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While I'm an American engineer who prefers working in metric, since this is a space-related article I have to point you to this: https://s-media-cache-ak0.pinim

While I'm an American engineer who prefers working in metric, since this is a space-related article I have to point you to this: https://s-media-cache-ak0.pinimg.com/736x/69/ae/01/69ae0104b424acd26a0f5c4a8588befa.jpg https://s-media-cache-ak0.pinimg.com/736x/69/ae/01/69ae0104b...

Someone1234 12y ago
And I have to point to this: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...
- mitchty 12y ago
  And? Someone output things in non SI units to something that expected SI. Shit happens. Want me to point to the Beagle probe? Space isn't easy.
  - aguywithamum 12y ago
    The point being that his particular failure could've possibly been avoided if we were not using two parallel measurement systems...
    - wtetzner 12y ago
      Not necessarily. One part of the code could have been using meters, and another using kilometers.
    - mitchty 12y ago
      How so? If I build something that doesn't conform to specifications, what does it matter if it happened to be unit conversions? They could have skipped a decimal point and not noticed, because they didn't conform to the specification. More importantly it never got checked or tested or simulated further on up the chain to catch the issue. Look at the Araine 5. Unit conversions had nothing to do with a computer saying "gimbal an engine 90 degrees". I'm sorry but this canard of two units being the problem is missing the entire point. Its an engineering issue and management failure. Just like the space shuttle O rings before them, space is hard. Distilling things down to "america should have used metric cause reasons" is trying to pass off complex problems with bite sized quotes. The only issue is it is wrong.
      - mturmon 12y ago
        This is a smart comment. It sucks to have to keep repeating this comment every time someone trots out this supposedly easy example. Sure, the units issue was the root cause, but the resulting navigation errors should have been acted upon. They were noticed ("The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed."), but the issue wasn't acted upon. This is a management and budget problem. Even if the units are given as SI, there are always interface issues -- which coordinate system to use, where the origin is, does z point up or down, degrees or radians. It can be hard to appreciate unless you have had experience with hard-to-find failures due to subtle numerical problems. As you say, space is hard.
- RankingMember 12y ago
  @mitchty, I don't see how the Beagle probe relates unless parallel but different measurement systems caused that, and I'm not seeing anything to indicate this (but let me know if I'm missing something, I'm curious).
  - aguywithamum 12y ago
    "The primary cause of this discrepancy was that one piece of ground software supplied by Lockheed Martin produced results in a United States customary unit ('American'), contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, that used those results expected them to be in metric units, in accord with the SIS."
    - RankingMember 12y ago
      That's in reference to the Beagle 2?
      - deleted 12y ago
        [deleted]
        deleted 12y ago
        [deleted]
      - aguywithamum 12y ago
        Yeah, that's in reference to the failure of Beagle 2. It's on the page that was linked by Someone1234 (https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...).
        TorKlingberg 12y ago
        The Beagle 2 and Mars Climate Orbiter are not the same thing. It is unknown why Beagle 2 failed and there is no reason to believe it was due to any unit mismatch. It may be that two of the solar panels failed to deploy.
venomsnake 12y ago
And imagine what would you have been able to do if you used sane measurement system ...
dweinus 12y ago
Ignoring the idiotic patriotism, that image is incorrect: Russia, China, and India have all placed landers on the moon.
- juliangregorian 12y ago
  Not people though.

Someone1234 12y ago

And I have to point to this: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...

mitchty 12y ago
And? Someone output things in non SI units to something that expected SI. Shit happens. Want me to point to the Beagle probe? Space isn't easy.
- aguywithamum 12y ago
  The point being that his particular failure could've possibly been avoided if we were not using two parallel measurement systems...
  - wtetzner 12y ago
    Not necessarily. One part of the code could have been using meters, and another using kilometers.
  - mitchty 12y ago
    How so? If I build something that doesn't conform to specifications, what does it matter if it happened to be unit conversions? They could have skipped a decimal point and not noticed, because they didn't conform to the specification. More importantly it never got checked or tested or simulated further on up the chain to catch the issue. Look at the Araine 5. Unit conversions had nothing to do with a computer saying "gimbal an engine 90 degrees". I'm sorry but this canard of two units being the problem is missing the entire point. Its an engineering issue and management failure. Just like the space shuttle O rings before them, space is hard. Distilling things down to "america should have used metric cause reasons" is trying to pass off complex problems with bite sized quotes. The only issue is it is wrong.
    - mturmon 12y ago
      This is a smart comment. It sucks to have to keep repeating this comment every time someone trots out this supposedly easy example. Sure, the units issue was the root cause, but the resulting navigation errors should have been acted upon. They were noticed ("The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed."), but the issue wasn't acted upon. This is a management and budget problem. Even if the units are given as SI, there are always interface issues -- which coordinate system to use, where the origin is, does z point up or down, degrees or radians. It can be hard to appreciate unless you have had experience with hard-to-find failures due to subtle numerical problems. As you say, space is hard.
RankingMember 12y ago
@mitchty, I don't see how the Beagle probe relates unless parallel but different measurement systems caused that, and I'm not seeing anything to indicate this (but let me know if I'm missing something, I'm curious).
- aguywithamum 12y ago
  "The primary cause of this discrepancy was that one piece of ground software supplied by Lockheed Martin produced results in a United States customary unit ('American'), contrary to its Software Interface Specification (SIS), while a second system, supplied by NASA, that used those results expected them to be in metric units, in accord with the SIS."
  - RankingMember 12y ago
    That's in reference to the Beagle 2?
    - deleted 12y ago
      [deleted]
      - deleted 12y ago
        [deleted]
    - aguywithamum 12y ago
      Yeah, that's in reference to the failure of Beagle 2. It's on the page that was linked by Someone1234 (https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_failure https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...).
      - TorKlingberg 12y ago
        The Beagle 2 and Mars Climate Orbiter are not the same thing. It is unknown why Beagle 2 failed and there is no reason to believe it was due to any unit mismatch. It may be that two of the solar panels failed to deploy.

venomsnake 12y ago

And imagine what would you have been able to do if you used sane measurement system ...

dweinus 12y ago

Ignoring the idiotic patriotism, that image is incorrect: Russia, China, and India have all placed landers on the moon.

juliangregorian 12y ago
Not people though.