Why did NASA use U.S customary units?Did NASA use metric units for the Mercury missions?Why was the LRV's speed gauge displaying metric units?Which unit system was used by german rocket scientists at NASA for calculations?Was Arthur J. Schwaniger one of very few US born NASA scientists using metric units?Did NASA use metric units for the Mercury missions?What NASA documents did SpaceX use to design their engines?Why didn't NASA use the shuttle to make a profit?Why did NASA set up a computing facility in Bermuda in the Mercury epoch?Why did NASA close the space shuttle program?Did Zuma “bump” NASA?Why does NASA still use film cameras?Why has NASA shunned the worm logo?Why did NASA wet the road in front of the Space Shuttle crawler?Did NASA muzzle Wernher von Braun during the moon landings?
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Why did NASA use U.S customary units?
Did NASA use metric units for the Mercury missions?Why was the LRV's speed gauge displaying metric units?Which unit system was used by german rocket scientists at NASA for calculations?Was Arthur J. Schwaniger one of very few US born NASA scientists using metric units?Did NASA use metric units for the Mercury missions?What NASA documents did SpaceX use to design their engines?Why didn't NASA use the shuttle to make a profit?Why did NASA set up a computing facility in Bermuda in the Mercury epoch?Why did NASA close the space shuttle program?Did Zuma “bump” NASA?Why does NASA still use film cameras?Why has NASA shunned the worm logo?Why did NASA wet the road in front of the Space Shuttle crawler?Did NASA muzzle Wernher von Braun during the moon landings?
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$begingroup$
NASA was using U.S customary units (inches, feet, nautical miles, pounds, tons, US gallons etc.) during the Mercury and Apollo programmes, and beyond.
There are significant disadvantages to using U.S customary units, the most obvious being that the ratios are not uniform or round numbers (e.g. 6076.12 feet in 1 nautical mile).
Considering that much of the maths involved was done by hand, this seems like an unnecessary complication. Why not just use metric? Metric was already widely used by scientists and some engineers anyway.
nasa
edited Jul 25 at 21:23
Vality
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
$endgroup$
|
show 2 more comments
$begingroup$
NASA was using U.S customary units (inches, feet, nautical miles, pounds, tons, US gallons etc.) during the Mercury and Apollo programmes, and beyond.
There are significant disadvantages to using U.S customary units, the most obvious being that the ratios are not uniform or round numbers (e.g. 6076.12 feet in 1 nautical mile).
Considering that much of the maths involved was done by hand, this seems like an unnecessary complication. Why not just use metric? Metric was already widely used by scientists and some engineers anyway.
nasa
edited Jul 25 at 21:23
Vality
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
$endgroup$
1
$begingroup$
Related: Did NASA use metric units for the Mercury missions?
$endgroup$
– DarkDust
Jul 23 at 10:19
37
$begingroup$
Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
$endgroup$
– Uwe
Jul 23 at 10:54
25
$begingroup$
@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
$endgroup$
– Ray Butterworth
Jul 23 at 12:47
2
$begingroup$
Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
$endgroup$
– chepner
Jul 23 at 18:43
2
$begingroup$
I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
$endgroup$
– Aaron
Jul 24 at 21:16
|
show 2 more comments
$begingroup$
NASA was using U.S customary units (inches, feet, nautical miles, pounds, tons, US gallons etc.) during the Mercury and Apollo programmes, and beyond.
There are significant disadvantages to using U.S customary units, the most obvious being that the ratios are not uniform or round numbers (e.g. 6076.12 feet in 1 nautical mile).
Considering that much of the maths involved was done by hand, this seems like an unnecessary complication. Why not just use metric? Metric was already widely used by scientists and some engineers anyway.
nasa
edited Jul 25 at 21:23
Vality
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
$endgroup$
NASA was using U.S customary units (inches, feet, nautical miles, pounds, tons, US gallons etc.) during the Mercury and Apollo programmes, and beyond.
There are significant disadvantages to using U.S customary units, the most obvious being that the ratios are not uniform or round numbers (e.g. 6076.12 feet in 1 nautical mile).
Considering that much of the maths involved was done by hand, this seems like an unnecessary complication. Why not just use metric? Metric was already widely used by scientists and some engineers anyway.
nasa
nasa
edited Jul 25 at 21:23
Vality
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
edited Jul 25 at 21:23
Vality
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
edited Jul 25 at 21:23
Vality
1031 bronze badge
edited Jul 25 at 21:23
Vality
1031 bronze badge
edited Jul 25 at 21:23
Vality
1031 bronze badge
1031 bronze badge
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
asked Jul 23 at 8:43
useruser
5401 gold badge2 silver badges10 bronze badges
5401 gold badge2 silver badges10 bronze badges
1
$begingroup$
Related: Did NASA use metric units for the Mercury missions?
$endgroup$
– DarkDust
Jul 23 at 10:19
37
$begingroup$
Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
$endgroup$
– Uwe
Jul 23 at 10:54
25
$begingroup$
@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
$endgroup$
– Ray Butterworth
Jul 23 at 12:47
2
$begingroup$
Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
$endgroup$
– chepner
Jul 23 at 18:43
2
$begingroup$
I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
$endgroup$
– Aaron
Jul 24 at 21:16
|
show 2 more comments
1
$begingroup$
Related: Did NASA use metric units for the Mercury missions?
$endgroup$
– DarkDust
Jul 23 at 10:19
37
$begingroup$
Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
$endgroup$
– Uwe
Jul 23 at 10:54
25
$begingroup$
@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
$endgroup$
– Ray Butterworth
Jul 23 at 12:47
2
$begingroup$
Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
$endgroup$
– chepner
Jul 23 at 18:43
2
$begingroup$
I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
$endgroup$
– Aaron
Jul 24 at 21:16
1
1
$begingroup$
Related: Did NASA use metric units for the Mercury missions?
$endgroup$
– DarkDust
Jul 23 at 10:19
$begingroup$
Related: Did NASA use metric units for the Mercury missions?
$endgroup$
– DarkDust
Jul 23 at 10:19
37
37
$begingroup$
Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
$endgroup$
– Uwe
Jul 23 at 10:54
$begingroup$
Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
$endgroup$
– Uwe
Jul 23 at 10:54
25
25
$begingroup$
@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
$endgroup$
– Ray Butterworth
Jul 23 at 12:47
$begingroup$
@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
$endgroup$
– Ray Butterworth
Jul 23 at 12:47
2
2
$begingroup$
Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
$endgroup$
– chepner
Jul 23 at 18:43
$begingroup$
Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
$endgroup$
– chepner
Jul 23 at 18:43
2
2
$begingroup$
I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
$endgroup$
– Aaron
Jul 24 at 21:16
$begingroup$
I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
$endgroup$
– Aaron
Jul 24 at 21:16
|
show 2 more comments
3 Answers
3
active
oldest
votes
$begingroup$
The Apollo Guidance Computer did use metric/SI units internally for its calculations. But it converted to imperial/USC units when it displayed data on the DSKY. This is probably because the Apollo astronauts (mostly trained as test pilots) had an intuitive "feel" for imperial/USC units.
Although data was stored internally in metric units, they were
displayed as United States customary units - Wikipedia
.
The computer display readouts were in units of feet, feet per second,
and nautical miles – units that the Apollo astronauts, who had mostly
trained as US Air Force pilots, would have been accustomed to using.
Internally, however, the computer’s software used SI units for all
powered-flight navigation and guidance calculations, and values such
as altitude and altitude rate were only converted to imperial units
when they needed to be shown on the computer’s display.
- UK Metric Association
edited Jul 24 at 9:40
JFL
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
$endgroup$
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
|
show 11 more comments
$begingroup$
NASA used English Engineering Units not Imperial units. (This phrasing is a reply to the original, un-edited question title)
They did this because the program was implemented by the US aerospace industry and that industry's industrial base was all in English units. Every manual, tool, data book, milling machine, and fastener used those units.
Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure.
Eventually they came around, the ISS is metric.
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
$endgroup$
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
$begingroup$
Eventually they came around, the ISS is metric.The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.
$endgroup$
– J...
Jul 23 at 19:14
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
add a comment |
$begingroup$
When I was trained in Aerospace Engineering at Texas A&M in the 1980s, we were taught to use what has been referred to as the Gravitational FPS system, where distance is measured in feet, force in pounds, and mass in slugs. This was a big disappointment to me at the time, since I had been quite comfortable with metric units in high school physics. However, at the time FPS still dominated the US engineering literature.
I remember that one semester we had a visiting lecturer in dynamics who was also continuing his work as an engineer at NASA (Johnson Space Center.) He announced to us early in his classes that he would only accept work in FPS, and not "those damned communist units."
When I got to NASA/JSC in 1984 I found that FPS was quite common in most of the Shuttle simulation code that I worked on (I never saw any actual flight code,) but metric units were also used by some teams, and if anyone harbored any political biases around systems of measurement, they kept it to themselves. In almost all cases, however, when data were presented to crew or (especially senior) engineers, they were converted from consistent units (whether SI or FPS) to feet, pounds, pounds-mass, nautical miles, knots, degrees (both Fahrenheit and angular,) and other "traditional" units.
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
$endgroup$
5
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
$endgroup$
– dan04
Jul 23 at 22:16
5
$begingroup$
This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
$endgroup$
– Organic Marble
Jul 23 at 23:04
4
$begingroup$
It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
$endgroup$
– JCRM
Jul 24 at 6:15
5
$begingroup$
"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
$endgroup$
– Uwe
Jul 24 at 10:17
4
$begingroup$
@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
$endgroup$
– DevSolar
Jul 24 at 10:46
|
show 8 more comments
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3 Answers
3
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3 Answers
3
active
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active
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$begingroup$
The Apollo Guidance Computer did use metric/SI units internally for its calculations. But it converted to imperial/USC units when it displayed data on the DSKY. This is probably because the Apollo astronauts (mostly trained as test pilots) had an intuitive "feel" for imperial/USC units.
Although data was stored internally in metric units, they were
displayed as United States customary units - Wikipedia
.
The computer display readouts were in units of feet, feet per second,
and nautical miles – units that the Apollo astronauts, who had mostly
trained as US Air Force pilots, would have been accustomed to using.
Internally, however, the computer’s software used SI units for all
powered-flight navigation and guidance calculations, and values such
as altitude and altitude rate were only converted to imperial units
when they needed to be shown on the computer’s display.
- UK Metric Association
edited Jul 24 at 9:40
JFL
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
$endgroup$
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
|
show 11 more comments
$begingroup$
The Apollo Guidance Computer did use metric/SI units internally for its calculations. But it converted to imperial/USC units when it displayed data on the DSKY. This is probably because the Apollo astronauts (mostly trained as test pilots) had an intuitive "feel" for imperial/USC units.
Although data was stored internally in metric units, they were
displayed as United States customary units - Wikipedia
.
The computer display readouts were in units of feet, feet per second,
and nautical miles – units that the Apollo astronauts, who had mostly
trained as US Air Force pilots, would have been accustomed to using.
Internally, however, the computer’s software used SI units for all
powered-flight navigation and guidance calculations, and values such
as altitude and altitude rate were only converted to imperial units
when they needed to be shown on the computer’s display.
- UK Metric Association
edited Jul 24 at 9:40
JFL
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
$endgroup$
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
|
show 11 more comments
$begingroup$
The Apollo Guidance Computer did use metric/SI units internally for its calculations. But it converted to imperial/USC units when it displayed data on the DSKY. This is probably because the Apollo astronauts (mostly trained as test pilots) had an intuitive "feel" for imperial/USC units.
Although data was stored internally in metric units, they were
displayed as United States customary units - Wikipedia
.
The computer display readouts were in units of feet, feet per second,
and nautical miles – units that the Apollo astronauts, who had mostly
trained as US Air Force pilots, would have been accustomed to using.
Internally, however, the computer’s software used SI units for all
powered-flight navigation and guidance calculations, and values such
as altitude and altitude rate were only converted to imperial units
when they needed to be shown on the computer’s display.
- UK Metric Association
edited Jul 24 at 9:40
JFL
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
$endgroup$
The Apollo Guidance Computer did use metric/SI units internally for its calculations. But it converted to imperial/USC units when it displayed data on the DSKY. This is probably because the Apollo astronauts (mostly trained as test pilots) had an intuitive "feel" for imperial/USC units.
Although data was stored internally in metric units, they were
displayed as United States customary units - Wikipedia
.
The computer display readouts were in units of feet, feet per second,
and nautical miles – units that the Apollo astronauts, who had mostly
trained as US Air Force pilots, would have been accustomed to using.
Internally, however, the computer’s software used SI units for all
powered-flight navigation and guidance calculations, and values such
as altitude and altitude rate were only converted to imperial units
when they needed to be shown on the computer’s display.
- UK Metric Association
edited Jul 24 at 9:40
JFL
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
edited Jul 24 at 9:40
JFL
1032 bronze badges
edited Jul 24 at 9:40
JFL
1032 bronze badges
edited Jul 24 at 9:40
JFL
1032 bronze badges
1032 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
answered Jul 23 at 11:43
gandalf61gandalf61
7862 silver badges5 bronze badges
7862 silver badges5 bronze badges
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
|
show 11 more comments
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
14
14
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
$begingroup$
That's fascinating. I wonder how much of its limited computing power and memory was wasted on those conversions?
$endgroup$
– user
Jul 23 at 12:51
40
40
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
$begingroup$
@user Well, it just involves storing a handful of constant scale factors in ROM and a single memory lookup and multiply or divide each time a value is written to or read from the DSKY. Compared to the really complex stuff that the AGC had to handle (real-time interrupts, task scheduling, hot restarts, multiple 3D reference frames, Kalman filters ...) it's not a big overhead.
$endgroup$
– gandalf61
Jul 23 at 13:58
5
5
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
$begingroup$
WP says 96 cycles of a multiply instruction, not actually that bad.
$endgroup$
– user
Jul 23 at 14:35
34
34
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
$begingroup$
Internal storage was almost certainly in some manner of small units unsuitable for human consumption. Given that computers are going to do math to display it for the humans no matter what (the only thing trivial for them is multiplying or dividing by 2), there is essentially no difference to the computers what multiplication factors are used. Powers of 10 are only easier for humans
$endgroup$
– T.E.D.
Jul 23 at 17:52
13
13
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
$begingroup$
@user, almost none. Since the physics calculations were done 100 times per second, almost every rate was measured "per centisecond". Additionally, many numbers (eg. "distance to Earth") had binary scaling factors to keep the numbers within reasonable bounds. Because of this, even a metric display would require conversions. You can see this looking at the variable definitions in ibiblio.org/apollo/Documents/j2-80-MSC-70-FS-2_text.pdf
$endgroup$
– Mark
Jul 23 at 21:41
|
show 11 more comments
$begingroup$
NASA used English Engineering Units not Imperial units. (This phrasing is a reply to the original, un-edited question title)
They did this because the program was implemented by the US aerospace industry and that industry's industrial base was all in English units. Every manual, tool, data book, milling machine, and fastener used those units.
Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure.
Eventually they came around, the ISS is metric.
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
$endgroup$
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
$begingroup$
Eventually they came around, the ISS is metric.The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.
$endgroup$
– J...
Jul 23 at 19:14
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
add a comment |
$begingroup$
NASA used English Engineering Units not Imperial units. (This phrasing is a reply to the original, un-edited question title)
They did this because the program was implemented by the US aerospace industry and that industry's industrial base was all in English units. Every manual, tool, data book, milling machine, and fastener used those units.
Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure.
Eventually they came around, the ISS is metric.
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
$endgroup$
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
$begingroup$
Eventually they came around, the ISS is metric.The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.
$endgroup$
– J...
Jul 23 at 19:14
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
add a comment |
$begingroup$
NASA used English Engineering Units not Imperial units. (This phrasing is a reply to the original, un-edited question title)
They did this because the program was implemented by the US aerospace industry and that industry's industrial base was all in English units. Every manual, tool, data book, milling machine, and fastener used those units.
Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure.
Eventually they came around, the ISS is metric.
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
$endgroup$
NASA used English Engineering Units not Imperial units. (This phrasing is a reply to the original, un-edited question title)
They did this because the program was implemented by the US aerospace industry and that industry's industrial base was all in English units. Every manual, tool, data book, milling machine, and fastener used those units.
Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure.
Eventually they came around, the ISS is metric.
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
edited Jul 25 at 21:36
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
answered Jul 23 at 11:10
Organic MarbleOrganic Marble
73.2k4 gold badges213 silver badges315 bronze badges
73.2k4 gold badges213 silver badges315 bronze badges
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
$begingroup$
Eventually they came around, the ISS is metric.The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.
$endgroup$
– J...
Jul 23 at 19:14
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
add a comment |
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
$begingroup$
Eventually they came around, the ISS is metric.The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.
$endgroup$
– J...
Jul 23 at 19:14
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
$begingroup$
When I earned my aerospace engineering degree in the late 1970s the industry was in transition, we had to deal with both sets of units. I would assume it's mostly metric now with some leftover English stuff in aviation.
$endgroup$
– Organic Marble
Jul 23 at 11:25
1
1
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
$begingroup$
"Conversion of the industry to metric would have taken time and NASA started out with a lot of schedule pressure." Time pressure certainly was the case through Apollo. But the Shuttle had a generous development period. Was the factor there that the Shuttle was seen as an aircraft, and therefore be tied to standard aviation units?
$endgroup$
– DrSheldon
Jul 23 at 14:56
4
4
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
$begingroup$
@DrSheldon there's a lot of Apollo DNA in Shuttle - look at the controls and displays alone. I don't think the real press to convert to metric in the US started till the Carter administration and Shuttle was approved under Nixon.
$endgroup$
– Organic Marble
Jul 23 at 15:10
6
6
$begingroup$
Eventually they came around, the ISS is metric. The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.$endgroup$
– J...
Jul 23 at 19:14
$begingroup$
Eventually they came around, the ISS is metric. The ISS is also part Russian, part European, part Japanese... the US section of the ISS mixes metric and English units, and NASA generally to this day continues to use a mix of units for other vehicles and missions. They're not done coming around just yet.$endgroup$
– J...
Jul 23 at 19:14
3
3
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
$begingroup$
@OrganicMarble I got my aerospace engineering degree within the last few years and we still had to use both sets of units. Despite what some condescending Europeans would have everyone believe, US Customary units are still widely used in industry.
$endgroup$
– zaen
Jul 24 at 17:17
add a comment |
$begingroup$
When I was trained in Aerospace Engineering at Texas A&M in the 1980s, we were taught to use what has been referred to as the Gravitational FPS system, where distance is measured in feet, force in pounds, and mass in slugs. This was a big disappointment to me at the time, since I had been quite comfortable with metric units in high school physics. However, at the time FPS still dominated the US engineering literature.
I remember that one semester we had a visiting lecturer in dynamics who was also continuing his work as an engineer at NASA (Johnson Space Center.) He announced to us early in his classes that he would only accept work in FPS, and not "those damned communist units."
When I got to NASA/JSC in 1984 I found that FPS was quite common in most of the Shuttle simulation code that I worked on (I never saw any actual flight code,) but metric units were also used by some teams, and if anyone harbored any political biases around systems of measurement, they kept it to themselves. In almost all cases, however, when data were presented to crew or (especially senior) engineers, they were converted from consistent units (whether SI or FPS) to feet, pounds, pounds-mass, nautical miles, knots, degrees (both Fahrenheit and angular,) and other "traditional" units.
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
$endgroup$
5
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
$endgroup$
– dan04
Jul 23 at 22:16
5
$begingroup$
This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
$endgroup$
– Organic Marble
Jul 23 at 23:04
4
$begingroup$
It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
$endgroup$
– JCRM
Jul 24 at 6:15
5
$begingroup$
"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
$endgroup$
– Uwe
Jul 24 at 10:17
4
$begingroup$
@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
$endgroup$
– DevSolar
Jul 24 at 10:46
|
show 8 more comments
$begingroup$
When I was trained in Aerospace Engineering at Texas A&M in the 1980s, we were taught to use what has been referred to as the Gravitational FPS system, where distance is measured in feet, force in pounds, and mass in slugs. This was a big disappointment to me at the time, since I had been quite comfortable with metric units in high school physics. However, at the time FPS still dominated the US engineering literature.
I remember that one semester we had a visiting lecturer in dynamics who was also continuing his work as an engineer at NASA (Johnson Space Center.) He announced to us early in his classes that he would only accept work in FPS, and not "those damned communist units."
When I got to NASA/JSC in 1984 I found that FPS was quite common in most of the Shuttle simulation code that I worked on (I never saw any actual flight code,) but metric units were also used by some teams, and if anyone harbored any political biases around systems of measurement, they kept it to themselves. In almost all cases, however, when data were presented to crew or (especially senior) engineers, they were converted from consistent units (whether SI or FPS) to feet, pounds, pounds-mass, nautical miles, knots, degrees (both Fahrenheit and angular,) and other "traditional" units.
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
$endgroup$
5
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
$endgroup$
– dan04
Jul 23 at 22:16
5
$begingroup$
This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
$endgroup$
– Organic Marble
Jul 23 at 23:04
4
$begingroup$
It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
$endgroup$
– JCRM
Jul 24 at 6:15
5
$begingroup$
"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
$endgroup$
– Uwe
Jul 24 at 10:17
4
$begingroup$
@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
$endgroup$
– DevSolar
Jul 24 at 10:46
|
show 8 more comments
$begingroup$
When I was trained in Aerospace Engineering at Texas A&M in the 1980s, we were taught to use what has been referred to as the Gravitational FPS system, where distance is measured in feet, force in pounds, and mass in slugs. This was a big disappointment to me at the time, since I had been quite comfortable with metric units in high school physics. However, at the time FPS still dominated the US engineering literature.
I remember that one semester we had a visiting lecturer in dynamics who was also continuing his work as an engineer at NASA (Johnson Space Center.) He announced to us early in his classes that he would only accept work in FPS, and not "those damned communist units."
When I got to NASA/JSC in 1984 I found that FPS was quite common in most of the Shuttle simulation code that I worked on (I never saw any actual flight code,) but metric units were also used by some teams, and if anyone harbored any political biases around systems of measurement, they kept it to themselves. In almost all cases, however, when data were presented to crew or (especially senior) engineers, they were converted from consistent units (whether SI or FPS) to feet, pounds, pounds-mass, nautical miles, knots, degrees (both Fahrenheit and angular,) and other "traditional" units.
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
$endgroup$
When I was trained in Aerospace Engineering at Texas A&M in the 1980s, we were taught to use what has been referred to as the Gravitational FPS system, where distance is measured in feet, force in pounds, and mass in slugs. This was a big disappointment to me at the time, since I had been quite comfortable with metric units in high school physics. However, at the time FPS still dominated the US engineering literature.
I remember that one semester we had a visiting lecturer in dynamics who was also continuing his work as an engineer at NASA (Johnson Space Center.) He announced to us early in his classes that he would only accept work in FPS, and not "those damned communist units."
When I got to NASA/JSC in 1984 I found that FPS was quite common in most of the Shuttle simulation code that I worked on (I never saw any actual flight code,) but metric units were also used by some teams, and if anyone harbored any political biases around systems of measurement, they kept it to themselves. In almost all cases, however, when data were presented to crew or (especially senior) engineers, they were converted from consistent units (whether SI or FPS) to feet, pounds, pounds-mass, nautical miles, knots, degrees (both Fahrenheit and angular,) and other "traditional" units.
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
answered Jul 23 at 22:09
Michael MatthewsMichael Matthews
993 bronze badges
993 bronze badges
5
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
$endgroup$
– dan04
Jul 23 at 22:16
5
$begingroup$
This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
$endgroup$
– Organic Marble
Jul 23 at 23:04
4
$begingroup$
It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
$endgroup$
– JCRM
Jul 24 at 6:15
5
$begingroup$
"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
$endgroup$
– Uwe
Jul 24 at 10:17
4
$begingroup$
@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
$endgroup$
– DevSolar
Jul 24 at 10:46
|
show 8 more comments
5
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
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– dan04
Jul 23 at 22:16
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This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
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– Organic Marble
Jul 23 at 23:04
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It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
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– JCRM
Jul 24 at 6:15
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"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
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– Uwe
Jul 24 at 10:17
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@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
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– DevSolar
Jul 24 at 10:46
5
5
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I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
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– dan04
Jul 23 at 22:16
$begingroup$
I was a student at Texas A&M in the early 2000s. ENGR 111/112 still heavily used English units (with both pound-mass and pound-force variants), although by then the faculty had at least stopped referring to SI as "damned communist units".
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– dan04
Jul 23 at 22:16
5
5
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This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
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– Organic Marble
Jul 23 at 23:04
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This is interesting, but it doesn't answer the question "Why did NASA use Imperial units"? Stick around, spend some time on the site, and you will soon be able to comment.
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– Organic Marble
Jul 23 at 23:04
4
4
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It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
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– JCRM
Jul 24 at 6:15
$begingroup$
It does, however, give some indication of the culture @OrganicMarble and as such is supplemental information.
$endgroup$
– JCRM
Jul 24 at 6:15
5
5
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"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
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– Uwe
Jul 24 at 10:17
$begingroup$
"those damned communist units."? When the metre convention was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela) there was no communist system, not in France and not in Russia. French revolution was over, Napoleon dictatorship too, France was a republic and Russia was reigned by the Zar.
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– Uwe
Jul 24 at 10:17
4
4
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@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
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– DevSolar
Jul 24 at 10:46
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@Uwe: To a certain part of the US population, everything originating in Europe is communist, or at the very least socialist. Their political scale of reference is somewhat skewed that way.
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– DevSolar
Jul 24 at 10:46
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show 8 more comments
protected by Mark Omo Jul 25 at 21:29
Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).
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1
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Related: Did NASA use metric units for the Mercury missions?
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– DarkDust
Jul 23 at 10:19
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Imperial units were used in aviation industry before and this industry was needed to built rocket parts. Astronauts were military and test pilots before, they were used to altimeters calibrated in feet. Aviation is still not full metric.
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– Uwe
Jul 23 at 10:54
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@Uwe, I think the OP was saying that in metric the ratio between any two units is almost always a power of 10, while in American, the ratio between any two units is almost never anything obvious or memorable. Conversion within metric conversion is trivial, while conversion within American is complicated and potentially error-prone. ("How many litres in a cubic metre?": 1000. "How many cubic feet in a gallon?": "Is that a dry gallon or a fluid gallon?")
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– Ray Butterworth
Jul 23 at 12:47
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Given the types of things being calculated, I hardly think being able to easily convert between meters and kilometers would be the biggest source of errors. Round constants of proportionality go out the window once you have start working with values like g, no matter what units you are using.
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– chepner
Jul 23 at 18:43
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I work at NASA. We still use all manner of units. It's relatively easy to convert, and so many things rely on historical data which is all recorded in imperial. Many US manufacturers (read: the contractors who build stuff for us) still mostly work in imperial. It would be great if we could only use metric, but we have to use imperial because we're in the USA. Any engineer in the world will almost be guaranteed to work with imperial units at least once in a while.
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– Aaron
Jul 24 at 21:16