Solder as glue

[amptramp]

.. Someday I may tell you the story of what Canadian Tire has in space and how it got there...

Curiosity piqued...

You asked for it:

The CTC Spacecraft

Even if it has been a bad day, whenever I walk past the automotive paint section at Canadian Tire, that large rack of rattle-can aerosol paints, it always makes me smile.  Many years ago, Spar Aerospace bought a case of twelve cans of Canadian Tire exhaust pipe enamel and sent it 22,000 miles away.  If you are wide awake, you will realize something:

It is no longer on this planet.

I was called in to do two hours' work on a proposal one winter Saturday at 9:00 AM – that miserable unpaid work that engineers have to endure in certain companies.  But by the time I left at 11:00 AM, the story I had heard made the day worthwhile.

Several years before, we had been working on the Communications Technology Satellite, CTS, later renamed Hermes when it was launched on 27 Jan 76. I was on that program for three and a half years and I will definitely miss some aspects of it. The craftsmanship was one: our component quality engineer once showed my a circuit board and asked what I thought of it. I thought the solder joints had too little solder on them. He said, "Look at it through this eye loupe and see what you think." The solder fillets went halfway up the leads of the gullwing circuit leads. He continued, "You will never see a better soldering job than that." That was in 1976 and what he said was true - I have never seen craftsmanship like that again (or I should say craftswomanship) - the three women qualified for this job were like gods in the industry. While I was working on that proposal, I heard the real truth about how some other things were put together.

CTS was the first synchronous communications satellite with 200 watts output, so it could be received with an 8-foot diameter antenna. Modern satellite TV users have a 20" dish, but before CTS, you needed a 30-foot diameter radio telescope antenna – not the thing for consumers. CTS was designed to broadcast into communities in the far north where the receiving antenna could be hauled up on the back of a pickup truck.

It was parked at 119 degrees west at synchronous altitude.  To get there, it was launched on a Thor-Delta 2914 rocket with the Thor stage taking it to a low orbit of 120 miles and the Delta stage sending it into an elliptical orbit between 120 miles and the synchronous altitude of 22,236 miles.  At the apogee, a solid-fuel rocket on the satellite itself burned for 28 seconds to circularize the orbit and bring the speed up to the synchronous speed of 6877.8mph.  Starting at a low orbit speed of 17000 mph, the speed at the apogee is 3777 mph and for a 28-second burn, the acceleration is 110.74 miles per hour per second.

This was getting pretty close to the limit for the Thor-Delta.  It can lift 1550 pounds into synchronous orbit and the satellite was slightly over 1500 pounds.  The rocket on board the satellite was the most beautiful piece of spun stainless steel I have ever seen.  It had a large combustion chamber about 4' diameter narrowing down to a convergent-divergent nozzle and the whole piece of metal stood about 4' high.  It was 0.100" thick and this had raised a concern: toward the end of the burn that the nozzle would distort due to the heat and the satellite would not be able to reach synchronous speed.  The rocket engine in the satellite was 723 pounds of which 692 pounds was propellant.

Someone suggested the simple idea that painting the outside surface of the nozzle with a flat black paint would enable it to radiate enough heat to retain its shape, so we contacted a supplier of space-qualified paint.  Now it should be noted that satellites are trailing-edge technology.  Nothing new ever goes into a spacecraft without an arduous testing process.  Everything has to have an established reliability and preferably years of use before it can be put on a spacecraft.  Every part, chemical or process has to be qualified by being subjected to rigourous qualification, or "qual" testing and until the entire suite of tests was over, it was never a slam dunk; parts could pass or fail qual.  A few companies specialize in space-qualified parts but normal military testing (as done back in the 1970's) was usually sufficient if the highest grades of components were used.  (Nowadays, most satellites are built with commercial parts – but it was unthinkable then to risk a $60 million launch on parts with no history.)  Anytime you wanted to add anything to the list of qualified items, you had to fill out a NONSPAR – a non-standard parts approval request and NASA would pass judgment on it.  That was an arcane process that kept us on tenterhooks until it was complete.

We called up one supplier of space-qualified paint and his reply was, "Sure, we can give you immediate delivery.  How many tank cars do you want and where is your railway siding?"

So we found a polite way to tell him no and called another supplier, who said, "Pints and quarts, sure, no problem.  Fifteen months delivery."  This meant they had not qualified or even formulated the paint yet and there was a definite possibility that the paint would fail qual and leave us with nothing.

So one of our engineers came up with an obvious idea – what about automotive exhaust pipe enamel?  We went to the nearby Canadian Tire store at Dufferin and Castlefield in Toronto and bought a case of 12 cans (which were $2.67 a can at the time).  We did not use the spray nozzle on the can – that would be too ghetto for any spacecraft – we had a very good De Vilbiss spray system, similar to what would be used for refinishing a car.  We established that the paint had to be really roasted onto the metal at high temperature or it would not adhere.  But once it was baked on, the adhesion was great.  It would not flake or chip when tested for scratch resistance or discolouration under salt spray, the bane of anything stored near the ocean at Cape Kennedy.

Canadian Tire exhaust pipe enamel was qualified and flown on the CTS spacecraft.  But before that, we had the problem of writing up the NONSPAR.  We used the stock number which at the time was three numbers followed by a dash and three more numbers and listed it as "Paint, CTC Corporation" in the description and we buried it among other chemicals we were getting approved.  NASA didn't ask any questions.  We certainly didn't volunteer any information.  According to the rules, only the paint from that particular case was qualified – approval is granted only for a certain manufacturer and run and there was no way to determine if any other paint was the same formulation or even came from the same company, since it is a private-label brand.

But in a world where product quality is a sore point for buyers of many items, isn't it nice to know that you can purchase space quality products without even knowing it?

[Ice-9]

I'm not sure I understand.
Do you consider all these joints in this random google image to be glued rather than soldered?

And, since the wire to a pot lug (apparently) needs to go through and then run back, aren't all through hole components (resistors, caps, diodes etc) glued instead of soldered?
Just trying to learn and understand to solder better.

I often do point to point and twisting leads of components before soldering is often virtually impossible and a nightmare when modding/replacing stuff afterwards.

Yes, I consider those glued together, solder is meant to be an electrical joint not a mechanical joint, all those joints are floating and have no mechanical joint. The through hole component has a mechanical joint as the hole is the mounting point and the solder the electrical joint.

Those circuits in the pics do look nice though.

[MrStab]

I was just watching a couple of Big Clive videos

i was thinking of Big Clive as i read through this thread, too. he definitely knows his stuff - industrial HV-level stuff - so i think he just does solder like that for pacing's sake. he's somehow really elegant at half-assed soldering, though.

talking of YouTube: i'm totally taking him out of context here, but i caught Dave Jones from EEVBlog saying that solder makes a good mechanical connection in a video he put out in just the past few days. unacceptable! you wouldn't find us saying such things in the "Old Dart"!

thanks for sharing that story, Ron - i love the idea of ad-hoc solutions in a field which otherwise seems so self-contained and (justifiably) paranoid.

[Rixen]

What I can't stand is the practice of tinning stranded wire before placing it in a screw terminal. The solder creeps over time and the termination looses tension, and the wire strands break due to shear within the solder when the termination is tightened

[stallik]

I've seen these kind of circuits cast into clear acrylic blocks. I suppose the joints become well supported at that point but completely unrepairable

[j_flanders]

Ok, so my example was probably to artsy.
How about these:


When I do stuff like this (with a lot less components) I simply make sure the leads of several components make contact and then solder them together.
Are the solder-is-not-glue proponents suggesting you should connect the leads in a mechanical way before soldering? How? And how would you replace a component afterwards?
I personally don't see how this would be glued or worse than through hole.
Bending the leads back and forth many times would break the leads long before the solder connection would break (imo)

[anotherjim]

What I can't stand is the practice of tinning stranded wire before placing it in a screw terminal. The solder creeps over time and the termination loses tension, and the wire strands break due to shear within the solder when the termination is tightened

It took me a while to un-learn that mistake since tinning was once the accepted practice. Until the late 80's, most UK consumer electrical products were supplied without a plug fitted and we were expected to fit our own. The wire ends were twisted and tinned ready to install. Of course, they often developed "hot plugs" when the wire became loose. Especially fun on a 2kW heater.

One group of workers who often use solder as glue are model engineers...

You can find a lot of tack and butt joints in something like that.

[tubegeek]

One group of workers who often use solder as glue are model engineers...

You can find a lot of tack and butt joints in something like that.

You just gave me an awful flashback to my first soldering experience, a complete failure. I tried to build a slot car out of brass sheet and tube, out of a hobby magazine. I didn't know anything about soldering and of course that's a project that requires a heavy-duty iron, some fluxing, jigs to hold stuff in place, etc. I didn't even get close, and I didn't have anyone to advise me.

[PRR]

> How about these:


Prototypes (I hope!). Never leave the bench. And there's a hot iron on the same bench, so when you break a connection you fix it right away.

You can cheat the rules if it's not going in a Jeep, a rocket, or the Econoline Tour of Maine (wicked potholes). Or if you do your own service. The rules were for clients who might beat their gear and then complain.

[davent]

My wife brought a bass home from school that had an intermittent output. Opened it up to find someone had used blue tack to secure the wires to the jack...
dave

[MrStab]

surely that crazy point-to-point stuff (if you can all it that) isn't at all helpful for efficient prototyping? it's three dimensions of headache.

that said, i think RG once said he used to drive colleagues crazy by doing something similar.

[vigilante397]

My wife brought a bass home from school that had an intermittent output. Opened it up to find someone had used blue tack to secure the wires to the jack...

I fixed a guitar last year that had similar problems, intermittent output. Turns out this guy looped the wires into the solder lugs and super glued them there.

You can't use solder as glue, and YOU CAN'T USE GLUE AS SOLDER.

[287m]

for me, this is badass 


plus with 9v batt in 1590A. Just wow!

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