Observation on TPS damage on Orbiter

NASA photos | 2-3-03 | BoneMccoy

[bonesmccoy]

saw your posting re: MLG door opening without MLG extension. The diagram of the MLG is interesting. Since there appear to be a mechanical link between the open MLG door and the MLG struts, are we supposing that the MLG opened earlier in California and that the burning debris was the mechanical linkage between the door and the gear?

They didn't lose tire temp sensors until a few minutes after heating occurred in the MLG bay.

So, that would mean that the tire sensors were functioning after the heating on the gear hydraulics started.

I had been thinking that the USAF photo showed an extended MLG door, but I am beginning to doubt that hypothesis after seeing the posted diagram.

[analyst2]

A couple of points from spaceflightnow.com:

I seem to remember that Dittemore said that sensors
failed low and failed high. This occurred while sensors centimeters away
continued to function. This seemed to support the theory that wires were
being melted away, either breaking connection or shorting.

He also mentioned that the timing may not be exact. One of the reasons
is that telemetry data is not sent continuously from all sensors. While the
slides speak of a "16 degree per minute rise" it actually may be that after
a several minutes of being stable, a larger rise occurred in a short amount
of time.

I don't see any way the wheel bay door could have come off and *any*
sensors continue to operate normally with 3000 degree gases entering.
Yet, telemetry reports that some sensors in the wheel bay continued
working up until LOS. Dittemore mentioned that in the final moments
right wing sensors began to fail too.

Another explanation for something large separating from the shuttle may
be the left wing glove, or portions of it coming off in pieces. It could
explain sensor rise on left side of the shuttle - unconnected to the wiring
of any other failed sensor. This is perhaps what the Air Force photo seems
to show.

There are several problems with the Air Force photo. First of all the aspect
ration doesn't seem to fit the outline of the shuttle. The ends of the wings
look rounded and the bay looks narrower than it should be. One
explanation is that it is an Infrared (not optical exposure). On intriguing
possibility mentioned by a Freeper two days *before* the AF photo showed
up was that there were Satellite photographs "showing the left wing coming off".
If the photo was taken in Kirtland Air Force Base at 7:58 and the entire wing
glove had blown off or was melted off (or wheel door had opened), it doesn't
fit with telemetry data. If the photo was take by Satellite at, say, 8:00 or later,
it would make more sense. (Could the photo have reduced contrast so
that no one would see that it was take from above, not below?)

Someone offered to fit a wire frame over the photo to determine the viewing
angle and missing (or melted) shuttle components. That would be really
interesting.

My own pet theory is re-entry profile turbulence or a failed RCC
gasket caused cracks or, allowing plasma to enter the glove area,
slowly peeling off the glove leaving the MLG compartment as the leading edge.

The shuttle flight was delayed since April because of cracks that had
been detected in the engine?

as per #1348
"Aluminum does absorb and transfer heat easily. It also melts a 800
or so degrees. Then it burns ferociously and emits light in a spectrum
that is blinding. Similar to a electric arc."

Perhaps these are the flashes?

[Thud]

John Jamieson's post on wind resistance at 250,000 feet was critical to my thinking. I had overestimated the rate of heat transfer to the wing interior from an RCC breach, having placed more weight on the 4 mile a second velocity than was appropriate.

I had focused on the observed rate of failure, and the rate of energy transfer to the wing structure, from the beginning. Tile shedding was an exterior event which mitigated the rate of energy transfer to the aluminum structure, while RCC failure let a blowtorch into the interior from the front.

But if I had overestimated the RCC failure rate of energy transfer, RCC failure became more credible. Then Xbob found a relatively simple interior path for the plasma from front to back which gave it access to the failed sensors, and additionally impacted the adhesive for the most vulnerable tiles.

Only tile-shedding could explain the observed multiple luminescent objects dropping back from Columbia without there being immediately fatal structural damage. Tile shedding had to be part of the scenario, and there was an obvious explanation for that - the initial burn-through occured at the tile damaged by the foam strike, with adjoining tiles just aft gradually coming off as their adhesive weakened.

I felt RCC damage was a possibility but not as likely due to my overestimate of the rate of energy transfer to the aluminum structure. But John showed my error there, and Xbob found an explanation for everything else including what I was focusing on.

[XBob]

1462 - points well taken:

"I don't see any way the wheel bay door could have come off and *any* sensors continue to operate normally with 3000 degree gases entering. Yet, telemetry reports that some sensors in the wheel bay continued ..."

---

I agree, and I don't know much about the aerodynamics/thermodynamics of this. So that is a good point against the door coming off.

However, I remember during the war in Vietnam, our aircraft dropping flares at night, and they went 'pop' pop pop - and looked just like the pictures from cal/nev. Those flares were made from burning magnesium - very similar metal to aluminum. So, IMO the pops were pieces burning, and the big pop was a big piece.

---

"Another explanation for something large separating from the shuttle may be the left wing glove, or portions of it coming off in pieces. It could explain sensor rise on left side of the shuttle - unconnected to the wiring of any other failed sensor. This is perhaps what the Air Force photo seems to show."

---

This is the theory Wirestripper and I have come come down to, and have been trying to get people to visualize. It also goes along with the longitudinal structural strength of the frame. last night I fixed up a picture with my very limited graphics capability which will be posted as soon as I can get it posted.

Budge, have you got it available for posting here yet?

[Thud]

NASA is concerning scenarios involving detachment of the port landing gear door. See:

http://www.nasa.gov/columbia/COL_landgear_email_030212.html

http://www.nasa.gov/columbia/COL_landgear_email_030212.pdf

[Budge]

I sent you one I modified, for you to post.

Have yet to recieve it, xBob. I don't understand.

[XBob]

thanks Thud.

We pretty much covered these items, perhaps except the extreem pressures and the degredation of the aluminum wheel.

Did you note how some of the words and some of the phrases fail to 'copy' and paste. They just disappear.

[Budge]

Tile shedding had to be part of the scenario, and there was an obvious explanation for that - the initial burn-through occured at the tile damaged by the foam strike, with adjoining tiles just aft gradually coming off as their adhesive weakened.

One thing that I had not mentioned when I was finally convinced the heat entered through a crack/hole in the RCC and heat buildup from the interior in the wheel well.

We all are talking of the shedding of the tiles, I concur that tiles were shed. But look at the cross section of the tiles below.

The tiles are designed with heat protection on the topside, not the underside.

Wouldn't the heat from the interior of the wing cause excessive shedding?

[XBob]

I sent you all those files and e-mails, and too your son, or someone's son too.

I modified one of your drawings, and sent it to you for posting early this morning.

I have my security settings on my Internet explorer set high at 168, and sometimes others have trouble recieving my e-mails.

This last one I sent you is very important.

Blackie - could you perform your valient e-mail transfer once again please. I will send it to you now, for forwarding it to Budge.

Many thanks to all.

[Budge]

I have seen nothing whatever to change my initial opinion that the foam strike was the underlying cause.

Nor have I. Only I would phrase that, "I have seen nothing whatever to change my initial opinion that the foam/ice strike was the underlying cause."

[XBob]

look at the gap filler, drawing from your site:

[XBob]

I agree with the glove coming off, and I have for several days now.

I thought the LG door came off, but perhaps not, however, if it idid, there was an eddy, and would it get that hot in it, right away?

The first big flash was either the gear door or the glove. The door would have ripped/burned off if it had extended into the slip stream, and there is no way that the USAF picuture could be the door.

[Budge]

Bob, have NOT recieved it yet. Please resend to Abudge@cablelynx.com

[XBob]

thanks for checking. and that's where I have been sending them.

I asked Blackie to forward it to you, as I have had this problem before with some people on some computers/servers or somewhere, and haven't been able to figure out the incompatibility. However, he can get my e-mails and can communicate with others who can't.

I hope it works. We did it before.

[Budge]

1465 - Holy cow, Thud, what a find!

[Budge]

1465 - Holy cow, Thud, what a find!

[Thud]

Yes, underside wing interior heat will cause tile shedding. NASA calls this the "unzippering" effect. Loss of one tile exposes the aluminum wing surface where the tile was to re-entry heat, which heats up all the area around it and tends to loosen the adhesive of the surrounding tiles, notably those aft of the missing tile. Then they come off too.

This is why the foam strike a single critical tile could destroy the spacecraft. The eddy effect described earlier could deepen a smashed-in cavity on the affected tile and either cause a small breach in it with plasma hitting the aluminum wing surface, or just reducing its insulative capability a whole lot. The aluminum skin underneath heats up, the adhesive for the affected tile loosens and then the whole tile comes off, and suddenly there is a bigger aluminum area exposed to the plasma and the unzippering effect starts.

An RCC breach was not needed to create the known evidence, other than the USAF photograph. The extra heat from Columbia's re-entry profile for this mission, its overweight and transition turbulence causing excessive drag (the latter happened on a dozen prior missions!) alone could have caused its loss. But there were detachment events starting no later than the Owens Valley indicating at least a tile breach much earlier in re-entry so I always thought, with one brief wavering when Xbob mentioned the elvon/elevon burn-through he personally inspected, that the foam strike had fatally damaged some part of the re-entry protection.

Until just recently I thought it was the TPS, specifically the tile between the RCC and the port wing landing gear cover. John Jamieson and Xbob showed me how tile loss could be explained by an RCC breach which was not immediately fatal. The USAF photo and their interpretation of it (I discount speculation by the clueless media but definitely consider some interesting guarded comments by NASA) got me to buy their theory of an initial RCC breach.

[Budge]

I asked Blackie to forward it to you, as I have had this problem before ...

I'll keep checking both accounts.
Nothing yet...

[XBob]

look at 1281, and you will see the geometies of the major groups of tiles. and look at the edge of the door, you will see where there is a group of tiles, one right after the other, forming a zipper.

I spoke with one retired NASA engineer who said that in order to save weight, in some places the aluminum skin was about the same thickness as a piece of news paper.

[XBob]

good - I just sent him another one with an inset picture, which to compare.

He isn't always on, but he is very reliable, and a great guy, and I am sure you will get them this evening.