Radial size

[[File:Radial size comparison.png|thumb|Comparison of radial sizes with a Kerbal for scale. From top to bottom: Tiny (Size 0), Small, Large, and Extra Large (Size 3).]]
The '''radial size''' is the diameter or mounting position for most parts. If the mounting position is not radial, then the part is either round or one of two special forms. Such rectangular parts as the [[M-1x1 Structural Panel]] lack a radial size or it's a size to the next bigger diameter like the [[Probodobodyne QBE]]. Four radial sizes exist with varying names. The size scale looks like the internal definition as the [[Mk2 to size 1 Adapter]] uses this term and starts with <tt>0</tt> and many values in computer programming are starting from 0 rather than 1.

Any stackable part can be connected to any other stackable part.  However, smaller parts have smaller attachment nodes, which result in weaker connections, so, say, putting a 1.25 meter part in between two 3.75 parts will make the stack wobbly.  Matching radial sizes also serve to give a rocket a cleaner visual appearance, and several adapter parts exist to allow transitions between radial sizes while maintaining an unbroken surface.

== Sizes ==

{| class = "wikitable sortable"
! rowspan = "2" | Radial size !! colspan = "3" | Fuel per m !! rowspan = "2" | Typical crash tolerance !! rowspan = "2" | Typical maximum temperature
|-
! Rocket fuel !! Liquid fuel !! Monopropellant
|-
| Tiny / 0.625m || 115 || n/a || 213 || 6 m/s || 2000°
|-
| Small / 1.25m || 213 || n/a || 438 || 6 m/s || 2000°
|-
| Large / 2.5m / Rockomax || 853 || n/a || 750 || 6 m/s || 2000°
|-
| Extra Large / 3.75m / Kerbodyne || 1925 || n/a || n/a || 6 m/s || 2000°
|-
| Mk1 || n/a || 213 || n/a || 20 m/s || 2000°
|-
| Mk2 || 213 || 213 || 213 || 40 m/s || 2200°
|-
| Mk3 || 1000 || 1000 || 1000 || 50 m/s || 2300°
|}

=== Rocket ===

The typical mass ratio for rocket fuel is 9.

* '''Tiny / 0.625m.''' Typically used for probes and nose electronics.
* '''Small / 1.25m.''' The most common size, and the primary size available at the beginning of the game, and about the same relative size to kerbals as the Redstone's tanks to humans.
* (DLC) '''Medium / 1.875m.''' This size is based on the Russian R-7 rocket family and the American Gemini program.
* '''Large / 2.5m / Rockomax.''' This size is about the same relative size to kerbals as the Atlas V or Falcon 9's tanks to humans.
* '''Extra Large / 3.75m / Kerbodyne.''' Styled after NASA's real-world [[w:Space Launch System|Space Launch System]], which uses Rocketdyne [[w:Space Shuttle main engine|RS-25]] and [[w:RL10|RL10]] engines.
* (DLC) '''Huge / 5m / Kerbodyne S4.''' This is styled after the Saturn V rocket used in the Apollo program. It is notable for not having ready-made engines of this size; the player is supposed to assemble custom engine clusters to move Huge rockets.

=== Spaceplane ===

Spaceplane parts may carry either rocket fuel or liquid fuel.  Compared to rocket parts they tend to have a poorer mass ratio (usually about 8), but better crash tolerance and maximum temperature.

* '''Mk1.''' Like the 1.25m rocket size, this size is a cylinder. All inline air intakes are of this size, but there are no rocket fuel tanks.
* '''Mk2.''' With its side chines, this spaceplane size is reminiscent of the real-world [[wikipedia:Lockheed SR-71 Blackbird|Lockheed SR-71 Blackbird]]. It is between the 1.25m and 2.5m sizes in cross-sectional area. These parts feature a small amount of lift.
* '''Mk3.''' Reminiscent of the real-world [[wikipedia:Space Shuttle|Space Shuttle]]. The cross-sectional area is similar to the 3.75m rocket size, that is, two Mk3 tanks stacked and then offset into each other will stack seamlessly with a 3.75 meter tank.

=== Adapters ===

* 1:1 parts between the same size are not shown.
* Note that all parts can be reversed so a nosecone can serve as a tail and vice versa.
* Fairings (Airstream Protective Shells) can be placed inline and thus serve as adapters as well as nosecones.

{| class = "wikitable"
! colspan = "2" rowspan = "2" | !! colspan = "7" | Fore size
|-
! Nose !! Tiny !! Small, Mk1 !! Mk 2 !! Large !! Mk 3 !! Extra Large
|-
! rowspan = "7" | Aft size
! Tail
| style="background-color: #bfbfbf;" |
| 
| [[Tail Connector A]]<br/>[[Tail Connector B]]
|
|
| [[Mk3 Cargo Ramp]]
| 
|-
! Tiny
| [[Small Nose Cone]]<br/>[[CH-J3 Fly-By-Wire Avionics Hub]]<br/>[[Stayputnik Mk. 1]]
| style="background-color: #bfbfbf;" |
| 
| 
| 
|
|
|-
! Small, Mk1
| [[Advanced Nose Cone - Type A]]<br/>[[Advanced Nose Cone - Type B]]<br/>[[AE-FF1 Airstream Protective Shell (1.25m)]]<br/>[[Aerodynamic Nose Cone]]<br/>{{Mark|crew}} [[Mk1 Cockpit]]
| [[FL-A10 Adapter]]<br/>[[FL-A5 Adapter]]<br/>{{Mark|fuelu}} [[NCS Adapter]]<br/>{{Mark|crew}} [[Mk1 Command Pod]]
| style="background-color: #bfbfbf;" | [[TVR-200 Stack Bi-Coupler]] (2)<br/>[[TVR-1180C Mk1 Stack Tri-Coupler]] (3)<br/>[[TVR-2160C Mk2 Stack Quad-Coupler]] (4)
| {{Mark|fuelu}} [[Mk2 Bicoupler]] (2)
| [[Rockomax Brand Adapter 02]]<br/>[[TVR-200L Stack Bi-Adapter]] (2)<br/>[[TVR-300L Stack Tri-Adapter]] (3)<br/>[[TVR-400L Stack Quad-Adapter]] (4)
| 
|
|-
! Mk2
| {{Mark|crew}} [[Mk2 Cockpit]]
| 
| {{Mark|fuelu}} [[Mk2 to 1.25m Adapter]]<br/> {{Mark|fuelu}} [[Mk2 to 1.25m Adapter Long]]
| style="background-color: #bfbfbf;" |
| 
|
|
|-
! Large
| [[AE-FF2 Airstream Protective Shell (2.5m)]]<br/>[[Protective Rocket Nose Cone Mk7]]
| 
| {{Mark|fuelu}} [[C7 Brand Adapter - 2.5m to 1.25m]]<br/>{{Mark|fuelu}} [[C7 Brand Adapter Slanted - 2.5m to 1.25m]]<br/>[[Rockomax Brand Adapter]]<br/>{{Mark|crew}} [[Mk1-2 Command Pod]]<br/>{{Mark|crew}} [[PPD-12 Cupola Module]]
| {{Mark|fuelu}} [[2.5m to Mk2 Adapter]]
| style="background-color: #bfbfbf;" |
|
|
|-
! Mk3
|  
| 
| {{Mark|crew}} [[Mk3 Cockpit]]
| {{Mark|fuelu}} [[Mk3 to Mk2 Adapter]]
| {{Mark|fuelu}} [[Mk3 to 2.5m Adapter]]<br/>{{Mark|fuelu}} [[Mk3 to 2.5m Adapter Slanted]]
| style="background-color: #bfbfbf;" |
| 
|-
! Extra Large
| [[AE-FF3 Airstream Protective Shell (3.75m)]]
| 
| 
| 
| [[Kerbodyne ADTP-2-3]]
| {{Mark|fuelu}} [[Mk3 to 3.75m Adapter]]
| style="background-color: #bfbfbf;" |
|}

== Assets ==
When creating assets, the correct diameter for a desired model can be found in the table below.  The "meter scale" refers to the actual model's diameter, which is then typically scaled up via the default [[CFG File Documentation#Asset Parameters|rescaleFactor]] of 1.25, to give the "actual" in-game diameter.  Size scale is used to denote the standard when selecting a [[CFG File Documentation#Node Definitions|node size]].

{| class="wikitable center"
|+ Conversion table between the different definitions
! Name
! Size scale
! Meter scale
! Actual size
! Example
|-
| {{Radial Size|t}}
| 0
| 0.5&nbsp;m
| 0.625&nbsp;m
| [[Rockomax 48-7S]]
|-
| {{Radial Size|s}}
| 1
| 1&nbsp;m
| 1.25&nbsp;m
| [[LV-T30 Liquid Fuel Engine]]
|-
| {{Radial Size|l}}
| 2
| 2&nbsp;m
| 2.5&nbsp;m
| [[Rockomax "Mainsail" Liquid Engine]]
|- 
| {{Radial Size|xl}}
| 3 
| 3&nbsp;m
| 3.75&nbsp;m

|[[Kerbodyne KR-2L Advanced Engine]]
|}

As a special radial size ''{{Radial Size|r}}'' appears. Parts like [[Rockomax 24-77]] so lack general metric counterparts as to eliminate confusion.

Non-cylindrical sizes named “Mk2”, and “Mk3” exist and are used by fuselage parts intended for [[spaceplane]]s.

== Additional sizes ==
Several [[addon]]s add additional, usually larger, radial sizes which are roughly following the stock size scale. There are up to 9 meter parts in the B9 Aerospace mod and mods like Tweakscale can scale parts more freely.

Two new official radial sizes were introduced in the DLC Making History: the Medium / 1.875 m and the Huge / 5 m, along with the parts that use them.