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.
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, 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.
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 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.
"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.