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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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  • by VEGETA_GT (255721) on Tuesday January 09, 2007 @03:31PM (#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.
  • by geoffspear (692508) on Tuesday January 09, 2007 @03:36PM (#17527958) Homepage
    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.
  • by Stanistani (808333) on Tuesday January 09, 2007 @03:45PM (#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 camperdave (969942) on Tuesday January 09, 2007 @03:58PM (#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".

  • by Vidar Leathershod (41663) on Tuesday January 09, 2007 @04:02PM (#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.

  • Urban Legend (Score:5, Interesting)

    by DerekLyons (302214) <fairwater&gmail,com> on Tuesday January 09, 2007 @04:07PM (#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'.
  • by StefanJ (88986) on Tuesday January 09, 2007 @04:11PM (#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.
  • Re:Yay!!! (Score:5, Interesting)

    by itlurksbeneath (952654) on Tuesday January 09, 2007 @04:26PM (#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?
  • 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.

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

    by Freultwah (739055) on Tuesday January 09, 2007 @04:34PM (#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.

  • by Malc (1751) on Tuesday January 09, 2007 @04:45PM (#17529664)
    The bigger irony is that they're not even proper "english" units! The fl. oz. is slightly bigger, there are fewer fl. oz. in a pint, the ton is lighter, and have you ever heard Americans measuring their weight in stones? Perhaps they were looking for somebody else to blame for the twisted unit system, and chose the name of the country they rejected in 18th century!
  • by alexhmit01 (104757) on Tuesday January 09, 2007 @04:55PM (#17529888)
    The Imperial system has some terribly convenient reasons that it sticks around... The Metric system is theoretically better, and its decimal based approach is useful for mathematics, although in a computer age (base 2), the imperial system is actually more "computer-friendly," as our system of halves and doubles actually makes more computer sense. As you said, it all depends what you are doing.

    For liquids, they all suck. Pints, Cups, Quarts, and Gallons all give you some reasonable amounts, but are useless for converting. However, if you look at recipes, it may call for 3/4 of a cup (not 6 oz), and if you double, it's easy, 1.5 cups.

    For short distances, feet is extremely useful. Most things that you eyeball are between 0 and 10 feet, which gives you 11 values without resulting to a decimal, which confuses people. Metric gives you values 0-3 for the same area. There isn't a huge advantage to miles compared with kilometers, but the conversion is kind of irrelevant. If I'm measuring something for working around the house, I don't need to know the fractions of miles, if I am measuring a long distance, who cares about feet?

    Similarly, temperatures are more useful for most people in imperial. For example, when looking at the weather, a really cold, freezing day is in the -20s, down in Florida, we don't get cold, but we get hot days in the upper 90s (areas of Texas get low triple digits, and heat waves can hit the 120s), this gives us a range of temperatures of 140 degrees. The same Celsius range is -30 C - 50 C, a useful range of 80, so for gauging temperatures, the Imperial system is easier for the weather. In addition, if I want to say something is in the low 80s (80 F - 84 F), I get 27 C - 29 C, so upper 20s does the same thing, but something like upper 80s or lower 90s collides in the metric system in the low 30s.

    The fact is, the "beauty" of metric is the large number of modifiers that let you convert easily, but we don't use it, in Imperial we use inches, feet and miles, in metric you use centimeters, meters, and kilometers. The conversion factor is largely irrelevant for most non-engineering/scientific fields.

    The pros to metric are the ability to easily convert down to smaller units. Converting from centimeters to millimeters is trivial, which is important when doling out medicine if you need precision, but not so important when I'm measuring holes for putting something in the wall. The imperial system is more useful for most people in their day-to-day lives, because it is based upon fractions (intuitive) instead of decimals (precise but not intuitive). If you get below an eighth of an inch for precision, you're probably doing something that requires precision that metric gives you.

    I can eyeball a person and easily describe their height... the range of heights in normal conversations of adults is 5'0" - 6'4", 1.52m - 1.93m. The fact is for describing heights, the discrete inches (17 here) component is more useful than the .4m over a continuous range.

    People that work in precision like metric. People that don't see know reason to switch. The scientific community grabbed metric because it solved a problem that they had. There was no compelling reason for people to switch, which is why it took government coercion to switch people in Europe. In the US, our government hasn't historically had the power to do something similar (coerce grocery stores to change, schools, etc.) so America hasn't switched.

    It seems that most Americans that want to switch base it on a "the Europeans are superior" inferiority complex that many Americans strangely have, or their field switched because it is useful for them, and want everyone to switch for their convenience. Things like construction are stuck because Americans have 8 foot tall ceilings (normal) or 10 or 12 for larger ones, so sheet rock needs to come in 8 ft sheets. The 2x4 is such a useful component coming in 8 ft, 10ft, and 12ft lengths. Switch construction to metric would be useless
  • Mixed opinions (Score:4, Interesting)

    by evanbd (210358) on Tuesday January 09, 2007 @05:18PM (#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 crlove (857212) on Tuesday January 09, 2007 @05:43PM (#17530878) Journal
    I've always maintained that it's a measure (no pun intended) of how much power America still has in the world. One day the world will rise up and say in one voice, "No! Screw you guys! From now on everything we export to your country is in metric. Deal with it."

    That's when we know we're f*cked.
  • by immel (699491) on Tuesday January 09, 2007 @05:52PM (#17531010)
    The conversion from electron volts to Joules is the value of a coulomb, which is another important metric unit in electrical calculations (although "metric" and "electrical" may be redundant; I have yet to encounter english units in circuits). The point is, if you know what a coulomb is (and you should, if you are doing this sort of calculation), you know how to convert between electron volts and Joules.

    Now the english unit for energy, on the other hand, is the Btu. Converting it to the next "logical" english unit is a factor of about 778 Btu in a ft*lbf. Anyone who has taken thermodynamics knows the Btu as an enemy because using it with things like pressure (usually lbf/in^2) and mass flow rate (remember, there are many types of pounds in English, some for mass and some for force) requires inches, feet, and two types of pounds. Now let's try to convert from Btus to electron volts for even more fun! Because english has failed to come up with any useful electric units (even in the US), this calculation gets extra-nasty.

    I suppose my point is as follows: Does the metric system always mesh nicely with physics? No. That's just the way the universe works. FSM made it that way. But some English units just seem to fit together with no rhyme or reason whatsoever! It's as if they made it up as they went along.
  • by willy_me (212994) on Tuesday January 09, 2007 @05:54PM (#17531046)
    this gives us a range of temperatures of 140 degrees. The same Celsius range is -30 C - 50 C, a useful range of 80, so for gauging temperatures, the Imperial system is easier for the weather.
    Now this is just terrible. Higher resolution != easier to use. Can you really tell the difference between 80 and 81 degrees fahrenheit? I would argue that celsius is a better standard because it has a lower resolution and is centered on freezing. Cold - 0, cool - 10, warm - 20, hot - 30. Doesn't this make sense? Of course you will adjust the values depending on the time of year and where you are located. But your argument that a larger temperature range is better is just fundamentally flawed. I can only reliably detect a ~ 3 degree celsius temperature difference so there is absolutely no additional value gained from using a scale with a range greater then that offered by degrees celsius.
  • by jesterzog (189797) on Tuesday January 09, 2007 @05:56PM (#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.

  • by logpoacher (662865) on Tuesday January 09, 2007 @06:05PM (#17531240)
    I don't think that the linking you describe is really much of a guide to the relative value of a weights and measures system. I think we can make some reasonable demands of a system and judge it according to them. The key values for me might be:
    1. broad acceptance, with the existence of strong standards backed by standards bodies;
    2. usable and convenient unit divisions (eg inches, mm, km, ...) across a wide spread of applications;
    3. simple arithmetic when scaling across those divisions;
    4. inter-unit correlations (eg one litre of water == 1kg == 1000cc); and
    5. meaning (a minor criterion, but I prefer units to be based on something non-arbitrary).
    Scoring out of 10: Imperial gets a point for (1), but only because it hitches on the back of metric. It gets 2 points for (2), because all the divisions are pretty practical across a narrow range. Then it gets 0 for (3), as anyone who tries to multiply 2'10" by 5 will tell you. It gets 0 for (4), because, like, how much does a cubic foot of water weight? And anyway, most of the units are missing - I mean, what's the imperial unit of voltage? luminosity? And then it gets one point for (5), because most of the measures have a slightly real basis in history, and I'm sentimental. And then there's a general 1 point deduction, because having US gallons that are different from Imperial gallons is just madness. And nautical miles. And so on. 2/10. What a crock.

    Now, I'd give metric a 9/10. It drops a point for being a bit arbitrary in places (criterion 5), (although water does feature fairly prominently and consistently). This is the basis of your comment above, I think, about the arbitrariness? Perhaps we should be harsher, and drop another point for it being French - a serious political barrier to acceptance!

    Anyway, this all suggests to me that metric really is superior - it's not just a matter of life-style. I take your point about getting good at handling units and understanding their limitations, but I think weights and measures is too important for us to have such a dog of a system as imperial cluttering up our lives. As you say, the people who need the exercise will get it anyway as soon as they start playing in the extremities.

    Perhaps we should rate God's Units [wikipedia.org] against my criteria above. Actually, they do better than I thought they would: they have the strongest standards body in the universe, the inter-unit correlations are out of this world, and you couldn't get more meaning in your units if you tried! 6/10 ...

  • Re:Good start (Score:2, Interesting)

    by ebichete (223210) on Tuesday January 09, 2007 @07:47PM (#17532754)
    That's not what it's about. Converting between inches, feet and furlongs is not a problem. Converting between inches, gallons and pounds is the issue.

    A water tank is 2 metres long, 2 metres wide and 1.5 metres deep. It's volumes is 6 m^3 (cubic metres) which is 6,000,000 cm^3 or 6,000 litres. This amount of water would weigh 6,000 kg.

    Doing that in imperial units is messier. Now imagine if you were trying to figure out how much energy your tank of rocket fuel contains.
  • by Warg! The Orcs!! (957405) on Tuesday January 09, 2007 @08:45PM (#17533390)
    I am studying at a reknowned European university who, bizarrely, have the default paper size on their printers set to "US Letter". This means that we can't just print stuff. Every time (Yes, EVERY time) you want to print something you have to go into the print menu and page setup options and change it to A4.

    EVERYGODAMNEDFREAKINTIME!!!!!!!
    Not that I'm bitter about it.
  • Re:Yay!!! (Score:2, Interesting)

    by Vhata (530820) on Wednesday January 10, 2007 @01:21PM (#17543064) Homepage
    Actually, the French worked out a fairly clever and consistent way to deal with a metric calendar ages ago. http://en.wikipedia.org/wiki/French_Republican_Cal endar [wikipedia.org] Mind you, I suppose that since it's French, the Americans would stay as far away from it as they can.

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