|Jool as seen from orbit.|
|Planet of Kerbol|
|Semi-major axis||68 773 560 320 m [Note 1]|
|Apoapsis||72 212 238 387 m [Note 1]|
|Periapsis||65 334 882 253 m [Note 1]|
|Orbital inclination||1.304 °|
|Argument of periapsis||0 °|
|Longitude of the ascending node||52 °|
|Mean anomaly||0.1 rad (at 0s UT)|
|Sidereal orbital period||104 661 432 s|
|4 845 d 2 h 37 m 12.1 s|
|Synodic orbital period||10090901.7 s|
|Orbital Velocity||3 927 to 4 341 m/s|
|Equatorial radius||6 000 000 m|
|Surface area||4.5238934×1014 m2|
|Standard gravitational parameter||2.8252800×1014 m3/s2|
|Density||4 678.7834 kg/m3|
|Surface gravity||7.85 m/s2 (0.8 g)|
|Escape velocity||9 704.43 m/s|
|Sidereal rotation period||36 000.000 s|
|1 d 4 h 0 m 0 s|
|Solar day||36 012.387 s|
|1 d 4 h 0 m 12.4 s|
|Sidereal rotational velocity||1 047.2 m/s|
|Synchronous orbit||15 010.46 km|
|Sphere of influence||2.4559852×109 m[Note 1]|
|Atmosphere present||✓ Yes|
|Atmospheric Pressure||1 519.88 kPa|
|Scale height||10000 m|
|Atmospheric height||138 155.11 m|
|Temperaturemin||-86.13 °C 187.02 K|
|Temperaturemax||976.55 °C 1249.7 K|
|Oxygen present||× No|
Jool is a gas giant and the sixth planet of the Kerbol star system. It is the Jupiter analog for Kerbal Space Program. Aside from Kerbol, Jool has the largest diameter and greatest mass of all celestial bodies. While its distance from Kerbin makes it difficult to reach, it is one of the most appealing targets for missions due to its large and complex system of five moons: Laythe, Vall, Tylo, Bop, and Pol. It was possible to land and plant flags on Jool before v0.23. What happens with 0.23 is the craft won't stop at an altitude of 0, instead it continues descending until it get to -250 m. At this point anything that hits this altitude at any speed will be completely destroyed.
|“|| Jool is particularly known for being a rather large, predominantly green planet. Kerbalkind has longed to visit it since it was first spotted in the sky. Philosophers reason that the swirling green planet must be a really nice place to visit, on account of its wholesome coloration.
If you look at Jool through a telescope, it is fuzzy.
— Kerbal Astronomical Society
Although Jool has a radius ten times greater than Kerbin, its atmosphere begins just twice as high (138.2 km). It is extremely dense, well suited for aerobraking from a high-speed interplanetary intercept. Orbiting just outside the atmosphere will give a period of 94.74 minutes, and an orbital speed of 6,785 m/s. Typically an altitude lower than 100 km is not needed for aerobraking, and it may be wise to stay in the upper atmosphere because a bug can occur causing the ship to spontaneously explode or glitch out Kerbals on EVA.
In general, the atmospheric pressure on Jool at an altitude expressed in meters is:
Closer to the surface, the physics of the game start to break down. Due to its extremely thick atmosphere, terminal speed is so low that lighter spacecraft will not even need parachutes or retrorockets. It was possible to land on its solid surface though spacecraft were inevitably and invariably devoured by the Kraken before 0.23. The craft can descend below the surface, but the parts will explode once they are 250 m below the surface. The message "... collided with Cloud" will be displayed in the mission summary. The game may glitch out and corrupt the save.
If a kerbonaut is put on EVA, he will not be destroyed, making one-way sacrificial landings possible. However, as seen near the end of this video, the kerbonaut will start to glitch out and shake uncontrollably. This only happens on 4× time warp. The game will later glitch and the Hell Kraken will strike. Unless you restart the game, Kerbin's atmosphere will be missing but it is unknown if this still happens.
This glitch, while most common on Jool, is not unique to Jool, and can even be experienced on Kerbin in extreme situations; for example, going on EVA from a high speed spaceplane as it takes off can occasionally cause this, or it can even, although much more rarely, happen in less extreme situations as simple as sliding slowly on the Mun. If you do experience this outside of Jool, it is very difficult to replicate, which is why recordings of this are so rare.
|Rotational/Inertial transition||1 000 000 m|
|5×||138 155 m (above the atmosphere)|
|10×||138 155 m (above the atmosphere)|
|50×||138 155 m (above the atmosphere)|
|100×||150 000 m|
|1 000×||300 000 m|
|10 000×||600 000 m|
|100 000×||1 200 000 m|
Jool has five natural satellites, each with an orbit well-aligned with Jool's orbital plane:
Laythe, Vall, and Tylo are in a Laplace resonance, with orbital periods of 1:2:4 respectively. Despite the fact that the moons can easily eclipse both each other and Jool, they do not.
Synchronous Orbits around any of the Joolian moons are impossible, as they all lie outside the Sphere of Influence of the moons, as is common with tidally locked bodies.
- → See also: Images of Jool
- Jool has roughly the same equatorial radius as the planets Earth and Venus.
- The sunsets and sunrises on Jool are a shade of yellowish brown.
- Like Jool's moons, Jupiter's three nearest moons, Io, Europa, and Ganymede, have a Laplace resonance of 1:2:4.
- Jool, Laythe and Tylo all have a surface gravity of 7.85 m/s² (≃ 0.8 g)
- The green gas which composes Jool could be chlorine.
- The barometric, gravitational and temperature measurements taken as close to 0 meters altitude are roughly 14.9785 atm, 0.785 m/s2, 989.45 °C, respectively.
- Despite not having a surface, the game files that contain what the Kerbals say in the different reports/observations (ScienceDefs.cfg) also contains some reports while landed on the surface of Jool.
- “Kerbal Space Program: Planting a Flag on Jool” by Dahud Lefthanded in version 0.20
- Added a new, more distant moon named Pol.
- Initial Release