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The CPUs of Spacecraft Computers in Space

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Re: The CPUs of Spacecraft Computers in Space

#81

Post by p_l »

klodolph wrote: post #34
gpm wrote: post #29

Earlier quoted context omitted.

I don't see any comments about water on this post? If we're talking about $50/kg [1] in the future... well... - Sending a few kg of water (or other shielding) to space costs a fraction of the price of a fast non-rad-hardened CPU. - It really costs less than the extra development cost associated with having to use bespoke toolchains. [1] Number from the other space post on the front page today: https://getmeflyingcars…

> I don't see any comments about water on this post? Looks like it was deleted. > - Sending a few kg of water (or other shielding) to space costs a fraction of the price of a fast non-rad-hardened CPU. It doesn’t sound like a few kg is going to cut it. Recall that a 1 kg of water is about 1 L, which gives you about 6 cm of shielding, which is simply not enough. That’s less than 50% attenuation of the ionizing radiati…

The most bespoke parts would be tool chain certification, which among other things, covers "if I have source A, then I can be sure resulting machine code does B, not anything else".

And that's something you'll get even if you're running MS-DOS on 286 in space ;-)

Re: The CPUs of Spacecraft Computers in Space

#82

Post by qayxc »

tkinom wrote: post #72
Rebelgecko wrote: post #66

Earlier quoted context omitted.

SpaceX doesn't have the same requirements--The radiation environment by Mercury or halfway to Jupiter is drastically different than LEO. SpaceX missions are also a lot shorter. Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long. If you mission is 10 years, it starts to become a problem (especially since some radiation damage can be cumulative) >NASA and DoD are still baselining n…

It would be interesting to know if someone put a raspberry pi inside and outside space station in exposed complete unprotected environment and run some continuous tests, how long would we start to see any failures and what kind failure would be that be.

This has been done multiple times. Amateur radio satellites and some cubesat kits [1] use primarily COTS components.

The lifetime and radiation environment for those applications are very limited, though. It seems that for short missions (e.g. It would be interesting to see what difference it actually makes for HEO or even BEO missions, especially if a high degree of redundancy is introduced as well.

[1] http://www.cubesatkit.com

Re: The CPUs of Spacecraft Computers in Space

#83

Post by mikepurvis »

geomark wrote: post #77
Rebelgecko wrote: post #66

Earlier quoted context omitted.

SpaceX doesn't have the same requirements--The radiation environment by Mercury or halfway to Jupiter is drastically different than LEO. SpaceX missions are also a lot shorter. Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long. If you mission is 10 years, it starts to become a problem (especially since some radiation damage can be cumulative) >NASA and DoD are still baselining n…

"Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long.Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long." Unless it happens in your attitude control system or your command and control system, causing you to lose control of or communication with your spacecraft.

I think the assumption is that a redundancy scheme is in place. So you have your unrecoverable issue in some module of compute A, but compute B and C vote them down and life proceeds. The problem is when your mission is long enough that the same module gets hit in one of the other two units, and now you're in trouble.

Re: The CPUs of Spacecraft Computers in Space

#84

Post by publicola1990 »

cpgxiii wrote: post #45
runeb wrote: post #37

Earlier quoted context omitted.

Could they not offload a lot of compute to ground based computers and submit results back via radio? Or are these real-time applications?

The whole point of implementing A* on Curiosity was to give it some navigation autonomy. The time delay in getting sensor data back to earth, coming up with a motion plan, then sending the plan back to be executed imposes tight limits on how fast the rover can drive, what kinds of terrain it can cover, and ultimately how much science can be done. Local autonomy for basic "go over to than weird-looking rock" tasks is…

With what kind of processing power did the recent Change'5 probe did the autonomous docking manoeuvre in lunar orbit..

Also it seems to be doing sometype of image processing to identify a suitable landing spot and guiding on to that point.

Re: The CPUs of Spacecraft Computers in Space

#85

Post by Rebelgecko »

geomark wrote: post #77
Rebelgecko wrote: post #66

Earlier quoted context omitted.

SpaceX doesn't have the same requirements--The radiation environment by Mercury or halfway to Jupiter is drastically different than LEO. SpaceX missions are also a lot shorter. Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long. If you mission is 10 years, it starts to become a problem (especially since some radiation damage can be cumulative) >NASA and DoD are still baselining n…

"Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long.Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long." Unless it happens in your attitude control system or your command and control system, causing you to lose control of or communication with your spacecraft.

I guess I didn't actually say so, but my implicit assumption was that you have a voting setup where a single failure isn't necessarily a problem

Re: The CPUs of Spacecraft Computers in Space

#86

Post by Rebelgecko »

tkinom wrote: post #72
Rebelgecko wrote: post #66

Earlier quoted context omitted.

SpaceX doesn't have the same requirements--The radiation environment by Mercury or halfway to Jupiter is drastically different than LEO. SpaceX missions are also a lot shorter. Having one unrecoverable latchup a week isn't a big deal if your mission is 2 weeks long. If you mission is 10 years, it starts to become a problem (especially since some radiation damage can be cumulative) >NASA and DoD are still baselining n…

It would be interesting to know if someone put a raspberry pi inside and outside space station in exposed complete unprotected environment and run some continuous tests, how long would we start to see any failures and what kind failure would be that be.

Typically those sorts of tests can be done on Earth if you have access to a cyclotron. My guess is that the SD card would be the weak link.

Re: The CPUs of Spacecraft Computers in Space

#88

Post by nzentzis »

cpgxiii wrote: post #15
verberant wrote: post #3

Space flight computers in the public sector are generally 15-20 years behind the types of hardware we commonly work with on the ground, as I think this page shows. We now have pretty capable low-power SoCs and FPGAs that we've yet to see broadly leveraged for govt. space applications. SpaceX flies Starlink with Xilinx FPGAs, while NASA and DoD are still baselining new platforms on incredibly expensive (albeit rad-har…

The RAD750 (edit - the whole RAD family, there are newer models available) remains the standard because it's the highest performance rad-hard design available, period. If you're putting an expensive satellite in orbit for 5,10 years, the cost of the processors is insignificant compared to everything else. The real problem is that we don't have good solutions for improving the performance of rad-hard designs, so we're…

> Look at the lengths involved in getting A* to run on Curiosity

Can you link to something that goes into detail? Googling it doesn't turn up anything relevant, but it sounds like it'd be interesting to read about.

Re: The CPUs of Spacecraft Computers in Space

#89

Post by gorgoiler »

JohnJamesRambo wrote: post #78
throwaway189262 wrote: post #68

Earlier quoted context omitted.

Does curiosity really move that fast? Roomba is maybe 2 mph. I thought curiosity was closer to 0.1 mph

His or her estimate seems wildly off. I had the same response because my Roomba moves fast! Some quick googling says- Curiosity max speed equals 0.08699 mph. Roomba equals a foot per second which is 0.682 mph. Off by about 7.82x.

Thanks: my estimate of Roomba slowness was way off. I’ve only ever seen them on TV.

I remember once hearing that Curiosity, flat out, could do 1km a day.

Re: The CPUs of Spacecraft Computers in Space

#90

Post by throwaway189262 »

gorgoiler wrote: post #89
JohnJamesRambo wrote: post #78

Earlier quoted context omitted.

His or her estimate seems wildly off. I had the same response because my Roomba moves fast! Some quick googling says- Curiosity max speed equals 0.08699 mph. Roomba equals a foot per second which is 0.682 mph. Off by about 7.82x.

Thanks: my estimate of Roomba slowness was way off. I’ve only ever seen them on TV. I remember once hearing that Curiosity, flat out, could do 1km a day .

Random but I highly recommend the new "mapping" type roombas. Best thing I bought all year.
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