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  STS-1 ET separation

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Author Topic:   STS-1 ET separation
Mary13
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posted 04-12-2007 03:48 PM     Click Here to See the Profile for Mary13   Click Here to Email Mary13     Edit/Delete Message   Reply w/Quote
Hi!
Today STS-1 launch is 26 years ago. I reviewed some photos of the launch and I noticed that on a photo of the ET after separation the tank is full of stains and looks really terrible. What caused that?

The text under the picture:
S81-30509 (12 April 1981) --- During the STS-1 launch sequence and orbital insertion, the external tank (ET) is jettisoned from the Space Shuttle Columbia, as photographed by a camera in the umbilical bay. http://www.jsc.nasa.gov/jscfeatures/articles/000000503.html

Can anybody help me to find an answer?

KSCartist
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posted 04-12-2007 03:52 PM     Click Here to See the Profile for KSCartist   Click Here to Email KSCartist     Edit/Delete Message   Reply w/Quote
From what I understand those "stains" are from the SRB separation motors.

Tim

Robert Pearlman
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posted 04-12-2007 03:57 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Indeed, you can see similar marks on more recent tanks (the linked example is from STS-114). The stains might be more visible on STS-1 (and STS-2) due to the white paint applied over its insulation.

spacecraft films
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posted 04-12-2007 04:06 PM     Click Here to See the Profile for spacecraft films   Click Here to Email spacecraft films     Edit/Delete Message   Reply w/Quote
The blackened areas are from interference heating during ascent (those that aren't clearly from the separation motors). If you'll note, they are in areas which receive the highest aerodynamic heating, as the stack increases velocity through the atmosphere. Highest areas of heating are at the top (naturally) and around the orbiter struts, where the airflow is disturbed and temperatures are highest (including around the areas where the tips of the SRBs are disturbing the airflow as well).

Our "Liftoff" DVD set has the onboard footage of the STS-1 jettison (as will our Space Shuttles: First Flights set coming later this year) and gives some great views of where this interference heating occurs, but virtually any of the footage of a jettisoned ET will show it.

Mark

Ben
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posted 04-12-2007 04:08 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
Edit: Mark beat me to it.

It is both, however. The SRB separation motors caused the black black areas. But some of it is also from atmospheric heating, which is the dark 'charcoal powder' look evident at the top of the tank there. The friction of going through the upper atmosphere at tremendous speed can char areas, especially towards the front.

In fact, the SRB exhaust plume also chars the aft come during ascent, so that is another contributor.

Mary13
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posted 04-12-2007 04:57 PM     Click Here to See the Profile for Mary13   Click Here to Email Mary13     Edit/Delete Message   Reply w/Quote
Thanks for your quick answers and the very helpful information. I also suspected that with the friction, but I didn't expect that to be so clearly visible.
Could you explain the thing with the SRB separation motors? How do they cause the black areas?

Ben
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posted 04-12-2007 06:17 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
On the nosecone and the aft skirts of the shuttle's SRBs are small solid motors that fire at the same time the SRBs are jettisoned. This is done in order to ensure the SRBs pull away from and behind the shuttle. As they pull away, the exhaust hits the sides of the ET.

On the same note, on STS-112 when they debuted the ET cam, the separation motor exhaust hit the lens and obscured the view from SRB separation onward. This was corrected a bit for the flights of 114 and since.

All times are CT (US)

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