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Author
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Topic: Skylab's micrometeorite shield as a sunshade
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Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-13-2017 04:08 AM
   
Just after its launch, the Skylab space station's micrometeorite shield prematurely deployed during the station's ascent into orbit and the shield was torn off. The Skylab micrometeorite shield also doubled as a sunshade for the body of the Skylab station. So when the shield was lost during ascent, two Skylab crews had to make spacewalks to install replacement solar shades on the station. The original micrometeorite shield that was torn off during ascent was relatively small and did not cover much surface area of the station. It would have been virtually useless as a form of micrometeorite protection. Does anyone know of what value such a small shield had? Secondly, as noted, the micrometeorite shield would have also acted as a sunshade for the station. But again, it was far too small to act as a sunshade by itself. The shield/sunshade apparently worked in conjunction with the gold foil that wrapped around the middle to aft part of the station.
And it is interesting to note that only half of the station was covered in gold foil. The upper half of the station was completely exposed to sunlight. Does anyone have any insights on why the micrometeorite shield was so small and about its function in promoting thermal cooling on the station? |
oly
Member Posts: 971
From: Perth, Western Australia
Registered: Apr 2015
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posted 02-13-2017 04:35 AM
The value such a small shield had, its loss was important enough to warrant NASA delaying a launch, designing repair schemes, manufacturing and testing equipment, developing training programs and exercises and risking EVA to facilitate repairs. The temperature inside Skylab was uninhabitable without a sunshield.Its function was to keep the temperature within Skylab at a liveable region. There are many good interviews regarding this subject in the oral history pages and many good references available online that will satisfy your eager curiosity. |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-13-2017 09:02 AM
quote:
Originally posted by Jim_Voce:
Does anyone have any insights on why the micrometeorite shield was so small and about its function in promoting thermal cooling on the station?
It wasn't "small" or "far too small" or "useless as a shield." It wrapped around the whole workshop and was 265" in length. Hence, it covered a large portion of the workshop. Without it, the thermal input from the sun was significant.Only half of the workshop had gold foil because the same side always faced the sun. The sun shield/micrometeorite shield blocked most of the thermal energy from the sun, but itself it would be come hot, and so the gold foil would reflect the remaining heat from the sun shield. The whole gold portion would have been covered by the shield. |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-13-2017 10:40 PM
Thank you Jim.
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Dwight
Member Posts: 577
From: Germany
Registered: Dec 2003
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posted 02-14-2017 12:35 AM
A good series of information about Skylab can be found in the recently published Skylab 1 & 2: The NASA Mission Reports, Skylab 3: The NASA Mission Reports, and Skylab 4: The NASA Mission Reports, from Apogee books.The first book covers a good deal of the Micrometeroid Shield Anomaly. |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-14-2017 12:42 AM
Has anyone seen a picture of Skylab's original micrometeroid shield? Was it a flat platform or was it curved and surrounding the belly of the station?If I understand correctly, then the micrometeoroid shield encircled half the station. So was the entire shield lost or only part of it? If the entire shield was lost then Skylab ran the risk of being damaged by micrometeoroids. I have seen photographs showing the pitting that happened to the skin of Skylab. So when NASA came up with its solar shade solution it does not appear that they attempted to replace the micrometeroid shield. Also it appears that the shielding would have only protected half of the length of the station. Any perspectives on this? |
rlobinske
Member Posts: 155
From: Crawfordville, FL
Registered: Oct 2014
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posted 02-14-2017 08:37 AM
If you look at a photo of the Skylab launch stack, the micrometeor shield was the black and white section between the stringers of the S-IV-B base structure. |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-14-2017 08:48 AM
quote:
Originally posted by Jim_Voce:
Also it appears that the shielding would have only protected half of the length of the station.
As I stated "it wrapped around the whole workshop." It was a cylinder. It had a little larger diameter than the workshop and there was some overlap at the two seams. As the shield deployed, it would move away from the workshop skin a few inches and the overlap would go away. Basically, the workshop and the shield were two nested cylinders. Only one half of the shield was missing (which ended up being the most important one). NASA assumed the increased risk of MMOD for the duration of the program. FYI, it wasn't pitting, it was blistering from the sun. Only the walls of the S-IVB LH2 tank needs protection. The rest of the workshop (LH2 forward dome, LO2 tank) were behind the forward and aft skirts of the S-IVB stage. You can see the 260 or so inches of LH2 tank that needed to be protected. |
Dietrich
Member Posts: 68
From:
Registered: Jul 2009
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posted 02-14-2017 04:24 PM
The Anomaly Report of the lost meteorite shield is available here or here. That report includes an exhaustive explanation of its design. |
GACspaceguy
Member Posts: 2516
From: Guyton, GA
Registered: Jan 2006
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posted 02-14-2017 05:27 PM
That description is great. If you really want to understand the shield then you have to visit that site. I have always been a big Skylab fan and there was info here I had never seen. Big thanks Dietrich!! |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-14-2017 10:25 PM
quote:
Originally posted by Jim Behling:
You can see the 260 or so inches of LH2 tank that needed to be protected.
Thank you for the excellent description again. Fundamental question is why was the micrometeoroid shield designed to cover only half of the station? The airlock and mid point of the station were both exposed to the sun and to potential micrometeoroid impacts. quote:
Originally posted by Dietrich:
That report includes an exhaustive explanation of its design.
That was a superb resource you sent over. Very much appreciated. quote:
Originally posted by rlobinske:
If you look at a photo of the Skylab launch stack...
Is it true that the micrometeoroid shield was left exposed at launch? In other words, the launch shroud did not extend over the micrometeoroid shield? |
oly
Member Posts: 971
From: Perth, Western Australia
Registered: Apr 2015
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posted 02-15-2017 12:36 AM
A good idea of the design of the shield can be seen here. You can see a case study into Skylab here.The shields wrapped around the section of the Skylab S-IVB that was exposed to airflow during the early phase of launch and not covered by the payload shroud. This was also the section of Skylab that was the crew living quarters and as it had the greatest surface area, was also the largest heat sink and largest target area for micrometeors. The telescope mount and airlock had protection of a differing design because it was not required to be exposed to airflow at supersonic speeds during launch. You can see he S-IVB without the airlock and mount and the shields are installed here. Note also that the solar arrays are not yet installed. This is what is on display at the National Air and Space Museum in Washington, D.C. without the shields. You can get a good idea of the solar array units before deployment here: 1, 2, 3. |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-15-2017 08:21 AM
quote:
Originally posted by Jim_Voce:
Fundamental question is why was the micrometeoroid shield designed to cover only half of the station?
It wasn't half of the station or the mid point. Like I said, the rest of the workshop was "behind the forward and aft skirts of the S-IVB stage." The skirts cover and shade the ends of the pressurized living compartment. The workshop cylinder needed it because the stage tank wall would directly be exposed to spaceThe docking adapter had its own shielding and thermal covers. The airlock was protected by the forward skirt and a shroud. quote:
Is it true that the micrometeoroid shield was left exposed at launch?
The micrometeoroid shield was "designed" to be exposed at launch. That is why it had to deploy after launch. It would be infeasible to have a fairing cover the whole station. |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-15-2017 11:34 PM
Jim, have a look at this picture of the station before the sunshade was installed. Does that look like sun damage or micrometeoroid damage? |
oly
Member Posts: 971
From: Perth, Western Australia
Registered: Apr 2015
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posted 02-16-2017 04:59 AM
Remembering that the micrometeorite shield was torn off during launch and this section of spacecraft was exposed to high speed airflow and friction heating, this area looks better than expected. There are areas where the tape has been stripped off with associated frayed edges, evidence that where the tape covers holes in the structure have been distorted by high pressure, areas of blistering from exposure to high temperature. For the size of the area photographed and the resolution of the photo the area near the fingerprint smears is harder to define any detail. Run this image through photo processing software and push the vibrancy, clarity and white balance up and dehaze the image does not reveal anything that resembles impact damage. |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-16-2017 08:26 AM
quote:
Originally posted by Jim_Voce:
Jim, have a look at this picture of the station before the sunshade was installed. Does that look like sun damage or micrometeoroid damage?
Air flow and sun damage. If that were micrometeoroid damage, the shuttle tiles would have lasted like a sugar cube in rain. Spacecraft wouldn't last for more than a few weeks if that were the micrometeoroid flux. |
Fra Mauro
Member Posts: 1624
From: Bethpage, N.Y.
Registered: Jul 2002
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posted 02-17-2017 10:14 AM
I wonder if the shield would have held up for the 3 Skylab missions. |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-17-2017 11:18 AM
Why wouldn't it?
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Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-18-2017 03:10 AM
So my understanding is the gold colored surfacing material that appears on one side of the station (the side that faces the sun) was never meant to be directly exposed to the sun. The micrometeoroid shield would have hidden this gold material completely. And the purpose of this gold material was to add an extra layer of thermal protection underneath the micrometeoroid shield. Is that correct?And it appears that during ascent to orbit, something triggered the deployment of the micrometeoroid shield and when that happened, the shield expanded a few inches beyond the circumference of the launch shroud above it which in turn, created a gap of space that had air flowing through it which at 5,000 miles per hour or more the air velocity finally ripped open the shield at an adjoining point and flung a piece of the shield away from the rocket. Is this correct? |
oly
Member Posts: 971
From: Perth, Western Australia
Registered: Apr 2015
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posted 02-18-2017 05:26 AM
More or less, yes you have it. As the shield was torn away, metal straps were left that wrapped around one solar panel and prevented it from deploying. This caused the station to not generate enough power and also caused higher than expected temperatures inside the station, leading to a rescue mission and some amazing makeshift engineering. |
Mike Dixon
Member Posts: 1428
From: Kew, Victoria, Australia
Registered: May 2003
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posted 02-18-2017 05:55 AM
What we should be amazed at was the ingenuity of turning that situation around and on the ground before the launch in mere days. An incredible effort. Looking back on it now after so so long, I still find it incredible. |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-19-2017 04:46 PM
One more comment about Skylab and its exposed state in orbit.The National Air and Space Museum has the back-up Skylab station displayed upright in the museum. If the gold thermal material on the body of the station was suppose to have been covered by the micrometeoroid shield, then it appears that the museum decided to remove the micrometeoroid from the back-up station as well. So rather than display the Skylab back-up station in is original form, they altered the station so that it approximated what the station was like in orbit. Is this correct? |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-19-2017 06:06 PM
No, it was more likely that the shield was never installed in the first place. |
Jim_Voce
Member Posts: 273
From:
Registered: Jul 2016
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posted 02-22-2017 12:48 AM
If the back-up station was identical to the first station, are you saying the back-up station was never fully assembled? Or was it fully assembled and held in storage? |
Jim Behling
Member Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 02-22-2017 05:45 AM
Never fully assembled. One solar array was not installed. |
Maia12
Member Posts: 11
From: Portugal
Registered: Nov 2015
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posted 03-07-2017 06:48 PM
Are there any pictures of Skylab B before it was donated to the Smithsonian? |
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