Shuttle - looking dirty

one thing that stands out, in particular with the night shots of
Discovery
on the launch pad, is how dirty or marked Discovery appears.

I thought dirt on airplanes caused aerodynamic issues, such as a loss of
performance. Is this not true?

Walter

Walter L. Preuninger II wrote:
one thing that stands out, in particular with the night shots of
Discovery
on the launch pad, is how dirty or marked Discovery appears.

I thought dirt on airplanes caused aerodynamic issues, such as a loss of
performance. Is this not true?


It's not dirt on the orbiter. It is thin sheen
of surface contamination deposited by the effects
of reentry heating. The deposits include calcium
and zinc oxide from gap filler materials and
RTV, bits of melted metal from surface-mounted
sensors, aluminum oxide deposited by the SRBs,
etc. Some of this stuff becomes embedded in
the outer layers of the TPS so that it can't
easily be cleaned.

- Ed Kyle

On Tue, 19 Jul 2005 08:25:38 -0500, Walter L. Preuninger II wrote
(in article ):

one thing that stands out, in particular with the night shots of
Discovery
on the launch pad, is how dirty or marked Discovery appears.

I thought dirt on airplanes caused aerodynamic issues, such as a loss of
performance. Is this not true?

Walter


Aircraft spend their entire lifetimes operating inside the atmosphere
and everything about them is a compromise weighted toward reducing
operating costs over their lifetimes. A few dollars' worth of fuel
saved per day adds up to substantial savings over 20 years of
operations. That makes it worth washing them every so often.

The Orbiter spends so little time accelerating through dense atmosphere
that any drag due to surface dirt is entirely inconsequential. Surface
drag from the tiles themselves as well as the lower-temperature thermal
blankets is much higher than any drag attributable to dirt.

--
"Fame may be fleeting but obscurity is forever."
~Anonymous
www.angryherb.net