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The article suggests that SpaceX does not use specialized, radiation hardened onboard computers, but rather they use triple redundant off-the-shelf computers.

The article suggests that SpaceX does not use specialized, radiation hardened onboard computers, but rather they use triple redundant off-the-shelf computers. Why wouldn't they use radiation hardened computers, though? Are they that much heavier and more expensive than the more commonly available components? Out of a $40 million spacecraft, the difference of a few thousand dollars or even a hundred thousand dollars seems rather trivial, in exchange for a more reliable avionics system.

speeq 12y ago
Here is some excellent info on their radiation-tolerant design: http://aviationweek.com/blog/dragons-radiation-tolerant-design http://aviationweek.com/blog/dragons-radiation-tolerant-desi... It's not about cost at all: > It's really not the expense that drives it. We're committed to having the best possible parts in all of our designs. So if it cost a lot and we needed it, we'd go get it. We were already required to have all this redundancy in the computers to meet all the different safety requirements. Then we started looking at what parts do we want to use and what is appropriate for this design. And what really is more important to us than the cost of the parts is the capability of the parts – how much power do they use, how much memory do they hold, how much do they process, and how physically big are they. That's the first thing. > The second thing is what tools they come with. We run the Linux operating system, we program everything in C++, and that enables us to tap into a huge pool of very talented people and find the absolute best people in the computer and software industry to work with us. If you go into the radiation hardened parts, they are very limited in terms of what languages you can work in, what support packages there are for them, who knows how to program in them. It really limits your ability to work with the parts. And the other thing it really does is they all take a little longer time to get and they're a little harder to come by.
- hga 12y ago
  And now an item that implies Orion uses the same type of setup: https://news.ycombinator.com/item?id=8746888 https://news.ycombinator.com/item?id=8746888
rzimmerman 12y ago
At least for Falcon, I imagine radiation-hardened components probably aren't much of a gain. A rocket's operational lifetime is on the order of an hour. Triple- or 5-redundant computers are really effective for shorter missions like this because loss of one computer (due to radiation damage) doesn't have a long-term impact like it would on a deep space mission. At least that's my guess.
- tankenmate 12y ago
  The first stage never steps outside the van allen belt so it would never get much in the way of serious radiation; the second stage would possibly go outside for GTO or SSTO.
- mkramlich 12y ago
  I think that guess is accurate and was a big consideration. If it were for an interplanetary vehicle, multi-months, etc, then yes clearly you'd want a design that assumed stronger/longer radiation exposure. Plus redundancy becomes even more desirable if you have humans inside the tin can.

speeq 12y ago

Here is some excellent info on their radiation-tolerant design: http://aviationweek.com/blog/dragons-radiation-tolerant-design http://aviationweek.com/blog/dragons-radiation-tolerant-desi... It's not about cost at all: > It's really not the expense that drives it. We're committed to having the best possible parts in all of our designs. So if it cost a lot and we needed it, we'd go get it. We were already required to have all this redundancy in the computers to meet all the different safety requirements. Then we started looking at what parts do we want to use and what is appropriate for this design. And what really is more important to us than the cost of the parts is the capability of the parts – how much power do they use, how much memory do they hold, how much do they process, and how physically big are they. That's the first thing. > The second thing is what tools they come with. We run the Linux operating system, we program everything in C++, and that enables us to tap into a huge pool of very talented people and find the absolute best people in the computer and software industry to work with us. If you go into the radiation hardened parts, they are very limited in terms of what languages you can work in, what support packages there are for them, who knows how to program in them. It really limits your ability to work with the parts. And the other thing it really does is they all take a little longer time to get and they're a little harder to come by.

hga 12y ago
And now an item that implies Orion uses the same type of setup: https://news.ycombinator.com/item?id=8746888 https://news.ycombinator.com/item?id=8746888

rzimmerman 12y ago

At least for Falcon, I imagine radiation-hardened components probably aren't much of a gain. A rocket's operational lifetime is on the order of an hour. Triple- or 5-redundant computers are really effective for shorter missions like this because loss of one computer (due to radiation damage) doesn't have a long-term impact like it would on a deep space mission. At least that's my guess.

tankenmate 12y ago
The first stage never steps outside the van allen belt so it would never get much in the way of serious radiation; the second stage would possibly go outside for GTO or SSTO.
mkramlich 12y ago
I think that guess is accurate and was a big consideration. If it were for an interplanetary vehicle, multi-months, etc, then yes clearly you'd want a design that assumed stronger/longer radiation exposure. Plus redundancy becomes even more desirable if you have humans inside the tin can.