Difference between revisions of "Kerbin"

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(Added v0.21 changes to Kerbin.)
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Kerbin r0 1.png | An unmanned probe on escape trajectory, flying past Kerbin, Mün and Minmus
Kerbin r0 1.png | An unmanned probe on escape trajectory, flying past Kerbin, Mün and Minmus
KerbalPolar1.png | Kerbin's North Pole
KerbalPolar1.png | Kerbin's North Pole
http://i.imgur.com/Jnu8UGFh.jpg | The mountains west of KSC

Revision as of 13:14, 28 July 2013


Kerbin is the home planet of the Kerbals, the location of the Space Center, and the main focus of Kerbal Space Program. It is the Earth analog for the game. It has two moons, named Mün and Minmus.

Kerbin is the third planet in orbit around the star Kerbol. It is the third largest planet (after Jool and Eve) and the fourth largest celestial object around Kerbol (with Tylo, a moon of Jool, being slightly larger).

Reaching a stable orbit around Kerbin is one of the first milestones a player might achieve in the game. Achieving such an orbit with a fuel-optimal ascent[1] requires a delta-V of ≈4500 m/s,[2] the second largest of all celestial bodies with a solid surface after Eve. For many interplanetary missions, this represents over half of the flight's total delta-V requirement. This is also true of Earth-based interplanetary spaceflights, leading one observer to remark that:

If you can get your ship into orbit, you're halfway to anywhere.

Robert Heinlein, quoted on page 194 of A Step Farther Out by Jerry Pournelle


Topographical representation of Kerbin's surface as of .18.2. Click for high resolution. by Zeroignite

Kerbin has a roughly equal distribution of surface liquid water and solid land, with polar icecaps and scattered deserts. There are mountains exceeding 4 km in height, with the tallest peak being just under 4044 m in altitude.


Terrain model centered on one of Kerbin's most pronounced craters

Unlike other bodies in its system, Kerbin has few visible craters. This could be attributed to many causes. The environment would cause erosion of many geological features. Also due to its atmosphere, and large moon, fewer meteorites would make it to its surface. However, some geological formations would lead one to believe Kerbin has been subjected to violent collisions in the past. It has two features that appear to be impact craters, separated coincidentally by nearly 180 degrees. The least eroded, and presumably youngest, of the two (both are in excess of 100 km diameter) is located along the coastline. The uplift is easily visible as a series of islands and it has a central peak poking out of the water. The other, and older of the two, is located near the prime meridian in the northern hemisphere. It is more easily missed, but its uplift rims are visible and it has a central rebound peak.


Kerbin's atmosphere contains oxygen and extends to roughly 69,078 meters. Its atmosphere becomes exponentially less dense as altitude increases (with a scale height of 5 km).[3] In general, the atmospheric pressure on Kerbin, at an altitude expressed in meters, is:

The thickness of Kerbin's atmosphere makes it suitable for aerobraking and using parachutes, useful for saving on fuel when spacecraft return to Kerbin. Note that debris is not affected by air resistance above approximately 10 km, so spent stages may continue in a stable orbit even if they are going through thick atmosphere that would stop an active craft (0.19). Crafts will experience re entry and supersonic air effects as of 0.19. This however will not damage or burn it.

The following table gives approximation of terminal velocities at different Kerbin altitudes. These are also the velocities at which a ship should travel for a fuel-optimal ascent from Kerbin, given the game's model of atmospheric drag.[4]

Altitude (m) Velocity (m/s)
75 107
1000 114
2000 124
3000 136
4000 152
5000 169
6000 188
7000 209
8000 232
9000 256
10000 281
12500 348
15000 419
20000 566
32000 2250


A Stayputnik Orbiter

Geosynchronous orbit is achieved at an altitude of 0.00 m and a speed of Expression error: Unexpected < operator. m/s. From a 70 km low equatorial orbit, the periapsis maneuver requires 676.5 m/s and the apoapsis maneuver requires 434.9 m/s. A semi-synchronous orbit with an orbital period of 1/2 of Kerbin's rotation period (3 hours or 10800 seconds) is achieved at an altitude of 0.00 m with an orbital velocity of Expression error: Unexpected < operator. m/s.

The Hill Sphere (the radius around the planet at which moons are gravitationally stable) of Kerbin is 136 185km, or roughly 227 Kerbin radii.

Interplanetary Travel

From the lowest stable orbit around Kerbin (70 km), the amount of delta-V needed to reach the orbits of other celestials is as follows:

Body Delta-V
Mun ~860 m/s
Minmus ~930 m/s
Eve ~1033 m/s
Duna ~1060 m/s
Moho ~1676 m/s
Jool ~1915 m/s
Eeloo ~2100 m/s
KEO (comparison) ~1120 m/s

Reference Frames

Time warp Minimum Altitude
5× 70 000 m (above the atmosphere)
10× 70 000 m (above the atmosphere)
50× 70 000 m (above the atmosphere)
100× 120 000 m
1 000× 240 000 m
10 000× 480 000 m
100 000× 600 000 m


Spoiler: Spoiler images


  • Terrain revised to produce more detailed and interesting landforms.
  • Fixed ladders on the fuel tanks near the launchpad.
  • New mesh for the launchpad and area (no launchtower anymore).
  • New mesh for the runway, with lights and sloping edges for rovers.
  • Terrain overhaul: Entire planet redo. Deserts, darker and greener grass, islands, darker ocean/water, snow capped mountains. Looks more realistic.
  • Several Easter Eggs added.
  • Airport added to island off of KSC coastline. (Not a launching point)
  • Improved atmosphere visuals.
  • Much more varied and taller terrain added. Prior to this, some mountain ranges exceeded 600 m in height, but the tallest point was at an altitude of approximately 900 m.
  • Terrain overhaul, oceans became wet.
  • Atmosphere extended from ~34,500 m to ~69,000 m.
  • Initial Release


Kerbin's continents are derived from libnoise [6], though they have been increasingly modified with time.


  1. A fuel-optimal ascent is one which (a) minimizes velocity losses to gravity and atmospheric drag and (b) launches eastward (toward the 90 degree heading) to gain 174.5 m/s of orbital velocity for free, thanks to Kerbin's rotation.
  2. See this challenge on the forum and a popular Kerbin delta-V chart
  3. Forum thread 16000, "[KGSS] Examining Kerbin's atmosphere"
  4. http://forum.kerbalspaceprogram.com/showthread.php/6664-Mini-challenge-max-altitude-with-this-supplied-spacecraft?p=100912&viewfull=1#post100912
  5. http://forum.kerbalspaceprogram.com/entry.php/247-A-Brave-New-World
  6. http://libnoise.sourceforge.net/examples/complexplanet/