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NASA Sticking To Imperial Units For Shuttle Replacement
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]."
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?
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.
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.
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.
Claim: The United States standard railroad gauge derives from the original specification for an Imperial Roman war chariot.
Status: False
XML is a known as a key material required to create SMD: Software of Mass Destruction
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.
Not sure if you are joking or not, but 1 foot is exactly .3048 meters, because 1inch is exactly 2.54 centimeters.
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.
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.
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....
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.
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:
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:
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.
In the land of the blind, the one-eyed man is king.