[bonesmccoy]

Good points.

At that altitude (ironically just greater than 200,000 feet) the vehicle is moving through Maximum aerodynamic pressure (Max Q) but the ice chunk probably would not sublimate. Turbulence in the atmosphere would probably not break up the ice chunk, because the turbulence probably wouldn't impart shear forces on the object. I would surmise that fractionation of the object would require sheer forces from the "slipstream" with differing vectors. Toss a piece of paper out of a window at 80 mph and you won't see shredded paper. You'll see a paper flipping and tumbling out of control. Hold the paper on one corner (imparting a opposite force from the force imparted by the turbulence) and you see shredding.

There must have been a larger ice chunk. The piece we see may have been only one part of a larger sheet on the ET.

KSC's PAO has posted better resolution video files.
http://www-pao.ksc.nasa.gov/kscpao/shuttle/countdown/sts107/vidtoc-b.htm

Clip One
http://www-pao.ksc.nasa.gov/kscpao/video/E212.mpg

This is the same angle as on the Florida Today website.

The initial frames are a bit confusing to an untrained person. You can see multiple white objects in a few frames. However, the forward orbiter attachment is between the tumbling white object and the camera. It appears that the object slides between the forward ET-orbiter attachment posts.


http://www-pao.ksc.nasa.gov/kscpao/video/ET208.mpg

This is a view of the stack port side and shows a large chunk of tumbling ice falling off of the area near the ET intertank region (area between the LOX and LH2 tanks).


http://www-pao.ksc.nasa.gov/kscpao/video/ET208Mag.mpg

This is a magnified and digitally enhanced view of the ice chunk appearing between the ET and orbiter.

[mikegi]

The initial frames are a bit confusing to an untrained person. You can see multiple white objects in a few frames. However, the forward orbiter attachment is between the tumbling white object and the camera. It appears that the object slides between the forward ET-orbiter attachment posts.

Thanks for posting these excellent links. I've been stepping through the video and disagree with your conclusion that it was a single piece that appears split because of an obstruction. Here's what I see (frames identified by the second in the mpg):

0:00-0:04 - object appears, flies up the tank, hits it

0:05-0:06 - object bounces off and either splits in two or dislodges another object. Call the lower one A and upper one B.

0:07-0:08 - "A" passes between the wing and tank. "B" reaches the front edge of the wing

0:09:0:10 - "A" emerges from underneath the wing, apparently broken up into two pieces. "B" probably impacts the wing at this point.

0:11-0:14 - "B" emerges as a cloud underneath the wing and spreads out all the way to outside the solid rocket.

0:15-0:16 - two fairly solid pieces of "B" pass in front of the SRB and are illuminated by the fire it.

[j_tull]

From the third clip, I can see how they blew this off as no damage. There is no detectable difference in the appearance of the lower wing surface after the impact. I'll bet the "Ice/Debris Team" isn't getting much sleep.