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

[dfred]

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:


Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original)

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]

[dfred]

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. 


Image Credit: NASA/JPL-Caltech/Malin Space Science Systems(Original)

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

[SS369]

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

SS

[dfred]

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

That's a great story, isn't it!

Here's a photograph of the "arts and crafts project" being held by astronaut Scott Horowitz:



Image Credit: NASA (Original)

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

[Dan_Lehman]

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*
====

[xarax]

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

[SS369]

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

[knot4u]

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.

[SS369]

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

[Luca]

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!

                                                                                                                      Bye!

[dfred]

[...]
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!

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.



Image Credit: NASA / JPL / UCLA (Original)
In the full size image one can see how pre-made (punched?) holes in the bound seams are used as lacing points.



Image Credit: NASA / JPL / UCLA (Original)
A slightly different angle.



Image Credit: NASA / JPL / UCLA (Original)
The thermal shield in an unlaced state being worked on.  The instrument is bolted to a "shake table" for vibration testing.



Image Credit: NASA / JPL / UCLA (Original)
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.

[SS369]

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

[dfred]

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?

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

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]

[Dan_Lehman]

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 ... .)

[robot1125]

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.