Could OpenRocket developers please consider switching to metric units

[Jowayen]

Doesn't matter which one.
Tried pushing that crap on us in the 70's...

Show me a metric clock...

Do you dislike lattitude/longitude because it isn't in radians?

 

[Cape Byron]

Doesn't matter which one.
Tried pushing that crap on us in the 70's...

Show me a metric clock

Strictly speaking, it's a decimal clock.

 

[Jowayen]

Which country uses that clock as official time? If the answer is "none", you proved my point

 

[Neutronium95]

Rocketry has always been a mixed bag with average thrust and impulse usually described in metric terms, motor case diameter always described in metric terms except for Kosdon, and lengths, weights, and altitudes usually described in imperial units.

Motor cases are weird. While they have metric designations, they're pretty much entirely designed in imperial, and then the diameter is just rounded to the nearest millimeter for the designation.

So 29mm motors are 1.125", 38mm motors are 2.125, 75mm are 2.965" and 98mm are 3.875".

I wasn't around when the community settled on those sizes, but from what I understand, 1.125" and 1.5" OD tubing is pretty commonly available and became a common choice for larger motors. I've heard that 54mm came from people making motor cases out of liners for larger motors, maybe 2.5". Either way it's not a super common tube OD in industry. And finally, I think that 75 and 98mm were actually sized to fit Loc tubes at the time, although again this is all half remembered on my part.

I wonder if hardware costs would go down appreciably if the community had settled on standard tubing sizes that didn't need any special orders or machining. Maybe 2", 2.5", 3", and 4".

 

[cwbullet]

I am pretty sure you can switch to metric yourself.

 

[rharshberger]

Motor cases are weird. While they have metric designations, they're pretty much entirely designed in imperial, and then the diameter is just rounded to the nearest millimeter for the designation.

So 29mm motors are 1.125", 38mm motors are 2.125, 75mm are 2.965" and 98mm are 3.875".

I wasn't around when the community settled on those sizes, but from what I understand, 1.125" and 1.5" OD tubing is pretty commonly available and became a common choice for larger motors. I've heard that 54mm came from people making motor cases out of liners for larger motors, maybe 2.5". Either way it's not a super common tube OD in industry. And finally, I think that 75 and 98mm were actually sized to fit Loc tubes at the time, although again this is all half remembered on my part.

I wonder if hardware costs would go down appreciably if the community had settled on standard tubing sizes that didn't need any special orders or machining. Maybe 2", 2.5", 3", and 4".

54mm iirc is because of the ID of 2" Sch80 aluminum pipe that the original cases were turned down from, at least I think thats what I heard, custom DOM 54mm tubing came later in an effort to save manufacturing cost by not having to turn the entire OD of the case down, even though that did leave a nice thrust ring.

 

[cls]

Do you dislike lattitude/longitude because it isn't in radians?

Actually, degrees minutes seconds is a great system for offshore navigation. Nautical miles (in latitude) make perfect sense, 1 minute of latitude. And sexigesimal arithmetic is pretty accessible, in a barely numerate and marginally literate time.

Km and grad works ok too, because 1km = 1/10,000 of 100 grad latitude, equator to north pole.

Approximately. As was known 300 years ago. Modern geometry, earth is pear shaped, wgs 84, blah blah blah.

Edit: need a different system for land surveying...

 

[Voyager1]

Modern geometry, earth is pear shaped

Actually, it’s an oblate spheroid! However, given what’s going on currently, you’re probably right. It is going pear-shaped!

 

[dhbarr]

"so, just like tires: 225/70R15. gah!" (the quote dhbarr was responding too).


It actually imparts a lot of information its a tire 225mm wide with sidewalls 157.5mm tall (70% of width) on a 15" rim, the old way would have been a 27x9.0x15.

Throw in backspacing in inches, offset in millimeters again, etc etc. Bah! I wanted a measurement system, not a word problem

 

[Jowayen]

 

[Steve Shannon]

View attachment 563045

The computer in the lunar module did its work in metric. It converted to imperial for display.

 

[Donnager]

The computer in the lunar module did its work in metric. It converted to imperial for display.

I've been known to convert from metric to imperial to do a calculation, and then convert back to metric to show my answer (usually because of some constants or conversion factors I have in memory, where younger me never bothered to store all the metric ones).

 

[Antares JS]

My hidebound, Rust-Belt industry has used SI units for 40 years. I am surprised rocket scientists at NASA would still use English units.

When I was in college, my professors told us that, for whatever reason, a lot of aerospace work is done in Imperial units, and made a point of making sure we could work in both systems. My thermodynamics professor in particular would give some test problems in metric, and some in Imperial, and the answer was expected to be given in the same units as the problem.

 

[Buckeye]

When I was in college, my professors told us that, for whatever reason, a lot of aerospace work is done in Imperial units, and made a point of making sure we could work in both systems. My thermodynamics professor in particular would give some test problems in metric, and some in Imperial, and the answer was expected to be given in the same units as the problem.

Sure, that is common in engineering classes. I think we were given two sets of steam tables - one SI, one English. My buddy wrote "SUCKS" in bold letters on the English version! All the students preferred SI problems.

 

[lakeroadster]

... I will heed your advice and refrain from commenting on the metric system for a good long time. ...

Bookmarked for future use...

 

[KC3KNM]

When I was in college, my professors told us that, for whatever reason, a lot of aerospace work is done in Imperial units, and made a point of making sure we could work in both systems. My thermodynamics professor in particular would give some test problems in metric, and some in Imperial, and the answer was expected to be given in the same units as the problem.

We use both pretty consistently where I work, I get a ton of parts with mixed metric/inch dimensions and thread call outs. Very fun.