EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Beamin on October 14, 2019, 08:30:13 pm
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When I was a kid I was in my front yard in rural NH. Glimmering in the sun really high up was something falling down really slowly. It came from straight up in a large area away from the trees so it wasn't something from the ground. When it came down I picked it up and it was a square of 1.5inX 4" of alien space craft foil! ... or so I hoped but realized it wasn't. It was kind of like the foil of a mylar balloon but crumpled differently. I'm guessing it was from a launch of a satellite where it was supposed to peel off high up. Definitely not some road side trash blown into the air.
Would be fun to have to just cover things with and look like space craft. Oh and its not real gold its something else from what I could tell.
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https://www.amazon.com/gold-foil/s?k=gold+foil (https://www.amazon.com/gold-foil/s?k=gold+foil)
Probably good enough.
;D
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I know they used regular aluminum foil on the Voyager spacecraft, but mostly what you see is metallized mylar. It may have been first used on the lunar modules. The bottom of the Gemini spacecraft were also covered with some kind of gold colored, foil-like material, which was probably the same stuff, or something similar.
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https://www.rebelsport.co.nz/product/8116600/rocky-mountain-emergency-blanket-gold/ (https://www.rebelsport.co.nz/product/8116600/rocky-mountain-emergency-blanket-gold/)
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I used similar stuff on my old car to insulate the oilpan from the headers (sporty modified this and that).
It claimed to be the same gold metallized mylar as used in aerospace, along with a thin layer of glassfiber and then adhesive.
Was good for spaces you couldn't quite fit a heatshield.
Here it is:
https://www.techflex.com/high-temperature/gold-foil (https://www.techflex.com/high-temperature/gold-foil)
You can see the gold foil applied to the oil pan in the attached image.
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I used similar stuff on my old car to insulate the oilpan from the headers (sporty modified this and that).
It claimed to be the same gold metallized mylar as used in aerospace, along with a thin layer of glassfiber and then adhesive.
Was good for spaces you couldn't quite fit a heatshield.
Here it is:
https://www.techflex.com/high-temperature/gold-foil (https://www.techflex.com/high-temperature/gold-foil)
You can see the gold foil applied to the oil pan in the attached image.
[offtopic] Damn son, what did you have running on that engine mate? That looks a serious amount of horses to tame with![/offtopic]
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[offtopic] Damn son, what did you have running on that engine mate? That looks a serious amount of horses to tame with![/offtopic]
Ha, it's a silvertop 4AGE (with the quad throttle bodies), fully rebuilt, balanced to within 1 gram, ceramic coated pistons (with low friction coating on the skirts), HKS cam gear on exhaust, HKS 4-1 ceramic coated headers, 2.5" straight through exhaust, thermostatic oil cooler, transmission cooler, shift kit in the transmission, slotted brake rotors, braided brake lines, etc etc.
Also a full bare metal respray and Bomex bodykit with lowered springs was fitted too. (Picture below is with the bodywork 90% finished)
It even got a stupid bonnet scoop from the supercharged version as well. lol.
It was purchased as a daily driver to get me by until I moved to Japan, then the engine blew on the way home from buying it (I expected as much, but not so soon) and then I 'slipped with the screwdriver' :-/O and all that stuff above was accidentally installed. :D
It had a bit of poke, went pretty good and was reliable as anything in the end. Not as fast as my previous supercharged Levin, that thing was sideways faaar more than was reasonable for a FWD.
I sold it to a good friend's brother who loves it and daily drives it (as was intended when I built it).
Oh, and the sticker-bombed front panel. I did that for a laugh :D
/offtopic
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You may be thinking of aluminized kapton tape, though you can get regular kapton tape as well.
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AFAIK the spacecraft cover is metalized Mylar foil/film, very close to what is now called "emergency blanket" or "space blanket", just a couple of $ for a blanket.
Have two of them in the standard 1'st Aid Emergency Kit, in the car, and bought a few more extra, for fun, from Aliexpress. They come in silver or gold/silver face, price varies with thickness. Once pierced, it is very easy to tear apart, don't pierce it.
Opened one for tests, very effective, can instantly feel your own body radiation if you cover yourself with such a Mylar blanket. Almost incredibly effective, hard to describe the feeling.
Depending on how it is wear (against cold or against heat), the golden or the silver side should be kept to the outside.
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Real gold is used in laser mirrors...
https://www.edmundoptics.com/p/5mm-dia-protected-gold-4-6lambda-mirror/5232/ (https://www.edmundoptics.com/p/5mm-dia-protected-gold-4-6lambda-mirror/5232/)
Reflects infrared light better, I guess.
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That's not gold. Its metalised kapton foil.
The reason it looks gold is that one side is coated in silver looking aluminium and the other side is the transparent yellowish kapton that lets you see the shiny aluminium trough it. Putting it together it gives the kapton side a shiny gold like color.
The reason that this stuff is useful is that aluminium has a very low emisivity value. This means that it refuses to act like a black body radiator that normally radiates its thermal energy away in the form of IR photons. Due to the way physics works this refusal to radiate thermal energy also makes it very reflective to these IR photons. This means that any thermal radiation that hits it is reflected away, this is useful on things going to space because you don't want the hot sun getting parts of your spacecraft too hot. Its refusal to emit photons also makes it cool down slower when facing away from the sun.(These effects are a much bigger problem when there is no atmosphere to provide convective heat exchange)
This technology turned out to be useful so you can buy it in the form of "space blankets". If you wrap yourself in this material the thermal radiation you are emitting is bounced back towards you so you loose less heat to the environment and that makes you feel warmer. Its also used for the opposite in the form of those heat resistant suits that steel mill or glass workers use, by wrapping yourself in the stuff any thermal radiation that hits you is bounced away and this makes it much more comfortable to stand next to extremely hot objects such as molten metal or glass. Yet unlike thick bulky insulation this material remains incredibly thin and light.
So if its the shiny aluminium that is doing the work why have the kapton too? Well turns out aluminum foil is incredibly fragile when made this thin while kapton is a lot tougher, so the kapton provides the structural strength while a incredibly thin layer of aluminuim provides the thermal properties.
EDIT: But yes you could also coat it with gold as it is known to also have very low emisivity. It is possible that some spacecraft used gold rather than aluminium to edge out a tiny bit more performance out of it, but i wouldn't know for sure.
EDIT 2: I did a bit of googling and found a PDF explaining the whole thing from one of the manufaturers:
https://www.sheldahl.com/sites/default/files/2017-09/Thermal%20Control%20Overview.pdf (https://www.sheldahl.com/sites/default/files/2017-09/Thermal%20Control%20Overview.pdf)
According to the PDF from the commonly used materials of gold, silver aluminum some are better at not radiating and some are better at not absorbing. And according to them the missions in the 70s indeed used gold because the NASA launch site is next to the sea and they didn't want salt corroding the metal film. But later on they figured out a special coating that prevents aluminum from oxidizing.
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https://www.amazon.com/gold-foil/s?k=gold+foil
Probably good enough.
No that just gold colored al foil. This stuff is like Kapton tape with foil and not sticky. It has all kinds of magical properties and would be good around the lab. It doesn't "crinkle or break"... Thanks though.
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I used similar stuff on my old car to insulate the oilpan from the headers (sporty modified this and that).
It claimed to be the same gold metallized mylar as used in aerospace, along with a thin layer of glassfiber and then adhesive.
Was good for spaces you couldn't quite fit a heatshield.
Here it is:
https://www.techflex.com/high-temperature/gold-foil (https://www.techflex.com/high-temperature/gold-foil)
You can see the gold foil applied to the oil pan in the attached image.
IS it pricey? I cant find prices on their site and they are not open now.
Its amazing how well you can insulate your house and save on your heating bill using these new materials. My ex and I bought a "fixer upper that was more like a "blower upper" that was built when oil was cheap and had no insulation in NH in the mountains in the winter time. We were spending $650-700 a month on oil and I would set the heat at 58'F during the day. Before the new windows and doors came I took those 4'X8' sheets of foam core with the aluminum edges. I glued them together like sandwiches and put those silver space blankets on the espoused edges inside and painted black on the sides that covered the windows that got the sun. I cut them to the shapes of all the windows that were not upgraded then sealed the edges with expanding foam (the old windows were going to be trashed anyways) and that thick aluminum duct tape for heaters, real duct tape (also insulates bal-uns and rf stuff really well). After sealing off five windows, building a door that blocked the bulk head in the basement and then making a 6" thick foil foam core that blocked the fire place and crawl space to the attic Our oil bill went down to $200 next month. She was arguing with me because she didn't like the way it looked so I said fine, you pay the 4 figure oil bill for the next three months and she agreed. I probably spent 70$ on all the stuff and built it all in the afternoon. It also made the house feel warmer because you wouldn't get blasted with heat then drafts would make you feel cold while the heat was on. If this whole country went around spending 100$ in foam core on old houses/poor peoples houses it would save hundreds of millions and cut down on subsidies and non payments from poor people who cant afford the heat in winter, not to mention save millions of tons of CO2. But the only changes made to this country right now have to be cleared by putin.!
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Space blankets are pretty cheap. Here is 4 of them for 6 bucks:
https://www.amazon.com/HanleyDepot-Emergency-Blankets-Survival-Outdoors/dp/B07P6XW29L/ref=sr_1_25?keywords=space+blanket&qid=1572596417&sr=8-25 (https://www.amazon.com/HanleyDepot-Emergency-Blankets-Survival-Outdoors/dp/B07P6XW29L/ref=sr_1_25?keywords=space+blanket&qid=1572596417&sr=8-25)
But if you are just after the low emisivity properties and don't need the structural strength of the kapton behind it, then you can just use regular kitchen aluminium foil.
For lab use aluminium foil tends to be more convenient since it holds its shape when crumpled around something. This is why you sometimes see fancy scientific apparatus just crudely wrapped in aluminium foil or in chemistry wrapping glass distillation setups in it. You can just grab a sheet of it off a roll, wrap it around and it stays on there without any attachment or adhesive and can easily be opened back up for when you need to take a peek at what is going on inside. Works just as well as space blanket since its the polished aluminium surface that is providing the insulation effect.
I have used aluminium foil for insulation when reworking aluminium core PCBs. It made it way easier to get the board up to soldering tempeature since it was not loosing heat so quickly. Also sometimes use it to shield components from heat when using hot air rework.
EDIT: Oh and for shielding PCB components adhesive kapton tape also works, but it is not as good since kapton has a very high emisivity. But this lead me to find another good use for that property. I have problems using a thermal camera on shiny objects since they tend to be low emisivity and that means no IR radiation for the camera to see. When this is a problem i just stick adhesive kapton tape on it and now i have great emisivity so i can see it on the camera perfectly.
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Space blankets are pretty cheap. Here is 4 of them for 6 bucks:
https://www.amazon.com/HanleyDepot-Emergency-Blankets-Survival-Outdoors/dp/B07P6XW29L/ref=sr_1_25?keywords=space+blanket&qid=1572596417&sr=8-25 (https://www.amazon.com/HanleyDepot-Emergency-Blankets-Survival-Outdoors/dp/B07P6XW29L/ref=sr_1_25?keywords=space+blanket&qid=1572596417&sr=8-25)
But if you are just after the low emisivity properties and don't need the structural strength of the kapton behind it, then you can just use regular kitchen aluminium foil.
For lab use aluminium foil tends to be more convenient since it holds its shape when crumpled around something. This is why you sometimes see fancy scientific apparatus just crudely wrapped in aluminium foil or in chemistry wrapping glass distillation setups in it. You can just grab a sheet of it off a roll, wrap it around and it stays on there without any attachment or adhesive and can easily be opened back up for when you need to take a peek at what is going on inside. Works just as well as space blanket since its the polished aluminium surface that is providing the insulation effect.
I have used aluminium foil for insulation when reworking aluminium core PCBs. It made it way easier to get the board up to soldering tempeature since it was not loosing heat so quickly. Also sometimes use it to shield components from heat when using hot air rework.
EDIT: Oh and for shielding PCB components adhesive kapton tape also works, but it is not as good since kapton has a very high emisivity. But this lead me to find another good use for that property. I have problems using a thermal camera on shiny objects since they tend to be low emisivity and that means no IR radiation for the camera to see. When this is a problem i just stick adhesive kapton tape on it and now i have great emisivity so i can see it on the camera perfectly.
Why would you want an al circuit board? I have never heard of such things. Do they use those on ceramic circuit boards? How do you solder to it? Lead/tin/copper won't wet aluminum. If things don't form alloys they can't be soldered or brazed, there's no way to bond al to steel that I know of, I tried that in welding class. So I'm not sure but I guess if you add lead/tin to molten copper it forms an alloy. Another thing I always wanted to try was to add two metal that didn't alloy together in a crucible like al to steel, I think the al would just float on top of the steel but I would think they wouldn't come apart if there was no slag.
That's a good idea for the Kapton tape. I have never used Kapton tape so what happens to the adhesive when it gets hot, does it just dry up and not leave residue behind? Isn't the whole point of it that its like scotch tape but works at really high temps? Next time I have to order parts I'm going to get a roll to play with.
The space blankets are made from the same plastic as Kapton so you can get them hot without melting? That would make sense as that yellow color would look like gold on al foil. As far as uses I just think it looks cool and I tend to way over build things I make. If I made all my own things they would be the total opposite of stuff you buy in the store, and would last forever.
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I have used aluminium foil for insulation when reworking aluminium core PCBs. It made it way easier to get the board up to soldering tempeature since it was not loosing heat so quickly. Also sometimes use it to shield components from heat when using hot air rework.
Why would you want an al circuit board?
Its aluminium CORE, layered with thin insulator and copper traces on top. Good for heatsinking the components. Very commonly used in led lamps for example.
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Why would you want an al circuit board? I have never heard of such things. Do they use those on ceramic circuit boards? How do you solder to it? Lead/tin/copper won't wet aluminum. If things don't form alloys they can't be soldered or brazed, there's no way to bond al to steel that I know of, I tried that in welding class. So I'm not sure but I guess if you add lead/tin to molten copper it forms an alloy. Another thing I always wanted to try was to add two metal that didn't alloy together in a crucible like al to steel, I think the al would just float on top of the steel but I would think they wouldn't come apart if there was no slag.
That's a good idea for the Kapton tape. I have never used Kapton tape so what happens to the adhesive when it gets hot, does it just dry up and not leave residue behind? Isn't the whole point of it that its like scotch tape but works at really high temps? Next time I have to order parts I'm going to get a roll to play with.
The space blankets are made from the same plastic as Kapton so you can get them hot without melting? That would make sense as that yellow color would look like gold on al foil. As far as uses I just think it looks cool and I tend to way over build things I make. If I made all my own things they would be the total opposite of stuff you buy in the store, and would last forever.
Yep its a PCB that is aluminium on the inside rather than FR-4. There is still a very thin non conductive layer insulating the copper traces that are on top where you actually solder your components. Very good at cooling SMD components and a huge pain in the ass to solder because it moves heat away so quickly.
The fact that kapton foil can survive a very wide temperature range is the reason why it is used in these "space blankets". You could have used any type of plastic foil and it would still do the job. But spacecraft get exposed to very high temperatures on the side that is pointing to the sun and very cold on the side that is pointing away from the sun, so the material has to be able to handle that, hence the use of kapton. Its also quite strong and hard to tear so its the perfect material for the job. The temperature resiliance might also help in the manufacturing process if the aluminium is sputtered on rather than chemically applied.
The adhesive on self adhesive kapton tape does survive high temperatures too, but its performance severely degrades once things get really hot so its not uncommon for the tape to get unstuck when you heat it up enough. But if you stick it on in a way that the adhesive is holding very little force it tends to stick just fine at the temperatures generally involved in soldering.
And yes the only reason why space blankets are gold on one side is because you can see the shiny aluminium trough the transparent yellowish colored kapton foil. So it can be hard to tell if the satelites are wrapped in real gold foil or its the new aluminium stuff they use nowdays