From Kerbal Space Program Wiki
Jump to: navigation, search

Kerbisynchronous Equatorial Orbit (or KEO for short) is the stationary orbit of the planet Kerbin, a very useful orbit for satellites. A spacecraft on this orbit will appear stationary when viewed from the surface. This can be useful when establishing a wireless connection between the craft and a structure on the surface, but it also makes observation of a certain spot on the surface easy. To achieve this orbit, the craft must have a/an:

Semi-Major Axis 3 463 334.06 m
Orbital Altitude 2 863 334.06 m
Orbital Speed 1 009.81 m/s
Orbital Period 1 Kerbin Sidereal Day (5h 59m 9.425s)

When fine-tuning the position over KSC, remember that lower orbits move at higher velocities and higher orbits move at lower velocities. This means circularizing the orbit just below the 2 863 334.06 m mark will cause the craft to move "East" relative to Kerbin's surface, and circularizing just above with will move the craft "West" relative to the surface.

Maneuver planning

The basic maneuver plan for reaching this orbit is to first achieve a low Kerbin orbit (LKO) and then perform two maneuvers to execute a Hohmann transfer. The first one, called the periapsis maneuver, is raising the apoapsis to the required altitude for a synchronous orbit. This places the spacecraft on a kerbisynchronous transfer orbit (KTO). The second one is at the apoapsis.

Depending on the required orbit the second burn also includes nearly all of the plane change to reduce the equatorial inclination to zero. For stationary orbits the periapsis maneuver should be executed when crossing the equatorial plane. Since the Kerbal Space Center is on the equator, the timing and trigonometry may be skipped.

The following are instantaneous impulse calculations for equatorial low energy orbits, and therefore the real maneuvers will always be somewhat more than these values.

LKO altitude Periapsis Apoapsis Total
70 km 676.6 m/s 434.9 m/s 1111.5 m/s
90 km 659.6 m/s 427.8 m/s 1087.4 m/s
100 km 651.5 m/s 424.3 m/s 1075.8 m/s
120 km 635.5 m/s 417.4 m/s 1052.9 m/s
150 km 612.7 m/s 407.3 m/s 1020.0 m/s
200 km 577.4 m/s 391.3 m/s 968.7 m/s
300 km 515.3 m/s 361.3 m/s 876.6 m/s

For direct launches, transfers from the lowest orbits will be more efficient because they require less delta-v to reach from the surface of Kerbin. Higher LEOs may be preferable if the spacecraft is visiting a tug or space station and requires altitude above the atmosphere to execute a rendezvous. These maneuver plans may also be useful for one who wishes to boost a large space station assembled in LKO to KEO (keep in mind that the craft may not have the thrust to make burns very efficient).

Other celestial bodies

In theory those orbits also exists for other celestial bodies, but may be outside the sphere of influence.

See also