Posted on 02/04/2003 1:34:19 AM PST by 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.
Placeholder PING - will read this one in full when I get the time.
ping!
And further down in that same article, the possibility of extending those 30 days (indefinitely?) in order to recover the crew and possibly Columbia as well.
http://msnbc.msn.com/id/3077565/
(bottom of article)
"Resupply rockets?
Gehman’s commission to NASA did not include studying the option of launching an unmanned rocket carrying half a ton of life-extension supplies, which Columbia could have chased down and grabbed in orbit. Several expendable rockets were indeed nearing launch at various world space ports, and if any one of them could have been diverted to such an emergency resupply, major pressure to rush the next shuttle launch would have been relieved.
In response to a question, he said that scenario “was not in the bounds of the study,” but he promised to have it studied as well."
I think an expendible re-supply rocket is impractical. Better to launch something up there in advance.
I don't believe NASA has fixed the supersonic airflow/foam interface problem either, and especially in such a short time.
And what's happened to NASA and Lockheed Martin's earlier statement??..
From XBob's post #4,413 above:
"...NASA and Lockheed Martin Space Systems Co. admit
they will never completely eliminate the decades-old
problem of foam popping off the tank during shuttle
launches..."
Under pressure to launch shuttles, a previously thought unsolvable problem is quickly fixed?! I don't think so, I predict plenty of foam damage on future flights despite these latest NASA assurances.
I think NASA managers are at it again, they've "solved the problem" because it's politically correct to say so.
I agree, but I am suspicious of NASA politics; spending money on prevention or preparation are monies lost, but emergency rescues, etc, provide extra *additional* money.
An example is the about $500 million that the Columbia investigation received from Congress; I wonder what kind of improvements on the shuttle could have been made with this money, instead of using it to figure out that NASA has internal problems (again)?
"Columbia investigation could cost $500 million"
http://www.spacetoday.net/Summary/1560
Of course that depends on how you figure it.
It was very expensive combing East Texas for Columbia debris.
Also, you have an entire workforce of tens of thousands of people sitting on their thumbs for the most part while NASA gets it's act together.
"The press likes a nice round number." --The Right Stuff
So, I agree that this is not a perfect RCC fix, but much better than NASA's, in XBob's words "steam boiler shrapnel bomb".
First, the site of RCC damage would be inspected, video-taped and sent to ground control for analysis.
Next, under ground control's supervision, specific and disperse, less-vulnerable areas of the orbiter would have HRSI tiles removed as intact as possible, collected and brought into the orbiter.
Again, under ground control's direction, the HRSI tiles would be re-shaped and glued to a plate of metal scavaged possibly from SPACEHAB and shaped to task.
Finally, the HRSI patch would be installed into the damaged RCC area.
Since the expected re-entry temperatures will be high for HRSI, it won't escape undamaged, but also consider that the HRSI won't be at 3000F during the entire re-entry. If the length of time laminar flow can be maintained at the damaged site is long enough, it may survive until re-entry temperatures start to drop.
I'm certain that there are many possibly difficult details to be worked out to actually produce this kind of repair, but if I were in the mortally damaged Columbia it would be my first choice, I think it is the only plan I've heard that has at least a chance of survival.
I hope this idea will at least create some new thinking-paths in possible emergency, no-other-options-remaining, RCC repair.
from:
http://www.zyn.com/flcfw/fwtproj/Toughene.html
"TUFI performs as well as the baseline RCG coated
insulation in a convectively heated environment at
temperatures in excess of 1260 degrees C (2300 degrees F)
and is very lightweight, can be machined and molded..."
4445 - I personally examined many (hundreds) of the damage dings and chips out of the heat tiles on the bottom of various shuttles on return. The majority were not a major problem. A few were. The most damaging were when tiles physically came off, leaving the wing exposed.
Most of these problems have been fixed, and now the tiles stay on.
I never saw any damaged RCC, however I am certain smaller pieces of ice and foam hit the RCC. It is a totally different material than the tiles, and is relatively strong, structurally. In appearance, it seems to remind me of the flexible rubber bumper coverings on cars. And the RCC pieces are formed and hollow, with only two attach points per RCC.
They have removed the large chunks of unreinforce foam from the external tank. The smaller pieces, as fatal damage makers - I don't think so.
I don't think the RCC was damaged by the foam on the tank I reviewed, at slow motion, the colombia foam impact, many times. IMO, the foam did not hit the RCC, but hit the tile near the wheel well, melting the supports for the RCC, so that the RCC collapsed back, unsupported.
Wing leading edge and nose:
The leading edge of the wings and the nose of the shuttle see the most heat by far of any other part of the orbiter. These areas are at or near the stagnation points of the shockwaves created by the orbiter and are subject to stagnation heating. The temperatures seen here are well over 2500°F for much of the reentry period. The Thermal Protection System (TPS) is considerably more robust in these areas as well. A location along the leading edge designated the 55% semispan location sees the highest temperatures due to an unusual crossing of shock waves from different parts of the orbiter, (a double shock region). The absolutely highest temperature at the leading edge occurs 5 inches below the midline of the wing at that point due to the shuttles 40° angle of attack as pointed out on Page C, "The Effects of Hypersonic Flow During Reentry of the Space Shuttle".
Cross sectional View of an RCC
Is it just me, or is there lots of room under the RCC for the slip stream to get under and blow tiles off?
I can envision a single missing tile leaving a gap like a jet engine intake.
RCC's are not 'tiles'. They are individually formed and carved, HOLLOW, heatproof 'plastic'/'rubber'. IMO losing 1 RCC unit could open up to 'blow' off other RCC units. But, as they are mounted on a solid wall, they would not blow off the 'tiles', which are 'horizontally' on the wing surface, mounted on the underside of the orbiter. However, losing or opening even a single RCC would expose the flat metal 'front' of the wing (varying in height IIRC from 6" to 3 feet) to the 3000 degree heat of re-entry, melt through the solid fore face, and open the interior of the wing to superhot gasses.
Damm. Sometimes, I hate being right.
http://www.columbiassacrifice.com/$D_temperature.htm
Temperature Variations During Orbit and Reentry of the Space Shuttle
This an interesting site on temps and heating. Read the last part, as heating of the orbiter continues, even on the ground, after landing.
That's why it is so important to 'fix the foam' on the external tank, so that nothing which will damage the RCC ever hits it.
IMO, a hole in the RCC is a fatal hole, and the only way to survive it is to abort before orbit. If it is found after getting into orbit, IMO, the only way is to rescue the crew, in space, and build a new RCC on the ground, or 'cannabalize' it from another shuttle, and then (if possible) figure out some way to replace the RCC unit in space. Then, bring it back to earth on autopilot, without a crew.
I cannot envision any 'patching' technique which would work, to stand up to the heat, vibration, and stresses, considering the way RCC is made and mounted.
To give you an idea of how big and thick the fore front of the wing and RCC is, remember that the whole landing gear assembly, tire and all, holds the tire vertically and door and supports, within the wing - so it is not a small 6"x6" tile, like the main 'tiles' on the wing surface.
You're right, of course, that bringing up an intact replacement RCC from a shuttle on the ground is a preferred course, and I think additionally sending up supplies via rocket until the rescue shuttle can arrive. I can see something like this as being something Gene Krantz (Mr. 'Failure is not an option') would have come up with.
The main point being, IMO many rescue scenarios were possible (and should be further explored *now*, before the next shuttle launch).
NASA management couldn't or wouldn't think of rescue/recovery when the possibility of severe damage was presented, but could only envision their certain doom.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.