Whats with the missing units when building a rocket?

[ShadowElite]

let me point out i am a new member for the Kerbal Space Program . My question is what are the missing units of the parts for building a rocket. I had to look up on wikipedia for rt-10 it is 1.75t which t=tons. I am am used to kilograms. Anyway I was wondering why the units are missing. Are they gonna be added in the future?

[AlexinTokyo]

I was going to write a post saying something like, "Where are you looking, the units are all there," but then I checked and indeed they aren't. This is an oversight on SQUAD's part, which should probably be fixed at some point.

Anyway, to answer your question, the units are as follows:

• Mass: tonnes (t) [1t = 1,000kg = 1Mg]
  
• Thrust: kilonewtons (kN)
  
• Specific Impulse (I_sp): seconds (s)
  
• Time: seconds (s)
  
• Velocity: meters per second (m/s)
  
• Electric Charge: Arbitrary unit known an 'EC' (Unknown what this represents in real units)
  
• Fuel capacity: Arbitrary unit known as a 'unit' - 1 unit of liquid fuel or oxidiser has a mass of 5kg. For mono-propellant, 1 unit is 4kg, for solid fuel 7.5kg, and for Xenon it's 100g
  
• Torque: kilonewtons (kN)
  

I think that covers all of the major ones. If I missed something, let me know.

Welcome to the forums and happy Kerballing

Edited December 7, 2014 by AlexinTokyo
Fixed the kilonewton symbol.

[The_Rocketeer]

There's really no need to use units because you don't need to make any conversions. If you know the algebra, the units are all the same size/on the same scale. The only exceptions are fuel capacaties, but these are arbitrary because they're a function of mass and thrust rather than a factor.

Also, technically kilo- is represented by a lower-case k (as in km, kN, kg etc).

And ISP is thrust per fuel. Mathematically it comes out as seconds, but knowing why is more useful than knowing what.

Edited December 7, 2014 by The_Rocketeer

[AlexinTokyo]

You are correct that the units aren't strictly necessary, but it is still nice to be sure that the game is using the units you think it is (or should be).

And I must have had a brainfail when I used a capital 'k' for kN; I have edited it to be correct.

[SRV Ron]

let me point out i am a new member for the Kerbal Space Program . My question is what are the missing units of the parts for building a rocket. I had to look up on wikipedia for rt-10 it is 1.75t which t=tons. I am am used to kilograms. Anyway I was wondering why the units are missing. Are they gonna be added in the future?

In the case of t=tons, figure the unit as a measurement of metric tons, not the English unit. 1,000 kilograms make up a metric ton. 2,000 pounds the English ton. With 2.2 pounds needed to make a kilogram, you can easily see that the two measurements are not the same. Using t for metric tons keeps the use of the accepted scientific world standard of the metric system in the KSP game.

[OhioBob]

Torque: kilonewtons (kN)

That's not a unit of torque. The correct unit should be kN·m.

[The_Rocketeer]

In the case of t=tons, figure the unit as a measurement of metric tons, not the English unit. 1,000 kilograms make up a metric ton. 2,000 pounds the English ton. With 2.2 pounds needed to make a kilogram, you can easily see that the two measurements are not the same. Using t for metric tons keeps the use of the accepted scientific world standard of the metric system in the KSP game.

The metric version is correctly spelt tonne. If the Imperial ton was being used, the symbol would be T rather than t.

2000 lbs is a 'short ton' which is actually equivalent to about 907 kg. A proper English ton (sometimes called a long ton, but actually the original) weighs 2240 lbs - that's only a shade over the metric tonne at about 1016 kg.

[NathanKell]

You do need to know the units: how else can you figure out the (very important) thrust-to-weight ratio without knowing that thrust is in kN and mass in tonnes?

[The_Rocketeer]

You do need to know the units: how else can you figure out the (very important) thrust-to-weight ratio without knowing that thrust is in kN and mass in tonnes?

Ratios have no units.

All a ratio tells you is the number of these to the number of those. The fact that the unit scales are equivalent makes naming the units totally unnecessary. To answer you question fully:

a) You don't need to work out the TWR at all, unless you choose to play by the numbers. I have never worked out a TWR, and I've flown to all over the place.

You can work out the TWR without knowing the units if u accept the principle that (1 mass X 1 distance) divided by (1 time X 1 time) = 1 thrust.

c) If you really want to know your TWR there are a lot of mods out there that work it out for you. I believe this is how 90% or more of TWR-desiring players get that data for their rockets.

[bakanando]

But then you have thrust to _mass_ proportion if you divide it, which will confuse you more than helping. Unless you know the local gravity, which is not mentioned either. And you can't measure it precisely before finishing half the science tree.

By that time, you already know well enough how to shoot things to space without crashing them most of the time.

All in all, the lack of (or oversight of) different values that would be useful for the users is mostly by design (I can't remember where I read them, but the developers have mentioned it in various places).

Whether or not that is a good choice, is an altogether different thing.

[cantab]

Ratios have no units.

Correct. However the game does not give you part weights, it gives you part masses. So you need to know the value of g in the applicable thrust and mass units, which amounts to knowing what the thrust and mass units are.

[SciMan]

Back in the old days of 0.13 I used to calculate my TWR manually. I had determined that 10 thrust would just barely lift 1t of mass, which matches well with 1g acceleration (9.81 m/s^2). From that, I figured that the game was using either Tons / kN or kg / N as units. Didn't matter which one it was, the ratio would have been the same, however the size of everything else suggested T/kN. It was an important step in the right direction, because soon after that I figured out how to get to orbit. I also figured out you can use a lot less rocket than the things I had been trying to make. Then I landed on the Mun and returned a few times, forgot about the game until version 0.15 or so, bought it, and I've been playing it ever since.

Of course now I use MechJeb, but to this day I build my rockets for a 2.0 TWR on the pad, and a first stage burn out altitude of about 18km, not including solids.

Edited December 8, 2014 by SciMan

[Kerbart]

Correct. However the game does not give you part weights, it gives you part masses. So you need to know the value of g in the applicable thrust and mass units, which amounts to knowing what the thrust and mass units are.

Knowing that all units are based on metric units is enough. If you can't tell from the answer if you're off a factor of 1000 then I doubt the TWR calculation is going to be meaningful in the first place.

[rkman]

Ratios have no units.

To calculate the correct ratio you need to start with the correct units.

a) You don't need to work out the TWR at all, unless you choose to play by the numbers.

Numbers a plenty in KSP. It's not like it's weird to to fly by the numbers in a rocket science game.

[ShadowElite]

back to this long thread . The units for me are very important. Even if the game is design so its kilo would cancel or something, I still like to be able to see the units. I already made a nice function, well not so nice but it works.

[Rhomphaia]

Not sure why the units are not listed in the part descriptions, but mass is listed as t in the engineers report and map view info box.

Thrust is listed as kN in the in flight context menu for engines.

[Red Iron Crown]

Ratios have no units.

Sort of. The magnitude of the units is very important, 10kN:1t is very different from 10kN:1kg or 10N:1t, even though the numerical ratio is the same. So you do need to know a bit about the units to calculate that ratio.

[GoSlash27]

Sorta-related:

The fuel flow "units" when you right-click on a running engine is tonnes/ sec.

Best,

-Slashy

[ShadowElite]

i wish I knew how to mark this as answered since this was a long time ago post. Anyway I calculate the fuel flow all the time. I like to change everything in terms of the metric system since I am a huge fan of it.

I am more comfortable with the kilograms instead of tons. Units to me are very important since it avoids errors that one might make.

[Rhomphaia]

i wish I knew how to mark this as answered since this was a long time ago post. Anyway I calculate the fuel flow all the time. I like to change everything in terms of the metric system since I am a huge fan of it.

I am more comfortable with the kilograms instead of tons. Units to me are very important since it avoids errors that one might make.

If you look up in the stickied threads you would see. http://forum.kerbalspaceprogram.com/threads/85063-How-to-change-Unanswered-to-Answered

Basically Edit your original post, hit go advanced and you can change it there

[Murph]

I am more comfortable with the kilograms instead of tons. Units to me are very important since it avoids errors that one might make.

There's really no scope for error, KSP uses tonnes, not imperial tons. 1 tonne == 1000kg. It's not a conversion, just standard mega/kilo/milli/micro magnitude scaling. Tonnes are the correct natural metric unit to use, as you're dealing with craft roughly ranging from 1t to 500t (yeah, there will be outliers beyond that range). Individual parts range roughly from 0.005t to about 50t.

You can call them megagrams, if you prefer. ;-)