Knots on Mars! (and a few thoughts on NASA's knots)

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…


http://upload.wikimedia.org/wikipedia/commons/thumb/4/44/ST-124_uncovered_(IMGP3445).JPG/400px-ST-124_uncovered_(IMGP3445).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”, 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? :slight_smile:

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 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)

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).

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…

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.

This thread is getting press coverage.

New Scientist
Adafuit Blog

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. :slight_smile:

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

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.

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

Image Credit: NASA/JPL-Caltech/Malin Space Science Systemsurl=http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0030ML0040000000E1_DXXX&s=30[/url]

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 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 and SAM. 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]

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 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

Image Credit: NASA/JPL-Caltech/Malin Space Science Systemsurl=http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=0034MH0059001000E1_DXXX&s=34[/url]

[Edited 2013-09-11 to move images back from AWS S3]

As an add to the topic of NASA’s knotty-ness, http://www.udel.edu/PR/Messenger/97/3/BLANKET.html

SS

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

Image Credit: NASA url=http://spaceflight.nasa.gov/gallery/images/shuttle/sts-82/html/s82e5686.html[/url]

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. 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

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

!! ?

(And I have to wonder how much those fancy binder clips
on the blanket cost!)

–dl*

http://www.360cities.net/image/mars-gigapixel-panorama-curiosity-solar-days-136-149#663.09,42.81,42.5

Rope use on Mars. 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

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

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!