New Eco-Friendly Foam Used on Columbias External Tank!!

Florida Today ^ | Feb 02, 2003

[fso301]

One suspected reason for the change in damage, according to reports by Katnik and outside organizations that helped Kennedy Space Center study the issue, is NASA changed the way it "foamed" the external tank sometime shortly before that mission in an effort to be more environmentally friendly by reducing the use of ozone-depleting materials.

"Freon was used in the production of the previous foam," he reported. "This method was eliminated in favor of foam that did not require freon for its production. MSFC is investigating the consideration that some characteristics of the new foam may not be known for the ascent environment."

Remainder of Article

[fellowpatriot]

Great - seven of our finest are dead but at least the environment is safe.

[coloradan]

Did ozone-friendly tiles kill the astronauts?

[templar]

The new foam may or may not have been responsible. But it might have been a good idea to test it more thouroughly before putting it into actual service. From what the article describes, it doesn't sound like much testing was done.

[The Other Harry]

Try not to get too enthusiastic with the exclamation marks and the bold & italic print on articles that were already posted more than a day ago.

[eddie willers]

I was going to post "This burns me up" and then noticed the tasteless pun and stayed my hand.

On second thought...I'll let it stand.

[Texas Eagle]

Thanks for posting this article. This is the first I've heard of this. I will file this for future reference.

[Mulder]

I don't guess the enviro-nazis, nor the corrupt bureaucrats who are their willing servants learning anything after their enviro-policies resulted in the deaths of several firemen a few years ago.

[Lancey Howard]

PING
This is the stuff you brought up the other night.
Maybe it's finally going to get legs that the foam-flying-off-the-tanks-and-damaging-the-tiles phenomena starts with the enviro-mice. Four or five launches of the space shuttle per year and NASA was forced to worry about freon and "environment friendly" rockets! Un-freaking-believable!

Think Peter Jennings will mention this? Nahhhh.

[fooman]

Yes we change components and then don;t regression test them to make sure they dont cause problems.

PC Kills!

[Let's Roll]

I am so sick of them sticking their no-nothing noses into any and everything!

[lizma]

I remember watching an expose on TV a several years ago about the fire extinguishing equipment on planes. It was changed to enviro-correct material but wasn't very effective.

There's a bad curve in a road in southern Maryland but an endangered frog lives there so it will not be fixed. (Who cares if there is a billion of them in Virginia!)

I really wish someone like the Heritage Foundation or someone would do a study to bring to light the cost in dollars and human life that political correctness makes us pay.

[Visioneer]

Have anyone ever considered the extreme hypocrisy of the environmentalists interfering with Darwin's survival of the fittest when they artifically protect a species due for extinction due to genetic limitations. If the enviro's had had their way eons ago, the earth would still be covered with primordial ooze and nothing more. This, of course, if you believe Darwin....

[Lancey Howard]

I hope that some enterprising journalist traces to their roots these decisions by NASA to go "environment friendly" for space shuttle launches.
I want names.
I want to know if there was lobbying of any kind by the scumbag socialist enviro-mice.
I want to know if the Clinton administration was responsible for foisting these requirements on NASA.
Or was it Clinton's EPA?
Or was it Congress?

Who on God's green earth decided to screw around with proven methods for space shuttle launches and make these changes which were soon shown to cause more loss of insulation from the fuel tank, thereby causing more damage to the critical tiles and putting our astronauts at greater risk?

"Environment friendly" space shuttle launches!! Utter insanity.
I want names.

[Steven W.]

won't know until investigation is completed but don't think this is applicable in that NASA has repeatedly confirmed Columbia used one of the last two existing OLD "lightweight" tanks, not the new "super-lightweight" tanks.

[Jael]

What was it? The tile? The foam? What??

FIELD JOURNAL FIELD JOURNAL FIELD JOURNAL FIELD JOURNAL

STS-87 is Home! The Post-Flight Inspection Begins

by Greg Katnik
December 23, l997

STS-87 rolled to a stop; the mission was complete! That statement would be true for the flight of the Columbia, however a new mission began when the wheels of the Columbia came to a stop -- the post flight inspections. My division is responsible for the overall analysis of these inspections and we insure that all changes made, due to these inspections, do not affect other areas that may jeopardize the flight-worthiness of the shuttle. This division does not focus on one specific area, but analyzes all information and ensures that all aspects are kept in balance.

Immediately after the Columbia rolled to a stop, the inspection crews began the process of the post flight inspection. As soon as the orbiter was approached, light spots in the tiles were observed indicating that there had been significant damage to the tiles. The tiles do a fantastic job of repelling heat, however they are very fragile and susceptible to impact damage. Damage numbering up to forty tiles is considered normal on each mission due to ice dropping off of the external tank (ET) and plume re-circulation causing this debris to impact with the tiles. But the extent of damage at the conclusion of this mission was not "normal."

The pattern of hits did not follow aerodynamic expectations, and the number, size and severity of hits were abnormal. Three hundred and eight hits were counted during the inspection, one-hundred and thirty two (132) were greater than one inch. Some of the hits measured fifteen (15) inches long with depths measuring up to one and one-half (1 1/2) inches. Considering that the depth of the tile is two (2) inches, a 75% penetration depth had been reached. Over one hundred (100) tiles have been removed from the Columbia because they were irreparable. The inspection revealed the damage, now the "detective process" began.

During the STS-87 mission, there was a change made on the external tank. Because of NASA's goal to use environmentally friendly products, a new method of "foaming" the external tank had been used for this mission and the STS-86 mission. It is suspected that large amounts of foam separated from the external tank and impacted the orbiter. This caused significant damage to the protective tiles of the orbiter. Foam cause damage to a ceramic tile?! That seems unlikely, however when that foam is combined with a flight velocity between speeds of MACH two to MACH four, it becomes a projectile with incredible damage potential. The big question? At what phase of the flight did it happen and what changes need to be made to correct this for future missions? I will explain the entire process.

The questions that needed to be answered were:

• what happened?
• what phase of flight did it happen in?
• why did it happen?
• what corrective action is required?

At this point, virtually every inch of the orbiter was inspected and all hits were documented and mapped to aid in visualizing the damage. Maps were constructed of the lower surface, the left and right surfaces and the top surface of the orbiter. At this point, a "fault tree" was created. The fault tree provides a systematic approach in considering all possibilities of what may have happened. Everything that is on the fault tree is considered to be legitimate until it is totally ruled out. Some of the considerations were where the damage occurred -- in the OPF, in the VAB, or on the pad before launch. These were quickly eliminated because an inspection at T-3 ("t minus three") hours takes place on each mission and everything was normal.

After these and many other considerations were eliminated, the focus was placed on the ascent, orbit and re-entry phase of the mission. Because of the fore and aft flow characteristics of the damage sites, and the angle of penetration, the ascent phase seemed most likely. The orbit phase of flight was eliminated because the characteristics of these types of hits (most likely meteorites or space debris) occur in a random pattern and direction. Re-entry was eliminated because the "glazing and re-glassifying" of the tiles due to heat upon re-entry (a normal process) indicated that the damage had occurred prior to this phase. The fault-tree was now pointing to the ascent phase.

The pictures that were taken by cameras mounted in the orbiter umbilical began to give the first clues. These cameras are designed to turn on during the solid rocket booster (SRB) separation, and turn off after the separation is complete, thereby recording the event. This process occurs once again when the external tank separates from the orbiter. The initial review of these photographs did not reveal any obvious damage to the external tank. No foam missing, no "divots" (holes) and no material loss. Everything appeared normal.

The SRBs were then focused on for the answers. After inspection of the SRBs, no clues were found. In fact, the solid rocket boosters looked to be in great condition. Where to now? The external tank photographs were magnified and reviewed once again. This time some material loss was noted, but not in a significant degree. The attention was now focused on the crew cabin cameras. These cameras gave more of a side view of the external tank as it tumbled back to Earth. These photographs revealed massive material loss on a side of the external tank that could not be viewed by the umbilical cameras!

Where are we now? One of the questions had now been answered. The ascent phase of flight was when the damage occurred. With the information provided by the photography and the mapped flow of damage, a logical reason could be established as to "what" happened. It was determined that during the ascent, the foam separation from the external tank was carried by the aerodynamic flow and pelted the nose of the orbiter and cascaded aft from that point. Once again, this foam was carried in a relative air-stream between MACH two and MACH 4!

Now the big question -- why? The evidence of this conclusion has now been forwarded to Marshall Space Flight Center (MSFC) because this is the design center for the external tank. MSFC will pursue the cause of damage. Here are some descriptions of some of the considerations:

• The primer that bonds the tank foam to the metal sub-stream was defective and did not set properly. This was eliminated as a cause because the photography indicated that the areas of foam loss (divots) did not protrude all the way down to the primer.
• The aerodynamics of the roll to "heads up." The STS-87 mission was the first time this maneuver had ever been completed.
• The STS-86 mission revealed a similar damage pattern but to a much lesser degree than STS-87. The STS-86 tile damage was accepted ruled as an unexplained anomaly because it was a night launch and did not provide the opportunity for the photographic evidence the STS-87 mission did. A review of the records of the STS-86 records revealed that a change to the type of foam was used on the external tank. This event is significant because the pattern of damage on this flight was similar to STS-87 but to a much lesser degree. The reason for the change in the type of foam is due to the desire of NASA to use "environmentally friendly" materials in the space program. Freon was used in the production of the previous foam. This method was eliminated in favor of foam that did not require freon for its production. MSFC is investigating the consideration that some characteristics of the new foam may not be known for the ascent environment.
• Another consideration is cryogenic loading, specifically hydrogen (-423 degrees Fahrenheit) and oxygen (-297 degrees Fahrenheit). These extreme temperatures cause the external tank to shrink up to six (6) linear inches while it is on the pad prior to launch. Even though this may not seem much when compared to the circumference of the external tank, six inches of shrinkage is significant.

This is where the investigation stands at this point in time. As you can imagine, this investigative process has required many hours and the skills of many men and women dedicated to the safety of the shuttle program. The key point I want to emphasize is the process of investigation, which is coordinated amongst many people and considers all possibilities. This investigation has used photography, telemetry, radar coverage during the launch, aerodynamic modeling, laboratory analysis and many more technical areas of expertise.

As this investigation continues, I am very comfortable that the questions will be answered and the solutions applied. In fact, some of the solutions are already in progress. At present the foam on the sides of the tank is being sanded down to the nominal minimum thickness. This removes the outer surface, which is tougher than the foam core, and lessens the amount of foam that can separate and hit the orbiter.

Check back with Space Team Online for future developments on this story!

[Lancey Howard]

bttt

[Jael]

NEWS RELEASE
United States Air Force
Air Force Materiel Command

Office of Public Affairs
Arnold Engineering Development Center
100 Kindel Drive
Arnold AFB, TN 37389-2213
(931) 454-5586
http://www.arnold.af.mil

Writer:  Danette Duncan
Date: March 19, 1999
Release # 99-041
Photo # none

AEDC Performs Shuttle Materials Test for NASA/Lockheed Martin

ARNOLD AFB, Tenn.—Arnold Engineering Development Center is assisting the National Aeronautics Space Administration with improvements in existing Space Shuttle materials.

According to NASA, during several previous Space Shuttle flights, including the shuttle launched Nov. 29, 1998, the shuttle external tank experienced a significant loss of foam from the intertank. The material lost caused damage to the thermal protection high-temperature tiles on the lower surface of the shuttle orbiter. The loss of external tank foam material and subsequent damage to reentry tiles is a concern because it causes tile replacement costs to significantly increase, however, it is not a flight safety issue. As a result, NASA-Marshall Space Flight Center selected AEDC to perform flight hardware materials tests on the shuttle’s external tank panels in the center’s von Karman Facility Supersonic Tunnel A. The purpose was to establish the cause of failure for the tank thermal protection materials at specified simulated flight conditions. "NASA chose AEDC due to its technical expertise and historical program successes," Steve Holmes, a NASA-MSFC technical coordinator, said.

The Lockheed Martin-manufactured non-reusable external tank, the largest element of the Space Shuttle, fuels the shuttle orbiter during powered flight and is comprised of three components—a liquid oxygen tank, a liquid hydrogen tank and an intertank assembly that connects the two propellant tanks. At the full capacity of 528,600 gallons of propellant, the external tank weighs 1.6 million pounds. The tank is covered with a multi-layered, spray-on foam insulation that provides thermal insulation for the tank against the extreme internal and external temperatures generated during prelaunch, launch and flight.

Wayne Hawkins, Sverdrup project engineer, explained the foam system is exposed to multiple forces, causing difficulty in determining the actual failure of the thermal protection system. "Multiple forces act on the foam system," Hawkins said. "The environmental factors include thermal protection system cell expansion, aerodynamic loading, highly variable local flow conditions, oscillating shocks, vibration, temperature and main external tank substrate flexure."

Although NASA and other facilities have performed a number of tests in an attempt to define the underlying root cause of this foam loss, they were not successful. At one time, the center’s 4-foot and 16-foot transonic aerodynamic wind tunnels were possibilities for the test, but Tunnel A’s ability to closely duplicate flight conditions and control both ambient pressure and test sample immersion time made it the facility of choice. Tunnel A is a continuous flow-variable density wind tunnel with an automatically driven flexible-plate nozzle and a 40- by 40-inch test section and can cover the Mach number range of 1.5 to 5.5.

"The ideal success for the test is the generation of foam loss on a consistent basis with simulated flight conditions," Hawkins said.

Although the AEDC Tunnel A tests did not replicate the in-flight failures, they did provide detailed measurements to better understand the flight environment and fundamental failure mode. From these tests, NASA determined the failure is caused principally by foam cell expansion due to external heating at approximately Mach 4 combined with pressure change and aerodynamic shear. Specialized miniature shear gages and other instrumentation were installed during the test to measure these forces. The customer and sponsor were pleased with the AEDC test results. "No other facility can test with articles/models as large as AEDC with conditions that can match flight," Holmes said.

[GailA]

What sort of adhesive or "glue" holds the tiles on? And is it the original or enviro whacko stuff like the "new" foam?

[Lancey Howard]

bttt