Author Topic: Knots on Mars! (and a few thoughts on NASA's knots)  (Read 155993 times)

Dan_Lehman

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #15 on: August 29, 2012, 08:40:25 PM »
It is so, because the 2nd half-hitch forms a binder vice the simple half-hitch finish Ashley shows

   I was not talking, of course, about the common knowledge that,
most of the time, two good things are better than one good thing !  :)
Actually, I don't agree with this in full, and had some time
of self-challenge on how adding a 2nd of something I was
finding deficient could do anything but put some trifling delay
in inevitable failure --that, okay, now the 2nd/last-done H-H
must loosen before the given one does, but then it does !?
Analysis IMO shows that the 2nd H-H imparts some tightening
and curvature into the first to increase its nip, and in some
cases there is also some friction added by parts now being
adjacent (there being 2 vs. 1).

Quote
I was talking about the evaluation of all Ashley's and non-Ashley's hitches,
that is obviously missing. Unless there are classified knotting secrets, which would be revealed
after a century or so - about the time I reckon you will publish your own notebooks  :).
///
So, you admit that the manual is (scientific) information-lacking...
That was my point, was nt it ?

As though one should expect any manual to contain such detailed
rationale!!!  Still, that wasn't the form/diction of your remark,
but rather a presumption of inferiority --not the mere lack of
some *proof*.  Where, btw, do you ever see this given for knots,
so that we might suggest a model for it ?  --or do you continue
to wear slippers/loafers, to keep on the safe side?!


Quote
it implies that you know better --and would have solved this problem in some other way!

   It states that NASA should know better, or that NASA should tell us about what it knows,
about the theoretical or experimental evidence that support the selection of the particular hitches,
and not of any other else.

Again, hardly to be expected in a manual of instruction,
and not quite the terms of your point --or in that "should
know better" there is implicit assumption that some "better"
exists, and that begs an answer from who asserts it, not NASA.


Quote
And that is a reason you should publish your notebooks before the MANNED NASA trip to Mars !  :)

My notes are now primarily just images of structures.
And I've remarked to myself about my "QRS" so-far format
being nearly entirely graphical vs. verbal, and the loss of
information (tied in what cordage, loaded or what minimal
experience with ...) is bad --a loss.  But I have some desire'
for the *purity*/cleaness/objectiveness of presenting just
an image ; let commentary come as it may beyond that ... .

Quote
I am not convinced by the quick and dirty, not-clever knotting "solution"
 to this non-critical, secondary knotting problem,...

If indeed this is Q&D, and has made the rounds in many
instances w/o hint of problem, why would you devote any
research hours to proving its evident working, or to seek
an alternative?  As you note, this binding doesn't have
anything like the importance of those O-rings (which were
functionally noted to be an issue, but overruled --without
consequence, ultimately, but for conscience?-- on other
grounds, tragically.  But perhaps NASA has done some
vibration testing of such bindings, to assure themselves
of the working.

Quote
My humble advice to knot tyers is to try to learn about hitches by reading books,
or tying their own - and not copying and pasting this "solution" NASA has happened to pick out,
for unknown reasons.

And what will which books teach you about hitches?
(Will you find anything about the NASA hitches anywhere?)


--dl*
====

[8/27 edit :  "could to" => "could DO" ]
« Last Edit: August 30, 2012, 07:49:51 PM by Dan_Lehman »

X1

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #16 on: August 30, 2012, 01:55:34 AM »
the 2nd H-H imparts some tightening and curvature into the first to increase its nip\

  Perhaps I should not say what I am going to say, but let it be :  This "two half-hitches" thing is nothing but a knotting paradox !  :) In such a situation, the first/inner knot is, in fact, nothing but a nipping loop, and only the second/outer one is a genuine half-hitch. If the two knots remain adjacent to each other - which can only mean that both legs of the inner knot remain under tension - the inner knot is not able to hitch the rope 100%, so it is not a hitch...

As though one should expect any manual to contain such detailed rationale !!!  Still, that wasn't the form/diction of your remark, but rather a presumption of inferiority --not the mere lack of some *proof*.  Where, btw, do you ever see this given for knots, so that we might suggest a model for it ?

   One should expect from a " NASA Technical Standard"  to refer to some published scientific work, yes - unless hitches can be used by extra-terrestrial terrorists as a lethal weapon against Earthmen !  :) Even if it is not given anywhere, I hope that somewhere , sometime, somebody will offer such a proof - and if this somebody will not be the "superior"  NASA, who will ? 

in that "should know better" there is implicit assumption that some "better" exists, and that begs an answer from who asserts it, not NASA.

   So, you are convinced that there is - and there will be - NOTHING better, never...and that solution is the "superior" , the only one, carved in stone and offered to us by the KnotGod....  Perhaps you are secretly informed by somebody, about things we are mot allowed to know... :)
   No, it is the responsibility of the expert to refer to evidences, indications or proofs about what he claims is the optimum option, not of the layman...It is the responsibility of the doctor, not of the patient ! If you are ready/happy to swallow anything that is sold to you, without any reasoning, by people that are paid by your taxes, please, let me prefer my safe slippers/loafers... :)
   The number of the known hitches is about one hundred or so (?). It would have been NOT a big deal, if they had examined all those knots in detail, qualitatively, on a variety of materials and temperature/vibration conditions. THAT would have convinced me that they know what they are doing, and why they are doing it so -  even in this non-critical, secondary issue - and I would had felt that your money are not spent on multi-pages blah-blah.

If indeed this .. .has made the rounds in many instances w/o hint of problem, why would you devote any research hours to proving its evident working, or to seek an alternative?

  I do not believe that we came down from the trees, or gone up to Mars, because there was something that " was not working " up there or down here. In NASA words, what drives us is "Curiosity" ! We were devoting thousands of hours to prove, again and again, that the Pythagorean Theorem was, evidently, working - until Gauss and Riemann went out of their safe slippers/loafers, and figured out an alternative to Euclidean Geometry.
   I am curious about all the simple knots that may exist, and I would be really happy if I could learn them all, and then settle to the few that would have been proved to be the best ones...Evidently, all sufficiently tangled ropes form sufficiently working knots - but that is not what we are talking about in this Forum, I hope.

perhaps NASA has done some vibration testing of such bindings, to assure themselves of the working.

   I am sure about it - but then, why on Earth or Mars they are keeping us in the darkness ? It would be so useful if they had published the results of those tests, and the alternative hitches they had tested and evaluated before they had settled to the particular solution.

« Last Edit: September 02, 2012, 05:19:02 AM by X1 »

TMCD

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #17 on: August 30, 2012, 10:45:33 PM »
May I suggest ABOK #1244 for NASA, it rivals the Constrictor in my experiences and would seem much better than the one they're currently using. My suggestion would also save precious space time, assuming they're tying these in space at some points.

ABOK #1244 isn't far behind the common Constrictor as far as security and binding power....and it can be tied in the bight!

Dan_Lehman

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #18 on: September 02, 2012, 03:24:13 AM »
May I suggest ABOK #1244 for NASA,
t rivals the Constrictor in my experiences and would seem much better than the one they're currently using. My suggestion would also save precious space time, assuming they're tying these in space at some points.

ABOK #1244 isn't far behind the common Constrictor as far as security and binding power
--and it can be tied in the bight!

Are you recommending a slipped knot for NASA?

Tying in the bight looks to be an unusable attribute for
most of what I'm seeing in NASA's binding.  (Interestingly,
the un-slipped knot (~= #1674) is also TIB (tyable inthe bight) [sic].

(Btw, more than the constrictor does, #1674 puts the
tails' nips farther from the tangent point of a line of tension
in setting the knot, so there is some degree of resistance
to being set tight (unless one pulls *around* the object
with resistance for it).  What I mean is that if the tangent
point to the setting axis of tension were 12:00, one would
find that the extent of the knotted parts puts the nips on
the two ends at, say, 11:56 & 12:04, requiring some bit
of deflection over this short arc, and maybe leaving some
slight, relative looseness therein.)


--dl*
====

TMCD

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #19 on: September 02, 2012, 01:26:48 PM »
Yes, of course #1674, sorry I didn't clarify..no slipped knot suggestion here.

I think more than anything this NASA Knot just goes to show that they haven't exactly done their homework on knot efficiency. There's so many better options in this situation than what they're using. JMO.

dfred

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #20 on: September 02, 2012, 08:28:16 PM »
I remember now the cable lacing from my own aircraft maintenance days. It seems that this knotting has been employed since before then (late 60's).

Here's a beautiful piece of late-60s craftsmanship: the ST-124-M3 inertial platform, a component of the Saturn V rocket's guidance system...


Image credit: EdgarDurbin/Wikimedia Commons

These cable management knots have indeed been used and documented for much longer.  The lineage of some of the lacing knots shown in the NASA standard appear to date back at least to the early days of telephony.   I haven't yet found any documentation on cable management in telegraphy, but it would not surprise me if some of them go back that far.  We can only hope that someday a researcher might even find the elusive Lineman's Rider lurking in one of these old telco references!  In any case, one finds more than a few similarities between the knots used on Curiosity and those recommended to telephone linemen in the early part of the 20th century. 

Compare the knots in these 100+ year-old documents:

Popular Mechanics (May 1905), "Cable Sewing Knots", bottom of page
Telephony (February 1907), "Manson's Practical Suggestions" (Part 1)
Telephony (March 1907), "Manson's Practical Suggestions" (Part 2)

...to these modern references:

Australian Civil Aviation Safety Authority (1998?),  AC 21-99 Aircraft Wiring and Bonding,Sect 2 Chap 8
Qwest Corporation (2007), "Qwest Corporation Technical Publication - Telecommunications Equipment Installation Guidelines" pp. 5-19 ? 5-24
NASA (2011) NASA-STD 8739.4 - Crimping, Interconnecting Cables,  Harnesses, and Wiring, pp. 40-44.


I find it quite interesting that several patterns not frequently found and/or recommended in general knotting literature are repeated in various forms:

- Regular use of Double Strap Hitch (#1695, but by threading the ends).  (C.L. Day called this knot "comparatively useless" in 1935!)

- A binding knot/hitch topped by one or more overhand knots.  (however, note the unusual underlying hitch in the older documents*)

- Overhand and reef knots being used as stoppers at the end of tensioned doubled cords.  (e.g.: finish of right-hand flat stitch in first post)

(* If I'm interpreting things correctly, it seems to be #1242 with the one of the two wrapping turns "hopped" over the other.   Removed from the spar it is a figure-eight knot.  It is also tied in the "reverse" manner, if I'm using/understanding Dan's terminology correctly, like the so-called Reverse Ground-line Hitch.  That is, the working end and standing ends are swapped as compared to how one might normally tie the hitch form of the knot.  The clearest illustration is the one shown in Popular Mechanics.)

There seems to be some evidence that the repertoire of cable management knots have evolved in isolation from those commonly known and used for general knotting.  These cable lacing knots might even provide an interesting case study for Pieter van de Griend's ideas on "Knot Knowledge Management" (KKM).   Or, to echo Budworth's query, what if Ashley had been a lineman?  :)

While some folks in this thread have suggested alternative knots for cable management, I actually find it quite fascinating that specific knot "user groups" tend to continue using the same related set of knots over very long time periods.  This seems to be true of humans' use of knots in general.  Anyone who has seriously studied knots and is familiar with a large range of them will, of course, have alternatives immediately spring to mind when they see a knot problem.  However, it seems to me these kinds of people have always represented an extreme minority of actual knot users.  But that line of thinking is getting a bit far-afield from the topic of this thread...

[And also on an editorial note, the question that X1 has brought up in this thread is actually an extremely important one.  It is perhaps the most important question we as knot-interested people face:  what is the reason for the lack of scientific progress in understanding of the behavior of real, physical knots?  While arguably they might be held to a higher standard, this lack of progress is not specific to NASA/JPL.  It seems to me to be a failing of imagination to realize that there can be a science of physical knot behavior, knot physics, knot mechanics, or Physical Knot Theory, if you will.   While there have been fits and starts, in the form of isolated scientific papers, no self-sustaining progress has really ever been made.  It is the area of knotting I am personally most interested in.  If people want to discuss the way forward on this important and neglected subject, it really belongs in--and deserves--its own thread.]

Quote
...If memory serves well I believe the cord/lace was waxed and that aided in the knot retention.

So I wonder if the Mars Rover has waxed tape? It looks quite shiny in the posted pictures.

It seems unlikely to me that NASA/JPL would have used a natural fiber.  However waxed linen and polyester appear to still be the preferred cordage in telephony and one can still find it sold for that purpose.  The wax may serve multiple purposes: knot holding, lubricant, and also to help the natural fiber resist rot/mold -- much the same as tar is used on hemp.  Regarding the lubricant function, if you look at the lashings used to affix large telephone cable bundles to support structures, lengths of the cord must be pulled between tightly packed cables with flat hook/loop tools.  The wax might help ease the passage as well as avoid the cord melting/sawing its way into the insulation. 

As far as what they're using on the exposed portion of the rover, I don't know.  It is quite possible it has some sort of coating for knot-retention, as mentioned in the original posting.  Here's a link to a current manufacturer's selection of lacing tapes and coatings showing the variety of both fiber and coatings.

The rover's lacings could be almost anything, as neither cost nor "exoticness" are likely deal-breakers in their selection process.  As far as "normal" fibers I might guess either UHMWPE or braided continuous filament fiberglass, both for their UV resistance.   I don't know if the latter can be knotted in the manner shown without excessive fiber breakage, but it would no doubt be very shiny.   There is also the issue of thermal cycling, for which I don' really have any data on how different materials might fare.

(EDIT: further reading indicates telcos now may use waxed polyester lacing cord, also fixed name of ST-124-M3, also it was Popular Mechanics not SciAm)
« Last Edit: September 05, 2012, 05:14:07 PM by dfred »

knot4u

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #21 on: September 02, 2012, 09:38:54 PM »
Marline hitching, as well as a similar technique of running lock-stitches using figure-eight knots, is used extensively in cable lacing in general.  The figure-eight form is indeed specified in that NASA document.  (Example Wiki photo)  This form is actually quite secure, easy to tighten, and holds tension well while the next stitch is made.   I'd suspect the RGLH form might be even more secure.   Does it tighten-up easily and evenly without much fiddling?

Interesting, when is a Fig 8 Marline Hitch preferred over an Overhand Marline Hitch?

dfred

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #22 on: September 02, 2012, 10:11:29 PM »

Interesting, when is a Fig 8 Marline Hitch preferred over an Overhand Marline Hitch?

My impression is that it is an aircraft/aerospace (and perhaps military?) thing and dates at least to the 60s.   I don't have all my references handy at the moment.   SS369, do you remember using these figure-eight running lock stitches?

I don't recall seeing the figure-eight style in many (any?) telephone-related references.  Generally it is recommended as being "more secure", the figure-eight stitch less prone to loosening while the next is made.   Perhaps it also might be less prone to shifting after it is made?



knot4u

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #23 on: September 03, 2012, 12:53:37 AM »

Interesting, when is a Fig 8 Marline Hitch preferred over an Overhand Marline Hitch?

My impression is that it is an aircraft/aerospace (and perhaps military?) thing and dates at least to the 60s.   I don't have all my references handy at the moment.   SS369, do you remember using these figure-eight running lock stitches?

I don't recall seeing the figure-eight style in many (any?) telephone-related references.  Generally it is recommended as being "more secure", the figure-eight stitch less prone to loosening while the next is made.   Perhaps it also might be less prone to shifting after it is made?

I do take note of your explanation. In my testing, I have found the Overhand Marline to be easier to tighten and adjust. I don't have a strong opinion either way on which is less prone to loosening while the next is made. I didn't find this to be an issue with either one. Also, I don't have a strong opinion on which is less prone to shifting.

If I wanted those features specifically (more secure and less shifting), then I'd tie a Marline that includes a series of Double Overhands (i.e., Strangle Knots).
« Last Edit: September 03, 2012, 01:08:02 AM by knot4u »

dfred

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #24 on: September 03, 2012, 01:46:11 AM »

I do take note of your explanation. In my testing, I have found the Overhand Marline to be easier to tighten and adjust. I don't have a strong opinion either way on which is less prone to loosening while the next is made. I didn't find this to be an issue with either one. Also, I don't have a strong opinion on which is less prone to shifting.

If I wanted those features specifically (more secure and less shifting), then I'd tie a Marline that includes a series of Double Overhands (i.e., Strangle Knots).

The figure-eight lock stitch, when tied in stretchy material, has a tendency to capsize into another form while tightening if excessive tension is present in the connecting portion between the stitches.  I laced down some carpet pads onto the rungs of a canoe trailer with paracord earlier this summer and noticed that behavior.  Otherwise, I did find it held tension better than simple marilne hitching while the next "stitch" was made.   But in any given lacing material on a particular bound object, one's mileage will probably vary.

I think your basic question about exactly why (and when) this pattern diverged from the classic marline style remains to be answered...

« Last Edit: September 03, 2012, 01:47:33 AM by dfred »

X1

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #25 on: September 03, 2012, 06:31:19 PM »
   Regarding the military jets ( where the G s and the vibrations are greater than those aboard NASA vehicles, I guess ) I have not found any better pictures :
 http://www.jsf.mil/gallery/gal_photo_sdd.htm
 http://www.jsf.mil/gallery/gal_photo_sdd_f35amanf.htm
 Not very imformative, I am afraid.   
« Last Edit: September 03, 2012, 06:33:10 PM by X1 »

KnotMe

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #26 on: September 04, 2012, 07:23:54 PM »
This thread is getting press coverage.

New Scientist
Adafuit Blog


squarerigger

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #28 on: September 06, 2012, 11:30:48 PM »
The responses all seem to point out the interest taken by knot-tyers in all things knotting, so I think you all are to be congratulated for keeping the discussion civil and on point - thank you!

SR

dfred

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Re: Knots on Mars! (and a few thoughts on NASA's knots)
« Reply #29 on: September 08, 2012, 08:45:50 PM »
The responses all seem to point out the interest taken by knot-tyers in all things knotting, so I think you all are to be congratulated for keeping the discussion civil and on point - thank you!

And also thanks to the Guild for hosting this forum.  It is quite gratifying that so many people this past week got to read about knots and were likely introduced to the Guild for the first time.