Kerbin

Kerbin is the home planet of the Kerbals and the location of United Kerbin, Kerbal Union, Kerbal Republics, Kerbal Kaliphate, Empire of Kerbin and Umbra Space Industries.
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.
==Topography==
Kerbin has a roughly equal distribution of surface liquid water and solid land, with polar icecaps 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===
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==
Kerbin's biomes show a loose correlation with Earth's biomes and geographic features. 
===List of Biomes===
*Ice Caps
*Northern Ice Shelf
*Southern Ice Shelf
*Tundra
*Highlands
*Mountains
*Grasslands
*Deserts
*Badlands
*Shores
*Water
==Atmosphere==
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%).
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.
===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.
==Orbits==
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 34.7 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 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.
==Trivia==
Kerbin has approximately 1/113th the mass and a 1/10th the radius of Earth.