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.
I do know that they can pickup quite a charge, but bleed offs are installed to minimize it and the electrical systems are shielded.
The airframe makes a damn good conductor, and lightning generally passes through without damage.
Anything can happen with the stuff, but damage in modern craft is somewhat rare and they learn from every experience.
It would not surprise me to have quite a corona formed around the craft during reentry. What was captured could have been a discharge to air from the craft when it found a path.
NASA studying Columbia photos
S.F. astronomer's is among those looked at by newly created panels
Sabin Russell, Chronicle Staff Writer
Tuesday, February 11, 2003
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NASA investigators of the Columbia space shuttle disaster have set up a study group to analyze a photograph, taken by an amateur astronomer from a San Francisco hillside, that appears to show a bolt of electricity striking the doomed orbiter as it streaked across Northern California.
General Michael Kostelnik, deputy associate administrator for the shuttle program, told reporters in Washington, D.C., Monday that "the lightning-strike photo . . . is being studied carefully to see what it means."
Separate study groups, consisting of both government and private experts, have been convened to analyze the San Francisco photograph and an image taken by a sophisticated tracking camera at Kirtland Air Force Base that was following the shuttle as it passed over New Mexico.
The Air Force shot shows a silhouette of Columbia with apparent damage to its left wing. Kostelnik confirmed Monday that a piece of the shuttle's left wing was found on the ground near Lufkin, Texas.
NASA is pooling the images from amateur videotapes, amateur photos and data from secret government cameras, and attempting to correlate them with data transmitted from the stricken craft to piece together the sequence of events that led to Columbia's breakup over Texas on February 1.
"We're looking at all the events during that time period," Kostelnik said.
In addition to visual images, investigators are poring over radar data and tapes from a bank of exotic "infrasonic" sensors that can actually pick up the noise of the space shuttle's re-entry over California. If the San Francisco photograph does indeed depict a bolt of electricity in the ionosphere, the "infrasonic" sensors in Colorado might be able to detect the faint thunderclap that accompanied it.
The San Francisco photograph, which has not been released publicly by the astronomer, was transmitted directly to the shuttle's chief engineer Ralph Roe Jr. on February 4, and a copy of the image, as well as the camera that took it,
were flown to Houston the next morning.
At previous press conferences, NASA officials have said they were trying to assess the "validity" of the image, which was taken during the time when sensors on the shuttle's left wing first showed indications of a problem.
On Thursday, shuttle program manager Ron Dittemore said there were no indications, based on flight data transmitted from Columbia at the time the photo was snapped, that the orbiter had experienced any unusual electrical event.
"There is nothing in the data stream . . . that would cause any concern on our part," he said.
The digital photograph, the third in a series of five taken by the San Francisco astronomer as he faced the northern sky, contains many visual cues --
such as a star field -- that should allow NASA scientists to pinpoint the moment the unusual image appeared, and compare it with signals transmitted from Columbia.
An analysis presumably could also quickly determine whether the image could have been caused by a jiggling of the camera during the time lapse photograph. It was taken using a Nikon M-880 camera, using an automatic exposure, triggered by finger.
Although the astronomer refuses to release the picture, he permitted two Chronicle reporters to view it last week. In the critical shot, a glowing purple rope of light corkscrews down toward the plasma trail created by the shuttle, appears to pass behind it, then cuts sharply toward it from below. As it merges with the plasma trail, the streak itself brightens for a distance, then fades. There were no unusual images visible in the other four pictures.
NASA administrator Sean O'Keefe told reporters that the agency has quickly established a system to collect photographic information from private citizens while protecting "their proprietary rights" to the images.
"We've even figured out how to move lawyers expeditiously," he said.
E-mail Sabin Russell at srussell@sfchronicle.com.
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The photographer invited The Chronicle to view the photos on his computer screen Saturday night, and they are indeed puzzling.
They show a bright scraggly flash of orange light, tinged with pale purple, and shaped somewhat like a deformed L. The flash appears to cross the Columbia's dim contrail, and at that precise point, the contrail abruptly brightens and appears thicker and somewhat twisted as if it were wobbling.
"I couldn't see the discharge with own eyes, but it showed up clear and bright on the film when I developed it," the photographer said. "But I'm not going to speculate about what it might be."
The current flows are no where close to the potentials, which can rise to millions of volts, but the durations are in milliseconds at fairly low amperages with respect to voltage. Plus, the behavior of the charge usually takes the easiest paths and therefore bypasses areas that may be resistive.
The same occurs in a capacitor, where extremely high potentials can be stored,but the discharge is limited to the storage capacity. If you do things to limit the storage, then the discharges are not as great but more frequent. I don't see the shuttle experiencing any more risk than a passenger liner that flies millions of miles over it's career.
I do not know what the factors are,but I can assure you that they have a good handle on this risk.
I can't speak intelligently regarding your theory on the RCC, but remember the "Italian Yo-Yo" tethered satellite experiment?
Some interesting points to ponder which I don't think we really have discussed.
So, actually, in determining the reason for the loss of the Colombia, we need to consider not only aero-dynamics, and thermo-dynamics, but also electro-dynamics.
Any more 'dynamics' we should consider?
A piece of 10ga wire could easily handle that current load without failure.
The airframe, BTW would ohm out far in excess of .1.
Aluminum has a "K" of 17.0/ft., Monel is 25.3 . These are the bulk of the airframe metals. (copper has a K of 10.8/ft)
(BTW, K =Ohms per 1 foot x 1 mil dia) We use this figure to determine resistances in estimating specific resistances. You need to quantify it on each part with diameters and specs to figure estimated totals. A piece of aluminum conduit, 10 feet long W/O fittings at .5 in dia has a resistance of a couple hundred ohms, the last time I ohmed one out.(been a while)
I guess what I am trying to get across to you is that you are fearing things that are unlikely, if not impossible.
As I said earlier, airframes and their related electronics are well thought out when it comes to electrons. That is what aviation electrical engineers do. I just mess with the stuff on the ground. We have similar difficulties in power plants however.
That is why we lay out ground grids, lightning arrestors and shunts to deal with HV spikes and the like.
Aircraft are built to even stricter tolerances and planned for events.
This is important, because monel is used as a fitting in the shuttle. It holds much of the shuttle subsections and other parts together IIRC. They also use other alloys of it that have higher ratings as being almost a dielectric.
Indeed! Remember Apollo 12? Struck by lightning twice on ascent. Survived just fine.
4512 - monel is specifically important, as it is what the bolts on the RCC segments - leading edges which take the most heat.
While it is not dielectric, it becomes insinuative and is as a medium resistor to dampen electrical transference from the skin. It can be used to direct any current flow.
Electricity also has another property that we use the knowledge of.
For some reason it travels along the surfaces of any conductive metal. Even with copper wire. Which is why stranded wire has a higher ampacity than solid of the same diameter.
In a plane, or the shuttle, it remains mostly confined to the skin in it's outermost layer. Resistive connections between the skin and the airframe are all it takes to direct something like a lightning strike from getting inside the craft. Further measures are taken to protect the inside at various levels, making a layered protective envelope.(especially fuel tanks) But the static charge is seeking a opposite charge and has little need to go further than the skin.
Like a thermos bottle, nothing gets in or out electrically. The skin however will collect charge that needs to be bled to ground before touching the craft. This is true with nearly any aircraft, but the shuttle is in a class of it's own regarding this and radiation.IIRC.
Accidents do happen. Sometimes scorch marks can be left on the skin. Sometimes instruments are affected with the modern digital sensitivities, but crashes are extremely rare, even with the cheapest and unprepared of aircraft however.
I am not a aerospace engineer, so I am not knowledgeable of what precautions other than the obvious that they might take. But I would look at the recovered recorders and the received data for any evidence of stray electrical activity in the ship. It would be the first place it would show up and it would be very obvious and system wide. From what I can gather, there is none.
That is why I am not convinced of any electrical causal relationship to the loss.
Have you seen this... http://www.local6.com/news/3975391/detail.html
Here's a photo of the purple corkscrew and some commentary:
http://www.rense.com/general63/shut.htm
"Most shocking of all is the explanation given by experts who examined the photograph. They said that the luminous corkscrew trail was an "artefact" caused by a camera wobble. The explanation left critics aghast, since the Columbia trail in the photo is crisp with no evidence of camera movement."
Wasn't there some video that survived impact that showed a couple of crew members and they commented about the bright flashes that could be seen outside the craft over the eastern Pacific? It was thought it was the heat shield heating and glowing but they were startled by brightness...
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