SOLVING THE NASA/DISCOVERY INSULATING FOAM DISASTER
NASA shoots itself in the foot again -- Grounds Shuttle fleet for the wrong reason
In September 1988, following the two and a half year grounding and analysis of the Challenger disaster, it was also the very same Shuttle Discovery involved in NASA's first "Return to Flight."
Discovery on the Pad 7/26/05
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Major systems and hardware changes were made and Discovery was stacked up and sent to the launch pad. Then just two weeks before launch, a major disaster was uncovered.
If the problem could not be quickly solved, then Discovery would need to be sent back to the Vehicle Assembly Building, unstacked and new hardware installed. This would delay the "Return to Flight" by many long months, and cost NASA about 10 million dollars.
Nobody at NASA understood nor knew how to solve the problem. One senior consultant engineer claimed he had a solution. NASA quickly convened an 8-member Materials Review Board investigating team to find out if that engineer really had an answer to the problem. I know that engineer very well, in fact, it was me, Marshall Smith.
I gave a half hour technical presentation to the MRB team describing the problem in detail, and showing how it could be solved right on the launch pad with no delays. At the end of the presentation, I finished with, "... and thus proving that this bird is ready to fly!" Before I could finish that sentence, the 8-member MRB and about 30 other Air Force generals, corporate presidents, NASA hdqrs people, and others who were flying satellites on Discovery, all started applauding, cheering and yelling.
For some reason, people in the space program have a tendency to do that kind of thing, especially it seems, if they have millions of dollars, and years of their lifetime, invested in the project. Two weeks later in 1988, Discovery took off right on schedule with no problems. That was not the first nor last time I saved NASA's bacon by solving or preventing major space disasters.
Now in July 2005, once again Shuttle Discovery and the NASA program have a major disaster – huge chunks of foam keep falling off the External Tank, and grounding the shuttle fleet. But it seems, nobody at NASA knows why. The reason is because NASA is looking in the wrong place. NASA engineers have incorrectly assumed that cracks, bubbles or voids in the spray-on insulating foam itself, and sharp angular edges in the ramp areas, are what cause big pieces of the foam to break off the huge External Tank. But not so.
Recent tests with new improved foam techniques applied to a large test plate and flown under a NASA test plane at supersonic speeds only shows small divots of an inch or less blowing off the surface. So what is causing huge chunks of foam several feet in size to come off the tank? It seems to be a NASA mystery.
The reason is because it is not the rapid supersonic air flowing along the side of the tank which is causing the problem. Instead it is caused by small tornadoes of swirling air created by the supersonic shock waves coming off the nose of the External Tank hitting and intersecting with the other shock waves coming off the nose of the Shuttle Orbiter and the nosecones of the two booster rockets.
These momentary tornadoes are invisible, not seen in photographs, and only occur around Mach 4 or 5, and around an altitude of about 28 miles high just before booster separation. They are also random swirls and may or may not occur on any given flight, and they only occur in the region just below the nose of the Shuttle Orbiter or the front of the two booster rockets just at separation. These powerful supersonic hurricane swirls rise up vertically from the surface of the External Tank and are then blown back underneath the Orbiter.
The existence of these clear air swirling tornadoes was first shown in the CAIB Final Report wind tunnel data with air flow in the Bi-pod area under the same conditions as when that large foam chunk came off the tank during the Columbia flight. The data shows all the air flowing along the surface of the tank just ahead of the bi-pod ramp was converging at a single point. It seems nobody at NASA noticed or knew what that meant. That is the exact same air flow pattern around a tornado in Kansas, as the air and everything else is sucked up into the very center of the swirling vortex.
There is no insulating foam, even if carefully applied without voids or cracks, which is strong enough, with sufficient tensile strength, to tolerate the huge sucking vacuum of the supersonic swirling tornadoes. Huge chunks of foam, several feet in size, will always be randomly sucked off the External Tank in the Bi-pod and PAL Ramp areas. And there is no way to stop these random powerful vortices from forming at the critical speed and altitude.
The Space Shuttle program has long been way over budget. The External Fuel Tank is supposed to be a cheap disposable item. Adding new expensive foam application procedures and even more expensive design changes to the ramp areas, are simply not feasible for a disposable item. There is no assurance that the changes would work until more risky flights were made, and that's not going to happen. It now seems there is no practical possible answer to the problem with the Space Shuttle configured as an Orbiter attached to the side of a foam-covered External Tank. Or is there?
Solution: Wrap a thin Kevlar fabric open-mesh all around the External Tank. Even if large vacuum vortices do form, the strong mesh fabric will hold the foam in place. No large pieces of foam will ever again be sucked off the Tank. The mesh is thin and light enough not to change the flight characteristics of the Tank. It could even be applied only in the critical high-vortex regions around the Bi-pod and PAL Ramp areas. It is cheap, easily applied, permanent and guaranteed to work. No expensive tank design changes are needed. No more huge chunks of foam will ever fall off the tank. Problem solved.
This is similar to using chicken wire to reinforce the stucco on houses and buildings. Without the chicken wire the unreinforced stucco will always eventually crack and fall off the building. In the case of the External Tank, using Kevlar mesh is more expensive but is much lighter in weight than chicken wire. With the Kevlar reinforcement the aerodynamic forces may cause the tank foam to crack but it can never fall off. And it's guaranteed to work with no further problems.
And I am not even going to charge NASA my usual consulting fee for solving their mission critical problems. Why? Because I am not going to tell them. Why? Because they didn't ask me. So I will do what I have done since 1975. Watch NASA management run around like Keystone Kops in a panic – until I solve their problem.
For more information about the Space Shuttle insulating foam problem, read the Columbia articles in the BroJon Gazette archives.
Marshall Smith
Editor, Brother Jonathan Gazette
newseditor@brojon.com
-- BROTHER JONATHAN GAZETTE
