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Fortsetzung von Teil5:

Myth - There was ice mixed in with the foam which struck Columbia

Many people refused to believe a block of foam you can puncture with your finger could destroy the shuttle. Their theory was the foam was like a sponge, absorbing water that changed to ice because of the supercold propellants inside the tank. These hypothetical “foamsicles,” if they existed, would be far stronger than ordinary foam.

The New York Times claimed Columbia spent two weeks longer than usual at the launch pad, where it was exposed to four times the usual amount of rain. The problem is the phrase “than usual.” The schedule from rollout to launch requires a minimum of two weeks, but it's extremely flexible depending on holidays and other scheduled activities. Columbia spent 39 days on the launch pad for STS-107 – exactly what was planned when it rolled out on December 9. – to the minute -–there wasn’t a single delay. The average time a shuttle spends on the launch pad is 38.2 days, so STS-107 was almost exactly average. (There were 33 missions that spent more time on the pad, as much as 5.3 months in one case.)

STS-107’s ET was exposed to rain, just like every other mission. Weather records show 12.78 inches of rain during Columbia’s stay on the launch pad, versus an average of 5.45 inches for all launches -– not the “four times” claimed by the Times. There was nothing extraordinary about rain and STS-107.

Could any amount of rain be absorbed by the foam and turn into ice? No. The ET's foam is formulated as closed cell foam and designed to repel water. (A Styrofoam picnic cooler is an example of closed cell foam; it doesn't absorb water. A sponge, in contrast is open cell.) Water is weight, and if the foam did absorb even a tiny amount of water, the vast amount of water-soaked foam would reduce the amount of payload that could be carried into space. CAIB head Hal Gehman noted, “In all the testing we did, we were unable to get this foam to absorb much moisture. It doesn't matter how much it rains on it.” No water, no ice. No ice, no foamsicles.

The reason a piece of foam could damage Columbia is simple - kinetic energy. Just like a pencil penetrating a tree during a tornado anything with a large velocity carries a large amount of energy. The 1.67 pound piece that struck Columbia's wing at over 500 m.p.h. carried as much punch as a compact car hitting a brick wall head-on at 9.4 m.p.h..

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Myth – The paint which was used on the STS-1 External Tank prevented foam from coming off

The first two shuttle launches, STS-1 and STS-2, had white-colored External Tanks. The tanks were painted white for thermal insulation purposes. After engineers determined that the paint wasn’t necessary and the foam had enough insulating properties by itself the decision was made not to paint any of the later tanks. Not painting the tanks saved 600 pounds which translated into additional payload the shuttle could lift into space.

However it’s a myth that foam wasn’t lost from the white colored tanks. NASA records show three areas where photographs showed that foam was missing from STS-1's tank. This rare photo is from the engineering film from the umbilical well camera mounted in Columbia's belly. At the limited resolution of the film a fist-size chunk of missing foam is just a single pixel so only larger divots can be seen.

NASA's internal engineering reports show three places where missing foam was seen on the liquid hydrogen tank: a 5" circular divot where it appears the substrate layer underneath was exposed in the aft tank (roughly 2/3 of the way to the right in this image), a 16" x 12" divot 27 feet from the bottom of the tank, and a 15" x 20" divot 37 feet from the bottom of the tank. All of these missing pieces were located close to the gaseous hydrogen pressurization line which runs horizontally at the top of this photo behind the much wider 17" liquid oxyen supply pipe.

After Columbia’s landing inspectors found 247 damaged tiles (more than the next two flights put together) with much of the damage due to the foam lost from the External Tank during the launch.

It’s also important to note that the white paint is almost the same color as the foam before it cures into its orange color, which makes it more difficult to detect any lost foam. So it’s likely there was more damage which went undetected because of the white paint.

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Myth - Left wing environmental policies doomed the shuttle

According to some claims, EPA regulations that eliminated Freon caused the foam to fall off.

CFC-11 Freon was used to apply the Spray On Foam Insulation (SOFI) to the ET, and the formula was changed because of EPA regulations. The new method did result in more foam falling off and hitting the shuttle, most notably STS-87, which had 308 damaged tiles, but that was not the type of foam which doomed Columbia.

In the mid-1990s, the EPA banned CFC-11 Freon. NASA has many waivers from the EPA for critical items. In each case a commercial supplier is licensed to produce the limited quantities NASA needs, but it’s incredibly expensive to manufacture the relatively small quantities just for one customer. Lockheed-Martin went through a major effort to find a more environmentally friendly propellant. (It wasn't something they wanted to do, but a necessity.) They selected HCFC 141b (Dichlorofluoroethane). HCFC 141b is only used to spray acreage foam –applied to the large cylindrical surfaces with a giant robotic sprayer.

The bipod foam which doomed Columbia was BX-250 foam, which was excluded from that EPA mandate. Technicians built the bipod by hand, layer by layer, and carved it into shape. The manufacturing process for the bipod and its chemical composition did not change and still used CFC-11. No changes to environmental regulations caused the Columbia accident.

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Myth - Israeli spy satellite photos show Columbia exploding

Another person with a sick sense of humor claimed that an Israeli spy satellite took photos of Columbia as it exploded. The photos are actually from the fantasy film 'Armageddon'. Israel's spy-Earth resources satellite EROS did take photos of Columbia, but it was the day before launch when it was still on Earth! Imagesat, the commercial firm which distributes EROS data proudly released images of the Vehicle Assembly Building and Columbia on Pad 39A during the STS-107 mission.

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Quelle: James Oberg / NASA / NBC