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.
Please read the article, it is very good, and here is a key paragraph:
"One NASA engineer who has worked with the external tanks said safety warnings had been minimized within the culture of the space agency. Speaking on condition of anonymity because of fears of retribution from his employers, he said that when an engineer pointed to possible flaws "you get a lot of other people coming back and saying, `It's fine,' because if you change it, it means it's wrong. And nothing can be wrong, because we're safe to fly."
This is interesting. It is possible that it works that way. Here's why:
Before liftoff, the entire "stack" is supported by the SRBs sitting on the MLP. The ET and orbiter are essentially hanging from the forward attach points, which means, they are hanging from the nuts in question.
After SRB ignition, the SRBs push the entire stack via the same FWD attach points, and the load on the nuts is no longer there.
So theoretically, the nuts are no longer needed after SRB ignition, because the SRBs are supporting the rest of the shuttle by virtue of their thrust. You can't turn them off, so you might as well break the FWD sep bolts. The AFT sep bolts are another matter...
I put away all my shuttle schematics again, but will dig them out when I have the time and see if they say if that's true or not.
These "frangible nuts" simply split in two pieces when the pyros go off. But if the "radar incident" was at 180 seconds, that doesn't jibe with the three-second pyro event.
What bothers me the most is that there is some A1C out there somewhere who discovered the "radar anomaly"...probably months ago...but nobody would listen. Just like the KSC people who requested the on-orbit photos of Columbia, they were "meddling above their pay grade".
From AP -- Newly Revealed Flaw Could Damage Shuttles and FRom Reuters - "Shuttles' Big Bolts Could Affect Return to Flight"
The bolts in question here are the ones near the pointy end of the SRBS, which hold them to the ET for the first two minutes of flight. One on each side.
105 SEC MET - Separation software intitited. Orbiter GPCs begin to sample SRM Chamber Pressure.105-137 SEC MET - SRM Chamber Pressure Que. When two or more transducers on both SRBs read below 50PSIA, the separation sequence will begin. If Pressure Que is not received by 137 SEC, the separation sequence will begin automatically.
PRIMARY PRESSURE QUE - Arm Commands are sent from Orbiter MECs (Master Events Controllers) to Sep System PICs (Pyro Initiator Controllers) A&B. A 4 SEC time delay begins to ensure SRBs have less than 60,000 lbs. thrust.
PRIMARY PRESSURE QUE + 2.3 SEC - Orbiter GPCs command SRB nozzles to null position.
PRIMARY PRESSURE QUE + 4 SEC - SRB SEPARATION. At the end of the 4 second delay, the shuttle dynamic pressure and vehicle body rates are chedked and if withing limits, MECS 1 & 2 will send FIRE 1 and FIRE 2 commands to separation PIC systems A&B. Forward and Aft struts will separate and BSMs (Booster Separation Motors) will fire, pushing SRBs away.
Didn't they mean CUE, not QUE? Also, the forward connection is not a "strut", but a bolted connection with a sperical thrust washer.
There is something else bogus about the press reports. The forward attachment separation is by a frangible bolt not a frangible nut. The bolt is (I'm guessing) 16" long and 2" in diameter), and is hollow. It has a grove around the circumference halfway up the shank at the separation plane. There is a NSI (NASA Standard Initiator) pressure cartridge screwed into the top, and another screwed into the bottom of the nut. When both NSIs are fired, the explosive pressure inside causes the bolt to separate into two pieces, a "head" and a "tail". The head piece stays with the ET (supposedly), and the tail and the nut stay with the SRB. There is a spherical bearing between the two.
It must be the top half of the bolt flying out of the ET "bolt catcher" that has everybody concerned. If I have time, I will scan in this diagram for everybody like I did with the tile diagram.
NASA: Kennedy Space Center director transferred / Marcia Dunn - AP
CAPE CANAVERAL, Fla. - In an abrupt shake-up prompted by the Columbia disaster, the chief of the Kennedy Space Center is being moved to another NASA installation to strengthen its engineering department for the shuttle fleet's eventual return to flight.
Roy Bridges, a former shuttle pilot who has directed the space center for six years, said Friday that NASA Administrator Sean O'Keefe asked him this week to take charge of the Langley Research Center in Hampton, Va.
"We are going to be looking at the Columbia accident report to see how we might bring some independent engineering talent to bear on the return to flight," Bridges said.
He will take over in August, replacing Del Freeman, who had been serving as acting center director for the past year until a permanent director was found. Freeman, 62, will retire.
A NASA engineer at Langley was among those involved in a flurry of e-mail discussions in the days before Columbia's breakup over Texas on Feb. 1.
The engineer raised the possibility of damage to the spaceship's thermal protection system from a flying piece of foam during launch. His concerns were forwarded to Freeman, whose staff was assured by Johnson Space Center in Houston that the shuttle was fine.
Bridges, 59, said O'Keefe indicated to him a need for better engineering integration at Langley.
Bridges is a retired Air Force major general who was commander of the Air Force Flight Test Center at Edwards Air Force Base, Calif., and headed the Eastern Space and Missile Center at Patrick Air Force Base near Cape Canaveral. He flew once in space, aboard Challenger in 1985.
He said it would be premature to discuss any future changes at Langley involving shuttle safety. The center is a leader in aviation and space research.
James Kennedy, deputy director of Kennedy Space Center, will serve as acting director until a permanent replacement is found.
This is the second major management change at NASA in less than a month. On May 20, the director of Marshall Space Flight Center in Huntsville, Ala., Arthur Stephenson, announced he was stepping down. The Marshall center was responsible for the fuel tank that has come under suspicion in the Columbia disaster.
And in April, shuttle program manager Ron Dittemore announced he would quit NASA as soon as the Columbia investigation was completed.
In other news, NASA announced Friday that Gemini and Apollo astronaut Thomas Stafford and former shuttle commander Richard Covey will lead a task force to assess the agency's return-to-flight effort and help carry out the recommendations of the Columbia Accident Investigation Board.
The board is expected to release its final report late next month.
ON THE NET
NASA: www.nasa.gov
I heard on the radio this afternoon that it was a hoax of sorts. She came foward and said she did not have the tape but she heard someone else did and she wanted NASA to investigate the rumor. Dumb Butch...
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