Synchronous orbit/es

Una animación distorsionada del tiempo de un pequeño satélite en órbita sincrónica alrededor de Kerbin.

Una órbita sincrónica es una órbita donde el período orbital es igual a la velocidad de rotación del cuerpo orbitado. La excentricidad y la inclinación no están unidas a valores específicos, aunque para ser sincrónicas, la órbita no debe cruzarse con la atmósfera o la superficie del cuerpo orbitado, lo que provoca el cambio de la órbita. Los satélites en órbitas sincrónicas tienen una pista de tierra que forma un analema.

¡Importante! Debe coincidir su período orbital con el período de rotación sideral no con el día solar. Por lo tanto, para Kerbin serán 5h 59m 9.425s en lugar de 6h lo que mucha gente busca.

Órbitas estacionarias

Órbitas estacionarias son un tipo especial de órbita sincrónica. Su inclinación de 0 ° y su excentricidad de 0 hacen que su trayectoria en el suelo sea solo un punto: un satélite en esta órbita no tiene movimiento en relación con la superficie del cuerpo. Como es imposible obtener todos los valores orbitales exactos para una órbita estacionaria, los satélites en órbitas estacionarias forman pequeños analematos.

Algunos cuerpos celestes no permiten la órbita síncrona debido a que la altitud requerida a la órbita de forma sincrónica está más allá de la esfera del cuerpo de influencia. La lenta rotación del cuerpo provoca este efecto: una gran altura es necesaria para permitir un periodo orbital tan largo. Las lunas bloqueadas tidalmente tampoco tienen posibilidades de órbita síncrona debido a su rotación lenta. Moho es el único planeta sin posibilidades para que una nave alcance una órbita sincrónica debido a su período de rotación muy lento; Moho completa aproximadamente dos rotaciones durante el tiempo que tarda un objeto en la órbita más alta posible en completar una revolución.

Orbitas semi-sincrónicas y similares.

When the orbital period is half as long as the rotational period, the orbit is usually described as semi-synchronous. It is possible to calculate the semi-major axis of a semi-synchronous orbit using Kepler's third law of planetary motion. With the knowledge about the semi-major axis of a synchronous orbit and the ratio between the two orbits:

$a_{\frac {1}{f}}={\frac {1}{\sqrt[{3}]{f^{2}}}}\cdot a_{1}$

The fraction f is the quotient of the period of the synchronous orbit (a₁) and second orbit (a_1/f). When the second orbit is a semi-synchronous orbit this quotient is 2:

$a_{\frac {1}{2}}={\frac {1}{\sqrt[{3}]{2^{2}}}}\cdot a_{1}={\frac {1}{\sqrt[{3}]{4}}}\cdot a_{1}$

An orbit where the orbital period is lower than the rotational period has some advantages, as some bodies don't allow synchronous orbits but opportunities for semi-synchronous orbits.

When dropping numerous payloads that should land nearby each other, the orbit should be an integer multiple of the celestial body's sidereal day. This way, the body stays the same relative to the orbit and has the same descent route, if each payload is detached at the same point in the orbit (e.g. apoapsis). The inverse factor f (= 1/f) defines how many days are between two detachments. For example, a super-synchronous orbit has f=1/2 so a payload could be dropped every two sidereal days or, when orbiting Kerbin, one every twelve hours.

An example of a semi-synchronous orbit for real world scientific applications is a Molniya orbit.

Sun-synchronous orbit

→ Ver también: Sun-synchronous orbit on Wikipedia

In the real world, there exists a sun-synchronous orbit. It's important to note that, although the name implies it, the orbit is not synchronous around the Sun. Instead, it describes an orbit around Earth which itself rotates, such that it appears the orbiting object is motionless relative to the Sun. Since it requires objects to have uneven gravitational fields, it is impossible to simulate in KSP.

Molniya orbit

A Molniya orbit is a semi-synchronous, highly elliptical orbit. The eccentricity should be as high as the central body permits. A three-satellite constellation in Molniya orbits can provide constant coverage to the high attitude regions. To set up such constellation, the mean anomalies of these three satellites should be spaced out by $120^{\circ }$ or ${\frac {2\pi }{3}}$. The longitudes of the ascending nodes can also be spaced out by $120^{\circ }$ to make the clover appearance.

For Kerbin, that equate to 70k for PE, 3117k for AP, and around 63 degree inclination.

Advantages of synchronous orbits

One advantage of a synchronous orbit is that they allow dropping multiple payloads from one craft, because the orbit will periodically travel above the same point on the body's surface. Usually, the orbit has a large eccentricity so that the payload has to complete a minimal amount of maneuvers to reach the surface. In this case the payload is detached at the apoapsis and decelerated such that it lands on the celestial body. After the payload has successfully landed, the next payload can be dropped as soon as the craft reaches the apoapsis again.

Stationary orbits

Communication to a satellite in a stationary orbit is easier than if it was in another orbit, as the ground based antennae do not have to move to account for the satellite's motion relative to the orbited body.

Orbital altitudes and semi-major axes of Kerbal's major bodies

The following table contains the altitudes for circular, synchronous orbits around all of Kerbal's celestial bodies, even when the altitude resides outside the SOI. The altitudes are relative to the body's surface, while the semi-major axes are measured from the body's center.

Body	Synchronous orbit		Semi-synchronous orbit		Tidally locked
	Altitude	Semi-major axis	Altitude	Semi-major axis
Kerbol	1 508 045,29 km	1 769 645,29 km	853 206,67 km	1 114 806,67 km	–
Moho	18 173,17 km †	18 423,17 km †	11 355,87 km †	11 605,87 km †	No
Eve	10 328,47 km	11 028,47 km	6 247,50 km	6 947,50 km	No
Gilly	42,14 km	55,14 km	21,73 km	34,73 km	No
Kerbin	2 863,33 km	3 463,33 km	1 581,76 km	2 181,76 km	No
Mun	2 970,56 km †	3 170,56 km †	1 797,33 km	1 997,33 km	Sí
Minmus	357,94 km	417,94 km	203,29 km	263,29 km	No
Duna	2 880,00 km ‡	3 200,00 km	1 695,87 km	2 015,87 km	No
Ike	1 133,90 km †	1 263,90 km †	666,20 km	796,20 km	Sí
Dres	732,24 km	870,24 km	410,22 km	548,22 km	No
Jool	15 010,46 km	21 010,46 km	7 235,76 km	13 235,76 km	No
Laythe	4 686,32 km †	5 186,32 km †	2 767,18 km	3 267,18 km	Sí
Vall	3 593,20 km †	3 893,20 km †	2 152,56 km †	2 452,56 km †	Sí
Tylo	14 157,88 km †	14 757,88 km †	8 696,88 km	9 296,88 km	Sí
Bop	2 588,17 km †	2 653,17 km †	1 606,39 km †	1 671,39 km †	Sí
Pol	2 415,08 km †	2 459,08 km †	1 505,12 km †	1 549,12 km †	Sí
Eeloo	683,69 km	893,69 km	352,99 km	562,99 km	No

• † indicates that the altitude resides outside the SOI
• ‡ indicates that the altitude is the same as the orbit of another object

See also

• KEO, the stationary orbit around Kerbin
• Geosynchronous Orbit (Math), some math on how to calculate a synchronous orbit
• Synchronous orbit on Wikipedia
• Stationary orbit on Wikipedia
• Geostationary orbit on Wikipedia
• Geosynchronous orbit on Wikipedia