An Orbital Rendezvous is a series of maneuvers which result in a craft achieving a stable condition of close proximity to a target object orbiting the same parent body.
In general, an orbital rendezvous involves two steps - encounter and velocity matching.
Possible usages of orbital rendezvous include:
- Docking two craft together
- Grabbing an asteroid with the Advanced Grabbing Unit
- Rescuing kerbonauts on EVA stranded in orbit
The process of creating an encounter with a target object requires the player to meet two conditions. The first is that the orbit of the craft must intersect the orbit of the target (this is usually tangential for efficiency). This can be from a lower orbit where you will be travelling at a slower velocity, or from a higher and faster orbit. The second is that both craft and target must be at the intersection at the same time.
Often only one craft does the orbital maneuvers and the other object is passive and does not change its orbit.
Once the craft is in close proximity to the target you must now bring your craft into the same orbital plane in a maneuver that also matches velocity with the target. When relative velocity is null, a more or less stable situation exists. The player can then EVA to the target, dock with the target (if craft and/or target are properly equipped), or perform any task which requires the craft to remain in close proximity to the target. Some situations make it simpler to match orbital planes first, then either play catchup or slow down till proximity is reached (2.2k or less for EVA from or to target, or to switch control between vessels using [ or]).
For low planetary orbits, it is easier to approach the target from a higher more elliptical orbit where you are initially in front of the target and your orbit slows your craft. For higher planetary orbits it is faster to approach from a lower orbit from behind. Your velocity will be slower but your orbital period will be shorter. Low planetary orbits take little time and allow many trial and error attempts. High orbits, especially solar orbits, mean days, months or years between passes, so planning is important. With practice, your craft can come from an oblique orbit at a vastly different velocity to intercept the target, changing plane and velocity in a single manoeuvre for a spectacular rendezvous!! Chasing asteroids, for example, or crash diving into a moon's SOI for ship to ship docking.
Several tutorials exist which can help the player learn the process of orbital rendezvous. As of version 1.0, there is also an ingame tutorial.
- Orbital Rendezvous
- Orbital Docking with the Kergena Target Vehicle
- A detailed discussion on how to meet objects in orbit, including how to synchronize orbits/phases
- In depth tutorial for an orbital rendezvous and docking by It's Just Rocket Science