Cable lacing on the Curiosity rover(igkt.net)
igkt.net
Cable lacing on the Curiosity rover
http://igkt.net/sm/index.php?topic=4028
11 comments
"Knot theory" always concerns strings that are joined at either end to form a closed circuit. Regardless, I don't think abstract mathematics does much for you when the problem is so simple and 'practical'.
I doubt it. See: http://en.wikipedia.org/wiki/Trefoil_knot
Why are the cables exposed ? Wouldn't it better to fix them inside the rover and only have the relevant ends pop out when there is a need to connect to a device located on the outside of the shell in order to reduce interferences and external damages ?
My guess is that they have cables on the outside _and_ inside, and putting yet another cover over the outside cables would mean more mass. As-is, they only have to worry about wind and sand, so extra metal shielding is probably not necessary.
Does anyone know why so much cabling on Curiosity is on top of the vehicle, exposed to the elements?
Surely it would be safer to contain those cables in the body? It would just take a rock to fall on the rover from a cliffside or similar to damage those cables.
Surely it would be safer to contain those cables in the body? It would just take a rock to fall on the rover from a cliffside or similar to damage those cables.
Just a guess, but maybe its to make diagnostics easier. If something is wrong they can image the cables and look for breaks.
There is not much in the way of 'elements' on Mars. If you look closely the cables are encased in something, but static electricity and dust storms are the largest problems and fairly easy to deal with.
For just a moment, I found myself worried about how they would hold up when it rained...
Wouldn't that be a nice problem to have. The only way to fix it would be to send some humans to the rover for a repair job...
Just had to post this photo which I found after looking around as it's related:
http://upload.wikimedia.org/wikipedia/commons/4/46/System_Te...
Saturn V instrument unit.
Awesome piece of engineering.
http://upload.wikimedia.org/wikipedia/commons/4/46/System_Te...
Saturn V instrument unit.
Awesome piece of engineering.
Cool picture. It looks to me like most of those long-running cable bundles are secured with black plastic zip ties--ironic given the text of the article.
This is awesome. I'm going to lace all my cables now.
In these kinds of applications, what do they use to attach the cables to something? It looks like on the rover they have special tie points built onto the rover surface -- is that what is done in other applications too?
In these kinds of applications, what do they use to attach the cables to something? It looks like on the rover they have special tie points built onto the rover surface -- is that what is done in other applications too?
Either they are laced parallel to a support strut, which can be thought of as a very hard wire, or lashed down to some support point. You can also see this in large data centers.
http://www.reddit.com/r/cableporn
http://www.reddit.com/r/cableporn
Great link. There goes my afternoon :-)
The first item is amazing as well (ST-124-M3 inertial platform i.e. Gimbal unit for Saturn V)
About: http://en.wikipedia.org/wiki/ST-124-M3_inertial_platform
Pron: https://upload.wikimedia.org/wikipedia/commons/4/44/ST-124_u...
This sort of engineering is as much art as engineering and I truly respect the people who designed and built it.
The first item is amazing as well (ST-124-M3 inertial platform i.e. Gimbal unit for Saturn V)
About: http://en.wikipedia.org/wiki/ST-124-M3_inertial_platform
Pron: https://upload.wikimedia.org/wikipedia/commons/4/44/ST-124_u...
This sort of engineering is as much art as engineering and I truly respect the people who designed and built it.
If anyone is interested in more of these standard practices in regards to aircraft construction the following book details the proper methods that should be used.
http://www.amazon.com/Standard-Aircraft-Handbook-Mechanics-T...
http://www.amazon.com/Standard-Aircraft-Handbook-Mechanics-T...
An entire forum about knot tying?! Sign me up!
Can I get an explanation as to how the OP is making the claim that these are IN FACT these kind of knots? I mean I cannot see how this image is of sufficient resolution to support this.
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I love the fact that there are people, who when faced with photographs sent from a robot on mars, will crop out all the bits of image with mars in them, so they can get a better look at the knots used to tie all the cables down. They must have absolutely immaculate sock drawers.
Its hacker news, not daytime television. We don't have to pretend to be boring middle of the road when talking to each other.
What I find fascinating about this story is I've seen much larger and much more elaborate cable lacing jobs that look just as good at telco central offices and data centers, but its always very vague about what exact part of my NDA or employment agreement I'd be violating by posting (or taking, or distributing) pictures. These mars pictures, cropped, may be the only chance for a civilian non-employee to ever legally see professionally done cable lacing, weird but true. There's a zillion other places to see the surface of mars, but only a few to see cable lacing.
Its interesting that in advertising pictures they always use superglue to make the cables look "PHB-good". So you can't see cable lacing in ads, which is too bad.
Done correctly, cable lacing is, literally, an art form. One guy I worked with "knitted" geometric patterns as he spaced the lacing in various locations and used different colors. Also I saw at least one large example of AT+T being "dot matrixed" into a large bundle of cables by careful spacing of lacing.
Artistic cable lacing is kind of an "apprentice" masterpiece situation, you learn lacing well enough to do art, then you show it to other techs (and your boss) to prove you're not an apprentice anymore, then, sadly, for most techs, no more lacing art work. Oh well.
What I find fascinating about this story is I've seen much larger and much more elaborate cable lacing jobs that look just as good at telco central offices and data centers, but its always very vague about what exact part of my NDA or employment agreement I'd be violating by posting (or taking, or distributing) pictures. These mars pictures, cropped, may be the only chance for a civilian non-employee to ever legally see professionally done cable lacing, weird but true. There's a zillion other places to see the surface of mars, but only a few to see cable lacing.
Its interesting that in advertising pictures they always use superglue to make the cables look "PHB-good". So you can't see cable lacing in ads, which is too bad.
Done correctly, cable lacing is, literally, an art form. One guy I worked with "knitted" geometric patterns as he spaced the lacing in various locations and used different colors. Also I saw at least one large example of AT+T being "dot matrixed" into a large bundle of cables by careful spacing of lacing.
Artistic cable lacing is kind of an "apprentice" masterpiece situation, you learn lacing well enough to do art, then you show it to other techs (and your boss) to prove you're not an apprentice anymore, then, sadly, for most techs, no more lacing art work. Oh well.
Well, there's always http://www.reddit.com/r/cableporn
They need to avoid the trend of using that suffix to mean "enthusiasm"; the compound word does not conventionally mean what they intend. Yes, languages evolve, but the etymology doesn't remotely support it.
Whoa! I literally had no idea there were sub-reddits so, um, specific.
There's way more than you can imagine (or at least, that I can).
Another interesting point is that in general, the more specific the sub-reddit, the less it is infected with the type of "reddit culture" that gets so much bad rep here on HN (although occasionally it always gets some, cause Reddit has a shared culture--I personally don't mind, really).
Another interesting point is that in general, the more specific the sub-reddit, the less it is infected with the type of "reddit culture" that gets so much bad rep here on HN (although occasionally it always gets some, cause Reddit has a shared culture--I personally don't mind, really).
Or they just really like knots. Why do you think that an interest in knots means that someone is going to be OCD about everything else in their life?
Different people like different things. Just because they geek out on something different from what you geek out on does not make them abnormal.
Different people like different things. Just because they geek out on something different from what you geek out on does not make them abnormal.
I was being nice. I genuinely do love them for this and I found it really interesting. I am also allowed to find it funny though. And I am sorry for stereotyping an entire group so lazily. I am sure that many of them actually have really messy sock drawers, if only in the hope of waking up to a really interesting variety of knot.
If you like this, then Ian's Shoelace Site will bring tears of joy to your eyes.
http://www.fieggen.com/shoelace/
I think it is perhaps the single greatest website on the entire internet.
http://www.fieggen.com/shoelace/
I think it is perhaps the single greatest website on the entire internet.
Tonight I learned that I've been tying my shoelaces the wrong way (granny knot) for as long as I can remember. Thank you, JonnieCache.
I've been using the Ian knot for years, it's absolutely brilliant.
http://www.fieggen.com/shoelace/ianknot
http://www.fieggen.com/shoelace/ianknot
Join the club, I was 31 when I finally learned how to tie my shoes properly. So much for doing as my mother taught me...
I've been using Ian's secure shoelace knot for about two years now, it's really fantastic.
http://www.fieggen.com/shoelace/secureknot.htm
http://www.fieggen.com/shoelace/secureknot.htm
It may be that their socks are all a mess, but I bet their shoes are laced perfectly.
I love reading about flight hardware. I have a bookshelf full of this stuff.
Mars itself is neat. But they haven't done much exploration with this rover yet, and so: Knots is what we got. :-)
Mars itself is neat. But they haven't done much exploration with this rover yet, and so: Knots is what we got. :-)
Your backhanded compliment is a bit disturbing for being the top comment. I've largely dismissed the complaints about the HN community becoming more negative, largely thinking that mature realism was being mistaken for unwarranted negativity.
However, this comment, along with the negative comments about the uptime of Tindie's blog (http://news.ycombinator.com/item?id=4472348), has me thinking that these complaints of undue negativity are justified.
I find the attention to detail involved in selecting knots to be a tremendously interesting aspect of sending a physical vehicle to mars, and I find it to be a testament to human specialization and intelligence that there's a whole community of knot experts that can provide so much insight into the knot choices. Implying some sort of OCD around sock drawers seems incredibly rude, and counter-productive to building or maintaining a culture of technical excellence.
However, this comment, along with the negative comments about the uptime of Tindie's blog (http://news.ycombinator.com/item?id=4472348), has me thinking that these complaints of undue negativity are justified.
I find the attention to detail involved in selecting knots to be a tremendously interesting aspect of sending a physical vehicle to mars, and I find it to be a testament to human specialization and intelligence that there's a whole community of knot experts that can provide so much insight into the knot choices. Implying some sort of OCD around sock drawers seems incredibly rude, and counter-productive to building or maintaining a culture of technical excellence.
I've read and reread ktizo and I'm not seeing the negativity. He drew a correlation based on their attention to detail and if mistaken should be about as insulting as mathematical error.
Perhaps there's a cross-cultural interpretation associated with sock drawers that I'm missing. Granted there has been negativity on HN lately, but are we not manufacturing drama here?
//edit: I read it that he's impressed with their focus and passion, which sounds more like a compliment.
Perhaps there's a cross-cultural interpretation associated with sock drawers that I'm missing. Granted there has been negativity on HN lately, but are we not manufacturing drama here?
//edit: I read it that he's impressed with their focus and passion, which sounds more like a compliment.
"I love that ..." is the rhetorical equivalent of "Don't take this the wrong way, but ..."
There's a pretty clear implication that it's silly to "crop out" pictures of mars, focus on knots, and the kind of people that would do that would be OCD in their maintenance of sock drawers.
It's a silly, vaguely cutting generalization. Observe the top reply, which takes a defensive stance: http://news.ycombinator.com/item?id=4474178
There's a pretty clear implication that it's silly to "crop out" pictures of mars, focus on knots, and the kind of people that would do that would be OCD in their maintenance of sock drawers.
It's a silly, vaguely cutting generalization. Observe the top reply, which takes a defensive stance: http://news.ycombinator.com/item?id=4474178
Perhaps there's a cross-cultural interpretation associated with sock drawers that I'm missing
I do hope so. As then there is a chance that we might find out what it is and then everything might just make sense. Otherwise I'm just going to paraphrase Keynes and assume that internets can remain irrational a lot longer than I can stay sober.
I do hope so. As then there is a chance that we might find out what it is and then everything might just make sense. Otherwise I'm just going to paraphrase Keynes and assume that internets can remain irrational a lot longer than I can stay sober.
Your commment strikes me as more negative than its parent.
I had no idea that sock drawers were such a touchy subject.
However I would say that if you want to maintain a culture of technical excellence, it should be built well enough in the first place to cope with things like occaisional wayward comedy about the possible sock organisiation habits of fans of practical topology, without getting too upset about it.
Otherwise it isn't a very good culture of technical excellence and it will all fall apart the first time somebody sneezes.
However I would say that if you want to maintain a culture of technical excellence, it should be built well enough in the first place to cope with things like occaisional wayward comedy about the possible sock organisiation habits of fans of practical topology, without getting too upset about it.
Otherwise it isn't a very good culture of technical excellence and it will all fall apart the first time somebody sneezes.
I don't think your reply (the tone can be effectively summarized as "Toughen up, nerd") is any more inclusive than the first comment.
Is nothing to do with being tough. You might as well ban stuff like Dilbert references as well if you get so upset at comedy that references stereotypes of engineers.
[edit] I was also not being backhanded in the first place. You are allowed to include jokes in complements and you do not have to show some sort of undue reverence for people whose work you appreciate when you point out that you like what they do.
[edit] I was also not being backhanded in the first place. You are allowed to include jokes in complements and you do not have to show some sort of undue reverence for people whose work you appreciate when you point out that you like what they do.
Your comments are simply misdirection of blame by cutting me down instead of the original knot expert you started with. The problem, as you see it, isn't that you ascribed a negative to the engineers (cropping out mars, focusing on knots, OCD attentiveness to sock drawers), but rather, you attempt to frame it as a simple lack of humor on behalf of external observers.
The problem with this analysis is that while Dilbert is funny (and fake), you were demeaning (of real people), and your defense uses the same subtly demeaning tone as your original comment.
The problem with this analysis is that while Dilbert is funny (and fake), you were demeaning (of real people), and your defense uses the same subtly demeaning tone as your original comment.
Speaking as someone whose really likes topology, and who has been around boats their whole life, I suspect that you have not got the first fucking clue what I think regarding people who obsess about knots.
Also, I would rather you didn't attempt to try and act as some sort of translator for me, as you appear to be a complete and utter dick.
Sorry for my undue negativity about this.
Also, I would rather you didn't attempt to try and act as some sort of translator for me, as you appear to be a complete and utter dick.
Sorry for my undue negativity about this.
The other replies made to your original comment are defensive. Perhaps we all misinterpreted your comment.
Can't blame them. So far it's just rocks.
Two words: zip tie.
When there is an 'obvious' answer, its always useful to ask the question "Hmm, zip ties would have been easier/quicker than knots, do they know something I don't?"
It is the 'curious' response.
If you have used zip ties in adverse conditions you would immediately know they suffer from two huge issues, the first is that under stress the ratchet nib can break and they release, the second is that on a strength to volume and strength to weight ratio they are grossly inferior to any number of threads.
So for something you are sending very far away, and for which you have to put 4.3 ounces of launch system together for every ounce you want to land on the surface, mass and volume add up, and you can't really go out and replace a broken one can you?
It is the 'curious' response.
If you have used zip ties in adverse conditions you would immediately know they suffer from two huge issues, the first is that under stress the ratchet nib can break and they release, the second is that on a strength to volume and strength to weight ratio they are grossly inferior to any number of threads.
So for something you are sending very far away, and for which you have to put 4.3 ounces of launch system together for every ounce you want to land on the surface, mass and volume add up, and you can't really go out and replace a broken one can you?
Also, zip ties are plastic. Most plastics decay when exposed to ultraviolet. As this is NASA, there is probably some funny polymer that can get the job done, but why fix what isn't broken?
Zip ties are certainly quicker, but when everything is vibrating they concentrate the cable flexing stress at the edges of the zip tie. I've seen wires crack in my own robots from cable ties.
I can't use zip ties on my boat. Two months in the sun and they're toast. They quite literally turn to dust.
Perhaps zip ties can't withstand the changes in pressures or heat. Expansion, contraction, and all that mess. I'm simply arm chair guessing here.
The link itself addresses this:
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.
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.
I'm not convinced by this explanation. A skilled person will do fine with a zip tie. Knots once tied should not be easy to untie in such applications - you don't want possibility of failure.
An over tightened zip tie can be quickly cut away.
The thing that seems reasonable to me is lacing works for thin cabling, but if you have a fat bundle of cables (say 5mm or more in diameter) I can't really see a big problem for zip ties.
An over tightened zip tie can be quickly cut away.
The thing that seems reasonable to me is lacing works for thin cabling, but if you have a fat bundle of cables (say 5mm or more in diameter) I can't really see a big problem for zip ties.
In the Aerospace industry, special applicator guns exist to zip bundles of wire in a specified tension. [1] But the use of butchers twine and wax line in still rather common.
A few more points:
- Zip ties are also made of ABS plastic - which has a Tg of <200*F...things start uncoupling around there.
- Kapton gets brittle, and most of these cable bundles are covered in the stuff.
- Mass. There are plenty of lightweight fibers (Aramid/Kevlar, carbonfiber, nanofibers, etc) whose tensile strength is greater than steel.
- Lastly, I'm biased against zip ties after multiple recabling projects while in IT...
[1] http://tools.tycoelectronics.com/cabletiegun.html
A few more points:
- Zip ties are also made of ABS plastic - which has a Tg of <200*F...things start uncoupling around there.
- Kapton gets brittle, and most of these cable bundles are covered in the stuff.
- Mass. There are plenty of lightweight fibers (Aramid/Kevlar, carbonfiber, nanofibers, etc) whose tensile strength is greater than steel.
- Lastly, I'm biased against zip ties after multiple recabling projects while in IT...
[1] http://tools.tycoelectronics.com/cabletiegun.html
Have you considered consulting for NASA? They've likely put no thought into materials selection and I'm sure they'd benefit from your vast experience in the performance of zip ties in non-terran environments.
It's not just NASA, zip-ties are banned in plenty of data centers and telecom facilities for the reasons cited.
Less of a concern on Mars, but the edge where the excess is cut away can be really sharp and hazardous as well.
Less of a concern on Mars, but the edge where the excess is cut away can be really sharp and hazardous as well.
Lacing is lighter, and mass matters.
Since there are no skilled persons on Mars, they have to do better than "fine."
The thermal extremes of space are severe, and can easily render a simple zip tie to be useless. Another issue is the potential for materials (plastics are a particular headache) to offgass in a vacuum, which can send nasty contamination into places that it shouldn't be (like sensitive instruments). They actually test these components in vacuum chambers while thermally cycling the assemblies to figure this out.
[deleted]
Some of the more higher resolution pictures suggest that the lacing is actually made from metal wire or synthetic fiber in a braid, which might have better environmental suitability than an injection molded solid plastic zip tie. Knots also provide endless tightening configurations, where as zip ties have quantified steps, which could simply be over tightened on an essential cable by accident providing a stress point for a small cable or wire to break at in a couple of years.
Also arm chair guessing.
Also arm chair guessing.
Well, neither wikipedia nor the linked article say why zip ties aren't used. I don't know what material the lacing is made from, but unless it is a natural thread I'm sure zip ties can be made from that material.
It might be that tension (which is what I worry about when I zip tie delicate things like optic fibre) is better controlled in hand tied knots, but zip ties can be tied pretty precisely.
It might be that tension (which is what I worry about when I zip tie delicate things like optic fibre) is better controlled in hand tied knots, but zip ties can be tied pretty precisely.
"but unless it is a natural thread I'm sure zip ties can be made from that material"
A zip tie requires a different combination of compression strength, tensile strength, and elongation stability compared with lacing. So the materials are not interchangeable.
Also, individual fibers bundled into a cable is MUCH MUCH stronger than the exact same amount of material as a single homogeneous cable.
And individual fibers can handle flexing and vibration far far better than a single large strand.
A zip tie requires a different combination of compression strength, tensile strength, and elongation stability compared with lacing. So the materials are not interchangeable.
Also, individual fibers bundled into a cable is MUCH MUCH stronger than the exact same amount of material as a single homogeneous cable.
And individual fibers can handle flexing and vibration far far better than a single large strand.
See this: http://code541.gsfc.nasa.gov/Uploads_materials_tips_PDFs/TIP... for acceptable lacing materials.
Zip ties are 'quantized' by the ratchet, so you can find an 'optimum' tension point that is between two ratchet points. Which doesn't happen with laces.
And for threads (like kevlar thread) it doesn't have the compression strength to be good zip tie. There is a lot of information about what NASA considers to be good and not good wrapping techinques here: http://workmanship.nasa.gov/lib/insp/2%20books/links/section...
Also they mention out gassing which is something I completely missed, plastic zip ties have that issue as well. Any void in the zip tie also becomes a real problem in vacuum.
Zip ties are 'quantized' by the ratchet, so you can find an 'optimum' tension point that is between two ratchet points. Which doesn't happen with laces.
And for threads (like kevlar thread) it doesn't have the compression strength to be good zip tie. There is a lot of information about what NASA considers to be good and not good wrapping techinques here: http://workmanship.nasa.gov/lib/insp/2%20books/links/section...
Also they mention out gassing which is something I completely missed, plastic zip ties have that issue as well. Any void in the zip tie also becomes a real problem in vacuum.
As a matter of fact, the article goes into some detail about both why zip ties aren't used and what the lacing might be made of.
Three words: read the link.
zip ties are addressed itfa.
[deleted]
For example, is it possible that there exists another, more optimal, type of knot that we should have chosen had only our knot theory had been more advanced?