4 ms·

> Once launched into space, satellites can no longer be serviced and contaminations increase the probability of malfunctions occurring during the planned lifeti

> Once launched into space, satellites can no longer be serviced and contaminations increase the probability of malfunctions occurring during the planned lifetime. Even a single dust particle can interrupt a circuit. How does a single dust particle interrupt a circuit? (I know nothing about this; it's interesting.)

rtkwe 5y ago
If it's conductive at all it could bridge contacts on a circuit board.
- userbinator 5y ago
  Due to https://en.wikipedia.org/wiki/Whisker_(metallurgy) https://en.wikipedia.org/wiki/Whisker_(metallurgy) I believe leaded solder is still the norm for aerospace applications.
  - pipe2devnull 5y ago
    It is, also in my experience boards get a conformal coating to minimize baby risk of FOD being an issue with the electronics.
    - rtkwe 5y ago
      Yeah they do a lot of individual things to bullet proof satellites because you can't repair them and they cost millions (generally, cheaper satellites are starting to be used more and more).
    - marsokod 5y ago
      They do, but for small scale projects like satellites we tend to push con-coat until we have a good confidence the unit is working. Removing conformal coating to replace a failed component or change a resistor can be quite tricky, especially for epoxy based coatings. So there is a long time without any coating (up to spacecraft assembly).
bArray 5y ago
I'm assuming it's the connectors and/or soldering. Given the pressure difference I imagine you could see a connector blow off or solder joints explode. I still imagine it's insanely overkill, but when you're paying millions of dollars to send something into orbit, you probably want to make sure it works well first time. With regards to malfunctions, I imagine this risk would actually be better mitigated with (fail-safe) circuit redundancy. After all, radiation is going to be causing bit flips and all sorts of weirdness.
- edrxty 5y ago
  Space is only ~14 psi of pressure differential from sea level, far less than in your car tires. Nothing is exploding. The issue is mostly off gassing contamination of critical surfaces like optics and sensitive circuit boards.
- giantrobot 5y ago
  Added circuitry is not free. Every gram or redundancy is one less gram of mission payload. Added circuitry is also increasing the number of failure modes. That's not to say redundancy is bad or should never be considered but it needs to be weighed (literally and figuratively) against every other part of the mission. Optimizing for mass and mission capability means manufacturing will get more expensive.
dkdk8283 5y ago
Material science is hard. Conductive contamination will destroy circuits in unpredictable ways. This also makes debugging and future iteration difficult as the satellite cannot be inspected. https://www.ibm.com/docs/en/power9/0009-ESS?topic=floors-conductive-contamination https://www.ibm.com/docs/en/power9/0009-ESS?topic=floors-con...
senectus1 5y ago
it might also attract other particles to it, growing it in size and potential to obstruct etc...
jasonwatkinspdx 5y ago
Not an expert but I'm acquainted with someone that builds high vacuum stuff for physics experiments. Cold welding is an issue. Essentially if two sufficiently clean metal surface come in contact in sufficient vacuum, they weld together without any heat or liquefaction. So if you had conductive metal dust shavings contaminating the sat, once it's in space they may find their way to a spot where they can create a short circuit. Apparently the welds behave pretty differently from ordinary welds like allowing movement.
aaron695 5y ago
> How does a single dust particle interrupt a circuit? It doesn't, it's wrong. Clearly, since massive amounts of dust are on circuits on earth. There are other things on satellites than circuits. > during the planned lifetime. It would be interesting to know how dust moves around on a satellite. Changes in orbit of course. Temperature changes maybe?
sytelus 5y ago
I also don't get this. Most circuits are usually vacuum sealed already. Hack, I can drop my iPhone in water, let alone dust. Reminds me of old days when people used to insist that PCs must be kept in air conditioned rooms.
marsokod 5y ago
That's a bit of an exaggeration for sure. But dust can be an issue in connectors, making the connection not as stable as expected or even break the connection on a pin if there is enough. There is also the risk of short circuit on non-coated PCB, increased ESD risk. And beyond PCB, there are a lot of other risks mitigated by clean room environments: dust on sensors, dust on bearings or gears, dust on optical cameras... And any deposit of dust will float around everywhere once in orbit, especially after being shaken and vented during launch. Could you make a satellite in your garage without a clean room environment? Yes sure, and you would even have a decent chance to have a working satellite once in orbit if you know what you are doing. Would you accept a 50% failure rate if you are flying a payload worth a few millions and need to spend a similar amount on launch cost? Probably not.

rtkwe 5y ago

If it's conductive at all it could bridge contacts on a circuit board.

userbinator 5y ago
Due to https://en.wikipedia.org/wiki/Whisker_(metallurgy) https://en.wikipedia.org/wiki/Whisker_(metallurgy) I believe leaded solder is still the norm for aerospace applications.
- pipe2devnull 5y ago
  It is, also in my experience boards get a conformal coating to minimize baby risk of FOD being an issue with the electronics.
  - rtkwe 5y ago
    Yeah they do a lot of individual things to bullet proof satellites because you can't repair them and they cost millions (generally, cheaper satellites are starting to be used more and more).
  - marsokod 5y ago
    They do, but for small scale projects like satellites we tend to push con-coat until we have a good confidence the unit is working. Removing conformal coating to replace a failed component or change a resistor can be quite tricky, especially for epoxy based coatings. So there is a long time without any coating (up to spacecraft assembly).

bArray 5y ago

I'm assuming it's the connectors and/or soldering. Given the pressure difference I imagine you could see a connector blow off or solder joints explode. I still imagine it's insanely overkill, but when you're paying millions of dollars to send something into orbit, you probably want to make sure it works well first time. With regards to malfunctions, I imagine this risk would actually be better mitigated with (fail-safe) circuit redundancy. After all, radiation is going to be causing bit flips and all sorts of weirdness.

edrxty 5y ago
Space is only ~14 psi of pressure differential from sea level, far less than in your car tires. Nothing is exploding. The issue is mostly off gassing contamination of critical surfaces like optics and sensitive circuit boards.
giantrobot 5y ago
Added circuitry is not free. Every gram or redundancy is one less gram of mission payload. Added circuitry is also increasing the number of failure modes. That's not to say redundancy is bad or should never be considered but it needs to be weighed (literally and figuratively) against every other part of the mission. Optimizing for mass and mission capability means manufacturing will get more expensive.

dkdk8283 5y ago

Material science is hard. Conductive contamination will destroy circuits in unpredictable ways. This also makes debugging and future iteration difficult as the satellite cannot be inspected. https://www.ibm.com/docs/en/power9/0009-ESS?topic=floors-conductive-contamination https://www.ibm.com/docs/en/power9/0009-ESS?topic=floors-con...

senectus1 5y ago

it might also attract other particles to it, growing it in size and potential to obstruct etc...

jasonwatkinspdx 5y ago

Not an expert but I'm acquainted with someone that builds high vacuum stuff for physics experiments. Cold welding is an issue. Essentially if two sufficiently clean metal surface come in contact in sufficient vacuum, they weld together without any heat or liquefaction. So if you had conductive metal dust shavings contaminating the sat, once it's in space they may find their way to a spot where they can create a short circuit. Apparently the welds behave pretty differently from ordinary welds like allowing movement.

aaron695 5y ago

> How does a single dust particle interrupt a circuit? It doesn't, it's wrong. Clearly, since massive amounts of dust are on circuits on earth. There are other things on satellites than circuits. > during the planned lifetime. It would be interesting to know how dust moves around on a satellite. Changes in orbit of course. Temperature changes maybe?

sytelus 5y ago

I also don't get this. Most circuits are usually vacuum sealed already. Hack, I can drop my iPhone in water, let alone dust. Reminds me of old days when people used to insist that PCs must be kept in air conditioned rooms.

marsokod 5y ago

That's a bit of an exaggeration for sure. But dust can be an issue in connectors, making the connection not as stable as expected or even break the connection on a pin if there is enough. There is also the risk of short circuit on non-coated PCB, increased ESD risk. And beyond PCB, there are a lot of other risks mitigated by clean room environments: dust on sensors, dust on bearings or gears, dust on optical cameras... And any deposit of dust will float around everywhere once in orbit, especially after being shaken and vented during launch. Could you make a satellite in your garage without a clean room environment? Yes sure, and you would even have a decent chance to have a working satellite once in orbit if you know what you are doing. Would you accept a 50% failure rate if you are flying a payload worth a few millions and need to spend a similar amount on launch cost? Probably not.