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  Apollo A7L spacesuit zippers and pressure tests

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Author Topic:   Apollo A7L spacesuit zippers and pressure tests
oly
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Posts: 19
From: Perth, Western Australia
Registered: Apr 2015

posted 05-12-2015 08:05 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
While there is no doubt the Apollo A7L spacesuit is an impressive engineering feat and a keg piece of hardware that protected astronauts from the harsh environment of space I am amazed about the fact that two special zippers kept the pressurised air within the suits and that Velcro was used to protect these zippers.

Is anyone aware of any additional information on the engineering of these items and what testing, failures and failure rates were experienced during the development of these suits and if this information is available online somewhere?

SpaceAholic
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From: Sierra Vista, Arizona
Registered: Nov 1999

posted 05-12-2015 11:13 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
By my count 3 zips associated with the suit's pressure vessel.

Apolloman
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From: Ledignan, Gard (30), France
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posted 05-15-2015 06:18 AM     Click Here to See the Profile for Apolloman   Click Here to Email Apolloman     Edit/Delete Message   Reply w/Quote
Really, are you sure?

For A7L suit: One zipper (red strap) on the pressure layer and one zipper (blue strap) on the restraint layer (TLSA)

On ITMG: A protection (shutter) with a Velcro (Velcro) and snaps for fastening, opening the rear base of the neck to the crotch, and ending with a small zip from the crotch to the pubis protects the zipper of TSLA.

For A7LB suit (Apollo 15/17): Three zip, but — two zip are located on the restraint layer of the suit and are the only visible.

A third zip fastener, clicking this time over the entire length of the cover opening and located under the two preceding ones, which ensures the confinement of oxygen.

(Thank to Bill Ayrey for the picture.)

SpaceAholic
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From: Sierra Vista, Arizona
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posted 05-15-2015 07:56 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Yep... pretty sure for the pressure (TLSA) layer there are 3 zippers required to maintain pressure integrity.

Apolloman
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Posts: 109
From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 05-15-2015 08:15 AM     Click Here to See the Profile for Apolloman   Click Here to Email Apolloman     Edit/Delete Message   Reply w/Quote
Please, have you a photo you would show a diagram that it? Because the pictures that I have in my possession, I can not know where this third would zip!

Example with A7L-B suit.

oly
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From: Perth, Western Australia
Registered: Apr 2015

posted 05-15-2015 08:26 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
This is very interesting detail. Thank you for posting these photos. What air leakage rate and suit pressure would these withstand?

SpaceAholic
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From: Sierra Vista, Arizona
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posted 05-15-2015 08:51 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Only one of the zippers on the upper portion of the TLSA are PRIMARILY responsible for maintaining pressure integrity. The other two zipper closures performing that function are on each of these

oly
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From: Perth, Western Australia
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posted 05-15-2015 09:18 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
Ok, I am at a loss to understand how the suit could maintain pressure integrity relying on these zippers, the pressure garment zipper must be of a unique design and suit pressure must be relatively low to be able to maintain pressure.

Apolloman
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Posts: 109
From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 05-15-2015 10:58 AM     Click Here to See the Profile for Apolloman   Click Here to Email Apolloman     Edit/Delete Message   Reply w/Quote
Ah YES, of course, the boot. I'm dumb.

Ok, so it makes us 6 zip for A7L: 2 for TLSA (1 pressure and 1 restraint) and 2 every boot 1 pressure and 1 restraint). And 7 zip for A7LB: 3 TLSA (1 pressure and 2 restraint) and 2 every boot (1 pressure and 1 restraint).

Thank SpaceAholic for the memory.

The pressure inside the suit is equivalent to only 1/3 of the earth's pressure (that found at sea level, 1013.25 hPa). The residual leakage does not exceed 0.0315 lb/hr.

Apollo 12 during flight: Before the first EVA, once closed and pressurized the spacesuit of Peter Conrad developed a leakage rate of 0.15 psi/minute and reached 0.25 psi/minute after the second EVA. Since the safety limit was set at 0.30 psi/minute, it would have been dangerous than a third EVA can be performed if it had been scheduled.

Kocmoc
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From: Washington, DC USA
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posted 05-20-2015 02:40 PM     Click Here to See the Profile for Kocmoc   Click Here to Email Kocmoc     Edit/Delete Message   Reply w/Quote
Here is the link to the BFG zipper.

The suits were built with the assumption of leakage, but all passed post-flight testing. I have to dig up the documents, but there was a published record of that.

------------------
Cathleen S. Lewis

DG27
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From: USA
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posted 05-24-2015 06:52 AM     Click Here to See the Profile for DG27     Edit/Delete Message   Reply w/Quote
The original post was inquiring about the special pressure sealing zippers. Both the A7L and A7LB suits only used one pressure sealing zipper.

As a point of clarification, the Apollo suits (A7L and A7LB) did not have pressure sealing zippers at the boots. The zippers seen in the boot photos of earlier posts are regular non-sealing zippers in the restraint layer and in the inner comfort layer. The boot bladder was glued to the leg bladder and was not detachable. The A7L boots used loop tape and lacing cord to secure the boot restraint layer to the leg restraint layer. This was later changed to a zipper in the A7LB suit. Loop tape takes some time to lace up so zippers are a lot quicker for suit assembly. No pressure sealing zippers were needed or used at the boots.

The A7L spacesuit had one BF Goodrich pressure sealing zipper which ran down the back of the suit and thru the crotch up to the lower abdomen. A separate regular heavy duty zipper was used over the pressure sealing zipper to help carry the pressure induced loads on the sealing zipper but was not part of the pressure sealing zipper. (On earlier suits, Mercury did not use the additional mechanical zipper over the pressure sealing zipper but the Gemini suit did).

The A7LB suit used only one pressure sealing zipper as well. The pressure sealing zipper was a BDM/YKK type sealing zipper instead of a BF Goodrich sealing zipper. The pressure sealing zipper ran diagonally the front of the suit and wrapped around the rear of the suit at the waist line. The BDM/YKK style sealing zippers are more flexible and due to their design can seal better when the zipper is bent in a tight radius. The pressure bladder was not secured to the restraint layer around the zipper opening. This allowed the pressure zipper to roll over on its side to make the bend between the straight diagonal run down the front of the suit to the horizontal run around the back of the suit. (See the link to the A7LB picture in Apolloman's earlier post). When closed, the pull tab on the pressure sealing zipper was at the wearers left side at the waist and completely hidden by the restraint zipper. Two regular zippers are used in the restraint layer over the pressure sealing zipper. One regular zipper ran diagonally down the front of the suit to the waist and a second regular zipper ran around most of the circumference of the waist. The two regular zippers met at a rather complicated latching mechanism that locked the ends of the zipper pull tabs together.

The use of other zippers and Velcro on the ITMG were unrelated to the pressure sealing of the suit. The ITMG provided thermal and ballistic protection to the pressure suit. The regular zippers and Velcro used on the ITMG was for securing and the ITMG to the suit and access to pockets, etc.

As mentioned in the first post to this thread, the pressure sealing zipper is a unique item. The sealing zipper was first invented by the BF Goodrich Company in the 1940's for aircraft aileron gap seals, weather seals, pressure duct seals, and exposure suits. The earliest patent I have for the Goodrich sealing zipper, US2385816, was awarded Oct 2 1945 (filed March 4 1943). Over the years the design modified somewhat as indicated by the later patent referenced in Cathy in her previous post, and other patents were granted after that. But the basic principal remained the same of two wedge shaped lips forced together by the action of the zipper teeth locking together. The tricky part was sealing the end of the zipper where the pull tab ended up when the zipper was closed, and they came up with a clever design that used the inner surfaces of two flanges on the inner and outer surfaces of the slider pull tab to compress the rubber around the opening of the zipper.

Wayne Galloway who worked with Russell Colley at BFG told me many years ago that the zippers used in the pressure suits were the heaviest of their line of zippers. Lighter weight ones were used on the exposure suits and aircraft components. BFG pressure sealing zippers were used in their line of high altitude pressure suits and and most soft spacesuits up through Apollo. Unfortunately BFG no longer makes the zippers, and no longer exists as a company. BF Goodrich lives on in name only thru tires made by the Michelin Co.

Current pressure suits use the BDM/YKK (New Zipper Co) style familiar to most as being used on scuba diving dry suits (and as used on the A7LB). The sealing mechanism of the BDM/YKK zipper is different than the BFG design and entails using a different type of zipper teeth to force together two up-turned edges of the rubber seal. The BFG pressure sealing zipper had a very low profile which was beneficial for sitting or laying on it. Whereas the YKK style zipper has a rather thick zipper section which sticks out from the suit fabric and is less comfortable to lie on.

One last bit of trivia: The name "zipper" was coined by BFG when they came out with their line of rubber boots in 1923 that used the "separable fastener" as the zipper was called at the time. They wanted a name that implied fast action for putting the boots on and came up with "zipper" for the fastener.

Hope this helps.

SpaceAholic
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From: Sierra Vista, Arizona
Registered: Nov 1999

posted 05-24-2015 09:59 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Thanks for the education ...I learned something!

oly
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Posts: 19
From: Perth, Western Australia
Registered: Apr 2015

posted 05-25-2015 05:22 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
Thank you all who have responded to my post, your information has helped me understand this subject and has assisted me researching this subject further. By sharing this information and helping each other satisfy these curiosities the efforts of the whole Gemini, Mercury and Apollo programs helps to keep them alive.

The information held within the cS universe will prove to be a great reference to future curious space nuts. This is one of the subjects that I have been curious about for years and hoped that my visit to the U.S. last month may have given me a chance to learn more about, in my travels I did not find any suits that were displayed to give an insight into this. All the suits on displayed are presented "zipped" up.

I have also got a better insight into how the astronauts functioned with such low pressure within the suit.

The deepest impression left on me after my visit was how brave these people were to undertake these missions. The fact NASA has disclosed so much information is fantastic and I hope that the private companies taking the reigns in spaceflight someday release similar information when it is no longer commercial in confidence information.

Apolloman
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From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 05-25-2015 05:31 AM     Click Here to See the Profile for Apolloman   Click Here to Email Apolloman     Edit/Delete Message   Reply w/Quote
If I understand correctly (sorry I'm french), the boot is presented by SpaceAholic none other than protection like a sock, bladder being bonded to the rest as for the Mercury spacesuit.

Where I lost the respect to the inner comfort layer... it should not be closer to the astronaut and therefore have the bladder on top of her and not inwards? Does it not help to put more correctly bladder? I'm lost...

oly
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Posts: 19
From: Perth, Western Australia
Registered: Apr 2015

posted 05-25-2015 06:42 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
From my understanding, the Mercury suit was manufactured with the foot as part of the suit, acting as a bladder with the astronaut contained within the bladder. The boots were relatively standard boots, fitted to contain the bladder inside. When laced up the boot acted to restrain the lower part of the suit from ballooning out, without the boot the suit would extend and balloon out about the foot and its volume would expand. The astronaut wears a harness, similar to a parachute harness, to retain the suit volume.

The Mercury gloves used a strap about the palm of the hand to also prevent the glove from ballooning about the hand.

Later suits were improvements upon these designs. There were problems with the Gemini suit ballooning during EVA causing problems with astronauts returning to the seat and closing the hatch. The Apollo suit improved on this further. I do not have photographs of these but perhaps someone else can elaborate on this further.

DG27
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From: USA
Registered: Nov 2010

posted 05-25-2015 08:09 AM     Click Here to See the Profile for DG27     Edit/Delete Message   Reply w/Quote
Here is a photo of the Apollo A7L boot parts. The inner most part is the comfort liner on the left side of the photo. This provides a smooth surface on the inside of the suit for the astronaut. It also holds the ventilation ducting that provides oxygen circulation in the suit.

The rubber boot bladder is shown in the center of the photo and goes over the comfort liner. This is the part off the boot that holds the pressure. This part is similar in function to the foot bladder you highlighted in the image of the Mercury suit in your posting.

The blue fabric boot on the right side of the photo goes over the rubber foot and is the restraint boot which keeps the rubber bladder from ballooning when pressurized. The restraint layer of the suit is what gives the suit its shape and contains the mobility elements that enable the suit to move. You can see the convolutes and the restraint cable with ferrules that make up the ankle mobility joint.

What is not shown is the ITMG layer that goes over the restraint boot. It is attached with lacing cord through the loop tape that runs around the edge of the boot were the boot is attached to the boot sole.

Hope this helps.

Apolloman
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From: Ledignan, Gard (30), France
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posted 05-25-2015 08:51 AM     Click Here to See the Profile for Apolloman   Click Here to Email Apolloman     Edit/Delete Message   Reply w/Quote
Please, have you an HD picture? If I understand well in order from the inside to the outside we:
  1. white liner (comfort layer) between the comfort layer and the pressure layer (black) the vent hose system

  2. Pressure sock (black) thus bonded to the remainder of the bladder pressure TLSA or of my question of how astronauts could get their comfort layer since it was supposed to be in the bladder and the latter more (comfort layer was fitted with a zipper)

    Unless the pressure sock (black) no glue or off on demand (on schema: neoprene adhesive and neoprene strap) a bit like Velcro.

  3. the retaining layer (blue) which covers the whole

DG27
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From: USA
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posted 05-25-2015 03:48 PM     Click Here to See the Profile for DG27     Edit/Delete Message   Reply w/Quote
I can email you a HD picture. Yes you have the assembly order correct.

The vent duct ends into a vent pad on the bottom of the foot liner (white fabric). This is all sewn together as one unit.

The pressure sock (black rubber) is lined on the inside with a soft white fabric which is bonded to the rubber during the manufacturing of the pressure sock. This is what is referred to as the scuff layer in the boot assembly diagram in your post. It helps prevent damage to the inside of the rubber pressure sock similar to flocking in a rubber glove.

The foot liner with foot vent pad is tack glued in three places to the inside of the pressure sock to hold it in place. (The rest of the suit liner is held in place by velcro to the inside of the TLSA pressure bladder.)

The black pressure sock has a layer of velcro on the bottom of the foot which holds the pressure sock in the blue restraint boot.

oly
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From: Perth, Western Australia
Registered: Apr 2015

posted 05-30-2015 05:28 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
The latest space history photo of the week is an excellent display of the suit pressure bladder and boots as discussed above.

bflmpsvz
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From: Czech Republic
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posted 06-25-2015 04:55 AM     Click Here to See the Profile for bflmpsvz     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by DG27:
The tricky part was sealing the end of the zipper where the pull tab ended up when the zipper was closed, and they came up with a clever design that used the inner surfaces of two flanges on the inner and outer surfaces of the slider pull tab to compress the rubber around the opening of the zipper.
That's what I would like to understand. I cannot imagine how this was done. (Except if the inner zipper was closed from inside. )

quote:
Current pressure suits use the BDM/YKK (New Zipper Co) style familiar to most as being used on scuba diving dry suits (and as used on the A7LB). The sealing mechanism of the BDM/YKK zipper is different than the BFG design and entails using a different type of zipper teeth to force together two up-turned edges of the rubber seal.
I do not understand how this zipper works. If I had one in my hands, I would probably found how the hell does this thing work, but I haven't. Is there any picture which would show how the zipper teeth lock together?

oly
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From: Perth, Western Australia
Registered: Apr 2015

posted 06-25-2015 05:28 AM     Click Here to See the Profile for oly     Edit/Delete Message   Reply w/Quote
NASA Johnson Space Center Oral History Project has an interview with Larry E. Bell.

This provides some detail of the history of the zippers and also about the doubts regarding these. I still find it fascinating that the Apollo exploration relied on these.
I guess this was a factor being addressed here regarding the cancellation of Apollo 18 at the moment.

DG27
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From: USA
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posted 06-26-2015 02:11 AM     Click Here to See the Profile for DG27     Edit/Delete Message   Reply w/Quote
The zipper teeth on the BDM (YKK) zippers are the small rectangular tabs you see on the inside edge of the zipper. They don't stick out much and are almost flush with the rubber surface.

The flat curved metallic bands on the outside of the zipper clamp the zipper teeth in a fold of the zipper rubber that runs the length of the zipper. The interlocking teeth are rectangular shaped "knobs" or "hammer heads" that are guided to interlock with the teeth from the opposite side by the slider as it pulls the zipper halves together.

As the zipper slider is pulled it brings together each side of the zipper rubber which is the up-turned edge of the flat zipper rubber. The pressure seal is between the faces of the up-turned zipper rubber which are pressed together by the interlocking of the zipper teeth. This is why the closed zipper has a high ridge running down the middle when the zipper is closed.

Hope this helps.

bflmpsvz
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From: Czech Republic
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posted 06-29-2015 09:11 AM     Click Here to See the Profile for bflmpsvz     Edit/Delete Message   Reply w/Quote
Thanks a lot! The drawing is essential.

And what about the BF Goodrich zipper end, how the pull tab was sealed, could you make some drawing of it?

All times are CT (US)

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