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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
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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
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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
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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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