Capacitors for use in Vacuum Environment?

Other Hardware General Electronics
1

I'm trying to find step-down DC-DC regulators that would take input voltages of ~30V and convert it to 5V and ~24V. This is for a student project that would see use in space.

I was originally looking at linear regulators such as the 7805T, but the specific project I am working on would need to perform in a vacuum environment. As far as I understand, electrolytic capacitors cannot work in space as they have a high probability of popping due to the vacuum environment. Since the 7805T linear regulator and many other regulators require capacitors in order to function properly, I need to find an alternative option for a step-down regulator.

I searched online, but it appears to be that the vast majority of these voltage step-down regulators/converters require capacitors in one form or another. From breakout transformers to linear regulators, it appears that I can't find any without capacitor(s).

I therefore started looking for capacitors that would be appropriate for use in vacuum environments. I heard about tantalum capacitors before, such as these ones, however I wasn't exactly sure what brand or type to look for. Until now, I've only really looked at capacitance and rated voltage when looking for capacitors. There over 500 different types of capacitors on that catalogue itself, and I'm looking for some guidance on which type/brand to choose, as I'm not familliar with any of the brands or types of these capacitors out there.

Are there any well-known brands or types of capacitors suitable for space/vacuum applications out there? Would a tantalum capacitor like this work?

Thanks for reading my post, any guidance is appreciated.

2

Your way of thinking makes sense: "would a cap manufactured on earth pop up in space?"
I do not think so.
Why?: have you seen the Tesla car in space? Why the tires did not pop up like a balloon?
Because: the difference is just one atmospheric pressure (but the tires have already 3 or even more and can withstand even 4 times earth pressure). The pressure difference between earth and space is just one atmospheric pressure (as difference).

I would assume, nothing pops up. OK, when it is sealed perfectly - the cap will bent - but just if it has still "air inside". But why? Even an electrolyte capacitor has just a fluid inside, not any air (or you make sure to release the air before space launch). So, there should not be any pressure in the cap (just a fluid) and nothing should happen in space.

If you would use a foil capacitor - maybe there is air inside. But I assume the housing is not perfectly sealed, so the air will escape during launch (and even you can drill a hole to let release the air).
Otherwise, use ceramic capacitors, if you are skeptical (you might need just many in parallel for same capacity due to low capacitance). But are you sure is there not any air encapsulated in the housing/coating...? (and the coating would crack, not the capacitor itself?)

Nothing pops up in space: it is just a misunderstanding: the difference between pressure on earth and pressure in vacuum is just ONE atmospheric pressure. It is not really huge (a vacuum does not mean "infinitely small", space is just minus one atmospheric pressure).
A cap does not need any air (it can be released, or cap has anyway just a fluid inside, an no pressure at all).

Otherwise: any micro-chip would blow up as well, if a bit of air is enclosed in the housing.
And not any airplane would be able to fly so high with standard electronics aboard.
All chips, components, circuits are ready to fly to space (I am sure, because we have sent EPROMs 30 years ago into space without any special treatment).

The biggest concern for electronics in space is the radiation! (not the atmospheric pressure):
chips and components are bombarded with gamma rays, cosmic radiation, particles... which create bit errors in the device, even high voltages on circuits if a stream of electrical charged particles (e.g. a solar flare) hits a circuit.
Electronics for space missions must be "hardened" (be able to resist "flares", radiation, built in error corrections...), but I have never heard of an issue with pressure inside a device (and why? electronics do not need any air, not any air pressure required to function).

3

Thanks for your reply;

Thanks for clearing up the fact that in space, things don't "pop". I guess it was just a misunderstanding on my part, I didn't think of it from that perspective.

Nothing pops up in space: it is just a misunderstanding: the difference between pressure on earth and pressure in vacuum is just ONE atmospheric pressure. It is not really huge (a vacuum does not mean "infinitely small").
A cap does not need any air (it can be released, or cap has anyway just a fluid inside, an no pressure).

So, correct me if my understanding of what you're saying is incorrect, but from what I've read here, you're saying that an aluminum electrolytic capacitor would not malfunction in space? Or would it just bend, and become inoperable after that happens?

If you would use a foil capacitor - maybe there is air inside. But I assume the housing is not perfectly sealed, so the air will escape during launch (and even you can drill a hole to let release the air).
Otherwise, use ceramic capacitors, if you are skeptical (you might need just many in parallel for same capacity due to low capacitance). But are you sure is there not any air encapsulated in the housing/coating...? (and the coating would crack, not the capacitor itself?)

Thanks for providing the types of capacitors for that, however, what would be some of the best options? There are many, are there certain brands/types that are the most common, and that have documentation? Any guidance is appreciated.

And thanks for mentioning the radiation danger. Is there a material that the electronics could be encased in for better protection from the radiation? Metals, or something like that?

4

When it comes to space missions with electronics - it is much more complex.
But in general, I think: in general the electronic components are able to fly (functional wise).
When it comes to "pressure issues" it is "just" related to enclosed air pockets (which is not needed for the function but can be part of the manufacturing process).
If "air bubbles" are enclosed (but not needed for function, just due to manufacturing process) - this is bad (but any component, even micro-chips can be affected by this).

Electronic components for space
electronic parts rated for space

5

BTW:
if your capacitor would blow up - not good.
But I would be more concerned if my MCU (my silicon, my chips) start malfunctioning due to radiation. Even your cap would "survive" the launch: at least a processor in space will behave so "strange" due to electrons flying through the chip.

6

Alright, thank you for all the advice you've provided, it was really helpful.

As far as the capacitors go, another person reccomended me to use ceramic layered capacitors.

From your experience, would something like this work:

?

I'm mainly looking for something that'd work, but that's relatively affordable.

Thanks for your time.

7

Yes, ceramic makes more sense (hoping the manufacturer has not left "air bubbles" in the ceramic coating). I would place the entire board anyway into a vacuum chamber before flight. :grinning:

Oh, BTW:
I was working on space mission and electronics for it. Another very big topic is this: "G-Force".
We have stressed our PCBs, parts, boards ... with 10G and even more (like throwing against the wall). We have handed over the PCB to a test lab which have generated 10G forces (to simulate the rocket launch).
And most of the time - the legs on the components broke!
So, at the end: we have placed all the components on board into a silicon shield, like spay silicon all over the board, place any part in a silicon bed.

The mechanical stress might be your next enemy (e.g. not standing capacitors, no through-hole components, nowadays all just as SMT..., the smaller the better...)

8

The normal domestic type Electrolytics can be prone to outgassing but there are types that are rated for space\vacuum use, doubt they are cheap though, so maybe just use Tants.

Outgassing in general is a significant issue, in particular you need to be careful about the plastics used, no PVC etc. So the 'prototype' will need a vaccuum test. And of course a vibration test.

As for needing special precautions against radiation, for a typical Cubesat type thing, bit of a myth really, its just not necessary, you can use COTS (Commercial Off The Shelf) parts throughout.

9

Thanks for your reply;

Do you think the ceramic layered capacitors like the ones I linked above would work though? I was reccomended that type by some other people.

10

Possibly, but I have not used them.

When I built a satellite board I used standard surface mount ceramics, there was some concern that they would be damadged by vibration, but they survived the vibration test, and it worked to.

$50SatFront
$50SatFront474×520 68.3 KB

11

You may find this an interesting read Mil-Spec Components . Either ceramic or tantalum are fine.

Buy quality, reliable components. Nothing from Amazon. Counterfeit's are a real problem. You don't want to go through everything to get your hardware launched and it fails because you decided to save a few bucks.

We use mainly Vishey and Bourns components.

12

I'll take an interest!
Is the antenna coated with zinc?

13

Hi, @Svarun123
When you say space, do you mean orbit for quite a bit of time, or a suborbital leap above the Karmen Line?

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

14

Nope. The antenna connection on the board is a gold plated SMA connection. The antenna connection was then via a short bit of non-pvc co-ax to the actual antenna which was a dipole made from bits of steel tape measure.

15

And I have already begun to look for where to buy a galvanized steel tape measure and, I can’t find it ... :wink:

Then another question is how the stabilization of the position of the satellites is organized so that the antenna is always oriented to the ground

16

Why use galvanised, things dont rust in space, leave the printing on so its easy to measure to the appropriate length .........

As for stability, you can do that with strong magnets, with so little friction in space (no air!) even if the satellite spins on ejection from the launcher the magnets soon align it to the earths magnetic field.

17

If we take the losses in the copper antenna as a unit, then the losses in the same antenna made of other materials will be greater: aluminum - 1.25 times, brass and duralumin - 1.4 ... 2 times, zinc - 1.85, titanium alloy - 7...10 times. In VK antennas, losses in dB will be about: aluminum - 0.01..0.04db, brass and duralumin - 0.04..0.15 dB, zinc - 0.05..0.16db, titanium alloy - 0.2..0.7db.

18

So in pratical terms what loss have you actually measured ?

For say 434Mhz, the total loss of plain steel tape versus steel galvanised tape ?

And on the same topic, how will you know if the antenna length is correct ?

19

the thickness of the skin layer is about 2 -2.5 microns, that is, more than one decibel will run up, I didn’t measure it exactly, I should try to make an antenna from a ruler. And the idea of ​​ self-expanding antenna is beautiful !!!

20

There is soem use for all this theory stuff on antennas, all those fancy charts etc, but I am a firm believer in checking out the real World reality for myself.

I do recall trying out different types of 'tape' but found no actual measurable difference between them.

What made a huge differance was matching the antenna to the specific RF module in use. Low cost RF modules do not use highly accurate components in the antenna matching circuits neither are they tuned for a perfect 50R match. So the optimum antenna length will vary for each module, you can improve output by circa 3dB with individual module matching.