 x h
that's 3.14 x 0.25 x 0.05 = 0.0393 cubic meters
The density of ice is 917 kg/cubic meters

The mass of the ice was about 36 kg!

---

From Snopercod's posting of the tile map for OV-102, it appears that the forward ET-orbiter attachment bipod is about 7500 cm from the LH main landing gear door.

Let us assume that the video frame rate is 29.9 frames per sec. Movement of the object from one frame to the next correlates to 1/30th of a second (or 0.0333 sec).

Let us also assume that the object moves in one frame from the bipod to the LH main landing gear door (roughly 200 inches) about 500 cm.

The velocity of the object is 500 cm/0.033 sec = 15151 cm/sec = 5965 in/sec = 500 fps = 0.09 miles/sec = 338 mph!

Only NASA or the contractor knows if a 35 kg object going 340 mph can destroy tile in the area of the LH MLG door assembly.

(Snopercod...regarding shuttle engineers... you really do need to move to California... and don't get Hollised in the process :) )

[XBob]

I saw the amature video of the flashes, and big flash, behind the shuttle by an amateur in California. They appeared like a couple of tiny flares, then a big one, if you have ever seen electronic counter measure military flares (to distract IR missiles).

IMO the big 'flare' was the left wheel well door.

[bonesmccoy]

Does anyone know what this is?

[Cold Heat]

I have been looking for the pics they showed today.

No luck so far.

[Cold Heat]

I think we figured it to be a gasket for a exaust manifold or something like that. It does not look very much like a shuttle part.

[Cold Heat]

Ya know, it ccould be a fireproof gasket for a explosion proof electrical j-box, but someone with intimate knowledge of the electrical system would have to make that call.

[bonesmccoy]

yeah, i'd say that's not an orbiter structure.

if it's not inconel or Al or Ti, then it's not STS in origin.

[XBob]

Let us assume that the video frame rate is 29.9 frames per sec. Movement of the object from one frame to the next correlates to 1/30th of a second (or 0.0333 sec).

---

someone said that the Frames Per Second was 97 (or something like that), not 29.

[XBob]

it's an exhaust manifold gasket from an internal combustion engine.

[XBob]

it APPEARS TO BE an exhaust manifold gasket from an internal combustion engine.

[XBob]

Ya know, it ccould be a fireproof gasket for a explosion proof electrical j-box, but someone with intimate knowledge of the electrical system would have to make that call

---

I disagree - the darker part on the upper right appears to be glue, just enough to stick it to the part for installation, which is normal when building/rebuilding engines, but not shuttles.

[XBob]

also, notice the 'raggady' part of the opening on the right side, that means that is a 'standard' gasket which fits more than one size exhaust port.

such 'imprecision' would never be allowed in a shuttle component.

[Cold Heat]

I put it in my photo thingy and blew it up. All I can tell is that what ever it is, it is no good anymore.

As to exaust gaskets, I have done a great deal of engine repair on both diesel and gas from chevy and briggs to cummins and detroit but I have never seen one exactly like it.

The absence of bolt holes indicates a possible exaust dougnut, but I cannot call it for sure.

[Gracey]

I got the impression he was stalling and playing rope-a-dope.

Why, Why are you making such idiotic statements when you know NOTHING, absolutely NOTHING of which you speak? Keep your ignorance to yourself or do some homework, first.

Dittemore is an honest, decent manager, and well respected for his integrity by his peers.

[Cold Heat]

I just took another look. The ragged area is where it burned out. The dark color appears to be carbon and it probably fell out of a trash truck someplace.

That's what I see.

[Moonman62]

Dittemore is an honest, decent manager, and well respected for his integrity by his peers.

He may well be under noranl circumstances, but I'm commenting on what's happening in the press conferences.

BTW, do you know him personally?