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  debris on STS 121

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Author Topic:   debris on STS 121
lucspace
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From: Hilversum, The Netherlands
Registered: Oct 2003

posted 07-04-2006 01:44 PM     Click Here to See the Profile for lucspace   Click Here to Email lucspace     Edit/Delete Message   Reply w/Quote
...around T + 3 min... at least three parts of foam from the bottom part of the ET... did I see correctly??

Luc

DwightM
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posted 07-04-2006 01:57 PM     Click Here to See the Profile for DwightM   Click Here to Email DwightM     Edit/Delete Message   Reply w/Quote
There did appear to be some shedding near the strut that attaches to the Orbiter. Didn't look like there were any strikes, but I haven't seen a replay yet. We'll just have to wait for the experts to have a look. Hopefully it's something minor. Otherwise, great launch!

lucspace
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From: Hilversum, The Netherlands
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posted 07-04-2006 02:35 PM     Click Here to See the Profile for lucspace   Click Here to Email lucspace     Edit/Delete Message   Reply w/Quote
http://www.nasaspaceflight.com/

mjanovec
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From: Midwest, USA
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posted 07-04-2006 02:46 PM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
I replayed the ET camera footage and you can also clearly see shedding 2:46 after SRB sep. A piece breaks off, hits the underbelly, breaks into a couple smaller pieces, and can be seen exiting past the right wing (to the camera's left). It's hard to tell how big of a piece it was. Not tiny, but not briefcase sized either. Perhaps 6 inches (just a guess, mind you).

Granted, at this point in flight, I think airflow over the orbiter is thin enough that any piece breaking off will do much less damage than it would if it happened before SRB sep. Griffin said to expect shedding, but it should be of the nature that it wouldn't damage the orbiter. The piece moved a lot slower than the one you see in the Columbia footage.

I think the liklihood of ever seeing a perfectly "clean" launch is close to zero. There will always be some shedding.

Having that ET tank camera is a mixed blessing. It shows sheding events very clearly. But any shedding event witnessed by the public can be taken the wrong way.

[This message has been edited by mjanovec (edited July 04, 2006).]

Robert Pearlman
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Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 07-04-2006 03:15 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by mjanovec:
Having that ET tank camera is a mixed blessing. It shows sheding events very clearly. But any shedding event witnessed by the public can be taken the wrong way.
Exactly. NASA made it very clear before launch that foam would fall off during ascent but that it was where, when and why that was important, not just the fact that it did. Early analysis seems to suggest that the debris seen was shed after the point of concern however that loss, if indeed from the ice frost ramps will be very helpful to learning how to redesign those areas, as is already planned.

There will be a media briefing tonight with Wayne Hale wherein he plans to share the initial imagery analysis. Its too early right now to say what, if anything was seen by the ET camera (and others) and what, if any impact it might have on the mission.

[This message has been edited by Robert Pearlman (edited July 04, 2006).]

mjanovec
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From: Midwest, USA
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posted 07-04-2006 03:53 PM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
Replaying the ET footage again, the two shedding events can be seen at approximately 0:45 and 2:26 after SRB sep. I use SRB sep as the point to mark the time, because ET tank footage starts after launch has already taken place. I post this just in case someone wanted to replay the footage to see these events.

The event at 0:45 after SRB sep appears to miss the orbiter. The event at 2:46 after SRB sep appears to hit the underbelly of the orbiter, break into 2-3 pieces and exit the orbiter behind the right wing.

Robert Pearlman
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From: Houston, TX
Registered: Nov 1999

posted 07-04-2006 04:20 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From Bill Harwood at CBS News:
quote:
A camera mounted on the shuttle's external tank provided spectacular views of the spaceship's heat-shielded underside as Florida's east coast dropped away in the background. The ascent appeared free of foam debris from the tank until about two minutes and 47 seconds when a half-dozen seemingly small pieces of debris could be seen suddengly separating. NASA managers said before launch that foam debris shedding after about 165 seconds was of no concern because by that point, the atmosphere is so thin it cannot carry debris to a dangerous impact. The debris seen today separated around 167 seconds after launch.
Read the full article here.

Robert Pearlman
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Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 07-04-2006 05:02 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
From the Orlando Sentinel
quote:
managers say that engineers already have noted foam loss in two separate incidents. Shuttle program manager Wayne Hale said three or four small objects appear to break off the tank about 2 minutes, 47 seconds into flight. Then more debris is seen liberating from the tank about 4 minutes, 50 seconds after launch.

However, Hale said, both incidents occurred when the shuttle was high above Earth with little atmosphere. The lack of air means that the foam could not gain enough speed to damage the spaceship if it struck it.


Read the full blog entry here.

Robert Pearlman
Editor

Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 07-04-2006 07:35 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
According to Space Shuttle Program Manager Wayne Hale (who just concluded an early imagery analysis press conference), of the five debris events observed on STS-121's ascent, all five occurred after the time in Discovery's flight profile when they would be a concern to the orbiter (in other words, after the vehicle had reached the upper edges of the atmosphere such that aerodynamic forces were no longer involved in moving about the debris).

Further, Hale said that they know with certainty that four out of the five events involved fragments that were below the size threshold that are of concern (the fifth may very well be too, but they need to wait for better imagery to be downlinked to determine that with the same degree of certainty).

Per Hale, these events were within NASA's expectations of the tank's performance and though the crew will proceed with the full inspection of Discovery's heatshield (using both the orbital boom inspection system and the "back-flip" maneuver before docking with the ISS) they have little reason for concern.

One piece of debris did appear to "touch" the orbiter, but its lack of velocity and more importantly, its lack of being obliterated in the process (nor any color change to the area of the "touch" on the orbiter's belly) has led Hale and his team to be certain that no damage was caused.

The "blanket" filmed and reported by MS Mike Fossum is, in fact, ice that formed around the bell(s) of the space shuttle main engines. Hale has seen this before (most recently on STS-114) and if you watch the video, you can clearly see the ice breaking apart, the result of sublimation.

Lastly, the reports of flapping ice frost ramps and/or paper are the result of both confusion with the paper RCS jet covers falling off (as they are designed to do) and a video artifact.

[This message has been edited by Robert Pearlman (edited July 04, 2006).]

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