[HN Gopher] Workmanship standard for crimping, interconnecting c...
___________________________________________________________________
Workmanship standard for crimping, interconnecting cables,
harnesses, and wiring
Author : throw0101c
Score : 98 points
Date : 2024-06-02 16:53 UTC (6 hours ago)
(HTM) web link (standards.nasa.gov)
(TXT) w3m dump (standards.nasa.gov)
| OldGuyInTheClub wrote:
| Before I worked in aerospace, I wondered why that industry cost
| so much. Now I understand that every requirement within each
| requirement document has to be "flowed down," maintained,
| verified, documented, and that compliance has to be proven along
| the chain from design to operation. The number of these documents
| grows at some beyond-linear rate with project complexity.
|
| Of course, this is not all the source of cost but it is a good
| chunk. But, if you're building spaceflight hardware that can't be
| repaired once launched, it is necessary.
| mschuster91 wrote:
| ... and all of the documentation has to be kept around _for
| decades_ , same for the knowledge of how it was constructed and
| maintained. That's what makes missions like Voyager or even the
| ISS _possible_ in the first place - a lot of the people who did
| the early work on either are probably dead now.
| tekla wrote:
| When I worked on some aircraft, every single line of code that
| was added or changed had a digital and paper record of the
| change and the reason for it.
| neilv wrote:
| Inspired by very serious traceability, like for aerospace
| engineering, I did a very-very simple and lightweight system,
| for the security practices & assurances of a non-aerospace
| startup.
|
| I was proud of not only of how effective yet non-encumbering
| the practices, and how smart our external assurances, but the
| lightweight way of implementing traceability between the two. A
| single, short _internal_ document tracked not only practices,
| but sections were annotated with all the _external_ documents
| /instances that made assurances wrt to those practices. So when
| we did need to change something, we knew what was easy and hard
| to change. (Interface vs. implementation.)
|
| Of course, the very first externally-shareable document side of
| this, I explained to our enterprise salesperson that it would
| convince the partner's savvy IT people that we were fully
| competent and diligent, and said a bit about how everything in
| there was carefully designed and traceable... Well, maybe you
| can guess how that went.
|
| Not everyone is familiar with building things that really have
| to work correctly, nor with how a little bit of judicious
| process can actually make things dramatically more efficient,
| nor with any kind of traceability rigor. If you're not familiar
| with that, or aren't aligned with that, then the most efficient
| thing in your mind might be to quietly change a copy of
| engineering document, to say whatever is most expedient in the
| moment. And don't tell anyone that you changed a copy of an
| engineering document, since that would not be a happy vibe when
| everyone likes what you're saying, and so not a good use of
| your time. :)
|
| (I default to confidentiality about such things, even in
| absence of NDA. But I can mention this anecdote, in this
| professional practice discussion within the field, since the
| company is no longer in business, and there are no unresolved
| liabilities.)
| newsclues wrote:
| I think it may be seen as a feature not a bug when there is
| cost plus contracts and regulatory capture limits
| competition.
| OldGuyInTheClub wrote:
| I will agree that there is a lot of overhead per
| engineering hour in this market area. But, I also think
| there's a great deal of misunderstanding about how
| government contracting works. Cost-plus fixed fee means the
| fee is agreed upon at the outset. If you overrun you may
| get the cost of the extra work performed but you get no fee
| (profit) on it. When the corporation sees that dilution,
| there is usually hell to pay. If the government gets tired
| of the overruns, it can and does cancel the contract.
|
| There are different contract types with award fee and/or
| incentive fees each with its own peculiarities.
|
| The Federal Acquisition Regulations (FAR) make for
| interesting reading:
|
| https://www.acquisition.gov/far/part-16
|
| " Part 16 - Types of Contracts"
| euroderf wrote:
| Oh but we're bringing in some hotshots from McKinsey who have
| some ideas about how we can trim all this unnecessary overhead.
| They have assured me that absolutely nothing can go wrong.
| nickt wrote:
| There were some good comments last time around, I can't believe
| that was 9 years ago!
|
| https://news.ycombinator.com/item?id=9905875
| Modified3019 wrote:
| A personal favorite, the Fastener Design Manual:
| https://ntrs.nasa.gov/citations/19900009424
|
| In particular
|
| >Lockwashers
|
| >The typical helical spring washer shown in figure 14 is made of
| slightly trapezoidal wire formed into a helix of one coil so that
| the free height is approximately twice the thickness of the
| washer cross section. They are usually made of hardened carbon
| steel, but they are also available in aluminum, silicon, brome,
| phosphor-bronze, stainless steel, and K-Monel. The lockwasher
| serves as a spring while the bolt is being tightened. However,
| the washer is normally flat by the time the bolt is fully
| torqued. At this time it is equivalent to a solid flat washer,
| and its locking ability is nonexistent. In summary, a lockwasher
| of this type is useless for locking.
| petee wrote:
| Someone on YT did a demonstration on a paint shaker, and the
| bolts loosen nearly as fast as having none. Internal/external
| tooth washers or nylocks are the way to go
| cuSetanta wrote:
| Nordlock washers are the best, but they are expensive and a
| little space inefficient.
| analog31 wrote:
| One useful property is that when partially tightened, they
| allow slight re-positioning of an assembly, before driving the
| fastener all the way home. In other words, they're actually
| used as springs.
| cuSetanta wrote:
| As a spacecraft Assembly, Integration and Test (AIT) Engineer,
| one of my areas of expertise is harness manufacture and routing.
| So this naturally involves an awful lot of crimping. I am a
| certified crimping operator and inspector under the ECSS
| standards (which go a bit overboard at times in their
| requirements when compared to the NASA standards).
|
| I am lucky to have built a large amount of harness has/is/will
| fly on many spacecraft for many customers. There are a lot of
| unique challenges to crimping for spacecraft harnessing, but in
| almost all circumstances the main issue has be schedule. Very few
| project managers that I have worked with, even those who have a
| lot of experience, plan for enough time to complete the
| harnessing side of a project.
|
| Depending on the number of crimping configurations that are
| present in a system, it can take days to calibrate all of the
| crimp tools before starting. Every crimp needs to be inspected
| before the heatshrink can be shrunk, and often before the next
| crimp can be performed if the routing is critical. Routing
| involves labeling, gluing of tie-bases, bundling of harnessing,
| and the shielding.... jesus christ the shielding can be a
| nightmare...
|
| Man I love making harness, honestly one of my favourite things to
| make. Not sure if anyone cares enough to have questions, but
| happy to answer them if they exist.
| goy wrote:
| I'd like to know more about the education & career path that
| lead you there ...
| cuSetanta wrote:
| At undergraduate level I studied Physics and Astronomy, and
| then did a research MSc as an optical astronomer, which I
| hated and drove me away from Physics and Astronomy as a
| whole.
|
| I spent a few years working in IT Support before deciding to
| go back to University to study Spacecraft Engineering at
| Surrey University. Which was a wonderful course, that gave an
| incredible overview of how one builds a spacecraft. More than
| most of the Master programs I have seen in the field since,
| the guys at Surrey had very real experience building quite a
| few spacecraft, which shone through in the projects and
| courses.
|
| After that I started a PhD in Southampton that had an
| industrial sponsor, who eventually ended up offering me a job
| to build spacecraft before I finished the PhD itself (which
| was a little complicated in itself), which I took.
|
| After I started with them, I basically apprenticed under an
| experienced AIT engineer who was coming up to retirement.
| This is where I really learned a lot. If you ever get the
| chance to work under someone in the later stages of their
| career, you really can learn a lot from them.
|
| That was at OHB Sweden, which was an excellent place to see a
| broad range of things in the industry. I go to work on
| multiple spacecraft and various stages of development, from
| proposal, to qualification, to final assembly and test, and
| to launch as an operations engineer. Really a super
| experience I am not sure I could have been luckier ending up
| there.
|
| After that I joined a very small team building the ispace
| lunar lander, which I am fairly certain will remain the
| pinnacle of my career. Never have I worked with such a great
| team on a great project. Everything just worked between us,
| and a small team really achieved something spectacular (even
| if it ended up in a crater on the moon).
|
| Now I am working in Ireland for a data acquisition system
| developed for flight and launch vehicles. Learning the ins-
| and-outs of ethernet communication and analog circuitry. So
| far my complete lack of understanding of electronics hasn't
| been a problem, somehow.
| mechhacker wrote:
| In my brief stint working on spacecraft in the private sector I
| worked with guys like you that did beautiful things with wiring
| that I loved to see.
|
| I hear you on scheduling too. I've given best estimates and
| they then get chopped up and halved (or worse) by management
| types, then things start to slip and we end up being closer to
| what was originally estimated, but somehow everyone then gets
| surprised.
| cuSetanta wrote:
| As you say, things shift around, promises get made,
| everything gets delayed and all of a sudden there is no
| margin left. Unfortunately AIT has to do all of the hardware
| work with no margin so much of the time.
|
| Secretly I love the power that can give us. You can shout at
| me all you like in the meetings Mr. ESA engineer, but if the
| holes don't line up, I cant put a bolt through them. Nothing
| quite like drilling holes in spacecraft on the launch pad.
___________________________________________________________________
(page generated 2024-06-02 23:00 UTC)