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.
My grandfather used to work on telephone field network boxes (e.g., the big boxes full of messes of wires in residential areas).
One job was to look for outliers in the network, and they spent time studying areas with an unusually large number of issues and ones with an unusually low number of issues.
There was a part of the phone network that was decades overdue for an overhaul but had no issues, so they inspected it. (This was decades ago, so the replacements for this antique could be modern day museum pieces).
When they took a look, everything was corroded beyond reason, as expected. However, the connections were still low noise / low resistance.
The old boxes used some sort of post connector and a crimp. It had something like two or four points of contact for redundancy (all contact points would need to corrode before it failed).
In the boxes with no failures, the (long gone) technician simply stuck the end of the wire into the post crimp hole, then wrapped slack wire around it a dozen times.
This gave it 100’s of contact points, and (after reverse engineering the technique) it took something like 1/10th as long per connection.
Sadly, we’ll never know if the installer was a genius, lazy or both.
Anyway, the crimp connectors in fig 19-25 and 19-28 of the nasa article look like the same concept but turned inside out.
I'm not sure why more of those didn't use wire-wrap, it's super fast and is really reliable. I've seen some bell terminals that were wirewrap but punchdown was more common in my experience.
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.
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.
I once rewired a racecar engine loom with red 18gauge wire and used different colour heatshrink to differentiate power, ground, signal etc.. also happy to answer any questions.
Haha we had one roll of wire and it was 1am so we made do, I would have much preferred something a little more suitable. But hey you gotta do what you gotta do.
What is involved in correctly inspecting a crimp? I find it hard sometimes to tell the difference between a crimp that's halfway to severing the wire and one that can come adrift at a moment's notice.
But then those are mostly the cheap ones with the plastic rings so you can't really see what's going on inside them.
The inspection is primarily visual, to ensure that the stands are well aligned in the crimp, with no protrusions. And to check there is no damage to the wire due to stripping or a mis-crimp.
For under/over crimping, thats mostly taken care of with the tool calibration. And every shift (work day or X crimps) samples are taken to check the tool is still performing well.
Interesting, so it's mostly in the tool setting! I shall have to see if it is practical to find some way of calibrating my (fairly rubbish!) crimp tool and see if they even keep a setting.
If you have a fish scale, you can see what the retention force is fairly easy. Thats the primary method we use for calibration, albeit with a specific testing hardware.
During college I had a job wirewrapping circuit boards and putting printed circuit boards together. Most people would make a rat's nest out of the wiring, but I would lay everything out in a pattern. With a pattern, it's much easier to spot errors.
So as neither an EE nor an ME (nor a qualified SE!) I've been in charge of some fairly complex mechatronic systems development for the last near-decade. IMHO the whole harness thing seems to be on the way out, excepting very specific situations where every last bit of weight really matters. Why? First, cost. Not having point to point means you aren't an off the shelf item, which means costs 10x immediately. Second, communications friction. While numerous providers can create arbitrarily complex harnesses as a commercial service, they generally disagree on everything from the manner by which cable qualities are specified to the sequence by which a termination should be made to what a length means with respect to a radius, etc. especially when crossing national boundaries. Third, complexity. Shared buses are harder to manage from a project evolution standpoint, and make it much harder to isolate and debug misbehaving nodes. Now I can see why all of this is worth it on a spacecraft, where weight matters, or in a car, where volume is assumed, custom connections are probably needed owing to a high vibration environment and every communicating component is probably either relatively well tested (auto grade transceivers) or relatively simplistic (window or door controller) or both, but for the rest of us where a smaller volume is assumed it seems to me harnesses are falling out of favor. Their chief benefit is weight reduction and nominal material cost reduction but the accrued costs in real terms outweigh these savings for the majority of projects, IMHO. Does this echo your own experience?
Space is very slow to change, and traditional harnessing is going anywhere for the time being.
I cannot speak to the newer systems on the market like Starlink, their economies of scale are closer to car manufacture, so for harnessing, they likely do it similar to that industry. Form boards and very repeatable methods for producing a harness that has been well designed into the chassis of the spacecraft to be installed at a specific point. But much of those techniques are relatively unchanged from what I do, just the timing and overall design is more optimised.
Most of the harnessing I have done is very bespoke, and happens at many stages throughout the integration as things are installing, finalised, and what-not.
Thanks for taking the time to reply. I'm going interpret that as a soft yes with reservation since you seem to be extremely knowledgeable in this specialist area and additionally state that you are doing 'very bespoke' work within that. Interesting stuff, great to hear from someone with such knowledge. I suppose Starlink/SpaceX people are NDA'd to the point they can't comment, maybe we'll hear from them in future. FWIW internally we've achieved autonomous cable production ex termination (length, strip and cut including measured splice-points - rarely used), and custom bus bars which I guess are a nominal harness in a sense. Anything more complex we need pre-terminated still gets sent out.
I would also add that the 'New Space' scene is going to be much more willing to accept autonomous manufacturing methods. People like ESA are much much more resistant to change, and will take a lot of convincing that it is as good as the slow manual method.
Honestly, as things are looking, I am likely to be leaving the space sector in the near future, so I am not too worried about protecting my job or future on that front. The more accessible space is the better, even if that means people like me become less common.
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.
What brand of connectors do you favor using professionally and for personal projects? I imagine the list of spacecraft certified companies isn’t that long.
The main brands I would see would be Glenair, Souriau, and ITT Canon. Once you are paying the the space quality hardware, its all much of a muchness really. Glenair would probably be top dogs in this space.
I have used other manufactures with their own propriety connectors, like Harwin, which are a bit awkward.
The various styles of connectors do matter a bit. Micro-DSUB and Nano-DSUB are a bit of a pain, as you generally get the connector with flying leads, so have to inline (butt) splice.
38999 Circular connectors are great to work with the hardware, but order the right parts is a nightmare as they all have phone number part names.
Crimping is essentially quite a low skill method of connecting wires, when compared to the high skill and experience to do it reliably with solder. I would have a lot of trust in the Boeing crimpers, and I have worked with the SpaceX guys, and they were all very good.
Recently the Peregrine Lander had wiring issues that led to using the NASA payload to perform the landing. The Vega-C launcher was lost not long ago as two connectors were swapped, connecting two engines in reverse order.
Wiring issues cause a lot of failures that are found on-ground for the most part. But plenty have made it through to fail on orbit.
>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.
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
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.
(OCR error: s/brome/bronze/. Just pointing this out as a warning because I read it literally, and was very confused and spent some time search querying silly things).
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.
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.)
> 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.
You might be joking here but in case you're not, there is serious configuration control and change management at play. Documents go into a controlled repository, are watermarked, and have other protections applied to them. Anyone trying this especially on a government contract is risking a lot.
Yep, I was speaking vaguely, of a non-aerospace, non-government enterprise salesperson, quietly modifying a copy of an engineering assurances document, before handing off the copy to a partner.
Right after being told that things are written as they are for good reasons, and there's traceability, and how this is good for our credibility, and the exact way things were done is a big win for our engineering agility.
I brought small bits of inspiration from aerospace engineering there, but sometimes an organization has surprise pockets of more remedial learning that are needed. Like the lesson of, "You can't just say whatever you think will have a good vibe with the partner/customer in the moment, when it's about engineering, contracts, etc."
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:
The government contracting scam is to agree to a set percentage of the total cost as profit, so the contractor has an incentive to increase the total cost in order to maximize the dollar amount of profit they can extract. And that’s without using subcontractors to transfer even more wealth.
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.
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.
... 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.
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.