Re: They said the APU fire is normal?

maxson@xxxxxxxxxxxxxx wrote:

I'm not even so sure about the idea that one can "see the [APU] heat
being exhausted in the infrared for every night landing."

See: <http://tinyurl.com/2lr94x>

You must remember, in that shot, Discovery is still traveling at well over 100 knots--the exhaust is being dissipated by the slipstream between the vertical stabilizer and the OMS/RCS pods (if you view the visible light version of the "on fire" landing, even during rollout, the flames are dragged back along the body).

But, that being said, if you look at video of that same landing (STS-114 http://tinyurl.com/25sg39), you can start to see the APU exhaust "strobing" at the about the 1:16 mark. And it looks like the still image was taken just between "puffs" of exhaust some where around the 1:46-1:50 range of the video... by that time, the puffs are quite clearly visible (in IR).

Now, changing gears here: I'm wondering if we're all "arguing" about this just because the commentator used the word "normal" to describe the fire. I wonder if he should have said the phrase "not unexpected". As described elsewhere, the exhaust is flammable... maybe this is the first time it stayed alight all the way to the ground--every other time, the slipstream was able to put it out well before going sub-sonic...

.

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