Apollo 15 Lunar Surface Journal

Apollo 15 Drilling Problems

Commentary Copyright © 2003 by David Carrier.
All rights reserved.
Last revised 27 August 2013.


As we all know, there were problems with the core drilling and the heat flow probe drilling on Apollo 15. Some of this is also described in my chapter in the Lunar Sourcebook. The cause of the problems were basically the same thing: the designers had assumed the lunar soil was looser than it really was (the lunar soil mechanics team had not been involved in the original design).

What happened on Apollo 15 with the drill core was that the crew pushed too hard and essentially screwed the core into the ground. We have probably all done this with hand drills during wood or metal shop! What they should have done was to take their time and let the drill do the work. The solution for Apollo 16 and 17 was better training and to provide the foot-treadle mechanism that would allow them to extract the core if it got stuck again.

And what happened on Apollo 15 with the fiberglass heat flow probe is that the original design used press-fit joints; the helical "flight" was discontinuous across the joints. This did not matter when the probe was drilled into loose soil: the particles of soil riding up the helix were simply pressed into the surrounding soil. But in dense soil on the Moon, the soil particles had no where to go and bound up the probe so that it could go no farther. Dave Scott reported that it felt to him like the fiberglass probe had actually sheared off. The reason for the selection of this type of joint is that, in order to make precise heat flow measurements, they did not want metal in the probe; they wanted it to be all fiberglass.

In fact, when we had the first meeting after Apollo 15 to discuss the problem with the heat flow probe, we were sitting around a table brainstorming. Marc Langseth (the Heat Flow Principal Investigator) was there - I think it was the first time I met him - and he already knew that the problem was in the joints. Later, a group of us, led by Tony England, flew out to Martin Marietta in Denver. Martin had a bin filled with a reasonable lunar soil simulant that they had used in developing and designing the drill. We had them remove the soil and compact it to a much denser condition. In the first test with the fiberglass heat flow probe, the probe went in to the same approximate depth as had occurred on the Moon -- and sheared off because of the heat and friction. Thereby duplicating the Apollo 15 problem exactly.

So, for Apollo 16 and 17, the heat flow probe joints consisted of titanium inserts, such that the fiberglass sections could be screwed together and the helical flight would remain continuous. A scientific compromise for an engineering necessity.

Well, I had been working with Ray Zedekar's crew training group all along, and they asked me to come to the Cape to help them set up a more accurate simulation for the drilling exercises for the crews. Someone had already inserted a closed-end pipe in the ground. We brought lunar soil simulant and compacted it in the pipe. In order to get the desired density, the soil had to be placed in very thin layers and tamped with a special piece of equipment we devised. It was a very slow process, and we worked into the night - I think we finished at 1:00 am - in order to be ready for the first excercise the next day.

I've included two photos from that next day.

The first photo* shows me kneeling over the simulated lunar soil drilling 'pipe', with Fred Haise at the controls of the drill. One of Ray's people is off to the side; I do not recall his name. Please note my sideburns and general amount and color of hair - which is no longer the case. Note, also, the flared pants and buckled shoes. I have no idea what I was doing! But I think it is a great photo.

The second photo was taken when we were discussing something about the drill exercise. You can see clearly that it is Fred Haise in the spacesuit. That is Roger Koppa, one of Ray's people, in the middle. And that other guy in the background whose name escapes me.


*Editor's Note: AFJ Editor David Woods works for the BBC as a post-production editor and writes "I colour balance TV programmes as part of my duties at the BBC. I just couldn't help myself. The picture had classic yellowing from age and I just knew a truer colour rendition was waiting to come out. So, since I've gone ahead and done it. The result it attached.".

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