From NASA engineering film: Sequential pix of debris hitting Columbia's wing

NASA via CNN Online & Yahoo News ^ | 2/3/03 | Wolfstar

[Wolfstar]

Released Monday morning, a high-speed NASA engineering film shows a piece of debris falling from the large external tank on the space shuttle Columbia's liftoff and hitting the orbiter's left wing. Bear in mind that these are extreme close-ups of a high-speed event. In the top couple of photos, you see only the top of the broken-off piece. Most of it is in the shadows. Depending on which clip you see and how slowly it is run, to the uninitiated person's eye, it can look either like the debris strikes the wing hard enough to pulverize the debris, or the debris strikes a glancing blow and bounces off in the direction of the main and booster engine exhaust.

[freepersup]

I kept watching the video and at the point where the suspect object strikes the wing, I see a diffusion of the material into a spherical, 'cloud of dust'. Or is it ice that sprays and streams off the wing into what appears to be, a plume of flame from the firing engine ?

[TheDon]

They should not use shuttles that are incapable of reaching the ISS for example. Other posters have stated that Columbia can't reach the ISS orbit. If so, they should have retired it. Shuttles should always have enough fuel to reach the ISS.

Also, they have a shuttle ready to launch next month. They can make sure that a followup shuttle is available for rescue missions.

I'm certain the clever engineers of NASA can come up with many other ways to save the crew in a situation like this.

[Cold Heat]

So you are saying that all future launches should go to the ISS for inspection prior to re-entry until a new design that does not have these weaknesses can be developed.....................................

I agree that this would mitigate the tile damage on launch problem, but so would changing the tank coating or perhaps building the insulation into the tank like a thermos bottle.

[TheDon]

Only if they suspect a problem. Or perhaps a spacewalk to specifically give the tiles a visual check before de-orbiting for a landing.

[Rain-maker]

So I presume you would NOT tell the astronauts about impending problems or possible death? You would NOT let the astronauts live a few more days in orbit giving them time to say goodbye to family and friends.

Rather sadistic, what gives anyone the right to choose the hour of death for the crew while keeping them in the dark?

[spunkets]

"What I found was the bullets barely made a mark and one brick (standard house type) was gouged about a 16th of a inch. This was at a 90 degree angle to the brick."

That's because the brick is a high density ceramic. It has a relatively high compressive strength. It's not very uniform though, so if the brick were on the table top and you shot it, it would crumble. When the brick is connected with others by another ceramic like concrete the stress is distributed, so the most of the brick is supported and all the compressive stress from the bullet is applied to the small area.

The brick is essentially incompressible, so as long as the energy of the bullet is insufficient to turn a cone of the height of the wall thickness into dust it will only make a partial cone. If you noticed, as you look deeper into that 1/16" hole the width of the damage was bigger. The outside, were the bullet struck was the same dia. as the bullet.

If you have a ceeramic that has a high void density, the voids are infinitely compressible. The structure containing the voids is collapsible. It's ceramic, so shear and compression forces only have to reach the buckling strenth of the walls, the films, and or fibers.

The urethane foam is a lot more massive and resilient than the silica layer on those tiles. The silica columns snap when the mass and velocity of the foam is big enough. The force would be the change in momentum with time, dp/dt and the compressive stress F/area. If the relative momentum is small enough, the foam bonces off, because it is resilient and the energy goes into deformation and rebound. As the momentum increases more of the silica structure is turned to dust when the foam has reached it's max deformation and the load on the silica is the highest.

[Clean_Sweep]

Well that makes it 8 1/2 inches thick. Bricks are not normally considered composites even though walls are made of two differing materials. Yes you can break single bricks with a 357. In fact they are a fun target. Some bricks break in your hand if you hit the end of it against something hard. But I don't see any bearing on the insulation/tiles/aluminum combination.

What needs to be measured is the impact energy of the foam hitting the tiles and what the friction coefficient between the materials is. I suspect looking at the video that most of the available energy was absorbed by the tiles considering the powdered aftermath of the impact. The angle of attack doesn't matter it the two materials stick to each other, in fact the oblique angle may cause more shearing and damage than a straight on hit.

[NightWriter]

<< I have just one question for Dan Goldin...etc. >>

Goldin left NASA in November, 2001, and was replaced by Sean O'Keefe in December, 2001.

[DaGman]

"Why is not every mission equipped with the ability to dock with the ISS and why is not every mission required to have an additional shuttle in backup role in case of the need to rescue a crew."

One word: MONEY!

[spunkets]

"Air has a fairly good abrasive factor and is considered to be rated pretty high."

On the atomic scale the momentum imparted by the moving air particles is not sufficient to knock the components of the silica out of place. These tiles also have a very thin dense outer layer of borosilicate, that behaves just like a high density ceramic for atomic impact purposes. Atoms wacking it might be similar to 22 rounds hitting hardened concrete.

[Cold Heat]

My point, was that as a unit, the tiles do have strength.

I would have to dissagree about the voids in the tiles, as constructed. They are not compressable as some might think, and with the coating, and pretty resiliant to damage.

I had never seen anything quite like them but if I had to compare them to something, I wouls say a dinner plate type of material but lighter. Like a ceramic insulator in heating appliances such as a oven.

[dickmc]

Back around Post 295 more or less there is a discussion about the relative velocity and some earlier analysis. In any event the relative velocity is clearly known by NASA because they know the frame rate of the camera and the distances involved. Thus the theoretical energy in the impact is easily calculated (at least by NASA which has the frame rate and scale of the photo sequence).

I think the key is more these later posts which discuss the fact that the tank foam block was largely pulverized. In effect the issue becomes: if wing tiles were mounted on a one or two foot diameter grinding wheel say 6-inches wide, how much would you have ground off of the wheel diameter pulverizing a block of tank foam that size???

[Cold Heat]

I just cannot see how a large area, say 10 x30 inches (as some have purported) could have been stripped away completely or even 80 % by some relatively soft product with little mass. Since most of the energy would be absorbed by the break up of the insulation, the applied energy at any one point would not be sufficient to destroy enough tile to be a factor.

[Cold Heat]

Thus the theoretical energy in the impact is easily calculated (at least by NASA which has the frame rate and scale of the photo sequence).

Yup, they could get it in some sort of range, because the angle is not known exactly.

There would also be the non-linear flow under the wing. (They should have some data on this from testing.)

[spunkets]

Did you see these NASA pages? They're from that link I posted in #295.

The voids themselves are vacuum, just empty space with no support. When I mention compression stregnth that's the ultimate strength of the material before it breaks. As the density of this stuff goes up the compressive strength goes up also.(all other things being equal) The modulus of this stuff is all the same, regardless of density. That means the strain in these ceramics is always tiny with a huge stress. The modulus is the deformation/applied stress. That's why this high void material seems like a dinner plate material. If you applied successive weights to the high and low density mat'ls, you'd find the low density stuff being crushed with a lower applied weight than the high density stuff. It has a lower bulk ultimate compressive strength.

[NightWriter]

<< I have just one question for Dan Goldin...etc. >>

You might want to direct your questions instead to the Office of the Vice President, who replaced Dan Goldin with Sean O'Keefe, and who is believed to have been one of the driving force behind the initial, multi-year $1 billion cut in the shuttle program's budget made by the Bush administration.

For further information, see:

http://www.space.com/news/spaceshuttles/shuttle_budget_010711.html

And why, exactly, should anyone here excuse your bellicosity?

[spunkets]

Well if the foam weighed a lb. and it was going 300mph, that's 6012ft-lbs, or 3K ft-lbs if it's a 1/2 lb. If it's 1lb. going 150mph that's 1.5K ft-lbs. That's not a small hit. Imagine you, or a fine silica structure was hit by that.

[TigersEye]

bump

[Cold Heat]

I understand.

I believe the low density does in fact reduce the strength.

Part of my carreer was also spent in the steel business, so I am familiar with hardness and moh scales and such. I suppose what I am feeling is a gut reaction based on work experiances and knowledge of materials. I am familiar with heat and impact studies and all of it tells me that there is some other factor that is damaging these tiles.

I just don't know what it is, which leads me to believe it may be a event that is not consistant, not measurable and not avoidable since we do not know the source. It may be a one time thing with no way of anticipating.

This is why I came up with the space debris theory and or micro meteorites.

[NightWriter]

<< I have just one question for Dan Goldin...etc. >>

Final point for the record:

The 5 safety panel members and 2 consultants were dismissed following Sean O'Keefe's appointment as NASA Administrator.

For further information, see:

http://www.nytimes.com/2003/02/03/national/03NASA.html