# Difference between revisions of "Kerbin"

 Kerbin Kerbin as seen from orbit. Planet of Kerbol Orbital Characteristics Semi-major axis 13 599 840 256 m [Note 1] Apoapsis 13 599 840 256 m [Note 1] Periapsis 13 599 840 256 m [Note 1] Orbital eccentricity 0 Orbital inclination 0 ° Argument of periapsis 0 ° Longitude of the ascending node 0 ° Mean anomaly 3.14 rad (at 0s UT) Sidereal orbital period 9 203 545 s 426 d 0 h 32 m 24.6 s Synodic orbital period Not defined Orbital velocity 9 285 m/s Physical Characteristics Equatorial radius 600 000 m Equatorial circumference 3 769 911 m Surface area 4.5238934×1012 m2 Mass 5.2915158×1022 kg Standard gravitational parameter 3.5316000×1012 m3/s2 Density 58 484.090 kg/m3 Surface gravity 9.81 m/s2 (1 g) Escape velocity 3 431.03 m/s Sidereal rotation period 21 549.425 s 5 h 59 m 9.4 s Solar day 21 600.000 s 5 h 59 m 60 s Sidereal rotational velocity 174.94 m/s Synchronous orbit 2 863.33 km Sphere of influence 84 159 286 m [Note 1] Atmospheric Characteristics Atmosphere present ✓ Yes Atmospheric pressure 101.325 kPa 1 atm Atmospheric height 70 000 m 1.0×10-6 atm Temperaturemin -86.20 °C 186.95 K Temperaturemax 15 °C 288.15 K Oxygen present ✓ Yes Scientific multiplier Surface 0.3 Splashed 0.4 Lower atmosphere 0.7 Upper atmosphere 0.9 Near space 1 Outer space 1.5 Recovery 1 The distances are given from the bodies center, not from the surface (unlike ingame)

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

Kerbin is the third planet in orbit around the star Kerbol. It is the third largest celestial body that orbits Kerbol, following Jool and Eve. Jool's moon Tylo has the same radius of Kerbin, though it may be classified as larger, as the highest point on Tylo is about 5 km higher than the highest point on Kerbin. However, Tylo has only 80 % of Kerbin's mass.

Reaching a stable orbit around Kerbin is one of the first milestones a player might achieve in the game. With the introduction of version 1.0.3, attaining low Kerbin orbit requires a Δv of approximately 3400 m/s (vacuum), though the exact amount depends on the efficiency of the ascent profile and the aerodynamics of the launch vehicle and payload. The only planet that requires a higher Δv to attain orbit is Eve. Many interplanetary missions expend over half of their Δv in reaching Kerbin orbit. The velocity required to escape a body from a given altitude is always exactly the square root of two times the velocity of a circular orbit around the body at that height, leading one observer to remark:

 “ 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 ”

## In-game description

 “ A unique world, Kerbin has flat plains, soaring mountains and wide, blue oceans. Home to the Kerbals, it has just the right conditions to support a vast, seemingly undepletable population of the eager green creatures. Reaching a stable orbit around Kerbin is one of the first things budding space programs strive for. It is said that those who can get their ship into orbit are halfway to anywhere.'' ”

## Topography

Topographical representation of Kerbin's surface as of 0.18.2. Click for high resolution. by Zeroignite
Kerbal at Kerbin's highest peak

Kerbin has a roughly equal distribution of liquid surface water and solid land, with polar ice caps and scattered deserts. Some of its mountains exceed 6 km in height, with the tallest peak being 6764.1 m in altitude at the coordinates 46°20'17" E 61°35'53" N. The lowest point is almost 1.4 km deep and about 313° south-west of the Kerbal Space Center.

### Craters

Terrain model centered on Kerbin's most pronounced craters

Unlike other bodies in its system, Kerbin has few visible craters because its environment would erode craters from the few meteors that avoid the gravity or surface of its large moon and survive entry. Nevertheless, some geological formations indicate that bodies have violently collided with Kerbin: a planetary feature appears to be an impact crater, while a secondary rupture lies on the other side of the planet (made by the intense longitudinal, or P-wave earthquakes that ensue.) Both are in excess of 100 km diameter, and the main crater lies along the far-western coastline. The uplift is easily visible as a series of islands, and the feature has a central peak that pokes up through the water (also known as a rebound peak.) The other, and smaller of the two, is near the prime meridian in the northern hemisphere and is more easily missed, but its uplift rims are visible, and it also has a central rebound peak.

## Biomes

The biomes on Kerbin as of 0.90

Before 0.90 Kerbin was one of the few bodies with multiple Biomes, Kerbin was second only to the Mun in number of biomes it has. Following the 0.90 update all celestial bodies have biomes. Science experiments can be performed at all biomes, though Kerbin's low multipliers result in less impressive results than more distant worlds. Kerbin's biomes show a loose correlation with Earth's biomes and geographic features. Uniquely, Kerbin has 33 location biomes at KSC, these are comprised of each building and their props, the crawlerway, the flag, and KSC itself; these give a jumpstart to gathering Science points in Career mode. With 1.2 Kerbin had destinct Northern and Southern Ice Shelf added

Kerbin biome map as of 1.2

### List of biomes

• Ice Caps
• Northern Ice Shelf
• Southern Ice Shelf
• Tundra
• Highlands
• Mountains
• Grasslands
• Deserts
• Shores
• Water

KSC mini biomes
• Baikerbanur
• Island Airfield
• Woomerang Launch Site
• KSC
• Astronaut Complex
• AstronautComplex Grounds
• Crawlerway
• FlagPole
• Mission Control
• MissionControl Grounds
• R&D
• R&D Central Building
• R&D Corner Lab
• R&D Main Building
• R&D Observatory
• R&D Side Lab
• R&D Small Lab
• R&D Tanks
• R&D Wind Tunnel
• Runway
• SPH
• SPH Main Building
• SPH Round Tank
• SPH Tanks
• SPH Water Tower
• Tracking Station
• Tracking Station Dish East
• Tracking Station Dish North
• Tracking Station Dish South
• Tracking Station Hub
• VAB
• VAB Main Building
• VAB Pod Memorial
• VAB Round Tank
• VAB South Complex(only exist when VAB is Level 2)
• VAB Tanks

## Atmosphere

Temperature and pressure of Kerbin's atmosphere as a function of altitude.
Drag force is proportionate to atmospheric density.

Kerbin has a thick, warm atmosphere with a mass of approximately 4.7×1016 kilograms, a sea level pressure of 101.325 kilopascals (1 atmosphere), and a depth of 70,000 meters. The atmosphere contains oxygen and can support combustion. Kerbin is the only planet or moon with a breathable atmosphere.

The average molecular weight of Kerbin air is 28.9644 g/mol, and its adiabatic index is 1.40. This suggests that Kerbin likely has an earthlike nitrogen-oxygen atmosphere. The air-fuel ratio of jet engines operating in Kerbin's atmosphere suggests that the percentage of oxygen is similar to that of Earth's atmosphere (about 21 %).

Like all other atmospheres in the game, Kerbin's atmosphere fades exponentially as altitude increases. The scale height varies with altitude, which is a change from pre-1.0 versions of the game. The pressure-altitude profile is globally constant and independent of temperature. The following table gives the atmospheric pressure and density at various altitudes above sea level. Temperature-altitude profile is not globally constant, therefore neither is the density-altitude profile, however variance is slight.

Altitude (m) Pressure (Pa) Pressure (atm) Density (kg/m^3)
0 101 325 1.000 1.225
2 500 69 015 0.681 0.898
5 000 45 625 0.450 0.642
7 500 29 126 0.287 0.446
10 000 17 934 0.177 0.288
15 000 6 726 0.066 0.108
20 000 2 549 0.025 0.040
25 000 993.6 0.010 0.015
30 000 404.1 0.004 0.006
40 000 79.77 0.001 0.001
50 000 15.56 0.000 0.000
60 000 2.387 0.000 0.000
70 000 0.000 0.000 0.000

Kerbin's atmosphere can be divided into three major layers, comparable to Earth's troposphere, stratosphere and mesosphere. In the lower and upper layers, temperature decreases as altitude increases, while the middle layer spans of a region of increasing temperature. The boundary between the lower and middle layers occurs at an altitude of about 16 km at low latitudes, and about 9 km at high latitudes. The boundary between the middle and upper layer occurs at an altitude of about 38 km.

Air temperatures vary with latitude and time of day. At the equator, sea level temperatures vary between a nighttime low of 32 °C and a daytime high of 41 °C. At the poles, the temperature varies between -35 °C and -30 °C. The globally averaged sea level temperature is approximately 13.5 °C. Since Kerbin has no axial tilt, there are no seasonal temperature variations.

The atmosphere of Kerbin is patterned after Earth's U.S. Standard Atmosphere (USSA), though with the vertical height scale reduced by 20 %. Kerbin's "base" temperature and atmospheric pressure can be very closely approximated using the equations of the USSA, where Kerbin's geometric altitude, z, is converted to Earth's geopotential altitude, h, using the equation:

${\displaystyle h={\frac {7963.75\cdot z}{6371+1.25\cdot z}}}$.

The base temperature is the temperature less latitudinal and diurnal adjustments; it is roughly equal to the global mean temperature.

### Atmospheric flight

The thickness of Kerbin's atmosphere makes it well suited for aerobraking from a high-speed interplanetary intercept. The periapsis altitude required for a successful aerocapture depends on the spacecraft's drag characteristics, its approach velocity, and the desired apoapsis of the resulting orbit. For most conditions, a periapsis altitude of about 30 km should result in an aerocapture.

Parachutes perform well in Kerbin's dense air, allowing landings on both land and water to be accomplished without the aid of propulsion.

Because of the presence of oxygen, jet engines can operate in Kerbin's atmosphere. And, together with it's thickness, Kerbin's atmosphere is ideally suited for aircraft flight.

A modified Orbiter 1A prepares to dock with a space station.

## Orbits

A Sputnik-derived satellite

A synchronous orbit is achieved with a semi-major axis of 3 463.33 km. Kerbisynchronous Equatorial Orbit (KEO) has a circularly uniform altitude of 2 863.33 km and a speed of 1 009.81 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 synchronous Tundra orbit with eccentricity of 0.2864 and inclination of 63 degrees is achieved at 3799.7/1937.7 km. Inclination correlates with eccentricity: higher inclined orbits need to be more eccentric, while equatorial orbit may be circular, essentially KEO.

A semi-synchronous orbit with an orbital period of ½ of Kerbin's rotation period (2 h 59 m&nbsp34.7 s or 10774.7  seconds) is achieved at an altitude of 1 581.76 km with an orbital velocity of 1 272.28 m/s. A semi-synchronous Molniya orbit with eccentricity of 0.742[1] and inclination of 63 degrees can not be achieved, because the periapsis would be 36 km below the ground. The highest eccentricity of a semi-synchronous orbit with a periapsis of 70 km is 0.693 with an apoapsis of 3100.36 km.

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

## Delta-V Requirements

From the lowest possible stable orbit around Kerbin (70 km), the nominal amount of delta-V needed to reach other destinations is:

Body Δv
Mun ~860 m/s
Minmus ~930 m/s
Eve ~1033 m/s
Duna ~1060 m/s
Geostationary Orbit ~1120 m/s
Moho ~1676 m/s
Jool ~1915 m/s
Eeloo ~2100 m/s
Kerbol escape ~2740 m/s

## Reference frames

Time warp Minimum Altitude
Any
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

## Gallery

Spoiler: Easter Eggs Are Shown

## Changes

1.2
1.0.5
• Kerbin actually spun up to have a 6 h synodic day.
0.90
• Updated biomes.
0.22
0.21
• Terrain revised to produce more detailed and interesting landforms.
0.19.1
0.19
• New mesh for the launchpad and area (no launchtower anymore).
• New mesh for the runway, with lights and sloping edges for rovers.
0.18
• Terrain overhaul: Entire planet redo. Deserts, darker and greener grass, islands, darker ocean/water, snow capped mountains. Looks more realistic.
• Airport added to island off of KSC coastline. (Not a launching point)
0.17
• Improved atmosphere visuals.
0.15
0.14.2
• 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.
0.12
0.11
• Terrain overhaul, oceans became wet.
0.10.1
• Atmosphere extended from ~34,500 m to ~69,000 m.
0.7.3
• Initial Release

## Trivia

Kerbin's continents are derived from libnoise[3], a coherent noise generating library, though they have been increasingly modified with time.

### Real-world comparison

Kerbin has approximately 1/113th the mass and a 1/10th the radius of Earth.

## Notes

1. Some Major Orbit Types” uses that, the Wikipedia article mentions 0.74105, and “Orbital Parameters of a Molniya Orbit” uses 0.72.
2. http://forum.kerbalspaceprogram.com/entry.php/247-A-Brave-New-World
3. http://libnoise.sourceforge.net/examples/complexplanet/