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Electrolytics in a vacuum

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Turkey9

Tue May 19 2009, 06:14PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

What about these caps? Here
I don't know what they cost but I'm hoping they might give a sample of four to help with a science fair project:-D.

Sulaiman

Tue May 19 2009, 06:25PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

WOW !
Those are nice caps.

Being suggested as being suitable for "Aircraft inverters" there's a good chance that pressure will not be a major concern, which leaves just temperature - worst case use electrical heating tape etc.
The esr for those caps is fantastic.

How much do they cost?

Turkey9

Tue May 19 2009, 06:38PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I found one for 89 a piece at 270uf and 1200v. Unfortunately I would need 8 in order to get the energy that I want and Cornell Dublier doesn't have any in stock that they might want to sample to me.

Mattski

Wed May 20 2009, 01:32AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

I think it's worthwhile to step back a second and ask why you need capacitors to withstand a vacuum? It could be we're solving the wrong problem by recommending non-electrolytics when there might be a way to avoid exposing your caps to vacuum.

Turkey9

Wed May 20 2009, 01:42AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I'm building a electric propulsion system for the science fair. I'm going to design the unit with all systems in a single module so that testing in a vacuum chamber will be easier. I'm going to use a chamber at a university or most likely a lockheed martin facility and I don't want them to have to add a bunch of beefy feedthroughs. I could build a pressurized case for the caps but that would have its own problems.

WaveRider

Wed May 20 2009, 08:52PM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Dry tantalum electrolytics are standard in space use. Normal aluminium electrolytics are not good in vacuum because are not sealed and they outgas. I would recommend that you ask your vacuum testing facility what components they allow in the vacuum chamber. They will often have a list of permissible components that do not outgas. They are (should be) very strict about what goes in the chamber. Certain outgassing compounds can be very damaging to vacuum pumps and sensors.

Another option is to check the NASA parts selection list. This will give you some idea.. It can be found here.

Link to ESA list

Hope this helps!

rp181

Wed May 20 2009, 10:15PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

What kind of electric propulsion system?
See if you have a air force base near you. I live in colorado springs, and there is a air force base in walking distance (

They usually are willing to let people use there stuff.

Proud Mary

Thu May 21 2009, 12:55AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Bored Chemist wrote ...

if it fails it doesn't matter what else it takes out- the thing will be dead anyway.

Remember; In space nobody can hear you call the engineer.

It may well matter if you're a young chap who's spent his pocket money on a single capacitor!

I have a few electrolytics in stock - trade samples from the International Capacitor Manufacturer's Association Trade Fair - which are as thick as an elephant's foot. A small second mortgage, even in the stinks and bangs dept, n'est-ce pas?

Remember:

He's in chemistry and he's okay,
Wears his filthy white coat all day
(Ammonia's made his beard grow grey)
He skulks around the JCR by day
The abstracts that he so much needs
Are filed away like garden weeds
Alas, were he a physicist,
He'd have to learn to read.

Turkey9

Thu May 21 2009, 04:13AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

My design is based on the Pulsed Inductive Thruster. Here's the NASA report on it here.It's basically an induction launcher with plasma. I hadn't thought that they might not let certain components into their vacuum chambers... I'll definitely take a look at the NASA parts selection list if not use that to entirely choose my other parts, thanks!

rp181, that base is actually one of the ones I was considering but I heard they didn't like civilians there... Guess I better do my own looking into that!

Firefox

Thu May 21 2009, 04:46AM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

The last PIT I read about used capacitors at 15-25kV. I may have the white paper that detailed the construction of the PIT, and if so, I'll post it. In anycase, judging by what I remember, you're gonna want Maxwell Film caps, not a cheap bet. You may be going in over your head here.

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