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

Practical Knots
41

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 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 on the Lunar Reconnaissance Orbiter. Beyond traditional cable lacing, they used some distinctly corset-like 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 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

Image Credit: NASA / JPL / UCLA url=http://www.diviner.ucla.edu/gallery/div4lrg.jpg[/url]
In the full size image one can see how pre-made (punched?) holes in the bound seams are used as lacing points.


http://www.dfred.net/misc/igkt/20140117/small/div1lrg.cropped.jpg

Image Credit: NASA / JPL / UCLA url=http://www.diviner.ucla.edu/gallery/div1lrg.jpg[/url]
A slightly different angle.


http://www.dfred.net/misc/igkt/20140117/small/shaketestlrg.cropped.jpg

Image Credit: NASA / JPL / UCLA url=http://www.diviner.ucla.edu/gallery/shaketestlrg.jpg[/url]
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

Image Credit: NASA / JPL / UCLA url=http://www.diviner.ucla.edu/gallery/div_lro_lrg4.jpg[/url]
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.

42

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

43

No problem! When I saw it last week I knew it was just too nifty not to be added to this thread. :slight_smile:

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]

44

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*

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 … .)

45

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.