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NASA Moon Space

NASA Will Go Metric On the Moon 695

Posted by kdawson
from the late-conversion dept.
An anonymous reader writes "Space.com is reporting that NASA has decided to use the metric system for its new lunar missions. NASA hopes that metrication will allow easier international participation and safer missions. The loss of the Mars Climate Orbiter was blamed on an error converting between English units and metric units. 'When we made the announcement at the meeting, the reps for the other space agencies all gave a little cheer,' said a NASA official."
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NASA Will Go Metric On the Moon

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  • Yay!!! (Score:5, Insightful)

    by Spritzer (950539) * on Tuesday January 09, 2007 @04:24PM (#17527652) Journal
    Now if only American car companies will budge that extra 17/32" and finish going metric rather than forcing me to have 2 sets of tools for one car. Then I can "Compare Prices on Physics and Engineering" here at /.
    • Re:Yay!!! (Score:5, Informative)

      by pilgrim23 (716938) on Tuesday January 09, 2007 @04:34PM (#17527882)
      as I recall, the fittings on the Apollo 13 launch were metric, the Comamnd Module English. Some fittings were square, others round.... If I was on the moon I would hate to need to change my O2 bottle and in an emergency, the one from contractor B has a English nozzle fitting. Consisitency is not just a good idea here....
      • Re: (Score:3, Funny)

        by Spritzer (950539) *
        Watching that would be ever so slightly more amusing than watching one of my European customers when maintaining one of my employer's half-metric half-imperial products. It's fun hearing things like "This wrench won't fit, and this one is too big. Is this a 9.5mm nut? Oh shit. It's American."
        • Re:Yay!!! (Score:5, Funny)

          by mpe (36238) on Tuesday January 09, 2007 @05:32PM (#17529342)
          Watching that would be ever so slightly more amusing than watching one of my European customers when maintaining one of my employer's half-metric half-imperial products. It's fun hearing things like "This wrench won't fit, and this one is too big. Is this a 9.5mm nut? Oh shit. It's American."

          They'd read the instructions, but when they tried to print them out the printer just sat there flashing "PC LOAD LETTER"...
          • Re:Yay!!! (Score:4, Funny)

            by Spritzer (950539) * on Tuesday January 09, 2007 @05:37PM (#17529490) Journal
            What the fuck does that mean?!

          • No one has actually answered this legitimate question.

            "PC LOAD LETTER" ==> (P)rint (C)artridge, (Load Letter) Sized Paper now!"
            "PC LOAD LETTER" ==> (P)rint (C)artridge, (Load Letter) Sized Paper now!"
            "PC LOAD LETTER" ==> (P)rint (C)artridge, (Load Letter) Sized Paper now!"
            "PC LOAD LETTER" ==> (P)rint (C)artridge, (Load Letter) Sized Paper now!"
            "PC LOAD LETTER" ==> (P)rint (C)artridge, (Load Letter) Sized Paper now!"

            There's only 14 characters on the display, what should it say? "Put In Paper?"
      • Re:Yay!!! (Score:5, Funny)

        by el_womble (779715) on Tuesday January 09, 2007 @04:51PM (#17528384) Homepage
        I'm British, so I deal with both systems on a daily basis and I think we've got it pretty sorted. Doing something important, where you need accuracy do it in metric doing something fun, do it in imperial.

        Distance to the shops in miles, distance to the sun in kilometers
        I measure my weight in stones and pounds, but I cook in grams.
        Size of my wang in feet (ok, ok inches) size of my windows in cm.

        I'm not sure why Americans feel the need to stick to imperial, especially in light of computers. At least NASA has now seen the light.
        • Re:Yay!!! (Score:4, Insightful)

          by illegalcortex (1007791) on Tuesday January 09, 2007 @05:01PM (#17528626)
          I'm not sure why Americans feel the need to stick to imperial
          Because using a crappy system 95% of the time is better than using a good system 50% of the time and a crappy system 50% of the time?

          I wish everyone in the US had switched to metric before I was born. But if they were only going to do it half-assed (0.196850394-assed for metric folks), I'd just as soon stick with the crappy system. If you're going to do something poorly, at least by consistent.
          • Re:Yay!!! (Score:5, Interesting)

            by itlurksbeneath (952654) on Tuesday January 09, 2007 @05:26PM (#17529200) Journal
            Consistent? We (the US) buy soft drinks by the liter, booze by the milliliter and milk by the gallon. Where's the consistency there?
          • Thank You! (Score:5, Funny)

            by spun (1352) <loverevolutionar ... m ['o.c' in gap]> on Tuesday January 09, 2007 @05:55PM (#17529890) Journal
            But if they were only going to do it half-assed (0.196850394-assed for metric folks),

            I've always heard people talking about "a metric buttload" or "a metric assload" of this, that or the other thing. I never knew how much they were talking about, and I've been too embarassed to ask. Thank you for clearing up the conversion factor between a metric and imperial ass load!
          • Re:Yay!!! (Score:5, Insightful)

            by spagetti_code (773137) on Tuesday January 09, 2007 @06:21PM (#17530454)
            If you're going to do something poorly, at least by consistent.
            Yeah, because we know how consistent the imperial system is...

            Let me see...

            16 ounces to the pound
            14 pounds to the stone
            2240 pounds to the ton (more correctly a long ton)
            1000 pounds to the short ton
            40 cubic feet to the freight ton

            And this is my favourite:
            Both the long and short ton are 20 hundredweights, but the
            hundredweight differs from 100 to 108 pounds.

            Dont forget the furlong, rood, pole, chain, link, inches, feet, yards...

            Yeah... that looks pretty consistent. /sarcasm.

            • Re:Yay!!! (Score:5, Funny)

              by tobiasly (524456) on Tuesday January 09, 2007 @07:08PM (#17531280) Homepage
              16 ounces to the pound

              Not so fast... that's only true if you're using the regular "Avoirdupois" [wikipedia.org] pounds. In the Troy [wikipedia.org] system, which is used for precious metals and gems, a pound is only 12 ounces!

              I read a "brain teaser" once that asked: Which is heavier, a pound of gold or a pound of feathers? Of course, we've all heard a variation of this question (usually bricks and feathers), and know that the answer is that they weigh the same -- one pound. However, a pound of feathers weighs more than a pound of gold, because feathers are measured using the avoirdupois system (1 pound = about 453.59 g) while gold uses Troy (1 pound = about 373.24 g).

              • by WebCowboy (196209) on Wednesday January 10, 2007 @01:09AM (#17535140)
                However, a pound of feathers weighs more than a pound of gold, because feathers are measured using the avoirdupois system (1 pound = about 453.59 g) while gold uses Troy (1 pound = about 373.24 g).

                Hold on a minute--I always thought that a pound was a pound was a pound, and that a "Troy ounce" was different from a "normal ounce" (1/12 of a pound vs 1/16 of a pound). Now, becaus of you and Wikipaedia I now know that not only are the ounces different AND the number of ounces in each pound are Different, but the size of each pound is different too!

                Even more perverse--a Troy Oz is HEAVIER than a normal ox, but a Troy pound is LIGHTER than a normal pound!

                It's no wonder y'all down there in the US crash your space probes into planets.
            • Re:Yay!!! (Score:4, Funny)

              by Zaatxe (939368) on Tuesday January 09, 2007 @07:21PM (#17531494)
              And until last week, the speed of light for NASA was 1.8026174997852541159627773801002 terafurlongs per fortnight...
        • Re: (Score:3, Funny)

          by IdleTime (561841)

          Size of my wang in feet (ok, ok inches)
          WHY?

          It sounds bigger in metric!
        • Re: (Score:3, Funny)

          by Sponge Bath (413667)

          ...doing something fun, do it in imperial.

          I'll raise my pint and toast to that!

    • Re:Yay!!! (Score:5, Funny)

      by bgarcia (33222) on Tuesday January 09, 2007 @04:52PM (#17528422) Homepage Journal
      Both of my "American cars" were actually made in Canada, and are already metric.

      I think the only car companies still making cars in America are the Japanese. :-D

    • Re:Yay!!! (Score:5, Funny)

      by Simon Garlick (104721) on Tuesday January 09, 2007 @05:09PM (#17528798)
      I mess around with electric guitars in my nonexistent spare time. Last time I ordered a guitar neck from a US manufacturer it was described as being 43 millimetres wide and 0.85 inches thick, with tuning-machine holes pre-drilled at 11/32 inches.
  • That's Metrification.
  • by lbmouse (473316) on Tuesday January 09, 2007 @04:26PM (#17527694) Homepage
    The metric system is the tool of the devil! My spaceship gets forty rods to the hogshead and that's the way I likes it!
    • Finally, Atom [themadmusicarchive.com] will be happy.
    • by the dark hero (971268) <adriatic_hero&hotmail,com> on Tuesday January 09, 2007 @04:45PM (#17528216) Homepage
      for all of you that don't know, a rod was originally measured from the tip of the donkey's nose to the back of the plow. go america...
    • by camperdave (969942) on Tuesday January 09, 2007 @04:58PM (#17528554) Journal
      It secretly amuses me when Americans (one of only three backwards countries that haven't converted) argue about keeping the "imperial" system. All of your current units of measurement have been defined relative to the metric system for the past 50 years or so. From the wiki [wikipedia.org]: "One inch international measure is exactly 25.4 millimeters, while one inch U.S. survey measure is defined so that 39.37 inches is exactly 1 meter". "The pound avoirdupois, which forms the basis of the U.S. customary system of mass, is defined as exactly 453.59237 grams".

      • Re: (Score:3, Informative)

        by mpe (36238)
        All of your current units of measurement have been defined relative to the metric system for the past 50 years or so. From the wiki: "One inch international measure is exactly 25.4 millimeters, while one inch U.S. survey measure is defined so that 39.37 inches is exactly 1 meter".

        Actually it's more like 60+ years. Originally the "English" and Imperial inches were slightly different. The 25.4 mm inch was a compromise between the two values, so as to ensure that parts manufactured for the war (WWII) effort
  • by Anonymous Coward on Tuesday January 09, 2007 @04:28PM (#17527746)
    A metric moon? Not if this president has anything to say about it!
  • by User 956 (568564) on Tuesday January 09, 2007 @04:28PM (#17527750) Homepage
    The loss of the Mars Climate Orbiter was blamed on an error converting between English units and metric units.

    And to think when we were learning the metric system in school, the teacher told us it didn't take a rocket scientist to figure it out.

    I guess he was wrong.
    • by mangu (126918)
      the teacher told us it didn't take a rocket scientist to figure it out


      Actually, it's pretty simple. In NASA units, to convert one inch to centimeters, multiply by $254 million.

  • by octavian755 (588429) on Tuesday January 09, 2007 @04:29PM (#17527788) Homepage
    I was under the impression that most scientific agencies used metric as a standard (Guess US educational system failed me there). My father is a builder and I grew up seeing how contractors can be so loose with measurements. It amazes me that NASA got this far using a very inaccurate system (at times) for such precise operations.
    • Re: (Score:3, Insightful)

      It's still being used because there is a massive infrastructure of machine tools and instruments amongst the contractors. The move to digital instrumentation and CNC is facilitating the transition.

      It amazes me that NASA got this far using a very inaccurate system (at times) for such precise operations.

      It's actually quite precise, just more complicated to use.
    • I'm also rather surprised at all this; I thought that NASA already used the metric system for everything. When I was taking physics classes in high school and college, everything was done in metric units, and I always assumed that would be the case at a higher level. Huh. Well, hey, this is a great step forward - better late than never!
    • by porcupine8 (816071) on Tuesday January 09, 2007 @04:54PM (#17528458) Journal
      There's nothing inherently inaccurate about the measurement system itself. You can measure down to the millionth of an inch if you want. If a contractor is going to be loose with their measurements, they could just as easily say "Eh, that's about two meters" as "Eh, that's about seven feet". You can't make people measure down the the millimeter just because it's available on their measuring tape.
  • by VEGETA_GT (255721) on Tuesday January 09, 2007 @04:31PM (#17527812)
    Metric is a very easy system to deal with and has been adopted over a large portion of the world. Technically Canada has been metric for over 20 years. Tho things like construction has remained Imperial as we are next to the US. If not for the Us Canada would be completely metric, but since the Us is right next door, we end up in the metric camp with one foot still over in the Imperial side o things. But I don't see the Us converting to metric any time soon, but the scientific community moving to metric to do its work instead of continually converting would be a great leap in the right direction.
    • Re: (Score:3, Interesting)

      by geoffspear (692508)
      The scientific community has been using metric, even in the US, for years.

      Unfortunately, the manufacturing sector is as stubborn as the rest of the country. As mentioned in TFA, the Mars Climate Orbiter debacle was not caused by NASA not using metric, but rather because they were using metric and confusion ensued when one of their boneheaded vendors wasn't.
    • Canadians tends to talk about speed and distance in kilometres, distances on a golf course in yards, milk and gasoline in litres (and when they say a quart of milk everyone knows they mean a litre of milk), liquor in ounces, temperature in Celsius in Canada but Fahrenheit in the U.S. (e.g., it's 30 degrees in Toronto, but 85 in Buffalo), food weights in kilograms, and a person's weight and height in pounds and feet + inches.

      A bizarre polyglot, but not as bad as their cereal boxes, n'est-ce pas?

    • by Stanistani (808333) on Tuesday January 09, 2007 @04:45PM (#17528218) Homepage Journal
      Confusion can be fatal or just embarassing, such as in the Gimli Glider [wikipedia.org] incident, which was partially due to a units conversion error.
    • by KH (28388) on Tuesday January 09, 2007 @05:55PM (#17529892)

      we end up in the metric camp with one foot still over in the Imperial side o things.

      That's 30.48 cm, correct?
  • Soo.. (Score:5, Funny)

    by dbatkins (958906) on Tuesday January 09, 2007 @04:32PM (#17527832)
    when the first McD's is built on the moon, I have to order a "Royal With Cheese" ?
  • ... is that in the UK we've been using the metric system for at least 20 years!
  • "The loss of the Mars Climate Orbiter was blamed on an error converting between English units and metric units."

    As I recall, the conflict came into play partly because NASA was using metric. The federal government is about the only customer of the US aerospace industry that insists on using metric for everything (civilian air traffic control, even in other countries, measures altitude in feet instead of meters).

    So this announcement that NASA will keep on doing what they've been doing for decades really doe
  • by MouseR (3264) on Tuesday January 09, 2007 @04:34PM (#17527896) Homepage
    ...they're going right through it?
  • by Decaffeinated Jedi (648571) on Tuesday January 09, 2007 @04:37PM (#17527972) Homepage Journal
    I have a bad feeling about this. Has this whole metric thing been thoroughly tested?
  • The year 10,000? (Oh, sorry, that should be 5,280.)
  • by TheWoozle (984500) on Tuesday January 09, 2007 @04:40PM (#17528060)
    I'm confused - are they only going to use the Metric system on the Moon?

    or is it more like: "Dude, did you see that?! NASA totally went Metric on the Moon's ass!"
  • "The metric system is the tool of the devil! My car gets forty rods to the hogshead, and that's the way I likes it!"

    Who keeps the metric system down? We do! We do!

    - Sincerely, you!ess!A! you!ess!A! ...

  • Good start (Score:5, Informative)

    by gregmac (629064) on Tuesday January 09, 2007 @04:47PM (#17528284) Homepage
    .. but when is the rest of the USA going to follow suit?

    According to wikipedia, As of 2005 only three countries, the United States, Liberia, and Myanmar (Burma) [wikipedia.org] have not converted to metric yet. Canada officially converted in 1970, but both systems get used on a day-to-day basis. Most tape measures, rulers, etc have both systems. Most older people still use imperial for most things, and younger generations seem to be mixed.

    It's actually interesting that a lot of people here (Canada) use mixed units. Personally, I usually use feet if I'm estimating a distance (it's just a very convienient size - the closest metric equivalent is a decimeter, just doesn't quite cut it), and pounds and feet/inches for human weight/height. We still order a pound of wings and a pint of beer (I think you get beat up if you ask for 568mL of beer in a bar). Most other things are metric: road signs are km/h, the weather report is in celcius. Most stores sell things by the kilogram, meter, or liter/milliliter. I'm not sure what they teach kids in school now, but my generation (mid 20's) seems to be decently fluent in both systems (I remember learning how to add inches as part of learning fractions).

    • Re: (Score:3, Informative)

      by WarwickRyan (780794)
      Sounds just like England. Everything's in metric except drinking, driving and weight watchers.

    • Re:Good start (Score:5, Interesting)

      by Freultwah (739055) on Tuesday January 09, 2007 @05:34PM (#17529418) Homepage

      I'm European and I've never been exposed to the imperial system. I am thus not tempted to use my hands or feet for measuring anything but the runway length for my long jumps. I've heard of no-one that uses decimetres for measuring distance, either. It's pretty much "metre twenty" or "two forty" everything. The pound thing, I think, would be "half a kilo", the beer issue is solved by asking "a beer". Or "a small beer" for a 0.33 l glass. (Other beer countries' customs and glass sizes do vary.) People weigh something like "75 kilos" and are "metre eighty" tall.

      I guess it shows that even if you would think one system is harder or more cumbersome for certain things than the other, people who have had exposure to only one of them tend to come up with a very flexible and convenient way of measuring stuff. I still get dizzy when a translator fails to translate all the measurements to the target culture's system (all right, there are those rare times when it's desirable to have cubic feet and furlongs in literature), but the North Americans don't.

      My favourite (not) is the standard PC case and its measurements. Have a metric ruler handy and go over it. Everything is very much metric. The 3.5 inch floppy? It's not 8.89 cm, it's exactly 9 cm. The 3.5 inch drive bay? Exactly 10 cm wide. The 5 1/4 inch bay? Not 13.335 cm, exactly 15 instead. Etc. Everything metric from the beginning, re-measured and rounded to fit the imperial system (what with the US probably being the biggest target market in the beginning of the PC). The sad thing is, the rest of the world seems to be accepting it unconditionally. It's as if no-one has had a ruler handy for quite some time.

    • Re: (Score:3, Insightful)

      by argStyopa (232550)
      ".. but when is the rest of the USA going to follow suit?"

      Well, why does everyone seem to care so much?

      I mean, the US is particularly full of people that don't like governments telling them what to do - hell, the US was FOUNDED by people like that.

      It's simply not practicable for the US gov't to say "you must all do it this way" for something so trivial.
    • by jesterzog (189797) on Tuesday January 09, 2007 @06:56PM (#17531098) Homepage Journal

      It's actually interesting that a lot of people here (Canada) use mixed units. Personally, I usually use feet if I'm estimating a distance (it's just a very convienient size - the closest metric equivalent is a decimeter, just doesn't quite cut it), and pounds and feet/inches for human weight/height.

      I've grown up using Metric, since New Zealand's been standardised on it since well before I was born. I use it all the time, and I love it. So many different units of measurement go between each other in logical ways, many of which aren't noticed by most, right down to things like standard pencil widths being designed to match standard paper sizes. There are definitely problems with using it for day-to-day use, though, which I think most people just put up with. (The metre is often too big, the centimetre isn't big enough, and so on. Blocks of 10 cm would make a lot of sense, and I'm a bit surprised they don't get used.)

      What imperial really has going for it, though, and one of the reasons it's so convenient, is that the units make it easier to divide things up for day-to-day tasks. In metric, it's easy to divide by 10, and often by 5 and 2, but outside of that the decimal places start getting long and often end up recurring. Dividing things into threes, fours and sixes really doesn't work if you also want twos and fives.

      This is more to do with base 10 than with metric. I've often wondered if metric would be better long term if everyone counted in base 12, instead, and if the relationships between metric units were based on multiples of 12 instead of 10. For day to day use, simpler fractions translate to decimals (or whatever decimals are called in base 12) more nicely with base 12 than base 10. eg.

      1/1 in base 10 is 1.0, in base 12 is 1.0.
      1/2 in base 10 is 0.5, in base 12 is 0.6.
      1/3 in base 10 is 0.333333..., in base 12 is 0.4.
      1/4 in base 10 is 0.25, in base 12 is 0.3.
      1/5 in base 10 is 0.2, in base 12 is 0.24.
      1/6 in base 10 is 0.166666.... in base 12 is 0.2.

      Base 12 makes the first 6 fractions easy to write as a decimal, whereas base 10 becomes a real problem. This probably wouldn't be practical because it's a huge learning curve for everyone, but it'd be quite interesting all the same.

      • Re: (Score:3, Insightful)

        by saforrest (184929)

        I've often wondered if metric would be better long term if everyone counted in base 12, instead, and if the relationships between metric units were based on multiples of 12 instead of 10.


        First off, there is an error in your list:

        1/5 is not 0.24 in base 12. 0.24 in base 12 is 2*(1/12)+4*(1/12)^2 = 7/36, which is 0.1944, not 0.20 as it should be. In fact, 1/5 does not have a terminating representation in base 12, for exactly the same reason as 1/3 does not have a terminating representation in base 10. For
  • by carambola5 (456983) on Tuesday January 09, 2007 @04:50PM (#17528374) Homepage
    This is a necessary, but difficult transition. Yes, difficult. Maybe it's pretty easy for the programmers, but for the mechanical guys out there (like myself), this introduces a huge relearning phase. Say, for example, I need some sheet metal to function as a structural piece. I can be pretty confident that my initial guess will be pretty close to the final thickness value if specified in imperial units. I also know what's typically readily available from suppliers (eg: 1/4" is far more common than 15/64"). Not only must I do a conversion from my ingrained inch units into "foreign" metric, but I must also look up which sizes are common.

    With time, I would be just as good with metric as with imperial units. And I want to change to metric for its obvious advantages. It's just that my design confidence and productivity would falter through the transition. I'm quite sure I'm not alone on this.
    • by Zackbass (457384) on Tuesday January 09, 2007 @05:33PM (#17529388)
      To follow up on this one of the other big difficulties with the switch is the need for metric tools. I'm not talking about a set of wrenches but the seriously expensive machine tools and metrology equipment that prototyping shops across the county rely on. I personally have several thousand dollars of just measuring equipment like micrometers, dial indicators, and gage blocks before even looking at the milling machine and lathe which have inch threaded screws. In a well equipped shop this could add up to several hundred thousand dollars of equipment that simply doesn't work in metric. To a shop that is perfectly happy using inch measurements there is no incentive to switch. On top of this, almost all machined parts are done in decimal inches. The whole power of ten advantage means nothing to a machinist because all the work is already done in decimal.

      As more modern NC equipment trickles down to the smaller shops that form of the base of American manufacturing the problem is getting less severe because it's as easy to programming a few lines to switch to metric or pressing a button on digital measuring equipment. I wouldn't hold my breath though.
  • by wile_e_wonka (934864) on Tuesday January 09, 2007 @04:51PM (#17528378)
    I should preface this post with the fact that I'm in the US. When I took physics and chemistry in college we barely discussed English units. There was one class period that we talked a little about conversion from English to metric units (I don't believe we even did the opposite), and that was about it. It was just assumed that we knew metric very well already. If I graduated and went to work for NASA and had to use English measures, I think I would have to almost relearn some of the physics--it would be awkward for me to work with the non-SI units, and even more awkward to have to learn new constants (I learned the constants in metric units). So I assumed that NASA had moved away from English units long ago since it hasn't been taught in so long.
  • by PingSpike (947548) on Tuesday January 09, 2007 @04:55PM (#17528482)
    These NASA rebels must be stopped. The moon was claimed in the name of the United States by Neal Armstrong, we can't allow them to fruit it up by going all metric on its ass the next time they land there. We should nuke all of NASA's bases from orbit. Some one see about coordinating that with our national space agency.
  • by Vidar Leathershod (41663) on Tuesday January 09, 2007 @05:02PM (#17528644)
    Somehow I doubt that the first moon landing teams felt that metric was important. Obviously, they made it (and back). Instead of trying to figure out ways to make things less divisible by three, they should focus on the actual logistics of getting there and back safely.

    Of course, the most of the Slashdot crowd think that the metric system is some sort of gift from God. All I know is the bar where I order pints serves them at a proper temperature and you get a little more than the rated 20 UK fluid ounces. Should they switch to the metric system? Will that improve the beer? Will it make the Thames Welsh Bitter taste better? How about Coniston's, or Fuller's, or Paulaner Salvator?

    All of my tractors parts are standard measurements. Will changing them to metric make the tractor last longer than the 40 years it already has? Of course, this will be unpopular here, but who cares what other space agencies think? Are they as successful as NASA? Have they broken more new ground? Do they care what we think about their use of the metric system, despite it's weaknesses? Don't think so.

    • by Anonymous Coward on Tuesday January 09, 2007 @05:52PM (#17529824)
      Using the metric or imperial system would not matter one bit if all you're measuring is distance or volume. But as soon as you start converting distance into volume (quick question: how many cubic inches in a pint?), or thrust into velocity (quick: you apply a one-pound force to a one-pound object for one second. What's the resulting speed, measured in mph?), or torque into power, or energy into force or power, the beauty of the SI (metric) system really stands out. In the imperial system, the only way to get these calculations right is to insert all sorts of wacky numbers. Which you need to remember with potentially infinite precision.

      Try this beauty: 1 Nm (Newton-meter) equals 1 J (Joule) equals 1 Ws (Watt-second). In the imperial system you'd have to insert all sorts of wacky numbers to go from pount-feet to calories to, strangely enough, Watt-seconds again. (Electricity, even in the US, is always measured in metric.)

      Or more practical: Ever tried to convert the torque that your car engine delivers (measured in pound-feet) at a certain rpm (rounds per minute) to the horsepower (hp) that it delivers? In SI, it's a simple multiplication: Power (measured in W, or more commonly kW) = 2 * pi * torque (measured in Nm) * rotation speed (measured in 1/s). No wacky, imprecise numbers. Just 2 * pi due to the rotation and that's it.

      The SI system and all the calculations you do with them are completely void of wacky numbers, with only a few exceptions:
      - 2 times pi for anything that involves rotation.
      - Natures constants like c (lightspeed), g (gravitational accelleration), e (elementry electric charge) and a few others, about half an A4 page full of them.
      - Natural properties (like density) of materials that you use.

      Since NASA does *a lot* of these calculations (how much force do you need to accelerate/decelerate the lunar lander, what's the effect of gravity?) I can understand why they switch to metric.
    • Re: (Score:3, Informative)

      by drinkypoo (153816)

      If you had ever done anything like engineering work you would realize just how stupid the Imperial/SAE system[s] is (are). When we do engineering work here in the states we use decimal inches anyway. 1/8" is never referred to as 1/8" on a blueprint for some bracket or something; it's always 0.125 inches. This just makes the whole thing confusing and so it makes much more sense just to finally go metric. Besides, frankly, a lot of people (including myself) have a hard time remembering how many cups in a pin

  • Urban Legend (Score:5, Interesting)

    by DerekLyons (302214) <[moc.liamg] [ta] [retawriaf]> on Tuesday January 09, 2007 @05:07PM (#17528756) Homepage
    The loss of the Mars Climate Orbiter [wikipedia.org] was blamed on an error converting between English units and metric units.

    Exhibit #1 for why Wikipedia is not to be trusted - they continue to tell half the story. (On this and many other topics, they prefer the simple and popular explanation over completeness and accuracy. [1])
     
    MCO was lost not because of a metric conversion error - but because an increasing divergence between the planned and actual performance was ignored. The official report mentions this - but glosses over its importance. MCO was lost because NASA attempted to fly the mission on the cheap, because of this testing and analysis during the cruise phase was cut from the budget. Some analysis was done on the side by a few engineers - and their calls for a formal analysis went unheeded until too late.
     
    [1] And before the Wikipedia cheerleaders chime in, yes - I have tried to fix many articles to correct this problem. Without exception the corrections were either reverted out or edited into meaninglessness. On Wikipedia the win goes to the editor with time on his hands or who can cite a lightweight popular article as the source of his 'facts'.
    • Re: (Score:3, Insightful)

      by N. Criss (961443)

      The official report mentions this - but glosses over its importance.

      Sounds to me like you have a problem with the official report, not Wikipedia.

      Wikipedia places a high level of importance on citations. Were you able to come up with credible citations to backup your alternate conclusions? If not, you should start a "NASA MCO Conspiracy" page on MySpace instead editing the Wikipedia topic.

  • by StefanJ (88986) on Tuesday January 09, 2007 @05:11PM (#17528840) Homepage Journal
    Rocket nerds in the audiance will probably be familiar with the "Estes Alpha," a simple beginner's kit.

    There have actually been many versions, with and without plastic nose cone and fins. No die-hard collectors' set is complete without a "metric" Alpha, briefly produced in the 70s for educational purposes.

    Now the instructions have both English and metric measurements . . . where measuring is required at all.

    * * *

    One model rocket measurement has been metric for going on four decades; the average thrust and total impulse figures for motors. Before 1968 or so, you'd save your paper route money for "A.8-4" or "B.8-2" motors, with an average thrust of .8 pounds. After the change to metric, these became A5-4 and B4-2 motors, with average thrust given in newtons.

    Mmmmm, newtons.
  • by banditski (163064) on Tuesday January 09, 2007 @05:14PM (#17528914)
  • about time (Score:4, Insightful)

    by smash (1351) on Tuesday January 09, 2007 @05:20PM (#17529058) Homepage Journal
    All the standard scientific units are metric. It's an international standard. Metric "just works" nicely in conversions/calculations. Fair enough if the US wants to keep it's general populace crippled with the imperial units - but science really is better off with metric.

    Note that you don't see any movements to "bring back the imperial system" elswhere in the world, because metric *works*.

  • President Reagan, in an effort to show he was cutting taxe(which he actually raised) cut the funding to convert everything to metric.
    There was a time when American cars had both Metric and english and some roads had metric and english signs(very few). we would be done with the conversion 10 years ago.

    More reagan legacy.

  • Mixed opinions (Score:4, Interesting)

    by evanbd (210358) on Tuesday January 09, 2007 @06:18PM (#17530378)
    As someone working on an early prototype for one of the engines involved, I'd like to say I have mixed opinions on this.

    Metric is good for all the obvious reasons -- SI units haver fewer weird things going on, conversions are easier, interoperable tools and fittings, etc etc. For all things like discussing distances, velocities, thrust levels, trajectory simulations, and more, I'm completely in favor of metric everywhere.

    The one place I don't like this is when it comes to fittings, fasteners, plumbing, etc. Partly it's that metric nuts, bolts, and fittings are harder to find. You can't buy metric pipe fittings around here. Sure, you can order them, but that takes longer and costs more. The cost isn't a big issue on most things, but turnaround time is -- if you find a problem, it's really nice to be able to order a different part and have it the next day, rather than waiting a few days for something from Europe to clear customs and arrive. On some things, though, it actually makes a big difference. A lot of things like large pressure regulators, specialty valves, and more are even harder to find with metric fittings on them -- specifically, they become custom parts, with associated cost increases and weeks of lead time, which is frequently unacceptable.

    And before anyone says you can buy metric parts in the US -- sure, you can, as long as they're "normal." It's the specialty parts that are hard. For example, McMaster-Carr stocks 3798 different socket cap screws in English sizes, but only 1610 in metric. If you need a weird metric screw, you may very well be out of luck.

    The other major thing is subcontracts -- if I hire a consultant or send a part out to be machined, the machinist needs to have metric tools. Again, most machinists have a basic set of metric tools, but not an entire shop's worth. If the consultant or machinist has to start buying new tooling, your costs and the delivery time start going up.

    I'll say it again -- having to buy parts from out of the country is not just a minor nuisance; it has a direct impact on how quickly you can revise a design and do the next test, which directly translates into how long it takes to complete the project.

    I'm in favor of working toward compatibility, but it's not nearly as obvious an answer as it looks when it comes to tooling, since the installed base of English tooling and suppliers is *so* *huge* while metric is really only supported because of a few foreign-made parts.

  • by 1.000.000 (876272) on Tuesday January 09, 2007 @06:18PM (#17530384)
    You know its time to change to the metric system when you can read definitions on imperial units from wikipedia like this:

    "Because the furlong was "one plough's furrow long" and a furrow was the length a plough team was to be driven without resting, the length of the furlong and the acre vary regionally, nominally due to differing soil types. In England the acre was 4,840 square yards, but in Scotland it was 6,150 square yards and in Ireland 7,840 square yards."

    If we keep the imperial system i guess its important to ask what kind of soil the distance is supposed to be? Is it English soil when traveling to the moon? Is the ox well fed? Is it an experienced plough team leading the expedition? Maybe its raining that day and the soil becomes softer?

    Come to think of it why should we ever abandon the imperial system!?!
  • by Socguy (933973) on Tuesday January 09, 2007 @06:30PM (#17530640)
    I come from Canada and we have yet to fully convert to the metric system; the Mulroney government decided that funding the metric conversion initiative begun by the previous Liberal government was a waste of money and they stopped pushing the issue... but I digress.

    Apparently the attempted conversion was disliked by a number of people. My favorite story was about the some of the old people. Somehow they got it into their heads that gasoline sold by the litre was inferior, quality wise, that if the same gasoline was sold by the (imperial) gallon. Yes, these poor individuals went around the country cautioning the masses against putting this 'litre of gasoline' in their cars!
  • by Asgerix (1035824) on Tuesday January 09, 2007 @07:40PM (#17531776) Homepage
    Q: So how are you going to implement this change to the metric system?
    NASA: We will do it inch by inch.
  • NOT English Units (Score:4, Insightful)

    by Roger W Moore (538166) on Tuesday January 09, 2007 @07:43PM (#17531820) Journal
    I wish Americans would stop calling them "English" units. Not only are they no longer generally used in England (with the odd exception like pints of beer and miles) but the even when they were used they were different from the American system. For example there are 20 fluid ounces in an Imperial pint vs. 16 fluid ounces in a US pint....so it is a very good thing than NASA is no longer using them for international missions since there isn't even an Imperial standard that anyone can agree on!

    "Err...Houston we may have a problem, when you told us to burn 10 pints of fuel was that Imperial pints or US pints?"

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