4 ms·

The really crazy part is that they never did a full up integrated test of all those systems together and in sequence before arriving at Mars.

layoric 6y ago
I was at a local radio telescope for the “live” event when it landed. Another crazy part was due to the time delay, by the time they were receiving info about entering the Mars atmosphere, it was was already over in reality and we all just had to wait those “minutes of hell” to find out what had happened.
- nine_k 6y ago
  There's no such thing as "in the same time" at distances where light propagation delays are comparable to the duration of the event.
  - p1mrx 6y ago
    Earth and Mars are practically stationary, and Occam's razor would say to assume that light travels at the same speed in all directions, even if we can't prove it. So the time of events on Mars has an "obvious", if technically not unique, solution.
    - saagarjha 6y ago
      That light travels at the same speed in all directions has been experimentally verified extremely rigorously.
      - p1mrx 6y ago
        Relevant video: https://www.youtube.com/watch?v=pTn6Ewhb27k https://www.youtube.com/watch?v=pTn6Ewhb27k
  - layoric 6y ago
    For perceiving the events happening, sure, that was my point. These time differences are nearly always imperceptible but at distances of planets it truly becomes a way of looking into the past. But to be clear, events happen concurrently, eg NASA knew _when_ relative to earth time and _perceived_ events, each stage was "happening" local to Mars vs Earth (assuming it all went well). They made videos about this "7 minutes of terror", I forgot the name of them but linking here [0] [0] https://youtu.be/Ki_Af_o9Q9s https://youtu.be/Ki_Af_o9Q9s
  - bigiain 6y ago
    As motherboard designers and HFT firms will tell us.
wiz21c 6y ago
Those guys have supernatural powers. Each time I by pass integration tests it always fails at the integration points :-)
- asxd 6y ago
  Agreed, the amount of validation work that goes into these projects must be amazing, and even then the engineers have to essentially cross their fingers that no issues were missed. I think I’m spoiled in my job in that our software can at least be rolled back if we detect an issue after the fact (also much lower stakes).
  - pm90 6y ago
    Keep in mind that a lot of investments are made in ensuring that these things don't fail. Not saying its not a great achievement. But it helps to remember that for most software shops, reliability improvements are often treated as 2nd class compared with new feature development, which reflect the reality that most software shops don't really need quite that perfect amount of reliability.
    - asxd 6y ago
      This is a good point, which I think was reflected by in nickpeterson's comment as well. There's still a bit of a culture of "move fast and break things" in my line of software engineering that I don't think ever existed in space travel. (or at least hope not)
  - steve_adams_86 6y ago
    Absolutely spoiled. My team does a lot of testing in production. We can find real world faults quickly and easily, roll back, and save ourselves time and effort by failing in production intentionally. It’s about as easy as it gets, haha.
    - bigiain 6y ago
      Tesla and Boeing appear to do the same...

layoric 6y ago

I was at a local radio telescope for the “live” event when it landed. Another crazy part was due to the time delay, by the time they were receiving info about entering the Mars atmosphere, it was was already over in reality and we all just had to wait those “minutes of hell” to find out what had happened.

nine_k 6y ago
There's no such thing as "in the same time" at distances where light propagation delays are comparable to the duration of the event.
- p1mrx 6y ago
  Earth and Mars are practically stationary, and Occam's razor would say to assume that light travels at the same speed in all directions, even if we can't prove it. So the time of events on Mars has an "obvious", if technically not unique, solution.
  - saagarjha 6y ago
    That light travels at the same speed in all directions has been experimentally verified extremely rigorously.
    - p1mrx 6y ago
      Relevant video: https://www.youtube.com/watch?v=pTn6Ewhb27k https://www.youtube.com/watch?v=pTn6Ewhb27k
- layoric 6y ago
  For perceiving the events happening, sure, that was my point. These time differences are nearly always imperceptible but at distances of planets it truly becomes a way of looking into the past. But to be clear, events happen concurrently, eg NASA knew _when_ relative to earth time and _perceived_ events, each stage was "happening" local to Mars vs Earth (assuming it all went well). They made videos about this "7 minutes of terror", I forgot the name of them but linking here [0] [0] https://youtu.be/Ki_Af_o9Q9s https://youtu.be/Ki_Af_o9Q9s
- bigiain 6y ago
  As motherboard designers and HFT firms will tell us.

wiz21c 6y ago

Those guys have supernatural powers. Each time I by pass integration tests it always fails at the integration points :-)

asxd 6y ago
Agreed, the amount of validation work that goes into these projects must be amazing, and even then the engineers have to essentially cross their fingers that no issues were missed. I think I’m spoiled in my job in that our software can at least be rolled back if we detect an issue after the fact (also much lower stakes).
- pm90 6y ago
  Keep in mind that a lot of investments are made in ensuring that these things don't fail. Not saying its not a great achievement. But it helps to remember that for most software shops, reliability improvements are often treated as 2nd class compared with new feature development, which reflect the reality that most software shops don't really need quite that perfect amount of reliability.
  - asxd 6y ago
    This is a good point, which I think was reflected by in nickpeterson's comment as well. There's still a bit of a culture of "move fast and break things" in my line of software engineering that I don't think ever existed in space travel. (or at least hope not)
- steve_adams_86 6y ago
  Absolutely spoiled. My team does a lot of testing in production. We can find real world faults quickly and easily, roll back, and save ourselves time and effort by failing in production intentionally. It’s about as easy as it gets, haha.
  - bigiain 6y ago
    Tesla and Boeing appear to do the same...