Difference between revisions of "Kerbin"

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m (Orbits: added KEO and its orbital period)
m (Removed possibly inaccurate, possibly misleading and misplaced claim "the second largest of all celestial bodies with a solid surface after Eve.")
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Kerbin is the third planet in [[orbit]] around the star [[Kerbol]]. It is the third largest [[celestial body]] around Kerbol after [[Jool]] and [[Eve]]. Jool's moon [[Tylo]] has the same radius of Kerbin but may be classified larger as the highest point on Tylo is about 5 km higher. Although the moon has only 80 % of Kerbin's mass.
 
Kerbin is the third planet in [[orbit]] around the star [[Kerbol]]. It is the third largest [[celestial body]] around Kerbol after [[Jool]] and [[Eve]]. Jool's moon [[Tylo]] has the same radius of Kerbin but may be classified larger as the highest point on Tylo is about 5 km higher. Although the moon 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. Doing so with a fuel-optimal ascent<ref>A fuel-optimal ascent is one which (a) minimizes velocity losses to gravity and [[atmosphere|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.</ref> requires a [[delta-V]] of ≈4500 m/s,<ref>See [http://forum.kerbalspaceprogram.com/showthread.php/24017-Least-delta-v-to-orbit this challenge on the forum] and a popular [http://i.imgur.com/CEZS1.png Kerbin delta-V chart]</ref> the second largest of all celestial bodies with a solid surface after [[Eve]]. Many interplanetary missions expend over half of their delta-V in reaching Kerbin orbit.  Many Earth-based interplanetary spaceflights also do so, leading one observer to remark:
+
Reaching a stable orbit around Kerbin is one of the first milestones a player might achieve in the game. Doing so with a fuel-optimal ascent<ref>A fuel-optimal ascent is one which (a) minimizes velocity losses to gravity and [[atmosphere|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.</ref> requires a [[delta-V]] of ≈4500 m/s,<ref>See [http://forum.kerbalspaceprogram.com/showthread.php/24017-Least-delta-v-to-orbit this challenge on the forum] and a popular [http://i.imgur.com/CEZS1.png Kerbin delta-V chart]</ref> Many interplanetary missions expend over half of their delta-V in reaching Kerbin orbit.  Many Earth-based interplanetary spaceflights also do so, leading one observer to remark:
 
{{Quote|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}}
 
{{Quote|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}}
  

Revision as of 19:54, 8 November 2013

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

  1. 1.0 1.1 1.2 1.3 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 around Kerbol after Jool and Eve. Jool's moon Tylo has the same radius of Kerbin but may be classified larger as the highest point on Tylo is about 5 km higher. Although the moon 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. Doing so with a fuel-optimal ascent[1] requires a delta-V of ≈4500 m/s,[2] Many interplanetary missions expend over half of their delta-V in reaching Kerbin orbit. Many Earth-based interplanetary spaceflights also do so, 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

Topography

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. Some of its mountains exceed 6 km in height, with the tallest peak being 6761 m in altitude. The lowest is almost 1.4 km deep and about 313  south-west of the Kerbal Space Center.

Craters

Terrain model centered on one of 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 reentry. Nevertheless, some geological formations indicate that bodies have violently collided with Kerbin: two planetary features appear to be impact craters that are coincidentally separated by nearly 180 degrees. The least eroded, and therefore presumably youngest, of the two (both are in excess of 100 km diameter) lies along the coastline. The uplift is easily visible as a series of islands, and the feature has a central peak that pokes up through the water. The other, and older 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 has a central rebound peak.

Atmosphere

Kerbin's atmosphere contains oxygen and extends to roughly 69,078 meters. Its atmosphere exponentially rarefies with altitude with a scale height of 5 km.[3] The atmospheric pressure on Kerbin at an altitude expressed in meters, generally is:

The thickness of Kerbin's atmosphere makes it suitable for aerobraking and using parachutes to save fuel during reentry and landing. Debris is not be above approximately 23 km: spent stages may continue in a stable orbit even if they are going through thick atmosphere that would stop an active craft (0.21.1[outdated]). Craft will experience harmless reentry and supersonic air effects as of 0.19.

The following table gives approximation of terminal velocities at different Kerbin altitudes, which are also the velocities at which a ship should travel for a fuel-optimal vertical ascent from Kerbin, given the game's model of atmospheric drag.[4] The optimal velocity after a gravity turn has been started is less than the corresponding value in the table. [5]

Altitude (m) Velocity (m/s)
75 100.8
1000 109.3
2000 119.3
3000 130.2
4000 142.2
5000 155.2
6000 169.4
7000 184.9
8000 201.8
9000 220.3
10000 240.5
12500 299.4
15000 372.8
20000 577.9
32000 1655.1

Orbits

→ See also: Kerbisynchronous equatorial orbit
File:Screenshot39.png
A Stayputnik Orbiter

KEO is a circular synchronous orbit is achieved at an altitude of 2 863.33 km, a speed of 1 009.81 m/s and takes 6 hours (or 1 Kerbin day) to complete. 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 ½ of Kerbin's rotation period (3 hours or 10800 seconds) is achieved at an altitude of 1 581.76 km with an orbital velocity of 1 272.28 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:

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
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: Spoiler images

Changes

0.21
  • Terrain revised to produce more detailed and interesting landforms.
0.19.1
  • Fixed ladders on the fuel tanks near the launchpad.
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.
  • Several Easter Eggs added.
  • 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 [7], though they have been increasingly modified with time.

Notes

  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://www.reddit.com/r/KerbalSpaceProgram/comments/1kov5z/a_handy_chart_i_made_for_the_most_efficient/cbrdvuo
  6. http://forum.kerbalspaceprogram.com/entry.php/247-A-Brave-New-World
  7. http://libnoise.sourceforge.net/examples/complexplanet/