7 ms·

A satellite engineer explains the basics of space electronics

183 points by natashabaker 8y ago

baybal2 8y ago
To some extend, space electronics have a lot in common with stuff used to manage industrial plants. For examples in Chinese megascale steel mills, while SCADA's are used for monitoring and higher level control, operational aspects are handled by handcrafted PLCs made of modern analogues of 7400 series, 8t sram, redundant sensors, quoruming and BCH coding, mram, mems oscilators, and all solid DC-DC conversion, and all of that is provided with manual overrides Most important feature of all of this is that it provides hard, near physical, impediment to wrong inputs from higher level control systems (SCADAs.)
solarkraft 8y ago
This is a decently embedded ad for Snap EDA and a pretty good ad for Astralis. Not hugely informative, but nice. The title over-promises pretty wildly.
- geomark 8y ago
  Not hugely informative, but nice. The title over-promises pretty wildly. That's practically an understatement. It just barely touches on the challenges of extreme temperature range and radiation hardening. The difficulty of getting your design to pass worst case analysis can be rather dispiriting when you have to drastically derate it to account for -55 to 125 degrees C temp range. Further insult comes from derating to account for total dose radiation effects (depending on orbit), although the article seems to only mention the need to account for single event upset events. Handling SEU's is actually a pretty interesting design challenge. Total dose, on the other hand, is just a bummer.
  - madengr 8y ago
    Where are you getting that temp range? The last payload electronics I designed (an RF PA) only had to handle -20 to 70 C, and the actual temp swing is less. Of course this is inside a bus. Military electronics are just as bad, as they have to operate from the Antarctic to the desert, and be thrown from the back of a helicopter onto concrete.
    - pocketstar 8y ago
      NASA’s box requirement is 70C. That means the ICs in the box are much hotter, parent is probably refering to IC temp, not unit.
      - madengr 8y ago
        Ok, makes sense. The 70C for my unit was the temperature of the plate to which the PA was mounted.
      - geomark 8y ago
        There were some non-NASA boxes that had long periods powered off on the shaded side of the bus and had to operate at powerup at initially very low temperature. And then operate on the sun side for extended periods at an elevated temperature. Depending on the configuration of the bus there were sometimes challenging heat transfer issues. The plate temp wasn't 125 C (I don't remember the exact number) but there was assumed a significant temperature rise from the plate to the electronics. And then additional margin added on to that in case something wasn't quite up to spec in the thermal path. So we had to perform worst case analysis assuming junction temperatures of 125 C. It was pretty awful.
    - asteli 8y ago
      Tangential, but designing devices to handle shock is surprisingly hard as well. I was once tasked with building 900MHz GPS transponders that would allow us to see the shape of a tether being pulled behind an airplane. The device was about the size and shape of a soda can. Occasionally they would get dropped, impacting at terminal velocity. One early prototype had a li-ion pouch cell (yes, I'd do things differently now). After an impact, I pulled it apart and found that the battery, via plastic deformation, had perfectly fitted itself to the contour of the inside of the enclosure. IIRC it was still working when I pulled it apart.
sandworm101 8y ago
I read so many stories about companies with new ideas for satellite internet. But i am visiting my parents next weekend. Their house is off grid in rural BC. They only have one internet option: a dish pointed to a geostationary sat which I will no doubt have to repoint on saturday. They pay insane rates for practically no bandwidth. There is only the one company: explorenet. When exactly are any of these innovations going to hit the canadian market?
- awake 8y ago
  Checkout starlink the satellite network being created by spacex. Here is a good FAQ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_faq/ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_f...
  - sandworm101 8y ago
    Great, but while i see lots of talk of this for ships and planes i've seen not a single file or application from spacex to become a residential provider anywhere, much less in canada. So they remain perpetually 10+ years away.
    - gammatrigono 8y ago
      https://www.fcc.gov/document/fcc-authorizes-spacex-provide-broadband-satellite-services https://www.fcc.gov/document/fcc-authorizes-spacex-provide-b... Residential service filing probably (!) appears on the priority list after launching the 4-12,000 satellites into LEO.
    - walrus01 8y ago
      It is much more likely that it will be economical to use in a similar method to o3b, to bring a decent amount of capacity to a single location (example: totally isolated very rural valley somewhere in northern BC), and then distribute bandwidth from there. The link budget problems for gain and EIRP, and cost of CPE, may make it cost prohibitive to put individual CPEs on peoples' roofs as a competitor to last mile WISPs. I can see a scenario where a WISP buys a $7000 to $15000 dual-antenna terminal and a monthly recurring service package in the $700 to $1200/mo range, for a decent chunk of semi-dedicated capacity, and then redistributes access from there. For those who want to understand how this works, o3b at MEO works on the same general concept, but at a more expensive and high bandwidth scale. It's been operational for years now. There's lots of good reference material out there on O3B. Take the same two-satellite make-before-break handoff system used by o3b and apply it to a much larger number of LEO satellites, and smaller terminals, that's the general idea of how oneweb and starlink are intended to work.
k__ 8y ago
I always had the impression 99% of all space-electronic problems come from the fact that you have to lift stuff from earth. You get plenty of sunlight to power your stuff and since gravity isn't as bad as on earth you can build stuff big enough to be shielded from almost everything. But well, it has to go up somehow :D
- rburhum 8y ago
  Extreme temperature changes? Solar flares?
- kevin_thibedeau 8y ago
  Launch is only a vibration and acceleration problem which are mechanical issues. Payload electronics are mostly powered off until on orbit.
  - deleted 8y ago
    [deleted]
- Dylan16807 8y ago
  You could install hundreds of tons of radiation shielding if you had easy lifting tech, but I still would point at the radiation as the root problem, not the difficulty of getting things into space.
lizknope 8y ago
I've been designing semiconductors for 20 years and I thought I would learn something but this article said nothing other than he wished there were more radiation hardened devices out there. You can learn more from wikipedia than this article. https://en.wikipedia.org/wiki/Radiation_hardening https://en.wikipedia.org/wiki/Radiation_hardening
- pseudobry 8y ago
  I have not been designing semiconductors for 20 years and I thought I would learn something...and I did!
- jl2718 8y ago
  Here’s something. Rad-hardened parts are mostly BS. An MSP430 takes 20krads without shielding. Process shrink seems to increase hardness, not decrease. I used flash FPGAs with parity circuits because flash was supposed to be better for SEU. This is all theory; it’s really hard to test SEUs. Store firmware as a low-rate RS and do circuit parity checks to trigger firmware refresh. There is probably a smarter way to do circuit ECC without the EC as a weakness, but I don’t know. That was years ago, and we were just space cowboys giving the middle finger to the rad-hard parts business.
dghughes 8y ago
I'm surprised electronics work on the earth. Such fragile things it's amazing how little it takes to destroy a device. And how much energy can be put through the same fragile device. And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons. A recent artie I read spoke about the reaction wheels of old spacecraft failing. Solar flares caused arcing in the metal ball bearings the would pit the bearing race. So if a steel ball bearing can't take it imagine fragile electronic devices.
- StavrosK 8y ago
  You're looking at it the wrong way. Electronics work on earth by definition, as that's where we want them to work. You can be surprised that electronics can be made so fragile and still work on earth, but being surprised they work is begging the question.
- creato 8y ago
  > And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons. To have any meaning, you also need to consider the distance between the points. Any two charged points can repel each other with a force of one million tons given a particular distance.
  - dghughes 8y ago
    I looked up the example and it's mentions the two objects are separated by one meter. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c2 http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.h...
- sandworm101 8y ago
  I read that article too and am skeptical. There is a less-than-perfect correlation between space weather an wheel friction increases, but these are not exposed bearings on the outside of spacecraft. These are deep inside, behind layers of metal parts. I don't see the mechanism for creating the imbalance of charges necessary to arc inside the bearings. If it is happening, I would expect this to be far more common in terrestrial bearings. Cars build up static charges. We aren't seeing their bearings degrading so suddenly when after they drive through lighting storms or other static charge imbalances.
irq-1 8y ago
Here's an interesting paper that discusses some design issues. https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7086415 https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7086415 > To mask the effects of upsets in the FPGA configuration memory, temporal or structural redundancy can be applied to the system. Temporal redundancy involves the replication of a computation or logic function in time to mitigate failures that occur during one of the redundant computations. Structural redundancy involves the replication of selected circuit structures to remove single-point failures. Failures in the circuit can be masked by performing the logic or computing function in more than one circuit location. > The most common form of structural redundancy is to apply triple-modular redundancy (TMR) [24]. As shown in Fig. 6, TMR involves the triplication of all circuit resources and the addition of majority voters at the appropriate circuit outputs.
broahmed 8y ago
Reminds me of this Stack Overflow question "Compiling an application for use in highly radioactive environments" where the top answer is from someone who worked on mini satellites: https://stackoverflow.com/q/36827659 https://stackoverflow.com/q/36827659
halfdan 8y ago
> We’re enabling people to reach their full potential by bring them Internet access and that’s really inspiring for me. On the other hand, they also get access to Twitter –- you win some, you lose some. Haha, brilliant. What I always wonder though is how many of those people can actually afford a devise to make use of satellite internet. I guess it's still important to at least enable them to get it.
gumby 8y ago
I am surprised he mentioned changing the SDR once the satellite had been deployed. What about the antennas?
- mng2 8y ago
  That really is the elephant in the room where SDR is concerned (along with front-end). More realistically you could change protocol/encoding after launch.
  - dahtguy 8y ago
    Not necessarily. I've never heard of anyone doing it for space (maybe SpaceX?) but you could have an SDR driving a massive MIMO/beamforming array. The SDR can then dynamically "change the antenna" (change the radiation pattern) with a fixed front-end.
    - mng2 8y ago
      The point is you are limited by the capability you build in at launch, SDR or otherwise. The hardware side is more restrictive than the software side.
  - gumby 8y ago
    One use case I have imagined is being able to have a single radio module that can be used with a variety of front ends, but honestly I am not sure how big a market that is. Certainly I don't see SDR adding much value to high volume applications.

183 points by natashabaker 8y ago

To some extend, space electronics have a lot in common with stuff used to manage industrial plants. For examples in Chinese megascale steel mills, while SCADA's are used for monitoring and higher level control, operational aspects are handled by handcrafted PLCs made of modern analogues of 7400 series, 8t sram, redundant sensors, quoruming and BCH coding, mram, mems oscilators, and all solid DC-DC conversion, and all of that is provided with manual overrides Most important feature of all of this is that it provides hard, near physical, impediment to wrong inputs from higher level control systems (SCADAs.)

solarkraft 8y ago

This is a decently embedded ad for Snap EDA and a pretty good ad for Astralis. Not hugely informative, but nice. The title over-promises pretty wildly.

geomark 8y ago
Not hugely informative, but nice. The title over-promises pretty wildly. That's practically an understatement. It just barely touches on the challenges of extreme temperature range and radiation hardening. The difficulty of getting your design to pass worst case analysis can be rather dispiriting when you have to drastically derate it to account for -55 to 125 degrees C temp range. Further insult comes from derating to account for total dose radiation effects (depending on orbit), although the article seems to only mention the need to account for single event upset events. Handling SEU's is actually a pretty interesting design challenge. Total dose, on the other hand, is just a bummer.
- madengr 8y ago
  Where are you getting that temp range? The last payload electronics I designed (an RF PA) only had to handle -20 to 70 C, and the actual temp swing is less. Of course this is inside a bus. Military electronics are just as bad, as they have to operate from the Antarctic to the desert, and be thrown from the back of a helicopter onto concrete.
  - pocketstar 8y ago
    NASA’s box requirement is 70C. That means the ICs in the box are much hotter, parent is probably refering to IC temp, not unit.
    - madengr 8y ago
      Ok, makes sense. The 70C for my unit was the temperature of the plate to which the PA was mounted.
    - geomark 8y ago
      There were some non-NASA boxes that had long periods powered off on the shaded side of the bus and had to operate at powerup at initially very low temperature. And then operate on the sun side for extended periods at an elevated temperature. Depending on the configuration of the bus there were sometimes challenging heat transfer issues. The plate temp wasn't 125 C (I don't remember the exact number) but there was assumed a significant temperature rise from the plate to the electronics. And then additional margin added on to that in case something wasn't quite up to spec in the thermal path. So we had to perform worst case analysis assuming junction temperatures of 125 C. It was pretty awful.
  - asteli 8y ago
    Tangential, but designing devices to handle shock is surprisingly hard as well. I was once tasked with building 900MHz GPS transponders that would allow us to see the shape of a tether being pulled behind an airplane. The device was about the size and shape of a soda can. Occasionally they would get dropped, impacting at terminal velocity. One early prototype had a li-ion pouch cell (yes, I'd do things differently now). After an impact, I pulled it apart and found that the battery, via plastic deformation, had perfectly fitted itself to the contour of the inside of the enclosure. IIRC it was still working when I pulled it apart.

sandworm101 8y ago

I read so many stories about companies with new ideas for satellite internet. But i am visiting my parents next weekend. Their house is off grid in rural BC. They only have one internet option: a dish pointed to a geostationary sat which I will no doubt have to repoint on saturday. They pay insane rates for practically no bandwidth. There is only the one company: explorenet. When exactly are any of these innovations going to hit the canadian market?

awake 8y ago
Checkout starlink the satellite network being created by spacex. Here is a good FAQ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_faq/ https://www.reddit.com/r/Starlink/comments/7zqm2c/starlink_f...
- sandworm101 8y ago
  Great, but while i see lots of talk of this for ships and planes i've seen not a single file or application from spacex to become a residential provider anywhere, much less in canada. So they remain perpetually 10+ years away.
  - gammatrigono 8y ago
    https://www.fcc.gov/document/fcc-authorizes-spacex-provide-broadband-satellite-services https://www.fcc.gov/document/fcc-authorizes-spacex-provide-b... Residential service filing probably (!) appears on the priority list after launching the 4-12,000 satellites into LEO.
  - walrus01 8y ago
    It is much more likely that it will be economical to use in a similar method to o3b, to bring a decent amount of capacity to a single location (example: totally isolated very rural valley somewhere in northern BC), and then distribute bandwidth from there. The link budget problems for gain and EIRP, and cost of CPE, may make it cost prohibitive to put individual CPEs on peoples' roofs as a competitor to last mile WISPs. I can see a scenario where a WISP buys a $7000 to $15000 dual-antenna terminal and a monthly recurring service package in the $700 to $1200/mo range, for a decent chunk of semi-dedicated capacity, and then redistributes access from there. For those who want to understand how this works, o3b at MEO works on the same general concept, but at a more expensive and high bandwidth scale. It's been operational for years now. There's lots of good reference material out there on O3B. Take the same two-satellite make-before-break handoff system used by o3b and apply it to a much larger number of LEO satellites, and smaller terminals, that's the general idea of how oneweb and starlink are intended to work.

k__ 8y ago

I always had the impression 99% of all space-electronic problems come from the fact that you have to lift stuff from earth. You get plenty of sunlight to power your stuff and since gravity isn't as bad as on earth you can build stuff big enough to be shielded from almost everything. But well, it has to go up somehow :D

rburhum 8y ago
Extreme temperature changes? Solar flares?
kevin_thibedeau 8y ago
Launch is only a vibration and acceleration problem which are mechanical issues. Payload electronics are mostly powered off until on orbit.
- deleted 8y ago
  [deleted]
Dylan16807 8y ago
You could install hundreds of tons of radiation shielding if you had easy lifting tech, but I still would point at the radiation as the root problem, not the difficulty of getting things into space.

lizknope 8y ago

I've been designing semiconductors for 20 years and I thought I would learn something but this article said nothing other than he wished there were more radiation hardened devices out there. You can learn more from wikipedia than this article. https://en.wikipedia.org/wiki/Radiation_hardening https://en.wikipedia.org/wiki/Radiation_hardening

pseudobry 8y ago
I have not been designing semiconductors for 20 years and I thought I would learn something...and I did!
jl2718 8y ago
Here’s something. Rad-hardened parts are mostly BS. An MSP430 takes 20krads without shielding. Process shrink seems to increase hardness, not decrease. I used flash FPGAs with parity circuits because flash was supposed to be better for SEU. This is all theory; it’s really hard to test SEUs. Store firmware as a low-rate RS and do circuit parity checks to trigger firmware refresh. There is probably a smarter way to do circuit ECC without the EC as a weakness, but I don’t know. That was years ago, and we were just space cowboys giving the middle finger to the rad-hard parts business.

dghughes 8y ago

I'm surprised electronics work on the earth. Such fragile things it's amazing how little it takes to destroy a device. And how much energy can be put through the same fragile device. And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons. A recent artie I read spoke about the reaction wheels of old spacecraft failing. Solar flares caused arcing in the metal ball bearings the would pit the bearing race. So if a steel ball bearing can't take it imagine fragile electronic devices.

StavrosK 8y ago
You're looking at it the wrong way. Electronics work on earth by definition, as that's where we want them to work. You can be surprised that electronics can be made so fragile and still work on earth, but being surprised they work is begging the question.
creato 8y ago
> And how much energy is in one Coulomb. The example I like is two points each with one Coulomb repel with a force of one millions tons. To have any meaning, you also need to consider the distance between the points. Any two charged points can repel each other with a force of one million tons given a particular distance.
- dghughes 8y ago
  I looked up the example and it's mentions the two objects are separated by one meter. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c2 http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.h...
sandworm101 8y ago
I read that article too and am skeptical. There is a less-than-perfect correlation between space weather an wheel friction increases, but these are not exposed bearings on the outside of spacecraft. These are deep inside, behind layers of metal parts. I don't see the mechanism for creating the imbalance of charges necessary to arc inside the bearings. If it is happening, I would expect this to be far more common in terrestrial bearings. Cars build up static charges. We aren't seeing their bearings degrading so suddenly when after they drive through lighting storms or other static charge imbalances.

irq-1 8y ago

Here's an interesting paper that discusses some design issues. https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7086415 https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7086415 > To mask the effects of upsets in the FPGA configuration memory, temporal or structural redundancy can be applied to the system. Temporal redundancy involves the replication of a computation or logic function in time to mitigate failures that occur during one of the redundant computations. Structural redundancy involves the replication of selected circuit structures to remove single-point failures. Failures in the circuit can be masked by performing the logic or computing function in more than one circuit location. > The most common form of structural redundancy is to apply triple-modular redundancy (TMR) [24]. As shown in Fig. 6, TMR involves the triplication of all circuit resources and the addition of majority voters at the appropriate circuit outputs.

broahmed 8y ago

Reminds me of this Stack Overflow question "Compiling an application for use in highly radioactive environments" where the top answer is from someone who worked on mini satellites: https://stackoverflow.com/q/36827659 https://stackoverflow.com/q/36827659

halfdan 8y ago

> We’re enabling people to reach their full potential by bring them Internet access and that’s really inspiring for me. On the other hand, they also get access to Twitter –- you win some, you lose some. Haha, brilliant. What I always wonder though is how many of those people can actually afford a devise to make use of satellite internet. I guess it's still important to at least enable them to get it.

gumby 8y ago

I am surprised he mentioned changing the SDR once the satellite had been deployed. What about the antennas?

mng2 8y ago
That really is the elephant in the room where SDR is concerned (along with front-end). More realistically you could change protocol/encoding after launch.
- dahtguy 8y ago
  Not necessarily. I've never heard of anyone doing it for space (maybe SpaceX?) but you could have an SDR driving a massive MIMO/beamforming array. The SDR can then dynamically "change the antenna" (change the radiation pattern) with a fixed front-end.
  - mng2 8y ago
    The point is you are limited by the capability you build in at launch, SDR or otherwise. The hardware side is more restrictive than the software side.
- gumby 8y ago
  One use case I have imagined is being able to have a single radio module that can be used with a variety of front ends, but honestly I am not sure how big a market that is. Certainly I don't see SDR adding much value to high volume applications.