Why does external tank on Space shuttle fall back to earth?

[Bjammin]

It would if it was on a treadmill!

See ya at Darwins.

 

[A Squared]

See ya at Darwins.

You gonna be there any time soon?

 

[Bjammin]

Not until July. Let you know when.

 

[avbug]

If an external tank burns in the outer atmosphere but there's noone there to see it burn, does it actually make a flame?

Yes, but it doesn't make a sound. Unlike a bear in the woods, which makes plenty of sound (especially if it's hit by a falling tree), even if there's nobody there to see it do it's thing.

The real question, then, if one hand clapping will eventually burst into flame.

 

[mzaharis]

Sorry to be the literalist here, but, my understanding is that while the tank substantially breaks up, some debris makes it to earth.

Here's chapter and verse from the Space Shuttle News Reference:

After initiation of the orbiter/ET separation sequence, there is approximately 11 seconds of mated coast before the orbiter and external tank separate. The ET tumble system produces a tumble rate of 10 to 50 degrees per second after separation. In Kennedy Space Center.launches, the external tank is on a suborbital trajectory that normally results in an impact location in the Indian Ocean. Except for direct-insertion launches from Kennedy Space Center. the tank impacts in the Pacific Ocean. External tank breakup nominally occurs during entry into the Earth's atmosphere at an altitude of approximately 185,000 feet.

http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html