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Ancient Egyptians used knots for purposes both practical and mystical. Ancient Inca used knots to record information. Modern sailors use knots for seamanship. NASA uses hand tied knots (caution PDF) to assemble interplanetary exploration robots like the Mars Science Lab and Curiosity Rover.

I was reminded of this today looking at some of the beautiful images in Troubador's rec listed diary. Examples of such knots are particularly visible in this image from that diary.

Come out into the tall grass for more information on how NASA uses one of mankind's most ancient technologies to advance some of our most modern scientific achievements.

It's no secret of course, that NASA requires hand knots for securing certain kinds of wiring assemblies that are used in the MSL. See NASA-STD 8739.4 Crimping, Interconnecting Cables,  Harnesses, and Wiring But, since the Curiosity mission has been in the news, folks who are particularly interested in knots have taken an interest. The Planetary Society took notice of this using close up images of the instrument deck of the rover and illustrations from the NASA assembly standards, such as you see here.
The Planetary Society piece drew upon a blog called The International Knot Tiers Forum where we find the following interesting observations:  
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.


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.

    Conservative design

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 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"?

    Even pressure

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.

    Controlled tightening

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.

So, ancient knowledge, knowledge so powerful and complex that ancient Egyptians imbued it with religious power, helps make it possible for our engineers and scientists to undertake the most advanced interplanetary robotic exploration ever attempted by Man. That is somehow comforting.

"Don't throw the past away. You might need it some rainy day."

Everything Old is New Again.

Here are my previous diaries in this series inspired by NASA's new roving science lab on Mars, listed in the order I have posted them.

Mars Curiosity Rover -- Meet the ChemCam

Ray Bradbury is Honored Today on Mars

What Curiosity Can Do, Part 2.

What Curiosity Can Do on Mars and in this Election

Will Curiosity Mission Finally Vindicate the Life Science Results from the 1976 Viking Lander?

From Mars: SAM Takes a Deep Breath and Flexes his Arm

From Mars: Here's Looking At You, Kid.

On Mars: Super Rover has X-ray Vision

On Mars: Let the Science Begin

On Mars: We have found an Interesting Rock

On Mars: Obama and Biden Campaign This Week

On Mars: Curiosity Does Contact Science

On Mars: A River Ran Through It

On Mars: Sol 52 Update

Originally posted to Astro Kos on Sun Sep 30, 2012 at 01:28 PM PDT.

Also republished by SciTech and Kossacks on Mars.

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