4 ms·

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

by runeb 6y ago

senkora 6y ago
For 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.
deleted 6y ago
[deleted]
arjun-menon 6y ago
I was thinking, instead of that, what if you had a separate isolated tiny computer on spacecraft, that was powered by its solar panels (so there's no electrical wiring, or other connection to it), and have its own radio. And this separate computer could use the latest bleeding-edge CPU, and be encased in a radiation-hardened shell. It would use its radio to talk to the slower main computer, and do math really fast locally, and if need be, beam the results to Earth, or to a nearby orbiting satellite.
- angry_octet 6y ago
  Unfortunately there isn't really any practical way to have a radiation hardened shell that is sufficiently effective. Eg. 5cm of aluminium stops only 30% of the galactic radiation. (Heavier elements (e.g. gold) are scattered by incoming particles causing incoming heavy ions which cause even more damage.) So practically it would still experience significant radiation. But having the main compute for Mars remain in orbit with the relay isn't a bad idea.
cpgxiii 6y ago
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 a major improvement.
- gorgoiler 6y ago
  You could A* your way around the whole planet by using an Earth based computation but only if you knew where every rock was. There must be some equation of motion in space robots that combines terrain difficulty, robot speed, round trip time to Earth, and how far ahead you’d need to be able to see. Curiosity moves about as fast as a Roomba. The ping is (min/avg/max) 10’/24’/40’. Ergo, it needs to be able to see X yards ahead of itself to plan A* from Earth, requiring a camera boom Y feet tall producing images with Z megapixels of resolution. I wonder what X, Y and Z are.
  - throwaway189262 6y ago
    Does curiosity really move that fast? Roomba is maybe 2 mph. I thought curiosity was closer to 0.1 mph
    - JohnJamesRambo 6y ago
      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.
      - gorgoiler 6y ago
        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.
throwaway189262 6y ago
Shannon limit implies a linear relation between bit rate and transmit power. The only way to get fast enough transfer would be to spend tons of the power budget on radio

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

by runeb 6y ago

Could 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 ago

For 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.

deleted 6y ago

[deleted]

arjun-menon 6y ago

I was thinking, instead of that, what if you had a separate isolated tiny computer on spacecraft, that was powered by its solar panels (so there's no electrical wiring, or other connection to it), and have its own radio. And this separate computer could use the latest bleeding-edge CPU, and be encased in a radiation-hardened shell. It would use its radio to talk to the slower main computer, and do math really fast locally, and if need be, beam the results to Earth, or to a nearby orbiting satellite.

angry_octet 6y ago
Unfortunately there isn't really any practical way to have a radiation hardened shell that is sufficiently effective. Eg. 5cm of aluminium stops only 30% of the galactic radiation. (Heavier elements (e.g. gold) are scattered by incoming particles causing incoming heavy ions which cause even more damage.) So practically it would still experience significant radiation. But having the main compute for Mars remain in orbit with the relay isn't a bad idea.

cpgxiii 6y ago

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 a major improvement.

gorgoiler 6y ago
You could A* your way around the whole planet by using an Earth based computation but only if you knew where every rock was. There must be some equation of motion in space robots that combines terrain difficulty, robot speed, round trip time to Earth, and how far ahead you’d need to be able to see. Curiosity moves about as fast as a Roomba. The ping is (min/avg/max) 10’/24’/40’. Ergo, it needs to be able to see X yards ahead of itself to plan A* from Earth, requiring a camera boom Y feet tall producing images with Z megapixels of resolution. I wonder what X, Y and Z are.
- throwaway189262 6y ago
  Does curiosity really move that fast? Roomba is maybe 2 mph. I thought curiosity was closer to 0.1 mph
  - JohnJamesRambo 6y ago
    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.
    - gorgoiler 6y ago
      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.

throwaway189262 6y ago

Shannon limit implies a linear relation between bit rate and transmit power. The only way to get fast enough transfer would be to spend tons of the power budget on radio