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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
just out of curiosity, whatwould happen if i took a electrolytic cap to 200,000 feet ASL? and what was done for the caps and pressure/heat sensitive PCB components on voyager and pioneer space probes?
Registered Member #1316
Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365
I believe most electronics for satellites are not even sealed from space. I don't know what they do for thermal design, besides using only conduction cooling to the body of the satellite.
For component selection, they use no parts prone to off gassing. No electrolytic caps are used, only ceramic and tantalum caps. (I don't know about film)
Registered Member #133
Joined: Fri Feb 10 2006, 10:27PM
Location: Pensacola, Florida
Posts: 47
Weston wrote ...
No electrolytic caps are used, only ceramic and tantalum caps.
There are a few select non-tantalum electrolytic capacitors that are designed for altitude (80,000 feet), but they are not cheap. They are sealed to prevent outgassing.
Registered Member #133
Joined: Fri Feb 10 2006, 10:27PM
Location: Pensacola, Florida
Posts: 47
The high altitude non-solid electrolyte capacitors utilize an aluminum case that may be attached to a heat sink. They are usable to +85 C and some even as high as +125 C. Due to the internal vapor pressure at altitude, the capacitors will swell and you need to mechanically account for this in the mechanical design.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
There is an entire area of engineering that deals with space hardened hardware. However, the orbital trajectory planner and control systems people suggest minimal changes to electronics are necessary. Most satellites have a deflated balloon bladder to detect pressurized atmosphere leaks (usually much less than 1 atm), fans to create artificial convection cooling, and heaters to prevent damaging the semiconductors.
Accordingly, these days even consumer grade electronics in satellites usually survive low orbits around earth as the radiation levels are much lower than in space.
NASA published quite a bit of information about odd failure scenarios most people rarely encounter on earth.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Ordinary electrolytics must be usable to some extent, since they don't die in Mexico City or the cabin of a passenger aircraft. I think Patrick's question is, what is the extent of that extent.
High voltage high altitude design can be challenging. The dielectric strength of the air decreases with altitude.
I believe spacecraft have active cooling for the power electronics. They are mounted to cold plates refrigerated by ammonia or something similar. The heat is dumped to a condenser on the side of the vehicle facing away from the sun.
Spacecraft often have batteries, which are just really big electrolytic capacitors from a construction point of view. Maybe reading about the battery systems could give you some ideas.
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Minimum altitude on electrolytic caps....
