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The CPUs of Spacecraft Computers in Space
- wiz21c 6y agoWhat about chinese/indian/japanese spacecrafts ?
- sanxiyn 6y agoChina's Chang'e 4 lander is known to use ATMEL AT697F. It is SPARC-compatible. Source: The scientific objectives and payloads of Chang'e 4 mission. DOI 10.1016/j.pss.2018.02.011. No free source, use Sci-Hub.
- verberant 6y agoSpace 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-hard) PowerPC RAD750 and similar. This is a huge bottleneck for any computationally intensive task we might want to do on-orbit, and I'm curious if or when it will change. It's one technical reason, in my opinion, that the private sector is currently calling the shots in space.
- dimator 6y agoMy understanding is that certification is the bottle neck, in both time and cost. No one wants to spend the money or time to flight certify something new when something already battle tested will suffice. But your comment makes me wonder if the private sector doesn't have those certification requirements? The other differentiating factor is that the private sector is not sending multi-year (indeed multi-decade) deep space missions, where the need for battle tested systems is paramount.
- inamberclad 6y agoTo answer - no we don't have the same certification requirements. NASA steps in when there's human lives and/or a lot of money on the line, but most smaller projects and just about every independent project is free to assume its own level of risk.
- bumby 6y agoYou know (and probably are implying) this but it’s completely program/project specific. Some projects out of Armstrong, for example, must meet FAA certification requirements
- pauldino 6y agoFlagship multi-year science missions are generally conservative with technology choices, but some NASA projects are intended as technology demonstrations and can on take more risks. So like the Perseverance rover on its way to Mars is powered by redundant RAD 750s (same as Curiosity), but the Ingenuity helicopter along for the ride is powered by a Snapdragon 801. It will be interesting to see how it holds up.
- dylan604 6y agoHow do you battle test a RAD prototype? Stick it in microwave like device with ionizing radiation and see how many bit-flips occur?
- sjburt 6y agoIt depends on where the spacecraft is going as radiation environments differ. I've taken parts to be exposed by a proton line at a particle accelerator. For some environments they just use Cobalt-60 as a radiation source.
- smueller1234 6y agoThis reminds me of a relevant anecdote: back in the naughts, I was doing research in cosmic rays at a large nuclear research facility. I did simulation and data analysis - office/computer work mostly. One day, a person with a clipboard comes into my office and asks about the whereabouts of some radiation source. I look at them confused - I had not touched sources since teaching nuclear physics labs. They show me their clipboard and lo and behold, it has my name next to a really high intensity source and they're looking to locate it. After a few minutes of awkward shock and denying all involvement, we realized it was a colleague at the same research institute (and of the same name). He was, one building down, doing his PhD research on radiation hardened detectors for the CMS experiment at CERN(1). He was using the source for the testing. But I had a minute of real stress before that came together in my mind... (1) I think this was his work: https://onlinelibrary.wiley.com/doi/abs/10.1002/pssa.200776327 https://onlinelibrary.wiley.com/doi/abs/10.1002/pssa.2007763...
- cpgxiii 6y agoThe 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 stuck with older, larger process sizes that limit what can be implemented. Look at the lengths involved in getting A* to run on Curiosity, and you see just how limiting the hardware is. Everyone, Nasa especially, wants more compute available. In low earth orbits and shorter mission durations, you can get away with redundant hardware instead of rad-hard. Most of the damage done by radiation is upsets, so you can reboot the affected hardware and keep going. But on an unprotected design some of the damage can be permanent, and thus redundancy alone isn't enough for longer/farther missions.
- formerly_proven 6y ago> The RAD750 remains the standard because it's the highest performance rad-hard design available, period. RAD5500?
- cpgxiii 6y agoYou're right, the RAD5500 and family are available. I should have said the whole BAE RAD family. The reality hasn't changed much, though, there's really only one game in town for high rad-hard performance, and it's still well behind conventional processors.
- runeb 6y agoCould they not offload a lot of compute to ground based computers and submit results back via radio? Or are these real-time applications?
- senkora 6y agoFor Mars, at least, that would be tens of minutes round trip because of the speed of light. It works for some things, but for pathfinding it isn’t a great fit. The other issue is bandwidth between the craft and Earth, which is quite limited. Maybe there would be benefits to a “orbiting datacenter” around Mars carrying a bunch of rad-hardened compute? I assume NASA has considered this and decided it would be a bad idea.
- mhh__ 6y ago> Starlink with Xilinx FPGAs, while NASA and DoD are still baselining new platforms on incredibly expensive (albeit rad-hard) PowerPC RAD750 and similar. Ignoring that Starlink isn't very far away, I would assume NASA stuff would also have FPGAs and ASICs on them - they aren't CPUs and aren't used like them.
- bumby 6y agoSome NASA orgs have tried using FPGAs as a way to get around software requirements, to varying levels of success
- mhh__ 6y agoInteresting, although I was more thinking about FPGA's in things like acquisition and processing rather than overall logic as the PC seemed to imply.
- bumby 6y agoThe high level NASA requirements cast a pretty wide net (to include data acquisition and processing) as to what falls under the purview of those requirements. From 7150.2: “ A.30 Software. Computer programs, procedures, scripts, rules, and associated documentation and data pertaining to the development and operation of a computer system. Software includes programs and data. This also includes COTS, GOTS, MOTS, reused software, auto generated code, embedded software, firmware, and open source software components.” https://nodis3.gsfc.nasa.gov/displayCA.cfm?Internal_ID=N_PR_7150_002A_&page_name=main https://nodis3.gsfc.nasa.gov/displayCA.cfm?Internal_ID=N_PR_...
- johnwalkr 6y agoIt’s pretty common in space to implement a soft core CPU (or redundant ones) on a space-grade FPGA.
- quazar987 6y agoThere’s more to it than just specs. Consumer grade silicon will not survive in space, radiation will just kill them.
- bryananderson 6y agoNASA has used Xilinx FPGAs on a number of missions (though still mostly smaller missions). They are doing so for precisely this reason: on-spacecraft computation for intensive tasks such as image processing. Here’s the website for the SpaceCube platform (developed at NASA Goddard). This is a little out of date (I worked on flight software for a mission called STP-H6 which I don’t see listed here), but gives an idea of how this idea is slowly but surely gaining steam in NASA. https://spacecube.nasa.gov/ https://spacecube.nasa.gov/
- throwaway189262 6y agoThe private sector has decided to put regular ground chips in spacecraft and just deal with errors using triple redundancy. Low earth orbit where most satellites hang out doesn't have much radiation anyways. The cost savings from using regular chips is so high that I bet SpaceX will continue to use them even in deep space. Just surround them with sheilding. When a $400 desktop cpu is 500X faster than a $40,000 space rated one a couple pounds of shielding is well worth it
- chmod775 6y agoThe kind of radiation you want to protect against is not "easily" shielded. The effectiveness of shielding is proportional to its mass and thickness, and both are at a premium for spacecraft.
- Rebelgecko 6y agoSpaceX 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 new platforms on incredibly expensive (albeit rad-hard) PowerPC RAD750 and similar NASA and DOD have also been sending up Xilinx and Altera boards for ages (even the non space-grade ones). However you can get rad-hard ARM CPUs that are cheaper and more powerful than the ones in a Zynq board.
- tkinom 6y agoIt 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.
- qayxc 6y agoThis 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. <2 years) and low orbits (<500km), COTS hardware should be fine if properly shielded. 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 http://www.cubesatkit.com
- Rebelgecko 6y agoTypically 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.
- geomark 6y ago"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.
- synack 6y agoESA uses an OpenSparc fork, LEON. http://www.esa.int/Enabling_Support/Space_Engineering_Technology/Onboard_Computers_and_Data_Handling/Microprocessors http://www.esa.int/Enabling_Support/Space_Engineering_Techno...
- snvzz 6y agoAnd that's expected to be succeeded by NOEL (LEON anagram), a radiation hardened RISC-V CPU focused on high reliability.
- kristoffer 6y agoIt is not related to OpenSparc. LEON is a SPARCv8 developed initially by ESA and later by swedish company Gaisler Research.
- bitcharmer 6y agoHow do these circuits deal with random bit flipping from cosmic rays?
- MichaelZuo 6y agoContinuous voting on hard real-time systems
- rzzzt 6y agoThe packaging can be different or redundancy can be added to the design: https://en.wikipedia.org/wiki/Radiation_hardening#Radiation-hardening_techniques https://en.wikipedia.org/wiki/Radiation_hardening#Radiation-...
- inamberclad 6y agoThere's three basic ways this is done: 1: By process, where chips are created with special or larger features to better resist cosmic rays. This is Expensive since they're made in very low volumes and the cost of the new fab line can't be spread among many millions of units. Instead, a few thousand chips might be made. 2: By design, where redundant systems such as triple redundant memory or voting computers are used. This is probably the most interesting as you can get into issues like the Byzantine Generals problem here. All the redundancy can be implemented in a single FPGA by simply routing out the design 3 times and using voting logic, assuming the FPGA is large enough. 3: By shielding. Just fly regular chips in a shielded box. This causes thermal issues, but is sometimes necessary, such as in Juno, which has to deal with the enormous radiation flux around Jupiter.
- gpm 6y agoAs sending mass to space becomes cheaper I wonder if shielding will become more popular... Maybe there is some oil-like material that could serve bath as a cooling bath and as a radiation shield?
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- snarkypixel 6y agoWhen I see posts like this, I always think about how insane it will be in 2520 if we keep the same innovation growth (and not die to whatever)
- abhinav22 6y agoStick an Apple M1 chip in it and be done with it :)
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- vntok 6y ago> Saying there are physical backup controls is a bit like saying there are backup controls at the bottom on your new TV. Can you expand on this? Are you against physical backup controls?
- cpgxiii 6y agoWhat they were trying to say is that physical backup controls are often incomplete and inconvenient, just like how you can control a TV using the buttons on it but doing so is far less effective than using the remote. The idea is that making physical controls the primary interface (rather than the backup) for critical tasks means that more effort would go into making them ergonomic and effective.
- randomstring 6y agoReminds me of this post comparing the CPU and RAM of the Apollo 11 flight computer with modern USB chargers. (spoiler alert: the USB charger wins) https://forrestheller.com/Apollo-11-Computer-vs-USB-C-chargers.html https://forrestheller.com/Apollo-11-Computer-vs-USB-C-charge... Hacker News comment link: https://news.ycombinator.com/item?id=22254719 https://news.ycombinator.com/item?id=22254719
- myself248 6y agoOn some of the silicon details: https://habr.com/en/post/518366/ https://habr.com/en/post/518366/
- anon2021 6y agoThere have been none RAD hard CPUs working in space. https://www.hpe.com/us/en/insights/articles/the-space-station-gets-a-new-supercomputer-1708.html https://www.hpe.com/us/en/insights/articles/the-space-statio...
- FredFS456 6y agoLow Earth Orbit (LEO) which the ISS is in is very different from deep space. You can get away with much less radiation hardening in LEO. For example, I know a company consumer-grade Xilinx MPSoCs with 4xA53 cores at 1.5GHz.
- phire 6y agoThey literally ship off the shelf laptops and smartphones to the ISS. They do modify them slightly to remove the lithium-ion batteries, which you do not want inside a space craft. I think they replace them wit NiMH cells if the devices still need to be battery powered.
- sephamorr 6y agoThey no longer do this, and are now happy with just testing li ion products. There are iPads all over the station (and used by the astronauts on the SpaceX Dragon)
- abeppu 6y agoDo we actually have much data on the failure rates to different kinds of chips to radiation in space? If so ... how? What conditions have to hold so that when a chip is damaged by radiation you get enough information about it to know which chip had what kind of problem?
- cpgxiii 6y agoTesting is done on earth in lab conditions, and some testing has been done in space. We've had good models of radiation energy and type in space for a while, so you can reproduce type and intensity of radiation on earth to test how the chip will behave. You can also fly chips for testing, where instrumentation and testing are controlled by known working hardware. Diagnosing novel failures on hardware in space is hard, but the overall types of failures and their underlying physical phenomena are known. Obviously, in the case of a satellite that goes completely unresponsive you can't answer 100%, but you may have sensor data in the leadup to the failure, or from other "nearby" satellites that would allow you partially reproduce conditions before the failure in a test scenario.
- webmonkeyuk 6y ago"A CPU for use in space must first be MIL-STD-883" Is this just for NASA craft? Are there any regulations for private craft or international standards?
- GlenTheMachine 6y agoDepends, but mostly no. No regulations.
- tibbon 6y agoSo my watch (or maybe headphones even) is several times faster than anything that's ever run a spacecraft? (I understand why, but that this is so just blows me away)
- LeoPanthera 6y agoThough true, it is important to remember that Computers Are Fast. https://computers-are-fast.github.io https://computers-are-fast.github.io
- dreamcompiler 6y agoEspecially when they don't have to deal with 37 layers of Windows/MacOS abstractions and backward-compatibility concessions.
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- p_l 6y agoA non-trivial amount of satellites have also used Transputers (and there's legacy of it in SpaceWire network)
- InitEnabler 6y agoPretty interesting. Wonder what SpaceX uses for there CPUs?