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> With modern CPU's having so many cores and threads being so cheap, couldn't NASA use these for redundancy? Power constraints and heat dissipation constraints

by shagie 4y ago

> With modern CPU's having so many cores and threads being so cheap, couldn't NASA use these for redundancy? Power constraints and heat dissipation constraints. https://arstechnica.com/science/2019/11/space-grade-cpus-how-do-you-send-more-computing-power-into-space/3/ https://arstechnica.com/science/2019/11/space-grade-cpus-how... > BAE RAD5545 is probably the most powerful radiation-hardened processor available today. Fabricated in the 45nm process, it is a 64-bit quad-core machine clocked at 466MHz with power dissipation of up to 20 Watts—and 20 Watts is a lot. A Quad Core i5 sitting in a 13-inch MacBook Pro 2018 is a 28 Watt processor. It can heat its thin aluminum chassis to really high temperatures up to a point where it becomes an issue for some users. Under more computationally intensive workloads, fans immediately kick in to cool the whole thing down. The only issue is that, in space, fans would do absolutely nothing, because there is no air they could blow onto a hot chip. The only possible way to get heat out of a spacecraft is through radiation, and that takes time. Sure, heat pipes are there to take excessive heat away from the processor, but this heat has to eventually go somewhere. Moreover, some missions have tight energy budgets, and they simply can’t use powerful processors like RAD5545 under such restrictions. That’s why the European GR740 has power dissipation at only 1.5 Watts. It’s not the fastest of the lot, but it is the most efficient. It simply gives you the most computational bang per Watt. The HPSC with 10 Watt power dissipation comes in at a close second, but not always.

nynx 4y ago
45nm is massive for a high-performance processor. Rad-hardening compute is frankly overrated. Have multiple and compare state at a high-rate.
- shagie 4y ago
  But you can't power multiple on the energy budget that you've got. Perseverance is running on 110 watts ( https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-power/ https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-p... ). The RAD5545 uses 20 watts of that budget. Tripling it means it doesn't have enough energy to power the rest of the rover. The Mars MAVEN ( https://spaceflight101.com/maven/spacecraft-information/ https://spaceflight101.com/maven/spacecraft-information/ ) is using a RAD-750 which uses 10 watts of power ( https://en.wikipedia.org/wiki/RAD750 https://en.wikipedia.org/wiki/RAD750 ) (also used in the JWST). The RAD-750... > The processor can endure radiation doses that are a million times more extreme than what is considered fatal to humans. And while you may argue "yes, that seems a bit excessive" - the goal isn't "it can run in those extremes" but rather... > Also, RAD750 will not suffer more than one event requiring interventions from Earth over a 15-year period. > “The RAD750 card is designed to accommodate all those single event effects and survive them. The ultimate goal is one upset is allowed in 15 years. An upset means an intervention from Earth — one ‘blue screen of death’ in 15 years. We typically have contracts that (specify) that,” said Vic Scuderi BAE Business Manager. ... because it can't be replaced easily. From Wikipedia: > The CPU can withstand an absorbed radiation dose of 2,000 to 10,000 grays
  - nynx 4y ago
    You can have one disruptive rad event every 10 minutes if you compare and correct state between three or five computers at something 100 Hz. And a more recent computer that isn't designed for rad-environments will automatically be way more efficnent than a rad-hardened one.
    - shagie 4y ago
      What set of processors would your recommend putting in Perseverance with a 110 watt power budget? Or on JWST with its heat dissipation requirements?
    - tlb 4y ago
      Yes, but you have to compare the complete state of each computer for this to work, including every bit of memory & cache. You can't have much RAM if you're planning to compare them in a few milliseconds. If you try to do this without comparing the whole state, and only comparing the outputs of some control algorithm between the computers, one of them could have some internal state corrupted and remain unnoticed for a long time, long enough for other corruptions to happen on the other computers, and then you have no straightforward way to figure out which one to trust and which to reset.
  - incrudible 4y ago
    I do not buy the power argument. A modern chip is orders of magnitude more power efficient, especially at low voltage. You could easily have multiples of these within the same power budget.
    - ilyt 4y ago
      But smaller size increases the chance for event (which might be compensated) but also increases chance for fatal damage to happen. The radiation in space is not dangerous because it just produces a bit of current that can flip a bit; it is dangerous because it is strong enough to bump a bunch out of their position in silicon crystal, causing permanent damage that will accumulate over time. And when your feature size is starting to measure in <100 atoms it would be easy for single high energy event to break whole core.
minimaul 4y ago
> Quad Core i5 sitting in a 13-inch MacBook Pro 2018 is a 28 Watt processor. It can heat its thin aluminum chassis to really high temperatures up to a point where it becomes an issue for some users. Worth nothing here with Intel's Turbo Boost stuff this processor will draw a LOT more than 28W during normal operation - which makes this an awkward comparison.

by shagie 4y ago

nynx 4y ago

45nm is massive for a high-performance processor. Rad-hardening compute is frankly overrated. Have multiple and compare state at a high-rate.

shagie 4y ago
But you can't power multiple on the energy budget that you've got. Perseverance is running on 110 watts ( https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-power/ https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-p... ). The RAD5545 uses 20 watts of that budget. Tripling it means it doesn't have enough energy to power the rest of the rover. The Mars MAVEN ( https://spaceflight101.com/maven/spacecraft-information/ https://spaceflight101.com/maven/spacecraft-information/ ) is using a RAD-750 which uses 10 watts of power ( https://en.wikipedia.org/wiki/RAD750 https://en.wikipedia.org/wiki/RAD750 ) (also used in the JWST). The RAD-750... > The processor can endure radiation doses that are a million times more extreme than what is considered fatal to humans. And while you may argue "yes, that seems a bit excessive" - the goal isn't "it can run in those extremes" but rather... > Also, RAD750 will not suffer more than one event requiring interventions from Earth over a 15-year period. > “The RAD750 card is designed to accommodate all those single event effects and survive them. The ultimate goal is one upset is allowed in 15 years. An upset means an intervention from Earth — one ‘blue screen of death’ in 15 years. We typically have contracts that (specify) that,” said Vic Scuderi BAE Business Manager. ... because it can't be replaced easily. From Wikipedia: > The CPU can withstand an absorbed radiation dose of 2,000 to 10,000 grays
- nynx 4y ago
  You can have one disruptive rad event every 10 minutes if you compare and correct state between three or five computers at something 100 Hz. And a more recent computer that isn't designed for rad-environments will automatically be way more efficnent than a rad-hardened one.
  - shagie 4y ago
    What set of processors would your recommend putting in Perseverance with a 110 watt power budget? Or on JWST with its heat dissipation requirements?
  - tlb 4y ago
    Yes, but you have to compare the complete state of each computer for this to work, including every bit of memory & cache. You can't have much RAM if you're planning to compare them in a few milliseconds. If you try to do this without comparing the whole state, and only comparing the outputs of some control algorithm between the computers, one of them could have some internal state corrupted and remain unnoticed for a long time, long enough for other corruptions to happen on the other computers, and then you have no straightforward way to figure out which one to trust and which to reset.
- incrudible 4y ago
  I do not buy the power argument. A modern chip is orders of magnitude more power efficient, especially at low voltage. You could easily have multiples of these within the same power budget.
  - ilyt 4y ago
    But smaller size increases the chance for event (which might be compensated) but also increases chance for fatal damage to happen. The radiation in space is not dangerous because it just produces a bit of current that can flip a bit; it is dangerous because it is strong enough to bump a bunch out of their position in silicon crystal, causing permanent damage that will accumulate over time. And when your feature size is starting to measure in <100 atoms it would be easy for single high energy event to break whole core.

minimaul 4y ago

> Quad Core i5 sitting in a 13-inch MacBook Pro 2018 is a 28 Watt processor. It can heat its thin aluminum chassis to really high temperatures up to a point where it becomes an issue for some users. Worth nothing here with Intel's Turbo Boost stuff this processor will draw a LOT more than 28W during normal operation - which makes this an awkward comparison.