My theory on shuttle illumination late in dark ascent.

Did anybody capture good views of the 'ring of fire' effect (with
apologies to Eric Flint) just prior to MECO? Since the ring collapsed
at MECO I'm presuming it was the shock wave of the engine plume and
the upper atmosphere. Even though shot backwards at 3000 meters/sec,
the combustion productions were impacting ambient upper atmosphere at
about that same speed because the stack was nearly at orbital velocity
(8000 meters/sec).

The light was not the plume -- LH2/LO2 flame is essentially invisible.

Why it should be green is a bigger question -- I wonder about color
imbalance
in the low light level situation. Ground observers were seeing orange and
yellow-orange colors, not green -- and that's the proper wavelength for the
source of the light, atomic oxygen recombination immediately following O2
dissociation from molecular impacts.

Illumination at ET sep, on the other hand, was white -- the color of flares
from RCS jets.

Jim Oberg wrote:

Did anybody capture good views of the 'ring of fire' effect (with
apologies to Eric Flint) just prior to MECO?


I'm sure Rocketcam will have it up in a few days; The effect was
noticeable for around 15 seconds prior to MECO and was really something
to see, as were the RCS firings, and APU exhaust.
The glow over the orbiter's wing leading edges at ET separation sure
looked to me like some sort of plasma event due to atomic oxygen at that
altitude.
Whatever it was, it knocked your socks off . =-O


Pat

Jim Oberg wrote:
Did anybody capture good views of the 'ring of fire' effect (with
apologies to Eric Flint) just prior to MECO? Since the ring collapsed
at MECO I'm presuming it was the shock wave of the engine plume and
the upper atmosphere. Even though shot backwards at 3000 meters/sec,
the combustion productions were impacting ambient upper atmosphere at
about that same speed because the stack was nearly at orbital velocity
(8000 meters/sec).

The light was not the plume -- LH2/LO2 flame is essentially invisible.

Why it should be green is a bigger question -- I wonder about color
imbalance
in the low light level situation. Ground observers were seeing orange and
yellow-orange colors, not green -- and that's the proper wavelength for the
source of the light, atomic oxygen recombination immediately following O2
dissociation from molecular impacts.

Illumination at ET sep, on the other hand, was white -- the color of flares
from RCS jets.



I had a similar experience on a launch out of Vandenburg. Basically, the
cause then was ice crystals at a very high part of the atmosphere were
in an area still exposed to sunlight from over the horizon. Was very
cool effect. Would have to see if this was the same or if it was
possible.

"Jim Oberg" wrote
Did anybody capture good views of the 'ring of fire' effect (with
apologies to Eric Flint) just prior to MECO?

Here's one view -- better than the digital images
I snapped off my monitor. It's awesome --
http://forum.nasaspaceflight.com/for...chmentid=15298

"Charles Buckley" wrote in message
...
Jim Oberg wrote:
Did anybody capture good views of the 'ring of fire' effect (with
apologies to Eric Flint) just prior to MECO? Since the ring collapsed
at MECO I'm presuming it was the shock wave of the engine plume and
the upper atmosphere. Even though shot backwards at 3000 meters/sec,
the combustion productions were impacting ambient upper atmosphere at
about that same speed because the stack was nearly at orbital velocity
(8000 meters/sec).

The light was not the plume -- LH2/LO2 flame is essentially invisible.

Why it should be green is a bigger question -- I wonder about color
imbalance
in the low light level situation. Ground observers were seeing orange and
yellow-orange colors, not green -- and that's the proper wavelength for
the
source of the light, atomic oxygen recombination immediately following O2
dissociation from molecular impacts.

Ground observers (I was one) are looking usually at low elevations through
thick atmospheric attenuation, so only red-yellow gets through. Green is
associated with excited (not ionized) oxygen beginning at altitudes above 60
km (similar to aurora) so it is not unreasonable for what was seen around
the orbiter. Incidentally the same glow was seen on the leading edges of
the OMS pods.

Pat Flannery wrote:

I'm sure Rocketcam will have it up in a few days; The effect was
noticeable for around 15 seconds prior to MECO and was really something
to see, as were the RCS firings, and APU exhaust.
The glow over the orbiter's wing leading edges at ET separation sure
looked to me like some sort of plasma event due to atomic oxygen at that
altitude.
Whatever it was, it knocked your socks off . =-O


Pat

It was definitely a cool video. Makes ya wish NASA did this or had this
capability on every mission from STS-1 on up. Crying shame it took the
loss of an orbiter and her crew to give us these vids.

Gene

Gene DiGennaro wrote:

It was definitely a cool video. Makes ya wish NASA did this or had this
capability on every mission from STS-1 on up. Crying shame it took the
loss of an orbiter and her crew to give us these vids.



They'd started using the ET camera prior to the loss of Columbia,
although they didn't say much about it at the time, the reason was that
they wanted to film the ascent was that they were trying to get info on
the foam shedding that was going on.

Pat