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Space Technology

NASA Sticking To Imperial Units For Shuttle Replacement 901

JerryQ sends in a story at New Scientist about the criticism NASA is taking for deciding to use Imperial units in the development of the Constellation program, their project to replace the space shuttle. "The sticking point is that Ares is a shuttle-derived design — it uses solid rocket boosters whose dimensions and technology are based on those currently strapped to either side of the shuttle's giant liquid fuel tank. And the shuttle's 30-year-old specifications, design drawings and software are rooted in pounds and feet rather than newtons and meters. ... NASA recently calculated that converting the relevant drawings, software and documentation to the 'International System' of units (SI) would cost a total of $370 million — almost half the cost of a 2009 shuttle launch, which costs a total of $759 million. 'We found the cost of converting to SI would exceed what we can afford,' says [NASA spokesman Grey Hautaluoma]."
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NASA Sticking To Imperial Units For Shuttle Replacement

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  • I want that! (Score:2, Informative)

    by Akir ( 878284 ) on Wednesday June 24, 2009 @11:06AM (#28452677)
    It must be some astronomic and powerful calculator they need for those conversions. I'm assuming that it's so expensive because it can calculate the highest prime number and last digit of pi in under a second.

    But that still doesn't account for the costs they're making up.
  • by mrvan ( 973822 ) on Wednesday June 24, 2009 @11:09AM (#28452733)

    I don't buy it

    I lived in guilders all my life, and the first couple years in Eurotime I could only "imagine" a price by converting back to guilders and thinking whether the price sounded right. Now, I can only "imagine" a guilders price by converting it to euros

    I've lived in the UK and US for 1.5 and .5 years, respectively, and I started thinking natively in most units pretty quickly, esp. inches and miles, and of course pints in the UK. Some units are more difficult, either because they have an offset as well as a scale difference (fahrenheit) or because they just don't make any sense (a 22 fluid ounces drink?? gimme a pint, damnit!)

    I think the UK is busy converting mostly to metric system, so maybe some UKians can chime in with their experience?

  • Re:really? (Score:5, Informative)

    by Useful Wheat ( 1488675 ) on Wednesday June 24, 2009 @11:12AM (#28452771)

    I work for an engineering company, and unit conversions are not a trivial operation. All of our drawings are created in autocad, and after several years it becomes difficult if not impossible to find the original file. As such, converting achieved documents requires recreating the document entirely from scratch. We also use a fairly vigorous quality control system that requires 3 engineers to check every document change, verify the calculation, and repeat the calculation using a different method to ensure that no mistakes were made.

    We recently acquired an older project where we needed to simply change the title block on each page, and this process took roughly 5000 hours. For something on the scale of the space shuttle, 370 million isn't unheard of.

  • by Darkness404 ( 1287218 ) on Wednesday June 24, 2009 @11:17AM (#28452847)
    Hahahahah, you really think so? It would never stick in the US, other than for soda, no one uses metric. Even if the kids started learning metric-only they would still have to know imperial units because thats what everyone else uses (as in, people who are out of school). Plus, the USA is large, scientists can usually convert, so whats the big deal if we use a different measurement system? We aren't a tiny country.
  • by jonbryce ( 703250 ) on Wednesday June 24, 2009 @11:17AM (#28452857) Homepage

    We have some people called the Metric Martyrs who think metric units are some unnecessary EU interference in our affairs.

    It gets confusing at times when for example the distance you drive in a car is measured in miles, fuel for it is sold in litres, and fuel efficiency is either miles per gallon or litres per 100km. We really need a miles per litre measure, but I guess that isn't going to happen.

    The same law that prevents the Metric Martyrs from selling their vegetables in pounds and ounces also prevents pubs from selling beer in litres. They are required to sell it in pints. This causes a problem for German and Australian themed bars who want to sell in the traditional metric measures found in those countries.

  • by IdleTime ( 561841 ) on Wednesday June 24, 2009 @11:20AM (#28452899) Journal
    The old British Prime Minister Sir Winston Churchill once said: "You can depend on the Americans to do the right thing once all other options have been exhausted!"
    No offense, Sir Winston, but after over a decade of living and working in the US, I have to change it to: "You can NOT depend on the Americans to do the right thing once all other options have been exhausted!"
    Get on with the program and get rid of the antiquated foot, inches lbs and what not and move into the 21st century!
  • by ivan256 ( 17499 ) on Wednesday June 24, 2009 @11:23AM (#28452923)

    Fahrenheit is one of the few units I prefer over the metric counterpart. At least when talking about weather or indoor climate.

    When expressed as an integer (temperature frequently is when talking about weather), Fahrenheit is a more precise unit.

  • by FTWinston ( 1332785 ) on Wednesday June 24, 2009 @11:27AM (#28453013) Homepage

    I think the UK is busy converting mostly to metric system, so maybe some UKians can chime in with their experience?

    Unfortunately, not really. All street signs still measure distance in miles, and eighths of miles, and the like, and half the population think that the metric system is (like the euro) just another damn frenchie scheme to undermine our sovereignty. We have a long history (this [], for instance) of coming up with crazy conspiricies to demonstrate why the imperial system is our God-given right, and why the French would like nothing better than to force their evil organised system of measurement upon us.

    Meanwhile, for at least a couple of decades now, kids grow up being taught nothing but metric, and wonder why the grown ups still insist on using imperial, and what on earth a fluid ounce actually is. Cos everyone seems to use it, but I don't think anyone under 25 has actually been taught it.

  • by Audiophyle ( 593650 ) on Wednesday June 24, 2009 @11:29AM (#28453045)
    Most systems engineers in the space industry know that it's difficult to completely use metric for space missions. There are usually many components and subsystems that are designed by different vendors that have their own paradigms set up. These paradigms are usually kept do a legacy of proven use, and engineers will agree with me that if a product works well on-orbit, why on earth would you want to change a product simply due to unit conversions. You simply take note of the units and move on. I never thought I'd have to deal with microinches, to be honest, but it's no big deal since everyone knows 1 uin = 0.0254 microns.
  • Re:Horses Asses (Score:1, Informative)

    by Anonymous Coward on Wednesday June 24, 2009 @11:31AM (#28453071)
  • Re:Horses Asses (Score:5, Informative)

    by H0p313ss ( 811249 ) on Wednesday June 24, 2009 @11:32AM (#28453087) []

    Claim: The United States standard railroad gauge derives from the original specification for an Imperial Roman war chariot.

    Status: False

  • by Anonymous Coward on Wednesday June 24, 2009 @11:36AM (#28453149)

    Here in Canada most regulators require measurements to be done in metric. Many people here still use imperial for common things, such as personal measurements (height, weight, waist size etc), but for any public projects people tend to use SI. Its an awkward mix of the two systems, but for the most part people recognize that metric is easier and more accurate. Temperature is probably the hardest one to convert. I think if the US converted to metric it would eventually phase out all imperial measurements within a generation or two. I'm rather shocked the scientists and engineers at NASA have been using imperial this whole time.
    I think NASA should be considered for restructuring, as their budgets are incredibly bloated for what they're trying to accomplish. I'm all for government funding going to successful space agencies and letting the under-performers die out.

  • by kazade84 ( 1078337 ) on Wednesday June 24, 2009 @11:39AM (#28453201)

    I'm from the UK, and my mental image of measurements is fucked.

    I know how much a pint is. I know how much 1kg is, but I don't know how much is 1 pound in weight. I know how tall I am in feet and inches, but not in meters.

    All because we use metric for some reasons, and we are still stuck in imperial for others. My milk comes in bottles that are labelled 568ml although *everyone* refers to it as a pint, obviously our alcoholic drinks come in pints and half pints. Our speed limits are measured in miles per hour, yet we used to run the 100 meters at school. My height has always been given to me in feet and inches (while growing up by my parents) and if you speak to pretty much anyone they will also give their height in feet and inches, yet if I go to the doctor, they want me to know how high in meters. If you go under a low bridge, the height is given in feet.

    When I go swimming the pool is in meters, when referring to medium distances anyone aged over 40 refers to yards, everyone below that refers to meters, at larger distances it's rare for anyone to use kilometers. Anyone over 40ish only understands Fahrenheit, everyone below uses degrees centigrade.

    Generally speaking things are moving to metric (thankfully) but it will take many many years for imperial to die here currently we are in one big measurement mess and we will be for some time, especially as every traffic sign is in imperial.

  • Conversion is Exact (Score:5, Informative)

    by dunc78 ( 583090 ) on Wednesday June 24, 2009 @11:39AM (#28453209)
    Not sure if you are joking or not, but 1 foot is exactly .3048 meters, because 1inch is exactly 2.54 centimeters.
  • Re:really? (Score:3, Informative)

    by afidel ( 530433 ) on Wednesday June 24, 2009 @11:44AM (#28453275)
    There's a VERY good reason to re-use the SRB's, they are a well tested design with the flaws worked out and the real operating parameters known. There is an existing assembly and refueling pipeline (figurative) with skilled workers who know exactly how to produce the parts. They are also reusing the main fuel tank (stretched in some configurations I believe) and the SME's which are a feat of engineering (especially now that we have the Russian designed turbopumps). Redesigning all of those components from scratch would cost probably hundreds of billions and probably another billion or two in lost test vehicles.
  • Re:really? (Score:5, Informative)

    by Useful Wheat ( 1488675 ) on Wednesday June 24, 2009 @11:59AM (#28453561)

    You don't seem to understand, even a little. These numbers are on a piece of paper that no longer exists on a computer. Not even the most advanced computer script in the world can adjust paper. So okay, I understand part of your point, put it into the computer first, and then run the script. These documents are crawling with numbers. Line numbers, electrical classifications, instrument identifiers. Even if I had a script to manage the process, you then have the problem of units. I'm not doing 5000 ft to meter conversions. We have lengths (using both ft, in, ',and "), weights, volumes, temperatures, powers (hp, MMBtu/hr, kW, MW) and so forth. Even if you could have a script smart enough to check for units, how would it tell the difference between a temperature and a temperature change? If I have a heat exchanger with a temperature change of 50ÂF, the correct metric temperature change is 27.8ÂC. If you got 10ÂC, you used the wrong method. The sheer amount of back checking I would have to do to make sure a rogue script didn't destroy my drawings would be insane.

    This is not a simple database you're playing with.

  • by maxume ( 22995 ) on Wednesday June 24, 2009 @12:10PM (#28453749)

    If I walked into a bar in Europe and they were unable to serve me a pint, with no further explanation on my part, I would leave.

  • by stonefry ( 968479 ) on Wednesday June 24, 2009 @12:19PM (#28453899)
    1 foot = 0.30480 meters

    Is that better?

  • Re:really? (Score:3, Informative)

    by Tyr.1358 ( 1441099 ) on Wednesday June 24, 2009 @12:32PM (#28454121)

    I know exactly what you are talking about. We had 2000 logic diagrams to change once, and we used a script to do it in AutoCAD. Took the farm 3 hours to do, but it took us 4 weeks to check over. It's even worse when the drawings didn't come from your department, or (god help us) an outside source. We got drawings from a sister company once that were not to scale, and the title blocks were scaled by hand to 'look' right. Half of them don't even use the same blocks either, so when you write the script it only works on half of them and you are left saying 'WTF?'. Then you add in a layer filter, for example, to help the script find the right block. Guess what? Some trade school graduate from drinkachusetts screwed up the layers on every individual drawing. So you add a filter for linetype. Turns out the linetypes are all different to, and in order to make each drawing look consistent they changed the linetype scale so the .5 linetypes look ok. ARGHH we should have just redrawn them.

    Speaking of databases, have you ever designed in AutoCAD using Bently AutoPlant? It links the drawings to a database. We use it where I work to design for power plants. It sucks, but we have tried many other solutions over the years and it works the best. Trying to link Pro-E or Microstation or Solidworks to a database we can use to generate Process Flow Diagrams, Piping and Instrumentation Diagrams, and Logic Diagrams is nigh impossible. Sure they are perfect for modeling, but taking the model data and converting it to schematic line drawings is a technological boundary for sure. Oh well.

  • by spaceyhackerlady ( 462530 ) on Wednesday June 24, 2009 @12:38PM (#28454237)

    Countries have changed, with varying success. You can do it if you want to.

    Canada sort of changed, but has slipped back a bit. However, our road signs are in kilometers, our weather forecasts are in degrees Celsius, we sell liquids by the litre, and few people under the age of 50 have any issue with this. I was in elementary school when we changed our weather forecasts (I'm 47), and I find U.S. weather forecasts and road signs and such meaningless unless I translate them to proper units.

    While the price per kilo is the legal one, supermarkets here still routinely advertise prices per pound. I order stuff by the kilo, on general principles. You cannot buy metric lumber in Canada, though we make it for export. Nor can you buy metric-size paper. I have a package of A4 paper (bought last time I was in England) that I use for testing printer drivers and things. When people ask me how tall I am I tell them 185 cm (I'm tall, which is why people ask...) and unless they're European or Australian they stare at me like I'm an alien.

    Australia and New Zealand changed in the 1960s and seem to have been a bit more committed to it.

    We've made bigger changes in the past. British Columbia drove on the left, the correct and proper side, until 1922. Then we changed to driving on the wrong side of the road. Most people don't know this.


  • Re:Oh the Humanity! (Score:5, Informative)

    by EEDAm ( 808004 ) on Wednesday June 24, 2009 @12:44PM (#28454363)
    Lets be clear there are an absolute hat-full of major countries that don't *use* the SI day to day whatever they may have 'adopted'. Forty four years on from UK adoption, my car has a speedometer which is in mph as are the road signs. There are public outrages on central european efforts to prosecute small shop owners for being unwilling to sell fruit and veg in grams yet I have never heard anyone ask for '200 grammes of carrots'. People talk about their weight in stones and pounds and the only time you hear kilos is in international sports. Aircraft power is rate in lbs per square inch....
  • by fm6 ( 162816 ) on Wednesday June 24, 2009 @12:56PM (#28454561) Homepage Journal

    Somehow the idea that U.S. units are called "Imperial" units has taken root. That term only applies to a system used in the British Empire/Commonwealth (hence the name) before they went metric. The U.S system is "English units" (because it's based on units that were widely used in England at the time of American independence) or "U.S. Customary Units." The two systems are very close (length and weight are the same) but not identical (volume units are quite different, even thought the names are the same).

    In most other contexts, I'd just say, "OK, sloppy usage eventually becomes the standard, like 'broadband' instead of 'high-bitrate'. Been happening since language was invented, not going to change."

    But in this case you have terms that are defined in standards. And miscommunication can cause much wackiness. For example, suppose I need 10 gallons of something. The nearest store is just across the border in Canada, and they're metric, so I use Google to convert units [] and come up with 45.5 liters. Nice and simple, right?

    Wrong. I only needed a little less than 38 liters []. The U.S. gallon is 20% smaller!

    OK, this particular example is kind of artificial, because most people would just say "gallon" and Google assumes that "gallon" means "U.S. gallon". Still, you need to be careful with this stuff. Like, suppose you're putting fuel in an airplane []!

    Of course, all this extra confusion is yet another reason for the U.S. to go metric. I work for for a computer manufacturer that not only sells widely in metric countries, our actual production is outsourced to companies that are mostly in metric countries. Does this cause headaches? You bet!

  • Re:Oh the Humanity! (Score:3, Informative)

    by element-o.p. ( 939033 ) on Wednesday June 24, 2009 @01:00PM (#28454623) Homepage
    Displacement in a lot of American cars -- even in the States, mind you -- are measured in liters as well. My first car, a Ford, had a whopping 1.6L engine (and went from 0-60 in 5.4 months, lol). My wife's F150 has a 5.4L V8, and her previous car, a Jeep Grand Cherokee had a 4L V6 (?).

    All of the other cars I've ever owned had engine capacities measured in liters too, but they were Japanese cars (even though two had the ostensibly American "Eagle" brand name...but in reality, they were Mitsubishis imported by Chrysler).
  • Re:Horses Asses (Score:2, Informative)

    by tuzo ( 928271 ) on Wednesday June 24, 2009 @01:07PM (#28454739)
    Another take on this: []

    "Funny? Sure. True? Yes and no."

    So it looks like everyone is right on this one. :)

  • by level_headed_midwest ( 888889 ) on Wednesday June 24, 2009 @01:11PM (#28454797)

    Engineers in the U.S. are trained in both, but the emphasis is generally on metric. Which system you actually use is dependent on where you work, as some shops are metric, some use the standard system. In my experience, metric is becoming more common as it was uncommon to find metric fasteners on equipment 20 years ago; now it's uncommon to find standard ones.

    Medicine in the U.S. is almost completely metric internally. Even though your doc may tell you your kid is 44 pounds, they write "20 kg" in the charts or EMR. It's just so much easier to do conversions for mg/kg and calculate BMI (kg/m^2) in metric rather than standard units.

  • by Buelldozer ( 713671 ) on Wednesday June 24, 2009 @01:16PM (#28454889)

    To paraphrase from a post above you:

    "How many 4.19cm pieces of wood can you cut from a length of wood that is 6m long?"

    I'll bet you can't do THAT in your head either and it's just as valid of a math example as your own that involves miles to inches.

    In the real world both systems can be a real PITA but it's not the fault of the system. It's the fault of the real world where numbers aren't some exact multiple of your base system.

  • by CherniyVolk ( 513591 ) on Wednesday June 24, 2009 @01:27PM (#28455083)

    France first adopted the Metric System in 1791 (according to Wikipedia). Let me repeat that... 1791.

    The first public, commercial, industrial use of the Metric System in America was Coca-Cola; Coca-Cola bottles have always displayed their volume in metrics, and they have been around since 1886. Let me repeat that... 1886.

    First shuttle flight was in 1977.

    Now here's the surprise on my part. For as long as I have been alive, all science and math text always focused on the metric system. Aside from off-tasks in grade school of converting Celsius to Farhenheit(sp?) or inches to centimeter... gallons to liters... everything has always been in metrics. Growing up, the total icon of science and math has been primarily NASA. It is very hard to for me to conceive, that given the adoption of the metric system in acadamia and almost exclusive to intellectuals and professionals... that NASA has for so long, and so widespread throughout any of their projects, adopted anything other than the metric system. Had this article not been published, I would have refuted any claim that NASA didn't use the metric system. All I can say in 2009 is "wow".

  • Re:Oh the Humanity! (Score:3, Informative)

    by BlackSnake112 ( 912158 ) on Wednesday June 24, 2009 @01:44PM (#28455411)

    There are very, very few exceptions. Speeds are measured in miles per hour, but engine capacity is in litres. Beer still comes in pints but a standard spirit measure is 25ml. And anybody actually building something (whether it's hi-tech or a house) will be using metric.

    Last I checked the houses being build around here: have all 16 inches (or 12 inches if you paid more or 24 inches if paid less) of space from center of the wall stud to next one, the house is so many feet by this many feet, the water heaters are 40, 50, 80 gallons. These were home build in the last 18 months.

    Maybe in Europe metric is king. Not yet over here.

    At least the schools are using metric for the science measurements. The university research programs are using metric. It is a start, all be it a slow one.

  • by vux984 ( 928602 ) on Wednesday June 24, 2009 @01:58PM (#28455715)

    humans find it much easier to divide into halves than into tenths [...] Give me a gallon of liquid and a set of unmarked jugs and I'll probably have pretty darn close to 1 fl. oz. long before you can cut 1 L down to 1 mL.

    a) Wow. Ok. Is that a problem you encounter frequently? This seems a bit artificial. :)

    b) Yeah, I'll grant you that dividing something physically in half is easier. But while YOU might be able to pull a fluid ounce from a gallon using unmarked jugs, lets be honest most people would still really struggle with that.

    c) Next, people like you and I who could solve this problem are also smart enough to realize that they don't have to physically divide into 10ths, but halves and fifths. So to cut 1L down to 1mL they need to divide by 1000... or 2x2x2x5x5x5. Fifths is harder than halves but not THAT hard.

    d) Further its bit of an unfair problem. The SI problem is a 1000th cut, your imperial problem is considerably less. Its only a 128th cut. A closer problem (both in difficulty, and in the actual amounts of liquid involved would be: 4L to 50mL, which 2x2x2x2x5.

    e) Further you are cherry picking imperial units. Tablespoon to Teaspoon is 3rds. Feet to inches is 12ths (2x2x3). Yards to feet is 3rds. And from yards to feet is 1760ths... and 1760 factors to 2x2x2x2x2x5x11. Yeah there's an 11 in that one. How many people do you know who are facile at 11ths? I suppose we could dig through rods and chains etc but I'd have to look up what those actually are...

    f) decimal is easier for any serious work, where you have paper and calculators and computers instead of sets of unmarked jugs and cherry picked problems.

  • by ivan256 ( 17499 ) on Wednesday June 24, 2009 @02:18PM (#28456051)

    It's easy to pull up a keyboard and get on your high horse.

    It's even easier when you're wrong.

    SI units were established as an international standard in 1960. That's 139 years after Napoleon died, in case you don't feel like doing the math. Before that, they were just yet another system of units like all the other random systems.

    The "fucking excuse" for building the shuttle using any other system is that they sourced parts from thousands of small machine shops throughout the country. Those shops were not tooled with metric equipment.

    The Space Shuttle was a new machine, but it was built by old machines. (Plus, it wasn't really a completely new machine. It contained plenty of stock parts from previous aerospace projects)

  • by rssrss ( 686344 ) on Wednesday June 24, 2009 @02:20PM (#28456073)

    The Imperial System of measurements is not the same as the customary measurements used in the United States. The legal arbiter of measurements in the United States is the National Institute of Standards and Technology. Apendixes B [PDF] [] and C [PDF] [] to their Handbook 44 provide a good overview of the structure of the respective standards and their relationship to SI (the science based International System, which was based on the Metric System).

    The word system seems misleading when applied to US customary measures. For example:

    Appendix B. Section 2.2.5. From 1893 until 1959, the yard was defined as equal exactly to 3600/3937 meter. In 1959, a small change was made in the definition of the yard to resolve discrepancies both in this country and abroad. Since 1959, we define the yard as equal exactly to 0.9144 meter; the new yard is shorter than the old yard by exactly two parts in a million. At the same time, it was decided that any data expressed in feet derived from geodetic surveys within the United States would continue to bear the relationship as defined in 1893 (one foot equals 1200/3937 meter). We call this foot the U. S. Survey Foot, while the foot defined in 1959 is called the International Foot. Measurements expressed in U. S. statute miles, survey feet, rods, chains, links, or the squares thereof, and acres should be converted to the corresponding metric values by using pre-1959 conversion factors if more than five significant figure accuracy is required.

    Does this make a difference? From one viewpoint, no, when do you ever need to keep something accurate within 2 mm over a mile? From another, yes, repeated iterations of computations based on incorrect conversions can produce just plain gibberish. Another bit of measurement chaos to keep in mind:

    Appendix B. Section 2.3. British and United States Systems of Measurement. ... In the customary British system, the units of dry measure are the same as those of liquid measure. In the United States these two are not the same; the gallon and its subdivisions are used in the measurement of liquids and the bushel, with its subdivisions, is used in the measurement of certain dry commodities. The U. S. gallon is divided into four liquid quarts and the U. S. bushel into 32 dry quarts. All the units of capacity or volume mentioned thus far are larger in the customary British system than in the U. S. system. But the British fluid ounce is smaller than the U. S. fluid ounce, because the British quart is divided into 40 fluid ounces whereas the U. S. quart is divided into 32 fluid ounces. ...
    1 U. S. fluid ounce = 1.041 British fluid ounces
    1 British fluid ounce = 0.961 U. S. fluid ounce
    1 U. S. gallon = 0.833 British Imperial gallon
    1 British Imperial gallon = 1.201 U. S. gallons

    We also must remember that NASA has proven itself incapable of managing the different systems of measurement before. Ten years ago NASA crashed a Mars bound probe [] because of botched conversions from customary to SI units. You would think that having paid $125 million for that lesson, they would want to avoid a recurrence. But, I suppose that they are from the government and they do not have to care.

  • by weiserfireman ( 917228 ) on Wednesday June 24, 2009 @03:34PM (#28457193) Homepage

    I live in Rural Idaho, Cow tipping is a lot like snipe hunting.

    We would take gullible kids out to a farm in the middle of the night. They would try to sneak up on a cow and tip it. It would either move or not tip, and then move. We would convince them that their shoes were making too much noise.

    After they gave up their shoes, we would hop in the car and leave them in the middle of a pasture, barefoot, in the middle of the night, miles from home.

    That is what cow tipping is really about.

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