What are the reasons for KSP not using SI units?

[Nobody_1707]

Nobody likes imperial units or kelvin.

Speak for yourself. Personally, I hate metric. We got to the moon on nothing but feet, pounds, and slide rules.

Edited April 26, 2015 by Nobody_1707

[Kerano]

If you try to put the force in kilonewtons and distance in kilometers, the thousands cancel each other out. Basic pre-algebra stuff.

They don't cancel, they multiply. Try a distance of 1 km and a force of 1 kN, see what you get for Work energy.

Work energy = Force * distance

Then try it converting to the correct SI units of meters and Newtons.

Edited April 26, 2015 by Kerano

[Borsek]

OP, your question is bad and you should feel bad. If you are stubborn enough to not use mods to calculate stuff for you, you can as well be stubborn enough to add a x1000 or /1000 into your equation. The reason for not using kg, m, etc. is that it would be dumb to measure a giant rocket in grams, when it weighs 1000t.

also, to the post above me

Energy = force * path, ergo k*k = M, so it's 1MJ, I honestly don't see what's so hard about that, jeez.

[Stealth2668]

Nobody likes imperial units or kelvin.

Americans like it!

[Torham234]

They don't cancel, they multiply. Try a distance of 1 km and a force of 1 kN, see what you get for Work energy.

Work energy = Force * distance

Then try it converting to the correct SI units of meters and Newtons.

I am really saddened to see post like this on KSP forum. Essentially, your entire complaint boils down to having to adjust for the correct prefix. I thought better of KSP players.

[Elthy]

Shouldnt anybody able to do basic physics also be able to convert those prefixes into numbers in his head?

[Fel]

They don't cancel, they multiply. Try a distance of 1 km and a force of 1 kN, see what you get.

Then try it converting to the correct SI units of meters and Newtons.

Step 1) Verify that we're not talking about grams (there are others, decibel I know of, but grams should do well enough)

Step 2) 1e3 m * 1e3 N = 1e6 J = 1 MJ

If we're talking about grams, because someone broke the system and didn't default all units to their base which would be logical.

1 Mg * 1 mm/s^2 = 1k (kg) * 1 mm/s^2 = 1e3 * 1e-3 N = 1 N

How hard is that? Most of the conversions you don't REALLY need to type out in a calculator either.

[Twreed87]

OP, your question is bad and you should feel bad. If you are stubborn enough to not use mods to calculate stuff for you, you can as well be stubborn enough to add a x1000 or /1000 into your equation. The reason for not using kg, m, etc. is that it would be dumb to measure a giant rocket in grams, when it weighs 1000t.

also, to the post above me

Energy = force * path, ergo k*k = M, so it's 1MJ, I honestly don't see what's so hard about that, jeez.

Yeah, pretty much this. I mean, what are you asking for exactly? The thrust of an engine to be listed as 250,000 instead of 250? 250 looks nicer on the screen and you can multiply by 1000 yourself, it's really easy.

[Temeter]

Americans like it!

See, basically nobody. And how many americans do actually like all those unnecessary conversions?

[Instresu]

If you try to put the force in kilonewtons and distance in kilometers, the thousands cancel each other out. Basic pre-algebra stuff.

What? Are you serious?

3.2 kN ∙ 6.34 km = 20.288 J (your incorrect method)

(3.2 ∙ 10³) N ∙ (6.34 ∙ 10³) m = 20.288 ∙ 10ⶠJ (the correct method)

You're drunk, go home.

[Stealth2668]

See, basically nobody. And how many americans do actually like all those unnecessary conversions?

IDK, I'm Canadian and happily use SI units

[r_rolo1]

People, really? Are we discussing SI prefixes usage? Anyone that knows about SI units has to know about proper methods to convert from prefixed quantities to the base ones. Or people are so lazy nowadays that they don't want to shift some decimals to either side? :/

[Brotoro]

I want to be spoon-fed. But only in kilogram units, so make it a big spoon.

[Instresu]

People, really? Are we discussing SI prefixes usage? Anyone that knows about SI units has to know about proper methods to convert from prefixed quantities to the base ones. Or people are so lazy nowadays that they don't want to shift some decimals to either side? :/

If you are doing many calculations, just plug in numbers and get a totally unrealistic result, you "Oh, something is not in SI units" and you must go back and control all numbers again... That's quite irritating.

[Twreed87]

I petition that we change all the units to American units. Convert from feet to miles, pounds to tons, from mile grains to foot pounds

That should be a mod. Just for fun, I think it'd be neat.

[Brotoro]

I petition that we change all the units to American units. Convert from feet to miles, pounds to tons, from mile grains to foot pounds

No. Distances should be in furlongs, forces in stones, and time in microfortnights.

[r_rolo1]

If you are doing many calculations, just plug in numbers and get a totally unrealistic result, you "Oh, something is not in SI units" and you must go back and control all numbers again... That's quite irritating.

It is irritating, but that is Physics 101: check your units ( and believe me on that, I teach Physics and Chemistry for a living ). If you can't or are unwilling to check your units, you better give the math to someone else for everyone around you sake. Don't be like that anonymous NASA tech that threw a mission to the gutter because he couldn't convince himself to check if he was using yards or meters

Edited April 26, 2015 by r_rolo1

[Kerano]

I am really saddened to see post like this on KSP forum. Essentially, your entire complaint boils down to having to adjust for the correct prefix. I thought better of KSP players.

Not everyone is familiar with physics conventions. There's no shame in not knowing something, it's just an opportunity to teach.

If you check my post I was correcting someone who believed that kilo prefixes would 'just cancel out'. If you already know that isn't the case, no problem. Not everyone does.

University physics tutor here for the record.

[Rhomphaia]

The kilonewton is a derived unit. the metric tonne may not be, but is officially accepted by the SI because kilokilogram is just stupid.

https://en.wikipedia.org/wiki/Non-SI_units_mentioned_in_the_SI#Units_officially_accepted_for_use_with_the_SI

Honestly anyone who can't manage these conversions should probably consider a career in another field.

[m4v]

The lack of SI units never prevented me from doing math in KSP, you just kinda have to know that thrust is in kN, fuel units x its density is mass, and mass is always in metric tons, Isp is seconds and ... that's probably all. ElectricCharge is an invention that behaves nothing like electricity so there's no point in trying to give it units, thinking it's Coulombs, EC or apples would work just fine.

[Instresu]

It is irritating, but that is Physics 101: check your units ( and believe me, I teach Physics and Chemistry for a living ).

And all could be solved by just using SI units – or letting those who want, use SI units.

[Stealth2668]

I petition that we change all the units to American units. Convert from feet to miles, pounds to tons, from mile grains to foot pounds

don't forget slugs

[Vanamonde]

KSP's terminology may be a little sloppy, but the game units are indeed metric. Except, that is, for the temperature system. It is a placeholder and the numbers make no sense in any scale.

That being said, please keep the discussion on-topic, and let's not get into another metric-vs.-Imperial spat, nor make fun of forum members who do not know the answers to the questions they are asking. Asking is how they will learn this stuff, after all.

[Drillgorg]

Wow, really? Using SI prefixes is standard practice and easy. I'm a mechanical engineer; in my field you'd be laughed at for avoiding prefixes (sadly I'm forced to use imperial most of the time due to living in the US. SI would make my job easier.) In practice, SI base units AND their prefixes are all considered SI. The whole point of them is to express very large (or very small) quantities concisely. In Kerbal we deal with very large quantities with frequency. I feel that adding an option for base units only is not a good use of Squad's time.

[Borsek]

KSP's terminology may be a little sloppy, but the game units are indeed metric. Except, that is, for the temperature system. It is a placeholder and the numbers make no sense in any scale.

That being said, please keep the discussion on-topic, and let's not get into another metric-vs.-Imperial spat, nor make fun of forum members who do not know the answers to the questions they are asking. Asking is how they will learn this stuff, after all.

No, the temp scale is in Celsius, iirc the temp in space is -273.15, which is close to 0K, or rather, what the temp would actually be. Also a lot of the temps are melting points of various metal alloys, so they make sense too. The only people who find this system difficult are americans, because they're not used to these units in their everyday lives. Get on with the times and vote for metric units.

EDIT: By that I mean the temperature in-game is -273,15 in space, which is about 0K in real life.