Sunday, November 25, 2007

Foaming at the Mouth

Remember back around Oct 20, we expressed some concern here about the pedigree of the STS-120 tank. The "Frankentank" had been pulled from STS-114, and was refurbed to address a number of problems, including:

- The Liquid Hydrogen Ice/Frost Ramps were modified at 14 locations.
- The Liquid Oxygen Ice/Frost Ramps were modified at four locations.
- The Liquid Oxygen Feedline Brackets were modified, as an interim measure, with a different foam configuration.
- Liquid Oxygen and Liquid Hydrogen PAL Ramps were removed.
- Bipod Harness Modifications including wire harness sealing/bonding was performed to preclude a debris event similar to the one observed on STS-114.
- Intertank Acreage Machining/Venting increased the area of vented intertank thermal protection system foam to reduce the potential for foam loss due to "popcorning," caused by air bubbles becoming trapped in foam and flaking off and falling away during heating and expansion during launch.

So, how did that all work out? Not too well it seems. In fact, more foam in bigger pieces came off the tank than any launch in recent memory. Fortunately, none of it hit the orbiter with enough dynamic pressure to do much damage.

And what did the minions do with this aberration? Why they "normalized the deviation," of course.

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