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Author
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Topic: Apollo lunar module surface sensing probes
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NJ CO
Member Posts: 23
From: Greenwich, NJ, US
Registered: Mar 2008
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posted 09-01-2014 06:08 PM
  
Regarding the Apollo lunar module landing probes, I'm sure we're all aware that a switch triggered the contact light once the probe struck the lunar surface.But photos show that the probes actually dug into the surface and some photos show that they even stuck up a bit. Nowadays, I'm sure we'd use a rope-like probe that simply coils and/or lays right under or near a foot pad... My question is: The landing probes appear to be rigid and tubular in make-up. If the probes are as mentioned, and a bit longer than say a rake handle, how is it that the lunar module was not affected, meaning tilted to one side or another? If the LM came straight down, how could three probes (as in Apollo 11) not get in the way? Not the most technical in the way of posting, but just one of those things I've wondered and not really found the answer, although I'm sure I will here. |
space1
Member Posts: 915
From: Danville, Ohio
Registered: Dec 2002
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posted 09-01-2014 06:48 PM
The probes were relatively fragile aluminum tubes that would be like toothpicks with the "heavy" Lunar Module above them. As far as I know they had no measurable effect on landing dynamics.I'm not so sure we would do it so differently today. The kind of rope-like probe you describe would not be rigid enough. You need to know exactly where the sensor is relative to the landing pad. We might prefer something that would retract while making contact, but the Apollo Lunar Module lunar surface sensing probe was a good lightweight solution at 2.52 pounds. |
schnappsicle
Member Posts: 409
From: Houston, TX, USA
Registered: Jan 2012
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posted 09-03-2014 05:25 AM
quote:
Originally posted by NJ CO:
But photos show that the probes actually dug into the surface and some photos show that they even stuck up a bit.
You bring up an interesting point. I've also wondered why some stick up (as in the Apollo 12 plus-Y probe) while the Apollo 11 plus-Y probe lays flat. If I had to guess, it probably has something to do with Buzz's comment just before landing that they were "drifting forward." Also, Armstrong landed with the engine still running while Conrad cut off the engine as soon as the contact light came on. In other words, Eagle had a relatively gentler landing than Intrepid. Also Eagle landed in a relatively flat area, while Intrepid landed on a very slight slope. Lastly, Conrad stated that the plus-Y probe hit the ground first and tilted Intrepid to Conrad's left before settling down to the surface. All that may have contributed to Intrepid's plus-Y probe sticking up in a dangerous position. I agree, something probably should be done to the probes with regard to future landings. It might be that they snap off at the footpads or something. Whenever I look at the photos Bean took of Intrepid's probes after landing, I'm amazed one of the astronauts didn't run into one of them and puncture his suit. |
Lou Chinal
Member Posts: 1374
From: Staten Island, NY
Registered: Jun 2007
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posted 09-03-2014 09:45 AM
That was discussed. Unfortunately the design was already frozen. The Apollo 9 LM Spider had four probes. By the time Apollo 11 flew the one on the front landing strut had been removed for that very reason. |
NJ CO
Member Posts: 23
From: Greenwich, NJ, US
Registered: Mar 2008
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posted 09-03-2014 04:00 PM
Thanks for the informative replies. Been around this site in "lurker mode" for some years, and again, many thanks. Along with most of the missions, I have the Apollo 12 mission report book (purchased back when we had only dial up internet rather to now viewing it in seconds...), and I certainly missed the tilting of the lander Conrad mentioned. Makes sense in that these things look sort of on the sturdier side to me, the way they dig into the surface and protrude upwards without appearing to be bent or crimped. But again, I'm sure they were designed to perform the way they did, and worked beautifully too, no matter how much it might curiously confuse a dumb prison guard from New Jersey 40 plus years later... |
Paul78zephyr
Member Posts: 762
From: Hudson, MA
Registered: Jul 2005
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posted 09-01-2020 10:29 PM
quote:
Originally posted by Lou Chinal:
The Apollo 9 LM Spider had four probes. By the time Apollo 11 flew the one on the front landing strut had been removed for that very reason.
Did Apollo 10 Snoopy (LM-4) have four probes or three? |
SpaceAholic
Member Posts: 5111
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 09-01-2020 10:48 PM
Snoopy: |
Space Cadet Carl
Member Posts: 292
From: Lake Orion, MI
Registered: Feb 2006
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posted 09-04-2020 05:32 AM
First time I've looked at a nice high resolution photo of Apollo 10 Snoopy and yes... you can clearly see a probe on the front Z+ (ladder) strut. You can also see the probe wiring wrapped around the landing strut, since there isn't Kapton foil covering the lower portion of the struts or the footpads. |
LM-12
Member Posts: 3635
From: Ontario, Canada
Registered: Oct 2010
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posted 09-04-2020 06:56 AM
In-flight photo AS10-34-5082 also shows all four probes. |
Headshot
Member Posts: 1098
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 07-19-2022 08:41 PM
Apologies if this has been discussed earlier.An April 1969 image shows Eagle with all four surface sensing probes in place, yet when Eagle was in orbit around the Moon, only three probes are seen. The probe attached to the forward, Z+ landing leg footpad had been removed. Does anyone hear know what happened to Eagle's fourth probe? Was it tossed out, installed on another LM, or is it in a museum someplace? |
oly
Member Posts: 1398
From: Perth, Western Australia
Registered: Apr 2015
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posted 07-19-2022 09:31 PM
The probe was deleted because of an identified risk the probe could become a hazard to the astronauts. A bent or broken probe could damage a spacesuit on the lunar surface.The probe was removed from the front landing strut, which is the only one visible to the crew from the cabin, it was considered that surface proximity sensing could be achieved using the other three probes. |
Headshot
Member Posts: 1098
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 07-19-2022 10:28 PM
Yes, but I am curious as to what NASA did with the probe after it was removed. It has some historical value since it was originally part of LM-5, Eagle. So what was its disposition? |
Jim Behling
Member Posts: 1732
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 07-20-2022 11:53 AM
Likely returned to stock and used on subsequent vehicles. |
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