International Guild of Knot Tyers Forum
General => Practical Knots => Topic started by: dfred on August 25, 2012, 02:20:36 AM
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(NOTE: All photographic images below can be clicked to view at higher resolution.)
In the last few days some of the first high resolution color images of Mars Rover Curiosity's (http://en.wikipedia.org/wiki/Curiosity_Rover) deck have been taken. These included some of the best images yet showing the knots visible on the exposed wire and cable bundles.
While a few of the folks here are no doubt aware, it might surprise most people to learn that knots tied in cords and thin ribbons have probably traveled on every interplanetary mission ever flown. If human civilization ends tomorrow, interplanetary landers, orbiters, and deep space probes will preserve evidence of both the oldest and newest of human technologies for millions of years..
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/0014ML0020000000E1_DXXX-levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/0014ML0020000000E1_DXXX-levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0020000000E1_DXXX&s=14)
Knots are still used in this high-tech arena because cable lacing (http://en.wikipedia.org/wiki/Cable_lacing) has long been the preferred cable management technique in aerospace applications. That it remains so to this day is a testament to the effectiveness of properly chosen knots tied by skilled craftspeople. It also no doubt has a bit to do with the conservative nature of aerospace design and engineering practices. Proven technologies are rarely cast aside unless they no longer fulfill requirements or there is something substantially better available.
While the knots used for cable lacing in general can be quite varied -- in some cases even a bit idiosyncratic -- NASA has in-house standards for the knots and methods used on their spacecraft. These are specified in NASA Technical Standard NASA-STD-8739.4 -- Crimping, Interconnecting Cables, Harnesses, and Wiring (http://www.hq.nasa.gov/office/codeq/doctree/87394.htm). As far as I've been able to identify in the rover images below, all of the lacings shown are one of two of the several patterns specified in the standard.
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/NASA-STD-8739.4-fig-9-2.gif) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/NASA-STD-8739.4-fig-9-2.gif)
The above illustration shows the so-called "Spot Tie". It is a clove hitch topped by two half-knots in the form of a reef (square) knot. In addition to its pure binding role, it is also used to affix cable bundles to tie-down points, as can be seen in many of the Curiosity rover images below.
Knot history buffs might find it interesting that a "Spot Tie"-like knot, with opposite Clove Hitch end orientation and topped only with a single half-knot was illustrated in 1917 by A. Hyatt Verrill under the name "Gunner's Knot". This was seemingly due to Verrill copying from J.T. Burgess, who had oversimplified "Bowling's" description of what possibly was the first known textual description of the Constrictor knot. But that's a whole different can of worms! ;D
So why has NASA standardized on this knot instead others which might serve the purpose? The following reasons are merely my own musings. I'd be interested to hear others' comments on this knot's strengths and weaknesses.
The Reef Knot and Clove Hitch are extremely ancient. Both were discussed in detail as surgical and orthopedic knots and slings by Greek physician Heraklas (https://en.wikipedia.org/wiki/Heraklas) in the 1st Century AD. The Reef Knot is depicted with varying degrees of realism in ancient Egyptian statuary and hieroglyphics as far back as 4000-5000 years ago. I presume there would be little disagreement here that these two knots must be among the oldest of the purposeful, standardized knots used by humans. You simply cannot get more field-tested than this!
But why combine these two well-known old knots in a somewhat novel way that, at first, might seem a bit "belt-and-suspenders"?
The inner profile of the clove hitch is smooth. Both turns bear on the bound object evenly throughout their contact. The contact area is increased by having two turns. When the reef knot is added, the ends are pulled up and away from the object. There is some extra pressure exerted by the reef knot on the riding turn, but this is distributed onto the two underlying turns. Evenness of pressure is important for the same reasons as the next item.
Overtightening of cable management bindings can cause conductor breakage, insulation damage, excessive chafing, and deformations between the conductive, dielectric, and shield parts of a cable, and no doubt a host of other issues. It is one of the classic problems with ratcheting plastic cable ties (i.e. "zipties") that they only have quantized adjustment steps and cannot be easily loosened. While zipties with a metal tooth insert do allow for smoother tightening, the possibility of this tiny metal part coming loose near electronics generally excludes their use. That zipties cannot easily be loosened or adjusted during tightening makes them more prone to being left in an overtightened state. Difficulty of adjustment might also be considered a possible strike against using the Constrictor Knot (and similar knots) for this application.
The clove hitch is not known as a particularly good binder alone, but that may be an advantage in this application. If the clove is initially made too tight it is easily loosened and readjusted. Once the proper snugness is achieved the addition of the first half-knot produces only a small and predictable amount of additional tightening. One thing I did notice in my tests is that if the first half-knot is made in the opposite orientation than shown in the standard, it tends to produce more tightening and also separates the underlying turns of the clove hitch.
- Resilience to errors in tying
As mentioned above, I did some tests tying the knot incorrectly in different ways. While these forms generally seemed inferior to the specified knot, they were not obviously destined to fail. Using these two basic knots in a compound form seems to be a reasonable way to make errors of tying less detrimental to the resulting knot.
(http://upload.wikimedia.org/wikipedia/commons/thumb/5/58/Cable-lacing-nasa-style-spot-ties.jpg/400px-Cable-lacing-nasa-style-spot-ties.jpg) (http://commons.wikimedia.org/wiki/File:Cable-lacing-nasa-style-spot-ties.jpg)
Image credit: David J. Fred/Wikimedia Commons (Original) (http://commons.wikimedia.org/wiki/File:Cable-lacing-nasa-style-spot-ties.jpg)
Above is a high resolution photo taken of these Spot Ties made in Gudebrod Nomex (http://en.wikipedia.org/wiki/Nomex) lacing tape. These types of lacing tapes are often coated or impregnated with materials (e.g. synthetic rubbers) to increase their knot-holding properties. I'm not sure what the tapes visible on the rover are made of, but I'd suspect the material was chosen for its behavior at extremely low temperatures and pressures as well as very good UV resistance.
The keen observer may note that some of the Spot Ties in the rover images show the ends perpendicular to the cable bundle and some parallel. Based on general experience with reef and granny knots, one might be tempted to assume the parallel examples are improperly finished with granny knots. Experimentation with Nomex lacing tape seems to show that it's more a matter of the knot preserving the orientation of the ends as the reef knot was tightened. I found that when the Spot Tie is finished improperly in the granny form but with the ends kept perpendicular to the wire bundle they tend to stay that way. While these experiments are hardly definitive, it doesn't seem to me that one can tell from orientation of the ends whether the knot was properly tied or not.
There is also the issue of the handedness of the first half-knot with respect the ends emerging from the Clove Hitch portion. The relative orientation shown in the NASA spec does appear to be preferable to the alternative.
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/NASA-STD-8739.4-fig-9-6.gif) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/NASA-STD-8739.4-fig-9-6.gif)
I won't go into much discussion about these stiches for the moment, but I believe the one on the left (the running clove hitches) appears on the extreme right edge of detail image "1" below.
And now for the pretty pictures...
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/context_rover_deck_PIA16063_crop1_scale.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/context_rover_deck_PIA16063_crop1_scale.jpg)
Image Credit: NASA/JPL-Caltech(Original) (http://photojournal.jpl.nasa.gov/catalog/PIA16063)
Multi-image panorama giving context of rover, deck, and its suroundings. The rim of Gale Crater is visible in the distance.
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/context_rover_deck_PIA16063_crop2_scale_zoomboxes.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/context_rover_deck_PIA16063_crop2_scale_zoomboxes.jpg)
Image Credit: NASA/JPL-Caltech(Original) (http://photojournal.jpl.nasa.gov/catalog/PIA16063)
Annotated context image showing locations of following five detailed images. Outlines do not quite align to following image borders due to panorama projection.
1 (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/1_0014ML0017000000E1_DXXX_crop1.levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/1_0014ML0017000000E1_DXXX_crop1.levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0017000000E1_DXXX&s=14)
Examples of one of the flat stitching methods (shown above) appear on the extreme right edge of this image.
2 (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/2_0014ML0017000000E1_DXXX_crop2.levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/2_0014ML0017000000E1_DXXX_crop2.levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0017000000E1_DXXX&s=14)
3 (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/3_0014ML0019000000E1_DXXX_crop1.levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/3_0014ML0019000000E1_DXXX_crop1.levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0019000000E1_DXXX&s=14)
4 (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/4_0014ML0020000000E1_DXXX_crop1.levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/4_0014ML0020000000E1_DXXX_crop1.levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0020000000E1_DXXX&s=14)
5 (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/5_0014ML0020000000E1_DXXX_crop_2.levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/5_0014ML0020000000E1_DXXX_crop_2.levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0014ML0020000000E1_DXXX&s=14)
[Edited 2013-09-11 to move images back from AWS S3]
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Awesome ! Thank you very much dfred.
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It seems that one can learn how to travel to Mars without knowing much about hitches and - and vice versa... :)
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Cool, thanks!
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It seems that one can learn how to travel to Mars without knowing much about hitches ... :)
Really? How does it seem so!?
???
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Above is a high-resolution photo taken of these Spot Ties made in Gudebrod Nomex lacing tape.
[...]
Indeed : for what is remarkable about what the image shows?!
Didn't intend it for anything other than illustration. Even these newest images coming down from Mars are still not extraordinarily clear in terms of the knots. If NASA did not have a published standard, it would likely be very difficult to deduce knots being used. Since I had the image handy from the Wikipedia cable lacing article, it seemed useful to see the knots tied in similar flat material than as shown on the rover.
(It looks as though not too much more line would be consumed
in making a binding like commercial fishermen use for headropes
and assorted other things --line running from reversed ground-line
hitch to next, spiral-wrapping the bound materials between.)
I'm not familiar with that exact knot/technique. I presume is it akin to marline hitching with RGLHs instead of overhand knots?
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 (http://commons.wikimedia.org/wiki/File:Cable_lacing_close-up_2.jpg)) 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?
My suspicion as to why they use individual, unconnected knots on the deck and exposed parts of the rover is due to concerns about differential thermal expansion. The rover includes a weather station and recently measured daily low and high air temps at the landing site of -2.2C (28F) / -74.9C (-103F). Ground temperatures were measured to vary between 2.7C (37 F) / -90.9C (-131.8 F). I don't know how the rover deck transfers heat in comparison, but there are no doubt huge temperature swings each day. If one of the running lock-stitch style of laces were used, there might be complications with the differential expansion/contraction of long lengths of the lacing material running parallel to the cable bundles. Just a guess on my part, though.
Much of the inside of the rover has active thermal controls. It would be interesting know whether that means other lacing styles are available/preferred in that more benign environment.
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Above is a high-resolution photo taken of these Spot Ties made in Gudebrod Nomex lacing tape.
[...]
Indeed : for what is remarkable about what the image shows?!
Didn't intend it for anything other than illustration. Even these newest images
coming down from Mars are still not extraordinarily clear in terms of the knots.
answer :
It is remarkable that the knotted/entangled part of the knot
occurs right at the gap between bound parts --i.e., at a point of
least material for clove/constrictor/... binding! Yes, tying off with the
overhand crossing atop the clove hitch --whose crossing part serves
well to *brace* this half-knotting-- makes the binder independent
of the bound surfaces, but you need to get to that point somehow
without losing tightness of the base knot (whose engagement comes
at this remarkable place). Hence the point about the nature of the
material helps to understand how this can be done --the compresssion
of the width of the small tape whose surface is (presumed to be)
frictive enables tying over the gap; it probably also makes drawing
the binding tight more difficult --the friction hindering transfer
of tension around the bundle.
(It looks as though not too much more line would be consumed
in making a binding like commercial fishermen use for headropes
and assorted other things --line running from reversed ground-line
hitch to next, spiral-wrapping the bound materials between.)
I'm not familiar with that exact knot/technique.
I presume is it akin to marline hitching with RGLHs instead of overhand knots?
With your points taken about the benefits of individual/independent
at-point bindings, attached is an image of the (what I've taken to calling)
"reverse ground-line hitch --which image might be among some I've
posted previously (but I am not so good w/Search for such things).
nb: The wrapping/tying *flow* is Right-To-Left for both of these
images --a half-hitch first reversing flow, then the 2nd re-reverses
and locks the knot (a duet sometimes repeated, even more than once).
[8/27 edit to add...] This finish would seem to be a preferable,
more sure one to use on many of the friction-gripping structures
shown by Ashley in #1732..1761 --esp. #1743/47/51/52/54.
--dl*
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ps : sipping some keemun + barooti tea
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Thanks dfred - an interesting read.
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This finish would seem to be a preferable, more sure one to use on many of the friction-gripping structures shown by Ashley in #1732..1761 --esp. #1743/47/51/52/54
Really ? Why is this so ? Where are the theoretical or experimental proofs, evidences, or even indications, about this claim ?
What we have seen is only a manual about how-to, but what about the why-so part on which this manual should have been based on ? Where are the scientific references, the experiments, the theoretical reasoning behind this decision, to use those particular hitches, and not any others ?
We wish to believe that such a technologically advanced organisation, as NASA, does everything it does the way it does only after a thorough examination of every other possible alternative, based on the most recent theoretical and experimental studies. Wishful thinking - that tends to ignore the fact that there are critical and sub-critical, or even non-critical, parts in every machine, and optimum and not optimum solutions in every technological problem. That there are good and bad solutions, decisions, tasks... and there are disasters as well as triumphs. When a hero like Armstrong dies of natural causes, we should also remember the heroes that have died at accidents because of other people s mistakes - the oxygen in the cabin, the O - ring, the loose tiles. Heroes that died because somebody told somebody else to "Take your engineering hat off and put your management hat on" . In sub-critical or non-critical parts - as the binding and the attachment of the wires inside the vehicle - this strategy works most of the time, but in some critical parts it might well fail - and it has failed tragically time and again...
So, until I see something that would really justify the use of the primordial two-half-hitches or two superimposed overhand knots solution to the wire binding and attaching problem, I will continue to see what I see : a so-so, quick and dirty way of dealing with a secondary non-critical problem - and a bureaucratic brochure that attempts to wrap the whole thing within some illustrated pages, using a superficially "scientific"-sounding language, but no scientific method at all.
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o, until I see something that would really justify the use of the primordial two-half-hitches or two superimposed overhand knots solution to the wire binding and attaching problem, I will continue to see what I see : a so-so, quick and dirty way of dealing with a secondary non-critical problem - and a bureaucratic brochure that attempts to wrap the whole thing within some illustrated pages, using a superficially "scientific"-sounding language, but no scientific method at all.
Mmmm ...maybe I wouldn't buy a second hand space module from NASA after all! Seriously it's perhaps nice to know that NASA (like other large organisations esp government) have people writing manuals who may not have a clue what they're talking about but once it's in the manual it becomes received wisdom. Perhaps a Martian will see it and give us some scientific analysis (as much chance as NASA responding here I imagine! But maybe it's all secret squirrel?)
Barry
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[...]
Hence the point about the nature of the material
helps to understand how this can be done --the compresssion
of the width of the small tape whose surface is (presumed to be)
frictive enables tying over the gap; it probably also makes drawing
the binding tight more difficult --the friction hindering transfer
of tension around the bundle.
Ah, yes, I misinterpreted your initial comment. Thanks for the clarification.
In addition to the mock-ups for the Wiki photos, I did the networking in a friend's new house and laced all the permanent cabling in the wiring closet with this tape. Total overkill, I know, but it was fun/interesting for me and they were the kind of person who appreciates this kind of thing. I found it was quite suitable for the task, as one might expect. I mostly used the running figure-eight style, but did use these spot ties for affixing some of the bundles to tie-down points and found there was no problem with the clove hitch maintaining tension while finishing the tie.
BTW, I got a few spools of this tape at Boeing Surplus when I lived in Seattle. Sadly they closed several years ago, but it was an amazing place to poke around. Wish I'd bought more of it, as I suspect it is very expensive to buy new.
[...]
nb: The wrapping/tying *flow* is Right-To-Left for both of these
images --a half-hitch first reversing flow, then the 2nd re-reverses
and locks the knot (a duet sometimes repeated, even more than once).
I do like how these ties flow, and also from one to the next. One minor concern I'd have about the spiral wrapping on wire bundles is that any torsion would tend to either loosen or tighten the binding against the bundle. Don't know how likely a scenario that is for most cable lacing, though.
BTW, I really like that second photo -- with the white wraps on the cyan-colored rope -- a very pretty, well-composed shot.
(Tieguanyin oolong for me today... )
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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). 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.
SS
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This finish would seem to be a preferable, more sure one to use on many of the friction-gripping structures shown by Ashley in #1732..1761 --esp. #1743/47/51/52/54
Really ? Why is this so ? Where are the theoretical or experimental proofs,
evidences, or even indications, about this claim ?
It is so, because the 2nd half-hitch forms a binder
vice the simple half-hitch finish Ashley shows --i.p.,
one of the miller's knots (in the form of the ground-line h.).
(I think that I'm partially misled in at least some of those
images by the spaced helical wrapping, which is done
for clarity but not expected to exist in the tied knot;
but even then, one can work in the 2nd half-hitch.
Otherwise (space intended), it seems to beg for this finish.)
Where are the scientific references, the experiments, the theoretical reasoning
behind this decision, to use those particular hitches, and not any others ?
...
So, until I see something that would really justify the use of the primordial
two-half-hitches or two superimposed overhand knots solution ... ,
I will continue to see what I see : a so-so, quick and dirty way of dealing with a
secondary non-critical problem --and a bureaucratic brochure that attempts to wrap
the whole thing within some illustrated pages, using a superficially "scientific"-sounding
language, but no scientific method at all.
Your brief, equally information-lacking criticism cited by me
above (post #4 / reply #2), is stronger than a mere question
for basis : it implies that you know better --and would have
solved this problem in some other way!
Here, you sound as though you won't be going out for a walk
any time soon unless Gauss & Reimann are reincarnated to
prove how to tie shoes validly in any possible geometry!
And yet, meanwhile, things are going far beyond a walk
in the park, into space (& back, sometimes)!
;)
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There is also the issue of the handedness of the first half-knot
with respect the ends emerging from the Clove Hitch portion.
Indeed : this essentially makes a squaREef structure.
(And was considered to be the constrictor knot verbally
introduced by "Bowling" as "gunner's knot" --a Verrill mistake
brought into graphics.)
(the running clove hitches)
Note that the structure implies that the "running"
isn't of cloves but of an orientation of the overhand
binding a pass of the other line --which pair of lines begin
from a clove hitch and finish with a pseudo-cloveness
akin to what I described in another thread about finishing
west country whipping with a (pseudo-)constrictor knot
--i.e., of mimicking the single-strand knot with two strands.
--dl*
====
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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 ! :) 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 :).
Your brief, equally information-lacking criticism
So, you admit that the manual is (scientific) information-lacking...That was my point, was nt it ?
it implies that you know better --and would have solved this problem in some other way!
It states that NASA should know better, of 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.
I am not an expert on knots - but if I were, I would have expected that NASA would have asked my opinion, or refer to my published work. Of course, if knotting solutions are classified, you would nt allowed to tell us that NASA has asked YOUR opinion, would you ? :) And that is a reason you should publish your notebooks before the MANNED NASA trip to Mars ! :)
you sound as though you won't be going out for a walk any time soon unless Gauss & Riemann are reincarnated to prove how to tie shoes validly in any possible geometry!
And yet, meanwhile, things are going far beyond a walk in the park, into space (& back, sometimes)!
If I were to walk on Mars, I would expect ( and feel much safer if that has been assured...) that somebody had examined the shoes I will wear there - and had not put me in his grandfather ( 1915 ?? ) boots ! :) Because if you happen to be into the wrong shoes on Mars, you will not going to be reincarnated on Earth any time soon to publish your notebooks, believe me...
I am not convinced by the quick and dirty, not-clever knotting "solution" to this non-critical, secondary knotting problem, and I have not bought the (scientific) information-lacking manual or the glossy pictures. If a similarly quick and dirty, not-clever solution would have been chosen ( should I better say "picked out", without any theoretical or experimental examination ) for a critical, main problem of the mission ( like the oxygen in the cabin, the O-ring, or the lose tiles ), I would not be happy to be on board, because sometimes quick and dirty, not-clever solutions are /were responsible for things/people that are /were NOT going to be back anytime soon - and neither would be you, I suppose.
There are two philosophies in life : The one says, pay the proper amount of attention to each part of life, according to the value it has in your life. ( A time-saving philosophy ). The other says, give as much attention as you can in every part of your life - because you can not know, in advance, which is, or will be someday proven to be, of the greater value - and because, perhaps, everything deserves to be dealt with our attention, because everything has a value that is related with the value if everything else. ( A soul-saving philosophy).
We are talking about KNOTS here... in Earth ( or Mars, or everywhere else in the Universe where there might be some form of intelligent life...) 99.99 % of the people do LAUGH when we tell them that we are paying as much attention to knots, as we do. Do knots have a value ? Should we lose our valuable time exploring knots ? Will Ashley congratulate us, when he will come back from his walk ? I do not know. I pay attention to knots, because I like them. That was what Gauss and Riemann did, for the things they did like, and what my grandfather and father did, and what I hope my son will do, too.
( 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.)
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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).
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?!
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.
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 ... .
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.
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*
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[8/27 edit : "could to" => "could DO" ]
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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.
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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!
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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*
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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.
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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 (https://en.wikipedia.org/wiki/ST-124-M3_inertial_platform), a component of the Saturn V rocket's guidance system...
(http://upload.wikimedia.org/wikipedia/commons/thumb/4/44/ST-124_uncovered_%28IMGP3445%29.JPG/400px-ST-124_uncovered_%28IMGP3445%29.JPG) (https://commons.wikimedia.org/wiki/File:ST-124_uncovered_%28IMGP3445%29.JPG)
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" (http://books.google.com/books?id=oN8DAAAAMBAJ&pg=PA550), bottom of page
Telephony (February 1907), "Manson's Practical Suggestions" (http://books.google.com/books?id=AfHmAAAAMAAJ&pg=PA83) (Part 1)
Telephony (March 1907), "Manson's Practical Suggestions" (http://books.google.com/books?id=AfHmAAAAMAAJ&pg=PA156) (Part 2)
...to these modern references:
Australian Civil Aviation Safety Authority (1998?), AC 21-99 Aircraft Wiring and Bonding,Sect 2 Chap 8 (http://www.casa.gov.au/rules/1998casr/021/021c99s2c08.pdf)
Qwest Corporation (2007), "Qwest Corporation Technical Publication - Telecommunications Equipment Installation Guidelines" (http://www.qwest.com/techpub/77350/77350.pdf) pp. 5-19 ? 5-24
NASA (2011) NASA-STD 8739.4 - Crimping, Interconnecting Cables, Harnesses, and Wiring (http://www.hq.nasa.gov/office/codeq/doctree/87394.pdf), 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.]
...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 (http://www.breydenproducts.com/WireHarnessingTapesTwinesBraidingYarns.htm) 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 (http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene) 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)
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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 (http://commons.wikimedia.org/wiki/File:Cable_lacing_close-up_2.jpg)) 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?
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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?
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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).
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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...
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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.
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This thread is getting press coverage.
New Scientist (http://www.newscientist.com/blogs/shortsharpscience/2012/09/ancient-technology-found-on-ma.html)
Adafuit Blog (http://www.adafruit.com/blog/2012/09/04/knots-on-mars/)
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Also on
http://news.yahoo.com/ancient-knots-keep-mars-rovers-laces-tied-red-141541222.html
http://www.popsci.com/science/article/2012-09/ancient-mariner-style-knots-tie-down-mars-rover-curiositys-cables-knot-fans-delight?cmpid=tw
Both refer to the IGKT forum. :)
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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
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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.
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For the thread, here's another close-up image that was taken in the last few days of the "turret" of instruments and devices on the end of the robotic arm in its deployed state:
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/0030ML0040000000E1_DXXX_levels.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/0030ML0040000000E1_DXXX_levels.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0030ML0040000000E1_DXXX&s=30)
There's a higher density of cabling on this device and it features a bit more diversity in the lacing.
The instrument at the center of the frame is the microscopic imager called the MAHLI (http://en.wikipedia.org/wiki/Mars_Hand_Lens_Imager) with its clear dust-cover closed. It will be used like a geologist's hand lens to examine Mars rocks and other surfaces at high resolution.
On the right, shown in profile, is (I think) part of the sample preparation/acquisition system that will be used in collecing materials to be analyzed by the rover's internal laboratories: CheMin (http://en.wikipedia.org/wiki/CheMin) and SAM (http://en.wikipedia.org/wiki/Sample_Analysis_at_Mars). The external ports leading to these instruments are the gray devices on the rover's deck and appear in several of the photos in the initial posting.
[Edited 2013-09-11 to move images back from AWS S3]
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So I was incorrect when I suggested that zipties were not used on the Curiosity rover. In looking at the NASA Cable and Harness - General Requirements (http://workmanship.nasa.gov/lib/insp/2%20books/links/sections/401%20General%20Requirements.html) document, metal-toothed zipties are indeed allowed in some cases.
Here is an image of the front Hazard Cameras recently taken by the MAHLI camera on the arm. Clearly there are bluish colored zip ties present.
(http://www.dfred.net/misc/igkt/20120823/back-from-AWS/small/0034MH0059001000E1_DXXX_levels_cropped.jpg) (http://www.dfred.net/misc/igkt/20120823/back-from-AWS/0034MH0059001000E1_DXXX_levels_cropped.jpg)
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original) (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0034MH0059001000E1_DXXX&s=34)
[Edited 2013-09-11 to move images back from AWS S3]
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As an add to the topic of NASA's knotty-ness, http://www.udel.edu/PR/Messenger/97/3/BLANKET.html (http://www.udel.edu/PR/Messenger/97/3/BLANKET.html)
SS
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As an add to the topic of NASA's knotty-ness, http://www.udel.edu/PR/Messenger/97/3/BLANKET.html (http://www.udel.edu/PR/Messenger/97/3/BLANKET.html)
That's a great story, isn't it!
Here's a photograph of the "arts and crafts project" being held by astronaut Scott Horowitz:
(http://www.dfred.net/misc/igkt/20120302/s82e5686.small.jpg) (http://www.dfred.net/misc/igkt/20120302/s82e5686.jpg)
Image Credit: NASA (Original) (http://spaceflight.nasa.gov/gallery/images/shuttle/sts-82/html/s82e5686.html)
Hard to say for sure, but I think the coiled orange material at the upper left of the blanket is the paracord. A small amount of the same stuff is also visible looped through a perforation at the upper right. The blue "dots" near the left coil appear to be the heads of zip-ties, similar to those visible elsewhere on the blanket.
Haven't been able to find too much coverage of them actually installing it. That occurred on EVA #5 according to the timeline here (http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-82.html). Here's some video of that EVA from an STS-82 highlight reel where they can be heard discussing rigging-related issues:
http://www.youtube.com/watch?v=J53_l6N_GJk&#t=2973s
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Good find!
I'm struck by the NASA article's :
"They have to filter out even the tiniest particles, because if even one of them gets on that lens, it's going to show up in all the pictures."
in light of this revelation:
http://www.lensrentals.com/blog/2008/10/front-element-scratches (http://www.lensrentals.com/blog/2008/10/front-element-scratches)
!! ?
(And I have to wonder how much those fancy binder clips
on the blanket cost!)
--dl*
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http://www.360cities.net/image/mars-gigapixel-panorama-curiosity-solar-days-136-149#663.09,42.81,42.5
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Rope use on Mars. http://www.planetary.org/blogs/emily-lakdawalla/2012/07060700-how-curiosity-land-part-3.html (http://www.planetary.org/blogs/emily-lakdawalla/2012/07060700-how-curiosity-land-part-3.html)
Nylon rope was used by the Sky Crane to lower the Curiosity rover to the Martian surface. Looks like eye splices were used.
The pictures are clickable.
SS
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I'm not sure if this has been mentioned. Is one reason for using knots instead of pre-fabricated zip ties to conserve space?
For example, an astronaut could have all the twine he needs in a relative tiny space, while pre-fabricated zip ties might take up 10 times more room.
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I'm not sure if this has been mentioned. Is one reason for using knots instead of pre-fabricated zip ties to conserve space?
For example, an astronaut could have all the twine he needs in a relative tiny space, while pre-fabricated zip ties might take up 10 times more room.
I should think that amongst other properties, weight savings rank higher than volumetric efficiency.
Quote from a manufacturer of lacing: "Unlike cable ties, the insulation on wires bundled with lacing tape has less chance of cold flowing (Creep in polymer plastics) and shorting. Also, there are no sharp edges to cut installer's hands when reaching into a tightly packed wiring cavity. Lacing tape is ideal for lashing wires or cables to ladder bars, conduit and other wire management solutions.
Lacing tape has a far greater operational lifespan than cable ties. Cable ties turn brittle and degrade over time due to environmental exposure and loss of plasticizers. This is particularly important when managing critical wire bundles in inaccessible areas. A single roll of lacing tape can manage any size cable bundle, from a couple of 22AWG wires to a fistful of heavy power cables, eliminating the need to stock and manage various size cable ties."
So much has to be considered for use in space that we don't normally ever consider and then we have to try to factor in what needs to be addressed on another planet!
Pretty amazing.
SS
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Hi SS,
Thanks, this clarifies me a lot: I also,like knot4u, had some questions in my head ever since last year I was reading this thread,because in my case I do not understand much about materials and their reactions to the environment, and other practical considerations that you mention;so what you quote helps me to get an idea;but it still amazes me that it seems that do not yet exist materials/different solutions to solve some of the technical problems that you mention, although, as a lover of knots, this makes me glad! ;D
Bye!
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[...]
but it still amazes me that it seems that do not yet exist materials/different solutions to solve some of the technical problems that you mention, although, as a lover of knots, this makes me glad!
I agree it is heartening and quite interesting.
In addition to the reasons already discussed in this thread, I think it may also have to do with the flexibility -- both literally and figuratively -- it allows in solving the variety of fastening problems faced on these missions.
It appears that during the design and testing phases, these instruments/spacecraft go through several cycles of assembly, disassembly, and possible modification. Anybody here who has worked on a complex cordage project (whether practical rigging or decorative) would probably agree that later iterations are often superior to one's initial attempts. Even things as subtle as how much tension to apply during the early steps so that the final result has the proper balance, or the direction the initial pass should take to end up with a suitable geometry for a clean finish, etc. Assuming the same technicians are involved throughout a project, presumably they gain valuable tacit knowledge (https://en.wikipedia.org/wiki/Tacit_knowledge) of the specific lacing task which would be difficult to specify a priori in any highly rigorous way. It would be interesting to understand how much of the final lacing design is actually left to the technicians themselves.
And not to let the thread languish...
Here's something that caught my eye last week on the Planetary Society blog regarding the "Diviner" instrument (http://www.planetary.org/blogs/emily-lakdawalla/2014/01081100-diviner-maps-of-the-change-3-landing-site.html) on the Lunar Reconnaissance Orbiter (https://en.wikipedia.org/wiki/Lunar_Reconnaissance_Orbiter). Beyond traditional cable lacing, they used some distinctly corset-like (https://commons.wikimedia.org/wiki/File:Back_lace_corset.gif) techniques to affix the thermal shielding around this oddly-shaped scientific instrument. I don't recall seeing something like this on a spacecraft before, but I think the result looks pretty cool. Here's the full photo gallery at UCLA (http://www.diviner.ucla.edu/gallery.shtml) that shows many more images giving some scale and context. Many of the closeup images appear to have been taken during vibration and thermal testing. Some selected images are below, click for full size.
(http://www.dfred.net/misc/igkt/20140117/small/div4lrg.cropped.jpg) (http://www.dfred.net/misc/igkt/20140117/div4lrg.cropped.jpg)
Image Credit: NASA / JPL / UCLA (Original) (http://www.diviner.ucla.edu/gallery/div4lrg.jpg)
In the full size image one can see how pre-made (punched?) holes in the bound seams (https://en.wikipedia.org/wiki/Seam_%28sewing%29#Finishes) are used as lacing points.
(http://www.dfred.net/misc/igkt/20140117/small/div1lrg.cropped.jpg) (http://www.dfred.net/misc/igkt/20140117/div1lrg.cropped.jpg)
Image Credit: NASA / JPL / UCLA (Original) (http://www.diviner.ucla.edu/gallery/div1lrg.jpg)
A slightly different angle.
(http://www.dfred.net/misc/igkt/20140117/small/shaketestlrg.cropped.jpg) (http://www.dfred.net/misc/igkt/20140117/shaketestlrg.cropped.jpg)
Image Credit: NASA / JPL / UCLA (Original) (http://www.diviner.ucla.edu/gallery/shaketestlrg.jpg)
The thermal shield in an unlaced state being worked on. The instrument is bolted to a "shake table" for vibration testing.
(http://www.dfred.net/misc/igkt/20140117/small/div_lro_lrg4.cropped.jpg) (http://www.dfred.net/misc/igkt/20140117/div_lro_lrg4.cropped.jpg)
Image Credit: NASA / JPL / UCLA (Original) (http://www.diviner.ucla.edu/gallery/div_lro_lrg4.jpg)
The back side of the instrument. From context in the other images this appears to be the final assembly and just prior to LRO being mounted on the Atlas V rocket. Note that two lacing holes (center right) remain unused.
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Thanks dfred!
Nice find.
So what do you suppose the knots used to complete the final tying are? Such as the ones directly below the "corset" crossings.
Could it be as simple as a Reef knot?
SS
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Thanks dfred!
Nice find.
So what do you suppose the knots used to complete the final tying are? Such as the ones directly below the "corset" crossings.
Could it be as simple as a Reef knot?
No problem! When I saw it last week I knew it was just too nifty not to be added to this thread. :)
Yes, I'd guess reef knots too. The shape is right, but the black-on-black makes it a bit hard to see for sure.
However during the flurry of interest after this thread got wider exposure I had a note from someone who had used "spot ties" professionally in the aerospace industry. He indicated that the surgeon's knot (aka ligature knot, #1209) was considered an acceptable substitute to the reef -- perhaps even preferred for a variety of reasons. However I haven't been able to corroborate this, beyond a passing mention in a document that seems to indicate the surgeon's knot may be used instead of a reef knot. In this case with the heat shield, since it's not really cable lacing, a bit hard to say exactly what they're using as a basis... Though it seems likely they would have a preference for the knots they're already comfortable with from cable lacing.
[Edit: added last sentence]
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One should be chary of making much of knot names
--i.p., that "surgeon's knot" might turn out to be the
*reverse*, or the *double* : respectively the finish, only,
or both halves, given the extra twist. (IMO, having the
extra twist only in the "first throw" --which purpose is
to gain temporary holding in slicker stuff so to give time
for making the 2nd throw-- leads to a less secure knot,
as the single-twisted finish (if only this, and not a series
of them) has a longer span to cover (its single twist atop
the double) and so will be less tight.
--dl*
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ps : E.g., today I answered a query about what was
the right "inline Fig.8" eye knot --there was a contrast
of ABOK's #1057 vs. 1058 (<-right). So, that knot
name was, in the world of the Net, able to confuse.
(No surprise ... .)
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dfred, just wanted to thank you for this awesome post. I refer to it from time to time. And having just started sailing, it's even more interesting that ever.