A satellite engineer explains the basics of space electronics • Hacker News Board

Re: A satellite engineer explains the basics of space electronics

#21

Post by sandworm101 » Sun, Aug 26, 2018, 4:47 PM UTC

walrus01 wrote: post #15

sandworm101 wrote: post #5

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…

Without asking too much detail, approximately where is there house? Is there any chance there is a regional WISP they could get service from? In general, consumer grade VSAT service via geostationary satellite should be a last resort, if anything else is available. The economics of launching 5000 kilogram satellites into geostationary orbits mean that transponder kHz in Ku/Ka-band spot beams need to be significantly…

Egmont BC. Only 80km (50 miles) from Vancouver. Not exactly remote by Canada or even British Columbia standards. It is also only 79km from Whistler, but look at what stands between Egmont and whistler to get an idea BC terrain.

https://www.google.com/maps/place/Egmont,+BC+V0N+2H4/@49.750...

I've looked into every option. The irony is that the nearest cell tower is just over a kilometer away. The problem is the rocky terrain and dense pacific coastal rain forest. Trees heavy with water droplets suck up everything, from sound to radio. It is shocking how a heavy mist dulls everyone's cellphone boosters. Voice calls only last a second or two even on dry days. Everyone uses text messaging.

There have been many multipoint proposals. The problem is the rugged coast. Even a 1000' tower wouldn't have line of sight to every house. It would take all sorts of relays atop individual hills. And those relays need power, which is tricky. Buried lines aren't an option (rock) and towers are expensive (forest).

Re: A satellite engineer explains the basics of space electronics

#22

Post by rburhum » Sun, Aug 26, 2018, 4:57 PM UTC

k__ wrote: post #6

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

Extreme temperature changes? Solar flares?

Re: A satellite engineer explains the basics of space electronics

#23

Post by kevin_thibedeau » Sun, Aug 26, 2018, 5:02 PM UTC

k__ wrote: post #6

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

Launch is only a vibration and acceleration problem which are mechanical issues. Payload electronics are mostly powered off until on orbit.

Re: A satellite engineer explains the basics of space electronics

#24

Post by [deleted] » Sun, Aug 26, 2018, 5:30 PM UTC

kevin_thibedeau wrote: post #23

k__ wrote: post #6

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

Launch is only a vibration and acceleration problem which are mechanical issues. Payload electronics are mostly powered off until on orbit.

[deleted]

Re: A satellite engineer explains the basics of space electronics

#25

Post by pocketstar » Sun, Aug 26, 2018, 5:30 PM UTC

madengr wrote: post #7

geomark wrote: post #4

Earlier quoted context omitted.

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…

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.

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.

Re: A satellite engineer explains the basics of space electronics

#26

Post by thebigspacefuck » Sun, Aug 26, 2018, 5:36 PM UTC

sandworm101 wrote: post #5

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…

Looks like you can get 25 Mbps with a 300GB cap for $120. That's not bad IMO. I'm paying $40/month for 25Mbps but I also live in the city so other things are more expensive.

Re: A satellite engineer explains the basics of space electronics

#27

Post by halfdan » Sun, Aug 26, 2018, 6:21 PM UTC

> 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.

Re: A satellite engineer explains the basics of space electronics

#28

Post by sandworm101 » Sun, Aug 26, 2018, 6:44 PM UTC

snowwindwaves wrote: post #17

sandworm101 wrote: post #5

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…

We get satellite internet from Infosat also in BC. It's not cheap either though.

Different company, same sats iirc.

Re: A satellite engineer explains the basics of space electronics

#29

Post by creato » Sun, Aug 26, 2018, 6:56 PM UTC

dghughes wrote: post #13

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 a…

> 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.

Re: A satellite engineer explains the basics of space electronics

#30

Post by asteli » Sun, Aug 26, 2018, 7:05 PM UTC

madengr wrote: post #7

geomark wrote: post #4

Earlier quoted context omitted.

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…

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.

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.