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.

[XBob]

I am not sure, but I think the original NASA film was in slow motion, and then this film was re-recorded at standard motion. I have heard several times that the NASA original was 96-97fps - is that slow motion?

And if so, what kinds of numbers do you get using the above info?

[XBob]

2409-"A question I have regaurding the color issue. "

the foam exterior color varies with age, the color is a light mocha color when first applied, and as the skin forms on the application, it gets darker. Then as it ages it gets darker yet, on the outside, but not the inside.

When the foam is repaired, as often happens, from damage from tool repairs, drops, weather, birds pecking holes in it to build nests, dropped wrenches, etc, foam is replaced with new foam. This new foam is ALWAYS the much lighter mocha color.

I think that the 'chunk' which fell off was a 'patch' or repaird section, which got sucked off.

[XBob]

2419 - "I guess they could put a gyroscope on a CCD camera and eject them out of the payload bay. The shuttle could rotate under it for a visual inspection. The camera USV would then deploy a light solar sail/drag chute to deorbit quickly."

good idea.

[XBob]

2420 - "Perhaps the plasma path inside the left wing changed from not immediately fatal in the right bank to rapidly fatal once it was in a left bank? "

good theorizing. The large flare, the 'roll reversal', the chunk out photo, they all line up in time - from Flagstaff to Albequerque.

IMO the roll reversal knocked out the 'web' wing section, alread seriously burned away, but the wing was still burning, but still in good enough structural and aerodynamic shape for that altitude and speed to maintain stability until just west of Dallas, where it lost aerodynamic stability and broke.

[Dark Wing]

We seem to have some evidence for a upper atmosphere lightning strike. NASA has impounded NOAA infrasound recordings that may be the result of a "blue streamer" that may be concurrent with the shuttle break up.

http://www.freerepublic.com/focus/news/845614/posts

This is one that has me sweating bullets because we know jack about such upper level atmospheric phenomina. Other than developing plasma control technology to shield incoming shuttles, I don't see how we can restart shuttle flights if it is in the fault tree.

[Dark Wing]

Excuse me, the terminology was "Blue Jet," not "blue Streamer."

[SlipStick]

You might want to check this URL out. I'm sure you're aware that even though we're past the solar max, the sun still runs the show.

[SlipStick]

Sorry -- I booboo'd. I'll try again.

http://www.freerepublic.com/focus/news/845059/posts

[SlipStick]

MORE THOUGHTS ON THE ASCENT STRIKE

Thinking about the booster in supersonic flight...
It generated a bow shock wave called a Mach cone. The
boundary of the cone contained air which had been elevated
in pressure to the extent that it could be felt as a sonic
boom. We've all heard tales of the cracked walls, broken
windows, etc.

There are two regions of particular interest in that cone.

A few feet away from the booster is the Shuttle. At this
point in the flight they are held rigidly together, with the Shuttle aft of the top of the booster. The shuttle, too, generated a cone shaped bow shock wave, of the same angular configuration as that of the booster.

The thing I find interesting is that these Mach cones will
of necessity INTERSECT in two regions, each of which forms
some sort of curve (perhaps a line) at the points of
intersection.

In each of these curves there are molecules of air that have
been compressed temporarily into superimposed shock waves.
It is possible that a piece of icy foam insulation, having by chance fallen just on the Shuttle side of one of these regions, could be thrown toward the lower wing surface of Columbia?

[The_Level_Head]

XBob wrote: Now, this proposed 'penetration, as far the falling 'block' is on 107 only. I talked to one NASA engineer who reviewed the falling 'block' video, did some calcs (un-officially) and his opinion was that the block would penetrate the tile, by 2 inches.

Well, that resolves the confusion. Your earlier post made me think that a NASA engineer had SEEN such damage on a prior flight.

I would share the opinion, I think, that THIS incident was perhaps enough to cause skin penetration; certainly at minimum it would go through one or more tiles. And going through one or more tiles might well have been enough, depending upon the tiles.

Exacerbated by the heavy landing weight, and near the hot leading edge--perhaps even involving it--this problem seems to be consistent with everything we've seen.

Now, what about implications? The investigators will test, and determine (most likely) that the foam impact was fatal. And rather than being a freak occurrence, foam spalling on ascent seems to be quite common. As they said, 90% of the previous orbiter tile damage has come from the foam coming off during ascent.

After Challenger, they reworked the O-rings to deal with the seal problem. It's going to be tough to solve this one, as the problem has extended through multiple foam formulations and attempts to deal with it when it was perceived as alarming if not yet fatal.

Upshot: The Shuttle system is grounded, probably permanently.

So what do we do now?

[Resolute]

I found a web-page with some ascent data for typical shuttle trajectory. From this data we can make reasonable engineering approximation about shuttle's speed and altitude at 80seconds into flight. This will be better than crude approximation of 28 km from earlier. The raw data is below. Will require either interpolation or curve fit.

Event Description	Time Since Launch (H:M:S)	Earth Relative Velocity (ft/s)	Altitude (ft)
Begin Roll Maneuver	0:00:09	165	627
End Roll Maneuver	0:00:17	374	2898
SSME Throttle Down to 65%	0:00:34	833	11854
Max. Dyn. Pressure (Max Q)	0:00:52	1260	28037
SSME Throttle Up to 104%	0:01:01	1499	38681
SRB Staging	0:02:04	4316	153873
Negative Return	0:03:54	6975	317096
Main Engine Cutoff (MECO)	0:08:27	24580	366474
Zero Thrust	0:08:33	24596	368460

Will provide supplemental analysis of foam deceleration shortly, based upon these data.

[XBob]

Resolute - before you do your calcs, take a look at this:

All - this is a very interesting story, go to the story, not the bump link. Quote from the story:

In the Columbia's case, Crater predicted "significant tile damage," with gouge depths that actually exceeded the thickness of tiles in several critical spots. For example, the tiles protecting the wheel well are about two inches thick. Yet Crater calculated that the foam would penetrate 3.4 inches in this part of the wing.

The Boeing team did not accept Crater's predictions at face value. The program was "designed to be conservative," they noted, and so has sometimes "overpredicted penetration of tile coating significantly."

Another factor in their judgment was data from a 1992 Columbia mission that they believed had absorbed a "potentially" similar debris impact. In that case, the debris left a gouge only a half-inch deep.

There was a difference between the flights, though. In 1992, the debris was thought to have struck at an angle of 3.2 degrees. This time, the predicted angles were far sharper, which the Boeing team was careful to point out would alone significantly increase the damage. Still, for reasons not spelled out, the engineers concluded that "even for worst case," the foam debris would leave behind at least the last quarter-inch of tile, giving the wing at least some thermal protection.

The report did not spell out another thing: why the Boeing team never calculated how much worse the damage would have been if the debris was actually ice, or partly ice, and not foam.

As the Boeing team noted, previous NASA research had documented the dangers of ice debris: if it struck the wing's leading edge at a sharp enough angle — greater than 15 degrees — it could penetrate the tough carbon coating that protects the edge from re-entry heat, potentially leading to a catastrophic burn-through. In the Columbia's case, NASA calculated that the debris could have hit the edge at an angle of 22 degrees.

Outside experts, including many with deep institutional ties to NASA, are expressing polite concern that the engineers erred by not considering more possibilities.

"It was very good as far as it went," Dr. William Schneider, former assistant director of engineering for NASA, said of two reports prepared by Boeing engineers. But, he added, "They still needed to do more tests."

http://www.freerepublic.com/focus/news/845414/posts?page=3#3

[bonesmccoy]

Thanks for the intriguing posting.

Snopercod seems hell bent on blaming OMDP at Palmdale. I don't know the work specs at the last OV-102 OMDP.

Speaking as a Californian, I must say that each time KSC returned a bird, they would find interesting things.

Snopercod apparently chooses to ignore these facts and only focus on the observations of NASA/USA teams at KSC.

As for my bias towards Palmdale, suffice it to say that I'm sick and tired of hearing KSC console operators pontificating about how poor the people at Dryden or at Palmdale are.

The work at Rockwell was done well and under schedule with the vehicles being returned to Florida on time and under schedule.

I suppose sometime between the previous OMDP and the one in 2000 that OV-102 had ongoing problems. LA Times today reports that there were wiring problems identified during the last OMDP.

While Snopercod can snidely whiplash the Boeing team at OMDP, the reality is that Rockwell International's crew always took their lickings and said little to argue. The reason was clearly reinforced with the RI guys. The execs always told RI employees that they were to view NASA as the customer and the customer's interests always came ahead of RI's interest. The reason was that Don Beall always reinforced that we were to love our nation greater than our own interests. I've taken that to heart with the rest of my life.

Snopercod doesn't make sense to me. He says he was sitting in the LCC FR during 51-L. Then, when questioned about Ken Hollis' fiasco, he claims that Hollis got fired for talking too much about his job (which is correct). Frankly, Jim Oberg is in the same boat. Ironically, Snopercod then claims that he doesn't know who Jesse Moore is. I believe that any personnel in the Firing Room could have looked up a few rows to see Jesse Moore looking back at them?

Or perhaps, I am just another pud-knocker from Edwards?

It's not Bo

[XBob]

2425 - "We seem to have some evidence for a upper atmosphere lightning strike. "

In the early 70's, I was flying in a 707, and we were hit by lightning. A ball about 18" in diameter went down the center isle and out the rear. The radome nose blew off, the lights went out, the intercom went out, and we made an emergency landing. No apparent physical damage to the plane, they put on a new ra-dome, fixed the lights, and we continued on in the same plane, and as we got airborne the intercom went out again, and we did another emergency landing. We flew on in another plane.

I understand that the shuttle has much better lightning protection, and has been hit several times, and survived, though I had assumed it was on take off, don't know really, if landing or take off or plasma or not.

However, another interesting thing to point out - I understand that there was a big solar flare/phenomenon, scheduled to arrive at 9am the same time as the reentry problems.

[bonesmccoy]

dunno where the "it's not Bo" line came from... strange... must be like finding left-overs from the previous crew on the wing strut or in the crew module. Amazing what you find behind a bulkhead.

[brityank]

However, another interesting thing to point out - I understand that there was a big solar flare/phenomenon, scheduled to arrive at 9am the same time as the reentry problems.

Here you go, courtesy of snopercod:
Scientists Seek Clues in Solar Storm That Enveloped Shuttle.
Interesting, especially if it coordinates to the picture purportedly taken in CA showing the 'blue flash' around the shuttle taken by the astronomer.

[tubebender]

Interesting, especially if it coordinates to the picture purportedly taken in CA showing the 'blue flash' around the shuttle taken by the astronomer.

This certainly makes me think a little more seriously about the pictures. I wonder if what the picture shows is really a discharge from the shuttle and not a hit. The reason I ask that is because they were already getting readings prior to the Ca coast. Could the charge been building up over the Pacific ?

[Boundless]

> Interesting, especially if it coordinates to the
> picture purportedly taken in CA showing the
> 'blue flash' around the shuttle taken by the astronomer.

Purple flash, but whatever... that as-yet-unreleased
image is unfortunately just as likely to turn to be a
known artifact of the Nikon 880 digicam when imaging
bright highlights on a black background. Plus it was
reportedly a time-exposure.

Anyone connected to the press briefings needs to keep
asking for a determination on that photo, and make sure
the answer gets out (so we can jump on it or ignore it).

[Boundless]

To no one in particular...

Does the CAIB have its own web site yet?
If yes, what's the URL?

If no, are they using NASA pages for anything
they might release? URL?

I see some "NMRS" stuff at:
http://spaceflight.nasa.gov/spacenews/reports/nmrs/index.html
and the NASA press releases have included some
from the CAIB.

CAIB: Columbia Accident Investigation Board
NMRS: NASA Mishap Response Status

[Resolute]

I used the data from post #2341 to "reverse engineer" some assumptions regarding Shuttle speed and altitude at T = 80 seconds. I took the approach of 2nd-order polynomial curve fit, through T = 124 seconds (SRB staging). This yielded good "correlation" of model to data (R > 0.999). In layman's terms this is a pretty good model. From these curve fits, I estimated altitude, earth-relative velocity, and axial acceleration of the shuttle at T = 80 seconds. Then given these initial conditions, I extracted the atmospheric density from KCA-71 winter atmosphere model, which is quoted in a reference that I found.

Then, I reconfigured the (simple) axial simulation, to exit when relative axial displacement reaches about 53.4 feet. This is the axial distance from the forward attach point to the external tank, to the inflection (strike point) on the left wing. Lastly I adjusted the drag coefficient (Cd) of the foam to yield 511 mph when axial displacement reached 53.4 feet. Cd = 0.65 did the trick. This is actually somewhat low. I would expect something more like 1.2-1.7, because the foam should be fairly ragged and thus draggy. However, higher values of Cd yield even higher deceleration and impact velocities. In this iteration, I mostly wanted to see if I could match NASA's number (511 mph). The table below shows that this goal was achieved.

Assumptions:

V0 = 682.5 m/s (reverse engineered from data at post #2341)
Accel_XB = 12.1 m/s2 (reverse engineered from data at post #2341)
Alt = 20 km (reverse engineered from data at post #2341)
Rho = 0.08823 kg/ms (from KCA-71 winter model for 20 km altitude)
Sref = 0.120492 m^2 (spherical approx for 1920 in^3 -- very conservative)
Mass = 1.211 kg
Cd = 0.65 (yields 511 mph Vrel at 53.4 ft axial displacement)

Time since separation (s)	Relative axial velocity (mph)	Relative axial displacement (ft)
0.000	0.00	0.00
0.030	85.66	0.96
0.060	162.37	3.70
0.090	231.46	8.05
0.120	294.04	13.84
0.150	350.97	20.95
0.180	403.00	29.25
0.210	450.74	38.65
0.240	494.70	49.05
0.252	510.93	53.37

My initial velocity is slightly different from the 1570 mph stated by Dittemore. I chose to stay with this number because (A) it's consistent with other assumptions that I made and (B) I think that Dittemore was quoting inertial velocity which includes Earth rotation. Not that much difference between them anyway.