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  Mercury - Gemini - Apollo
  Mercury spacecraft exterior corrugated plates

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Author Topic:   Mercury spacecraft exterior corrugated plates
ColinBurgess
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Posts: 1917
From: Sydney, Australia
Registered: Sep 2003

posted 05-09-2004 06:27 PM     Click Here to See the Profile for ColinBurgess   Click Here to Email ColinBurgess     Edit/Delete Message   Reply w/Quote
I was looking at a model of a Mercury spacecraft today and I wondered (as I have in the past) why the exterior cladding was made up of corrugated plates?

I'm sure there's a very fundamental answer, but all other spacecraft and aerospace research vehicles have had smooth surfaces, and corrugated shingles just do not seem to go hand in hand with aerodynamic or even ballistic principles. Anyone know?

micropooz
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Posts: 1422
From: Washington, DC, USA
Registered: Apr 2003

posted 05-09-2004 10:14 PM     Click Here to See the Profile for micropooz   Click Here to Email micropooz     Edit/Delete Message   Reply w/Quote
The exterior shingles on Mercury and Gemini were corrugated to help strengthen them. The shingles were in direct contact with the re-entry heated air, so buckling was a concern. By the time Apollo came around, it was made of a honeycomb material (similar principle for strength) and covered with ablative heat shielding. The shuttle is similar, only covered with tile.

Surface drag produced by the corrugations was not that crucial for Mercury and Gemini - they spent only a short time at low speed going uphill through the atmosphere, and coming back the surface drag was negligible compared to that produced by the blunt heat shield. Aircraft and lifting re-entry vehicles (like shuttle and X-15) can't tolerate large surface drag, so they are more streamlined.

hinkler
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Posts: 541
From: Melbourne, Victoria, AUSTRALIA
Registered: Jan 2000

posted 05-10-2004 02:19 AM     Click Here to See the Profile for hinkler   Click Here to Email hinkler     Edit/Delete Message   Reply w/Quote
The SR 71 Blackbird has a similar finish in different areas to allow for the expansion and contraction of the aircraft.

ColinBurgess
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Posts: 1917
From: Sydney, Australia
Registered: Sep 2003

posted 05-10-2004 04:53 AM     Click Here to See the Profile for ColinBurgess   Click Here to Email ColinBurgess     Edit/Delete Message   Reply w/Quote
Many thanks gentlemen, and especially our engineer friend, micropooz. Nicely explained.

KC Stoever
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Posts: 1011
From: Denver, CO USA
Registered: Oct 2002

posted 05-10-2004 11:40 AM     Click Here to See the Profile for KC Stoever   Click Here to Email KC Stoever     Edit/Delete Message   Reply w/Quote
Wouldn't the corrugated skin of the Mercury capsule also make sense given Harvey Allen's theory of a blunt-end high-drag reentry vehicle — the theory adopted so enthusiastically by Max Faget?

There's also this from "This New Ocean" (chapter 7), which suggests that the idea of shingling appears to have developed rather organically at McDonnell, which had experience with shingling, materials technology, 3000-degree heat, and jet afterburners:

By July 1959, [William] Dubusker, the tooling superintendent, had completed McDonnell's first surgically clean 'white room' for the later manufacturing phases, had taken on the job of manufacturing manager for Mercury, [193] and had moved some 200 workmen onto the new production lines. Learning to fusion-weld titanium .010-inch thin in an encapsulated argon atmosphere was his first challenge and proudest accomplishment. But before the year was over, Dubusker had to contend with retooling for other unusual materials, with rising requirements for cleanliness, with stricter demands for machined tolerances, and with higher standards for quality control.

[Edward M.] Flesh, the engineering manager, and Dubusker drew on all of McDonnell's experience with shingled-skin structures around jet afterburners for heat protection. Their machinists had previously worked with the patented metal, René 41, a nickel-base steel alloy purchasable only from General Electric, but arc-jet tests of the afterbody shingles on the outer shell of the capsule showed a need for some ingenious new fabricating techniques.

These men perfected the required fabricating techniques at McDonnell.

The endnote appended to this text cites an Aviation Week article: "For a more detailed description of fabricating technique and fusion welding, see David S. Anderton, 'How Mercury Capsule Design Evolved,' Aviation Week, LXXIV (May 22, 1961)."

micropooz
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Posts: 1422
From: Washington, DC, USA
Registered: Apr 2003

posted 05-10-2004 03:45 PM     Click Here to See the Profile for micropooz   Click Here to Email micropooz     Edit/Delete Message   Reply w/Quote
Holy cow, Kris!! And I thought I had done some in-depth research on the question. Thanks for digging deeper.

KC Stoever
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Posts: 1011
From: Denver, CO USA
Registered: Oct 2002

posted 05-10-2004 04:09 PM     Click Here to See the Profile for KC Stoever   Click Here to Email KC Stoever     Edit/Delete Message   Reply w/Quote
Thanks! I'm always stunned at the detail I find in "This New Ocean." And the writing is brilliant.

ColinBurgess
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Posts: 1917
From: Sydney, Australia
Registered: Sep 2003

posted 05-10-2004 06:37 PM     Click Here to See the Profile for ColinBurgess   Click Here to Email ColinBurgess     Edit/Delete Message   Reply w/Quote
Added thanks to you too, Kris. As always, you've come up trumps.

spaceuk
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Posts: 2113
From: Staffs, UK
Registered: Aug 2002

posted 05-12-2004 11:30 AM     Click Here to See the Profile for spaceuk     Edit/Delete Message   Reply w/Quote
For those who wondered what René 41 is, it is composed of:
  • 19% chromium
  • 11% cobalt
  • 9.75% molybdenum
  • 3.15% titanium
  • 1.6% aluminium
  • 0.09% carbon
  • 0.005% boron
  • and under 2.75% iron
Lovely exotic metal!

Aztecdoug
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Posts: 1379
From: Huntington Beach
Registered: Feb 2000

posted 05-12-2004 05:05 PM     Click Here to See the Profile for Aztecdoug   Click Here to Email Aztecdoug     Edit/Delete Message   Reply w/Quote
That all adds up to 47.345%... is there something missing?

spaceheaded
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Posts: 128
From: MD
Registered: Feb 2003

posted 05-12-2004 06:15 PM     Click Here to See the Profile for spaceheaded     Edit/Delete Message   Reply w/Quote
That would be the secret ingredient: Nickel.

DFBrunswick
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Posts: 40
From: California, USA
Registered: May 2015

posted 06-10-2017 04:34 PM     Click Here to See the Profile for DFBrunswick   Click Here to Email DFBrunswick     Edit/Delete Message   Reply w/Quote
The Mercury spacecraft had a series of linear indentations on its surface. I believe the engineers referred to the spacecraft as having a shingled surface. Does anyone know what the shingles were for?

Did this some how dissipate heat on the surface of the spacecraft during reentry? If so, how did the shingles make this happen?

Editor's note: Threads merged.

Spacepsycho
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Posts: 781
From: Huntington Beach, Calif.
Registered: Aug 2004

posted 07-11-2017 04:31 PM     Click Here to See the Profile for Spacepsycho   Click Here to Email Spacepsycho     Edit/Delete Message   Reply w/Quote
If anyone is interested, I have an exact copy of a Mercury shingle, that was molded off of a shingle removed from a flown spacecraft.

If you send me an email I'll try to find it in storage and send pics.

moonguyron
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Posts: 165
From: Salado, Texas, USA
Registered: Jan 2011

posted 07-15-2017 01:49 PM     Click Here to See the Profile for moonguyron   Click Here to Email moonguyron     Edit/Delete Message   Reply w/Quote
It is probably difficult at this late date to define who actually originated the idea of corrugations as an answer to heating problems. In the book "Lockheed A-12" by Crickmore, it mentions corrugations as an answer to warping of titanium panels when heated. Design of the Mercury spacecraft and the A-12 (later the SR-71) both took place in the late 50s. It is very conceivable that technical information circulating among engineers and companies at the time influenced one another. Here is a quote from the A-12 book.
One test undertaken studied thermal effects on sheets of large titanium... When a 4ft X 6ft element was heated... it resulted in the sample warping into a totally unacceptable shape. This problem was resolved by manufacturing chordwise corrugations into the wing outer skins. At the design heat rate the corrugations merely deepened by a few thousandths of an inch and on cooling returned to their original shape.
Kelly Johnson was quoted as saying "The concept worked fine."

So corrugations became the accepted answer to prevent warping of thin outer aircraft or spacecraft panels. Lay the answer at the feet of Kelly Johnson and his team of thermodynamicists at the "Skunk Works" or Max Faget and his team at NASA. Take your pick.

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