Metric system

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honeyjones

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I am new here and haven't read everything yet but what is up on the ISS? They are still torquing bolts with ft lbs/sq" ? The walkers are still requesting movement in inches and feet? I even heard Peggy say something about a 5/8" nut? Tell me there are no SAE connectors in space please.

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MeteorWayne

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Sorry can't tell you that, it's true.<br /><br />However, note when them move themselves around so they don't bump into things they use centimeters <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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vulture2

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The ISS carries duplicate sets of metric and "traditional" tools as well. Early in the program there was an attempt (a "change request") to metricate the entire ISS, but it was rejected as infeasible. But virtually all the non-US equipment is metric. <br /><br />Quick, try to divide a board 4 feet 7 and 13/16 inches long into three equal parts. <br /><br />

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josh_simonson

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It doesn't really matter as long as folks keep things straight. I design ICs in microns that get put on a die measured in mils, that goes in a package measured in mm, that gets soldered on a board which has a copper thickness in ounces... Everything works fine together. <img src="/images/icons/wink.gif" />

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Huntster

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(4 feet (7 13/16) inches) divided by three = 47.2545833 centimeters<br /><br />Eh, I cheated and used Google.<br /><br />Josh, that hurts my head. <div class="Discussion_UserSignature"> </div>

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venator_3000

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Well, as I so often remind my friends, when Armstrong and Aldrin landed on the Moon they used good old-fashioned British Imperial units...<br /><br />v3k <div class="Discussion_UserSignature"> </div>

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halman

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Venator_3000,<br /><br />I guess that the United States manned space exploration program is not real 'science', because it does not use the metric system. Every scientific discipline that I am aware of has been using the metric system for years. But getting American contractors to build things using a metric scale is like pulling hen's teeth. If anything, they will give the metric equivalents for SAE components. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

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usn_skwerl

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All specs in aviation, aside from Airbus use standard measurements, not metric. "Space<b>flight</b>" should also be included in the same standardisation. <div class="Discussion_UserSignature"> </div>

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eniac

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<blockquote><font class="small">In reply to:</font><hr /><p>All specs in aviation, aside from Airbus use standard measurements, not metric. "Spaceflight" should also be included in the same standardisation.<p><hr /></p></p></blockquote>Sorry, but metric IS standard. Metric is used everywhere except Liberia, Burma, and the United States. Space flight should use the standard, too, not "U.S. customary" units. At least one spacecraft was lost to unit conversion errors, a Mars probe if I recall correctly. Anyone remember which?<br /> <div class="Discussion_UserSignature"> </div>

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no_way

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what im more interested in, will lunar surface see right-hand driving or left-hand ? its kinda hard to convert once you have made the choice, and gets harder every day. <br />Considering that majority of China is right-hand drive, i would bet on lunar traffic to be right-hand as well...

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venator_3000

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Well, I teach my engineering students to use SI. And their reports are required in this system. However, when we send stuff out to our machine shop all the drawings etc, are in English. Sort of like the situation you describe about contractors in microcosm.<br /><br />I view it as more of a cultural/social issue than a technical one. Indeed, I've always viewed it as a form of versatility to be able to switch between the two. However, I do warn the students about potential problems by not understanding the inherent differences between the two systems. And one example I use is the loss of Mars Climate Orbiter. I also give them what i call the Eagle Anecdote, which I believe is ascribed to Arthur C. Clarke.<br /><br />-v3k <div class="Discussion_UserSignature"> </div>

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Guest
"Early in the program there was an attempt (a "change request") to metricate the entire ISS, but it was rejected as infeasible."<br /><br />No, we are officially supposed to be metric and did update a lot of stuff. Note that we are also officially English only (you hear the Russians use that every day right?) and paperless (ever see MCC with all the mission books out?).<br /><br />Constelllation just released that they will be officially metric.<br /><br />Just yesterday the ISS crew called down and said we have the metric torque wrench and the procedure says the value in ft-lbs. Could someone do the conversion for them? The flight director responded "I can't believe we are having this conversation in the 21st century.<br />yeah, right.

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MeteorWayne

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It is a culturally induced artifact of the 19th century <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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josh_simonson

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There can be conversion problems just in the metric system as well if people don't keep track of things. MCL could have been lost if a floating point in m/s were interpreted as km/s or cm/s. Also in space everything is relative, is the m/s relative to mars, earth, sun? Numbers need context no matter what system you're using, and as long as they're tracked adequately you can land on mars even if it's done in furlongs per fruitfly generation. <br /><br />Most countries use 'mach' to describe hypersonic speeds, and it's certainly not metric. <img src="/images/icons/wink.gif" /><br />

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no_way

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<blockquote><font class="small">In reply to:</font><hr /><p>Most countries use 'mach' to describe hypersonic speeds<p><hr /></p></p></blockquote><br />Quite confusing term, TBH, as its medium dependant. Mach 5 in air at sea level, standing air, atmospheric pressure is a different number in m/s relative to ground than Mach 5 in water at sea level or Mach 5 in air at 100km altitude.

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Testing

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Try working on some older equipment from Great Britain. Say a Rolls Royce Dart, old Triumph, BSA or Norton. They had British Standard, British Associate and Whitworth. I still have a set of BS combo spanners somewhere. <div class="Discussion_UserSignature"> </div>

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no_way

Guest
oh, with motorcycles, i was reminded of another annoying habit : wiring positive electric lead as ground. in civilized world, we use negative as ground.

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CalliArcale

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<blockquote><font class="small">In reply to:</font><hr /><p>All specs in aviation, aside from Airbus use standard measurements, not metric. <p><hr /></p></p></blockquote><br /><br />Actually, Boeing went metric with its airliners starting with the 767. And therein lies a tale: The Gimli Glider. (Actually, the metric/imperial unit confusion was only part of the problem that day. A number of errors combined to create what very nearly was a horrific accident -- but which everyone survived. Even the plane survived, and remains in service today.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

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thereiwas

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"...aside from Airbus use standard measurements, not metric."<br /><br />"Standard" only in the US. Actually the Airbus has a panel switch that selects English or Metric units for the displays. There is another switch for the altimeter that selects "inches of mercury" or "hecto-Pascals". European ATC will give you altimeter settings in the latter, while telling you an altitude clearance in feet, and distances in nautical miles.

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propforce

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Well... I think the good 'ol "English" unit works just fine. But I am old and set in my ways. <br /><br />You developed a "feel" of magnitude when you work with a convention of units. Most of us here in the U.S. knows how fast is 80mph is (some of us do drive that fast <img src="/images/icons/wink.gif" />), but heck do I know what is 120 km/h ???<br /><br />Oh you think it is easy to change the mindset? Wait till you drive on the "wrong" side of street ! Travel to another country and keep trying the currency conversion ratio everytime you ask "how much"? <img src="/images/icons/rolleyes.gif" /><br /><br />Now for those of you "foreigners" say the rest of world uses the SI unit and so should the U.S., I'd say "hog wash" !! May I remind you that it is the rest of world that should follow the U.S. standard & conventions. Afterall, <i>we</i> went to the moon, brought you the refrigerator, automobiles, airplanes, computers, got rid of communism, and introduced Pamela Anderson !!. We did all these just fine with the good 'ol English unit, what have you done for us lately?<br /><br /><br />OK, I've done enough damage. Discuss among yourself <img src="/images/icons/cool.gif" /><br /> <div class="Discussion_UserSignature"> </div>

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propforce

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<font color="yellow">Actually, Boeing went metric with its airliners starting with the 767</font><br /><br />Well, they're designing parts of 787 with english units. <img src="/images/icons/smile.gif" /><br /><br /> <div class="Discussion_UserSignature"> </div>

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earth_bound_misfit

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I was a boy when we rolled over to metric. I can remember the backlash though. People just don't like change, they get stubborn in their old ways. The same happen when they brought in the seatbelt laws.<br /><br />I'm pleased that I was brought up using metric, it's so much easier to work out stuff. We still use imperial as a yardstick though and it might take a generation to wipe that out. Some examples, the 100 mile an hour barrier (back when I was a lad, a car was a bomb if it couldn't hit the 100mph mark), wood: 4 by 2 (2 by 4 in the US), Personal height and length <img src="/images/icons/wink.gif" />. These just just a few that spring to mind. <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

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josh_simonson

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Yep, here breast sizes are measured in 'Fractional Andersons'. <img src="/images/icons/wink.gif" /><br /><br />And are international bras sold with sizes in liters?

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earth_bound_misfit

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Handfuls here <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

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propforce

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<font color="yellow">Yep, here breast sizes are measured in 'Fractional Andersons'. </font><br /><br /><br /><img src="/images/icons/laugh.gif" /> Now can you imagine a woman wakes up after a breast implant surgery and said "oh no, no, NO !! I wanted those measurements in SI units !!!" <img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> </div>

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