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  Thickness of Apollo 11 CM heat shield

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Author Topic:   Thickness of Apollo 11 CM heat shield
jklier
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Posts: 85
From: Austin, Texas
Registered: Aug 2007

posted 01-14-2022 04:36 PM     Click Here to See the Profile for jklier   Click Here to Email jklier     Edit/Delete Message   Reply w/Quote
I just watched an episode of Adam Savage's Tested. He was at the Smithsonian looking over the Apollo 11 command module.

The conservator stated that the Apollo 11 heat shield was thicker because "it was the first one and they didn't know how it would do on re-entry." Apollo 8 and Apollo 10 both came back from the moon and would have had similar re-entry velocities.

I would think she would know better. Am I missing something here or is she just wrong? (The heat shield comment is around 4:05.)

SpaceAholic
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Posts: 4989
From: Sierra Vista, Arizona
Registered: Nov 1999

posted 01-14-2022 08:40 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Umbilical guillotined manually? Sequential Events Control System (SECS) Service Module Jettison Controller (SMJC) initiated pyrotechnics.

David C
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Posts: 1314
From: Lausanne
Registered: Apr 2012

posted 01-15-2022 04:31 AM     Click Here to See the Profile for David C     Edit/Delete Message   Reply w/Quote
She's completely incorrect on all counts. Obviously it wasn't the first. It wasn't thicker, and they were well aware of how it would perform. For interest, Apollo 10 was the fastest manned vehicle (just after Entry Interface). Apollo 4 was the most demanding entry for the thermal protection system.

The Apollo Experience Report is worth a look. Figure 10 shows just how testing Apollo 4 was, and by contrast how "easy" the manned entries were.

Ken Havekotte
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Posts: 3368
From: Merritt Island, Florida, Brevard
Registered: Mar 2001

posted 01-15-2022 05:43 AM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
Apollo 4 with CM-017 did a complete lunar-type simulation return velocity and angle pitch when coming back from Earth orbit. The same also for Apollo 6/CM-020, if I am not mistaken, but it wasn't as successful and fell short of what Apollo 4 had achieved.

When you think about it, it's amazing how AS-501 had worked so well on its maiden flight of a fully rated Saturn V moon-type rocket with all launch support and flight objectives achieved. AS-502 was not so lucky.

Space Cadet Carl
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Posts: 276
From: Lake Orion, MI
Registered: Feb 2006

posted 01-17-2022 01:54 PM     Click Here to See the Profile for Space Cadet Carl   Click Here to Email Space Cadet Carl     Edit/Delete Message   Reply w/Quote
Supposedly all Apollo CMs had the exact same heat shield which varied in thickness from two inches thick in the very center, to one-half inch thickness at it's outer edges. Indeed, Apollo 4 was the most "extreme" reentry and Apollo 10 was the hottest manned reentry.

Robert Pearlman
Editor

Posts: 47717
From: Houston, TX
Registered: Nov 1999

posted 01-17-2022 04:19 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
I touched base with Lisa Young, who appears with Adam Savage in the video.

She acknowledged she misspoke about it being "the first" — she intended to say "one of the first." There was no opportunity for her to ask to go back and revise or correct what she had said.

As for the thickness of Columbia's heat shield, she was speaking from her own experience as a conservator at the National Air and Space Museum. She said she was not sure if the heat shields remained the same thickness throughout the program, but of the spacecraft she has worked on, it seemed to be more refined as the program evolved.

Ken Havekotte
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Posts: 3368
From: Merritt Island, Florida, Brevard
Registered: Mar 2001

posted 01-17-2022 05:02 PM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
To answer the topic question more precisely, but I think David C's posting above had a similar report that I have always been using since the 70's, of the Apollo Command Module (CM) spacecrafts were about the same in their ablator thickness.

The blunt-end side of a CM was between 2.0" to 2.7" in thickness and from 0.70" to 1.5" of thickness on the sides of a CM from top to bottom.

The ablator material used for the Apollo spacecraft program for NASA's thermal protection subsystem was Avco 5026-39G and consisted of an epoxy-novalac resin reinforced with quartz fibers and phenolic microballoons. Now how's that for getting technical (too much for me, huh)?

My records indicate that Apollo 16 did achieve the highest entry velocity (relative feet/second) at 35,502 with Apollo 11 not too far away at 35,024. But Apollo 10 did have the steepest inertial entry angle at -6542 degrees with the hottest temperature rating.

SpaceAholic
Member

Posts: 4989
From: Sierra Vista, Arizona
Registered: Nov 1999

posted 01-17-2022 05:18 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Block I's had thicker ablator (addition of the BPC on the Block II's allowed the thickness to be reduced).

David C
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Posts: 1314
From: Lausanne
Registered: Apr 2012

posted 01-17-2022 05:41 PM     Click Here to See the Profile for David C     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Ken Havekotte:
My records indicate that Apollo 16 did achieve the highest entry velocity (relative feet/second) at 35,502 with Apollo 11 not too far away at 35,024. But Apollo 10 did have the steepest inertial entry angle at -6542 degrees.

I think it does depend where you look as to what numbers you get. Table III of the previously quoted Apollo Experience Report agrees with you. However, other sources all line up with “Apollo by the Numbers” Table 57 which puts Apollo 10 in first place. Now I don’t much care for using “Forever Young” as a reference, but it’s pertinent in this case as John Young was on both Apollo 10 and 16 so should have known. He does quote the Apollo 10 inertial speed as “the fastest entry of any Apollo spacecraft”.

On the subject of Lisa Young’s remarks, really she has to back them up with a reference not a subjective remark. If the Block II heatshield thicknesses really did vary, where was this accommodated? Did the BPC thicknesses vary? Did the gap between the pressure shell and heatshield vary? Did the entire shape and hence L/D vary? I mean, just what is she suggesting here?

Robert Pearlman
Editor

Posts: 47717
From: Houston, TX
Registered: Nov 1999

posted 01-17-2022 06:01 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Lisa is a conservator; her responsibility is to understand the materials and overall structure of the artifacts in the National Air and Space Museum's collection. Her research includes the original processes and manufacturing techniques, but not necessarily the decisions that went into those practices.

The types of questions you are asking are more appropriately directed to a curator or historian, who would use the data collected by Lisa and her fellow conservators to then connect them with the history of the program.

Lisa was sharing her experience working hands on with the spacecraft, making exact measurements in the pursuit of preserving them and tracking changes to their materials over stretches of time. If what she has found doesn't match the published record, that is a reason for further research by others.

David C
Member

Posts: 1314
From: Lausanne
Registered: Apr 2012

posted 01-17-2022 06:21 PM     Click Here to See the Profile for David C     Edit/Delete Message   Reply w/Quote
OK. They were hand made spacecraft, so I can correlate her “more refined” comment, with the workers just getting more practiced at their techniques. That’s quite different from her earlier remarks.

oly
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Posts: 1332
From: Perth, Western Australia
Registered: Apr 2015

posted 01-17-2022 07:52 PM     Click Here to See the Profile for oly   Click Here to Email oly     Edit/Delete Message   Reply w/Quote
Perhaps some perspective should be considered. The Adam Savage's Tested episode appears to be a casual chat between objects conservator Lisa Young and Adam as she takes Adam through some of the work her team is doing on this historic artifact at the National Air and Space Museum's Mary Baker Engen Restoration Hangar.

Adams's opportunity to view the Columbia Apollo 11 command module up close as conservator Lisa Young differentiates between the pre-flight and post-flight marks on the exterior appears to be an unscripted general interest piece directed at the mass audience, not an article directed towards people who thrive on the intricate detail.

The access Adam gets to the behind-the-scenes workings of the Air and Space Museum is great. They provide some insight into the preservation of artifacts and allow us to see views of things that we can't get access to ourselves.

If people criticize the information provided, there may be a good chance that the conservators and curators will balk at doing more unscripted access pieces.

Information about the Apollo CM heat shield is available and easy to find for anyone interested to know more, which this kind of behind-the-scenes articles are great at generating interest in.

All times are CT (US)

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