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Author
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Topic: Welding techniques during Apollo program
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Buel
Member Posts: 664
From: UK
Registered: Mar 2012
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posted 05-03-2020 01:21 PM
   
Can anyone shed any light on any aspects of welding during the manufacturing of hardware used in Apollo, other than this document?Don Arabian mentioned that he thought he remembered that hydrogen embrittlement played a part in the parachutes failing during the Apollo 15 descent to Earth. This can be a fault inherent in the welding process so wanted to read more about welding in Apollo. |
Colokent
Member Posts: 12
From: Colorado Springs, CO USA
Registered: Jun 2013
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posted 05-03-2020 01:54 PM
My understanding about Apollo 15's chute failure is from Al Worden, the Apollo 15 command module pilot. During descent under the mains, there was no wind, and when the hypergolics were vented before splashdown, they rose and concentrated in the chutes. This burnt completely through one, and according to Worden, very nearly burnt through another before touchdown. |
Buel
Member Posts: 664
From: UK
Registered: Mar 2012
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posted 05-03-2020 02:14 PM
Thinking about it, he may have been talking about an issue in testing. I’ll check.Edit; in "Memories of the Apollo and Space Shuttle Programs" by Lawrence Korb, there's a chapter titled "Hydrogen Embrittlement of a Parachute Fitting." It was probably this he referenced. |
Headshot
Member Posts: 904
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 05-03-2020 03:45 PM
No details, but there is a fascinating image of a Grumman technician using a fusion welder on some of the RCS tubing in the descent stage of a lunar module. It is shown on page 49 of "Building Moonships: The Grumman Lunar Module" by Joshua Stoff (Image of America series). Talking about cramped working space! |
SpaceAholic
Member Posts: 4522
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 05-03-2020 03:52 PM
Are you certain it was the descent stage? RCS system including its propellant and pressurization supply were integral to the ascent stage. If it was the descent stage, it's likely the photo instead was showing work on the DPS. |
Buel
Member Posts: 664
From: UK
Registered: Mar 2012
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posted 05-03-2020 05:22 PM
Fascinating!Could one of you possibly post the image? I suspect the welding technique was fusion (no filler wire) but the process/hardware was TIG welding. |
oly
Member Posts: 1016
From: Perth, Western Australia
Registered: Apr 2015
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posted 05-03-2020 05:52 PM
There is a high possibility that the hydrogen embrittlement issue came from a cadmium plating process used as a corrosion prevention treatment in aerospace. Cadmium plating hydrogen embrittlement is a well known problem that is treated by a post plating heat treatment process. |
Buel
Member Posts: 664
From: UK
Registered: Mar 2012
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posted 05-03-2020 06:09 PM
Yes, I think I read that it was because the post treatment duration was reduced quite a lot. |
oly
Member Posts: 1016
From: Perth, Western Australia
Registered: Apr 2015
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posted 05-03-2020 06:43 PM
There may be some information on the welding techniques used in the Moon Machines series episode on the Saturn V. Many of the automatic weld machines had to be modified to suit welding thin materials, and the cryogenic fuel tank bulkheads used material that tapered in thickness requiring a change in amperage as the machine progressed. |
Headshot
Member Posts: 904
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 05-03-2020 10:48 PM
Yes, I am going to guess that the welding picture caption I mentioned earlier is in error. It looks a lot like a descent stage from the structure that can be seen, so I will surmise that it is not the RCS plumbing that is being repaired, but there seems to be a LOT of wiring and plumbing.I cannot post the picture as the book is copyrighted. It is a very worthwhile book to purchase. |
oly
Member Posts: 1016
From: Perth, Western Australia
Registered: Apr 2015
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posted 05-04-2020 02:48 AM
This episode of the Moon Machines documentary covers some welding techniques and issues Some film of the welding process for the cryogenic fuel tank bulkhead can be found here. And an interesting Astronomy.com article on Hap Brennecke can be found here. |
Space Cadet Carl
Member Posts: 231
From: Lake Orion, Michigan
Registered: Feb 2006
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posted 05-04-2020 10:16 AM
quote:
Originally posted by Colokent:
This burnt completely through one, and according to Worden, very nearly burnt through another before touchdown.
I'm getting off topic about welding, but that parachute situation was a huge disaster in the making. Was anything done on Apollo 16 through ASTP to avoid this again? |
oly
Member Posts: 1016
From: Perth, Western Australia
Registered: Apr 2015
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posted 05-04-2020 11:09 AM
From the Apollo 15 mission's Anomaly Report No. 1: Corrective actions for the reaction control system include landing with the propellants onboard for a normal landing and biasing the propellant load to provide a slight excess of oxidizer. Thus, for the low altitude abort land landing case, burning the propellants while on the parachutes will subject the parachutes to some acceptable oxidizer damage but will eliminate the dangerous burning fuel condition. In addition, the time delay which inhibits the rapid propellant dump is being changed from 42 to 61 seconds. This will provide more assurance that the propellant will not have to be burned through the reaction control system engines in the event of a land landing. The design of the suspension line connector links has been modified. to preclude the development of high stress levels due to torque levels and to reduce the uncertainty of loads due to tolerance buildup. The link material has been changed to Inconel 718 to eliminate the requirement for plating and, therefore, the possibility of hydrogen embrittlement. In addition, the link stud threads are rolled rather than machined to improve metallurgical properties of the material, and the studs are subjected to a proof test designed to screen flaws which could subsequently propagate under salt water exposure. |
Buel
Member Posts: 664
From: UK
Registered: Mar 2012
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posted 05-04-2020 04:23 PM
quote:
Originally posted by oly:
Some film of the welding process for the cryogenic fuel tank bulkhead...
The MSFC manufacturing link you posted is truly amazing. It's the first time I’ve seen a real indication in to the incredible manufacturing that went on behind the scenes. |
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