Knots on Mars! (and some ideas on NASA’s knots)

2024-02-22 03:33:35

(NOTE: All photographic photos under might be clicked to view at increased decision.)

In the previous couple of days a number of the first excessive decision shade photos of Mars Rover Curiosity’s deck have been taken. These included a number of the greatest photos but exhibiting the knots seen on the uncovered wire and cable bundles.

Whereas a couple of of the oldsters listed below are little doubt conscious, it’d shock most individuals to be taught that knots tied in cords and skinny ribbons have most likely traveled on each interplanetary mission ever flown. If human civilization ends tomorrow, interplanetary landers, orbiters, and deep house probes will protect proof of each the oldest and latest of human applied sciences for thousands and thousands of years..

Picture Credit score: NASA/JPL-Caltech/Malin Area Science Techniques(Original)

Knots are nonetheless used on this high-tech area as a result of cable lacing has lengthy been the popular cable administration approach in aerospace functions. That it stays so to this present day is a testomony to the effectiveness of correctly chosen knots tied by expert craftspeople. It additionally little doubt has a bit to do with the conservative nature of aerospace design and engineering practices. Confirmed applied sciences are hardly ever solid apart except they now not fulfill necessities or there’s something considerably higher out there.

Whereas the knots used for cable lacing generally might be fairly various — in some circumstances even a bit idiosyncratic — NASA has in-house requirements for the knots and strategies used on their spacecraft. These are laid out in NASA Technical Standard NASA-STD-8739.4 — Crimping, Interconnecting Cables, Harnesses, and Wiring. So far as I have been capable of establish within the rover photos under, the entire lacings proven are considered one of two of the a number of patterns laid out in the usual.

The above illustration reveals the so-called “Spot Tie”. It’s a clove hitch topped by two half-knots within the type of a reef (sq.) knot. Along with its pure binding function, additionally it is used to affix cable bundles to tie-down factors, as might be seen in lots of the Curiosity rover photos under.

Knot historical past buffs would possibly discover it fascinating {that a} “Spot Tie”-like knot, with reverse Clove Hitch finish orientation and topped solely with a single half-knot was illustrated in 1917 by A. Hyatt Verrill beneath the title “Gunner’s Knot”. This was seemingly resulting from Verrill copying from J.T. Burgess, who had oversimplified “Bowling’s” description of what probably was the primary identified textual description of the Constrictor knot. However that is an entire totally different can of worms!

So why has NASA standardized on this knot as a substitute others which could serve the aim? The next causes are merely my very own musings. I might have an interest to listen to others’ feedback on this knot’s strengths and weaknesses.

The Reef Knot and Clove Hitch are extraordinarily historic. Each had been mentioned intimately as surgical and orthopedic knots and slings by Greek doctor Heraklas within the 1st Century AD. The Reef Knot is depicted with various levels of realism in historic Egyptian statuary and hieroglyphics way back to 4000-5000 years in the past. I presume there could be little disagreement right here that these two knots have to be among the many oldest of the purposeful, standardized knots utilized by people. You merely can not get extra field-tested than this!

However why mix these two well-known previous knots in a considerably novel manner that, at first, might sound a bit “belt-and-suspenders”?

The internal profile of the clove hitch is clean. Each turns bear on the sure object evenly all through their contact. The contact space is elevated by having two turns. When the reef knot is added, the ends are pulled up and away from the thing. There’s some further stress exerted by the reef knot on the driving flip, however that is distributed onto the 2 underlying turns. Evenness of stress is necessary for a similar causes as the following merchandise.Overtightening of cable administration bindings may cause conductor breakage, insulation injury, extreme chafing, and deformations between the conductive, dielectric, and defend components of a cable, and little doubt a number of different points. It is without doubt one of the basic issues with ratcheting plastic cable ties (i.e. “zipties”) that they solely have quantized adjustment steps and can’t be simply loosened. Whereas zipties with a metallic tooth insert do enable for smoother tightening, the potential of this tiny metallic half coming unfastened close to electronics typically excludes their use. That zipties can not simply be loosened or adjusted throughout tightening makes them extra susceptible to being left in an overtightened state. Issue of adjustment may additionally be thought-about a attainable strike in opposition to utilizing the Constrictor Knot (and related knots) for this software.

The clove hitch is just not often called a very good binder alone, however that could be a bonus on this software. If the clove is initially made too tight it’s simply loosened and readjusted. As soon as the right snugness is achieved the addition of the primary half-knot produces solely a small and predictable quantity of extra tightening. One factor I did discover in my exams is that if the primary half-knot is made within the reverse orientation than proven in the usual, it tends to provide extra tightening and in addition separates the underlying turns of the clove hitch.

Resilience to errors in tying

As talked about above, I did some exams tying the knot incorrectly in numerous methods. Whereas these kinds typically appeared inferior to the required knot, they weren’t clearly destined to fail. Utilizing these two fundamental knots in a compound type appears to be an affordable method to make errors of tying much less detrimental to the ensuing knot.

Picture credit score: David J. Fred/Wikimedia Commons (Original)
Above is a excessive decision photograph taken of those Spot Ties made in Gudebrod Nomex lacing tape. These kinds of lacing tapes are sometimes coated or impregnated with supplies (e.g. artificial rubbers) to extend their knot-holding properties. I am unsure what the tapes seen on the rover are manufactured from, however I might suspect the fabric was chosen for its habits at extraordinarily low temperatures and pressures in addition to excellent UV resistance.

The eager observer could notice that a number of the Spot Ties within the rover photos present the ends perpendicular to the cable bundle and a few parallel. Based mostly on normal expertise with reef and granny knots, one could be tempted to imagine the parallel examples are improperly completed with granny knots. Experimentation with Nomex lacing tape appears to indicate that it is extra a matter of the knot preserving the orientation of the ends because the reef knot was tightened. I discovered that when the Spot Tie is completed improperly within the granny type however with the ends saved perpendicular to the wire bundle they have an inclination to remain that manner. Whereas these experiments are hardly definitive, it does not appear to me that one can inform from orientation of the ends whether or not the knot was correctly tied or not.

There’s additionally the problem of the handedness of the primary half-knot with respect the ends rising from the Clove Hitch portion. The relative orientation proven within the NASA spec does seem like preferable to the choice.

I will not go into a lot dialogue about these stiches for the second, however I consider the one on the left (the working clove hitches) seems on the acute proper fringe of element picture “1” under.

And now for the gorgeous photos…

Picture Credit score: NASA/JPL-Caltech(Original)
Multi-image panorama giving context of rover, deck, and its suroundings. The rim of Gale Crater is seen within the distance.

Picture Credit score: NASA/JPL-Caltech(Original)
Annotated context picture exhibiting areas of following 5 detailed photos. Outlines don’t fairly align to following picture borders resulting from panorama projection.

1
Picture Credit score: NASA/JPL-Caltech/Malin Area Science Techniques(Original)
Examples of one of many flat stitching strategies (proven above) seem on the acute proper fringe of this picture.