3 ms·

apparently list price for the RAD750 is $200,000! could you not externally harden the snapdragon for less?

ChuckNorris89 6y ago
That's not how hardening chips works. You need a specialized fab manufacturing, etching and packaging process for this and it's not like regular fabs are cheap to begin with. Plus you're working from the start with much larger nodes with dedicated cell libraries so everything has to be designed from scratch to fit that node which means you can't reuse consumer off the shelf designs very easily. Then there's the lack of economies of scale in building such custom parts in small numbers. I imagine if Apple would only order 100 5nm chips per year from TSMC, the unit price would be equally eye watering.
- abfan1127 6y ago
  I've only read this doc quickly [1]. I would have guessed a lead case of a particular thickness would do the trick. But I don't know the thickness needed, maybe too much? [1] https://nepp.nasa.gov/files/25295/MRS04_LaBel.pdf https://nepp.nasa.gov/files/25295/MRS04_LaBel.pdf
  - ChuckNorris89 6y ago
    In theory you could just cover everything in lead and call it a day, IF, lead wouldn't also be one of the heaviest metals in the world, which kinda goes against the mantra of space travel.
    - dylan604 6y ago
      yeah, but it'd only be 3/8 as heavy on Mars! seriously, that's something I haven't thought much about. when designing rovers, do they calculate solely on the weight of what it will be on the destination, or limit it to weight limits of escaping earth's gravity well?
      - ChuckNorris89 6y ago
        Weight on board the rocket is the most important consideration as payload weigh is the limiting factor.
      - bdamm 6y ago
        It's not just the mechanical weight at the destination and the work required to escape earth's gravity (which is enormous). Mass of the rover also means more fuel to speed up and slow down if there is any delta-V changes en-route, the heat energy that needs to be dissipated during re-entry, the forces on parachute and lander as well. So really, that mass penalty gets paid over and over... and not often linearly.
      - johnwalkr 6y ago
        Rover designer here. The weight at the destination is important to characterize performance but it’s not a big driver of design. For example, once you consider losses due to friction inside gearboxes, there’s no big difference to size a motor. You want to be able to test on Earth easily anyway, so you wouldn’t design without a margin to allow that. I suppose if you designed a rover for Uranus you might take a different approach. Launch mass is important as a constraint, but the launch environment is the main design driver for mass. The rover must be much stiffer than the rocket to not “couple” it’s response. The first vibration mode (think tuning fork) of a rocket is about 20Hz so the spacecraft inside needs a first vibration mode higher than 40Hz. Something inside the spacecraft similarly needs a first vibration mode higher than 60Hz or 80Hz, although you can make exceptions based on analysis. But that’s not all, the sustained load on components during launch can easily be 10 to 30 times gravity (30G) and the instantaneous load can be 100G. You can’t just add material for these kinds of loads, it would be an endless feedback loop because adding mass decreases stiffness. Look closely and you’ll see that every deployable or movable part of the rover is locked down by a mechanism until it has landed.
    - monadic5 6y ago
      Lead coating a critical and embedded component like a CPU, or even a SOC, has gotta be barely significant for the weight of the payload. I'm guessing the faster CPU is just not necessary for the core rover, so via KISS, use the proven chips.
    - johnwalkr 6y ago
      Actually it doesn’t work that way (solely based on mass). Radiation doesn’t just get stopped by lead, it generates secondary particles. Lead happens to be effective against x-rays, which is why we tend to think of “lead shielding” but it’s not effective against all types of radiation. So it would help but you couldn’t just call it a day, and other materials are more mass efficient.
- deleted 6y ago
  [deleted]
0xffff2 6y ago
Ha, if you think that's a lot, I've got some news for you. That might be the price for just the CPU, but the price for the avionics package (basically a RAD750 with the necessary boards to manage power and IO) is a whole lot more than that. (I'm probably not allowed to name the exact number, but you're going to need to add a zero for sure.)
- abfan1127 6y ago
  no way I'd be surprised by it. When you only sell 4-5 a year, its going to be pricey!

That's not how hardening chips works. You need a specialized fab manufacturing, etching and packaging process for this and it's not like regular fabs are cheap to begin with. Plus you're working from the start with much larger nodes with dedicated cell libraries so everything has to be designed from scratch to fit that node which means you can't reuse consumer off the shelf designs very easily. Then there's the lack of economies of scale in building such custom parts in small numbers. I imagine if Apple would only order 100 5nm chips per year from TSMC, the unit price would be equally eye watering.

abfan1127 6y ago
I've only read this doc quickly [1]. I would have guessed a lead case of a particular thickness would do the trick. But I don't know the thickness needed, maybe too much? [1] https://nepp.nasa.gov/files/25295/MRS04_LaBel.pdf https://nepp.nasa.gov/files/25295/MRS04_LaBel.pdf
- ChuckNorris89 6y ago
  In theory you could just cover everything in lead and call it a day, IF, lead wouldn't also be one of the heaviest metals in the world, which kinda goes against the mantra of space travel.
  - dylan604 6y ago
    yeah, but it'd only be 3/8 as heavy on Mars! seriously, that's something I haven't thought much about. when designing rovers, do they calculate solely on the weight of what it will be on the destination, or limit it to weight limits of escaping earth's gravity well?
    - ChuckNorris89 6y ago
      Weight on board the rocket is the most important consideration as payload weigh is the limiting factor.
    - bdamm 6y ago
      It's not just the mechanical weight at the destination and the work required to escape earth's gravity (which is enormous). Mass of the rover also means more fuel to speed up and slow down if there is any delta-V changes en-route, the heat energy that needs to be dissipated during re-entry, the forces on parachute and lander as well. So really, that mass penalty gets paid over and over... and not often linearly.
    - johnwalkr 6y ago
      Rover designer here. The weight at the destination is important to characterize performance but it’s not a big driver of design. For example, once you consider losses due to friction inside gearboxes, there’s no big difference to size a motor. You want to be able to test on Earth easily anyway, so you wouldn’t design without a margin to allow that. I suppose if you designed a rover for Uranus you might take a different approach. Launch mass is important as a constraint, but the launch environment is the main design driver for mass. The rover must be much stiffer than the rocket to not “couple” it’s response. The first vibration mode (think tuning fork) of a rocket is about 20Hz so the spacecraft inside needs a first vibration mode higher than 40Hz. Something inside the spacecraft similarly needs a first vibration mode higher than 60Hz or 80Hz, although you can make exceptions based on analysis. But that’s not all, the sustained load on components during launch can easily be 10 to 30 times gravity (30G) and the instantaneous load can be 100G. You can’t just add material for these kinds of loads, it would be an endless feedback loop because adding mass decreases stiffness. Look closely and you’ll see that every deployable or movable part of the rover is locked down by a mechanism until it has landed.
  - monadic5 6y ago
    Lead coating a critical and embedded component like a CPU, or even a SOC, has gotta be barely significant for the weight of the payload. I'm guessing the faster CPU is just not necessary for the core rover, so via KISS, use the proven chips.
  - johnwalkr 6y ago
    Actually it doesn’t work that way (solely based on mass). Radiation doesn’t just get stopped by lead, it generates secondary particles. Lead happens to be effective against x-rays, which is why we tend to think of “lead shielding” but it’s not effective against all types of radiation. So it would help but you couldn’t just call it a day, and other materials are more mass efficient.
deleted 6y ago
[deleted]

0xffff2 6y ago

Ha, if you think that's a lot, I've got some news for you. That might be the price for just the CPU, but the price for the avionics package (basically a RAD750 with the necessary boards to manage power and IO) is a whole lot more than that. (I'm probably not allowed to name the exact number, but you're going to need to add a zero for sure.)

abfan1127 6y ago
no way I'd be surprised by it. When you only sell 4-5 a year, its going to be pricey!