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  #1  
Old July 8th 06, 05:38 PM posted to sci.space.shuttle
Rich
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Posts: 4
Default white smoke/trail

Saw a footage of liftoff last July 4th. When the boosters separated
from external tank, did the shuttle's engine take over or had it been
running since launch? There is no smoke/trail coming from the
shuttle's engine, unlike the boosters. Why is there no smoke?

Thanks,


Rich

  #2  
Old July 8th 06, 05:52 PM posted to sci.space.shuttle
Craig Cocca
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Posts: 10
Default white smoke/trail

Rich wrote:
Saw a footage of liftoff last July 4th. When the boosters separated
from external tank, did the shuttle's engine take over or had it been
running since launch? There is no smoke/trail coming from the
shuttle's engine, unlike the boosters. Why is there no smoke?


The solid fuel in the SRB's is comprised of:

69.83% ammonium perchlorate
16% aluminum
12% rubber
2% curing agent
0.17% iron oxide catalyst

This combination produces the "smokey" exhaust that you see during
launch. Basically, the SRBs are the largest firework ever built (and
if you live in the US, you know how smokey it tends to get outside
after Indepenance Day!)

On the other hand, the space shuttle main engines burn liquid hydrogen
and liquid oxygen as fuel. As you've probably guessed by now, the
byproduct of this reaction is basically water vapor, which produces
little or no visible exhaust.

Craig

  #3  
Old July 8th 06, 09:20 PM posted to sci.space.shuttle
RandyL
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Posts: 7
Default white smoke/trail

Rich,
Yes, the Shuttles engines (SSME's) actually run all the way through
launch until the shuttle reaches orbit. The SSME's ignite a few seconds
before the solid rocket boosters (SRB's) ignite.
The SSME's burn liguid hydrogen and liguid oxygen for fuel. Water vapor
is the by-product of burning hydrogen and oxygen. The majority of the
billowing white clouds that you see around the shuttle at launch is simply
steam and condensed water vapor, as well as the exhaust from the SRB's. The
water vapor exhaust is mostly transparent, except when it condenses into
water droplets. Also at launch the exhaust from both the SRB's and the
SSME's are directed through channels that are sprayed with liquid water to
help control the sonic shock of the engines. This is done to help reduce
damage to the orbiter stack and the launch tower that can be caused by the
noise of the engines. This sonic blanket of water is immediately flashed
into steam by the hot rocket exhaust. Lower in the atmosphere, the
atmospheric air pressure is great enough so that water vapor can condense
into droplets and be seen along with the SRB exhaust. You won't see a
"smoke" trail after the SRB's seperate, because at that altitude the air
pressure is so low that the water vapor exhaust from the SSME's cannot
condense into droplets.
I once read (and I cannot say for sure if this is true or not) that the
solid rocket boosters thrust is simply used to cancel the incredible weight
of the entire shuttle stack, and the SSME's thrust is what is used to
accelerate the stack to orbital velocity. Hope this helps...

Randy L.
--
Remember: Any landing that you can
walk away from, is a landing that you
can be fined, sued, or prosecuted for.

"Rich" wrote in message
ps.com...
Saw a footage of liftoff last July 4th. When the boosters separated
from external tank, did the shuttle's engine take over or had it been
running since launch? There is no smoke/trail coming from the
shuttle's engine, unlike the boosters. Why is there no smoke?

Thanks,


Rich



  #4  
Old July 8th 06, 10:50 PM posted to sci.space.shuttle
Brian Thorn
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Posts: 510
Default white smoke/trail

On 8 Jul 2006 09:38:44 -0700, "Rich" wrote:

Saw a footage of liftoff last July 4th. When the boosters separated
from external tank, did the shuttle's engine take over or had it been
running since launch? There is no smoke/trail coming from the
shuttle's engine, unlike the boosters. Why is there no smoke?



The Shuttle's three Main Engines ignited at T-6.6 seconds before
liftoff. They burn liquid hydrogen and liquid oxygen. They produce an
orange flame during the startup, but quickly turn to clear, or blue
flame with no smoke trail. The byproduct of this is mostly water
vapor.

The launch pad uses water from a nearby water tower to prevent shock
waves damaging the shuttle when it is on or just off the pad and the
engines are running. Some of the water dumped onto launch pad is
vaporized by the engines, resulting in a huge, billowing, white cloud
of steam.

The Solid Rocket Boosters burn ammonium perchlorate and produce an
orange cloud of smoke.

Once the SRBs burn out, there's no more water being turned to steam at
that altitude and no SRBs producing orange smoke, so the Shuttle
becomes almost invisible.

Brian

 




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