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  Space Shuttles - Space Station
  Sparks under SSMEs before launch?

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Author Topic:   Sparks under SSMEs before launch?
Steve DeGaetano
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posted 09-20-2010 04:01 PM     Click Here to See the Profile for Steve DeGaetano   Click Here to Email Steve DeGaetano     Edit/Delete Message   Reply w/Quote
I have a question that I've been wondering about since the very early shuttle days.

Right before space shuttle main engine (SSME) ignition, close-up videos of the area show what appear to be several fountains of sparks shooting and arching toward the area immediately under the engine bells.

What is the purpose of these sparks?

mikej
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From: Germantown, WI USA
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posted 09-20-2010 05:02 PM     Click Here to See the Profile for mikej   Click Here to Email mikej     Edit/Delete Message   Reply w/Quote
As per NASA's Ask The Mission Team - Question and Answer Session:
Those sparks are called our hydrogen burn-off igniters and they are intended to burn free hydrogen. When we start up the engines, there is a little bit of hydrogen that comes out that hasn't ignited yet when combined with the oxygen in the system. Also, if we do have an on-pad engine shutdown after we've started the engines and have to turn them off for some reason, we shut down fuel rich as well meaning that the last bit of fuel that comes out of the engines will be hydrogen. So, those sparklers, that we like to call them, will burn off free hydrogen in the atmosphere rather than let it ignite on its own as it travels up the side of the ship. That's a safety consideration. It burns hydrogen before it causes us any trouble.

Rob Joyner
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posted 09-20-2010 05:07 PM     Click Here to See the Profile for Rob Joyner   Click Here to Email Rob Joyner     Edit/Delete Message   Reply w/Quote
The sparks burn off hydrogen gas that may accumulate under the main engine nozzles to prevent a possible explosion when the main engines ignite.

Steve DeGaetano
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posted 09-21-2010 08:07 AM     Click Here to See the Profile for Steve DeGaetano   Click Here to Email Steve DeGaetano     Edit/Delete Message   Reply w/Quote
Thank you very much! Very interesting.

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