Difference between revisions of "Orbital rendezvous"

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(An extremely in-depth guide to an orbital rendezvous and docking)
 
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In KSP, one of the hardest things to doing without leaving Kerbin's SOI is a docking procedure. It can be a very complicated procedure but once you understand it, you'll learn it's not as hard as it seems. Just, remember to quicksave often. (f5 to save and f9 to load last quicksave)
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== Designing a rocket ==
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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.
  
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A very important part of everything in KSP is of course the rocket, if you are at this page and don't know how to build a rocket capable of doing this, you should probably watch  some videos, read some tutorials, and re-visit this page in a few weeks. But there are some things that are necessary for docking which should always have on your rocket:
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In general, an orbital rendezvous involves two steps - '''encounter''' and '''velocity matching'''.
  
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-docking ports, A docking without a docking port is usually pretty hard to accomplish. A docking port is required on ALL ships to be attached. I usually use 2 around the center perfectly opposite each other to balance themselves out but it is also common to put multiple ports for the attachment of multiple pieces and/or shuttlecraft (The coolest thing you can have on a space station). This is only useful for complex stations though so don't worry about that now.
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== Usages ==
  
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-solar panels, don't wanna run out of power and explode? well you'll need solar panels. Alot of power is not usually required so if you just want to not die you can use OX-Stat Photovoltaic Panels or small unfolding ones, However, if you want your station to look super cool, use the gigantors! they're awesome (but heavy) ***Note! if you put gigantors just above a docking port and unfold it then they will hit any ship docked there! it is important not to put solar panels on the same side as the docking ports!
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Possible usages of orbital rendezvous include:
  
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-lights, if you have alot of power then lights can really help you out, you have a 50/50 chance of docking without any sunlight whatsoever so if you can afford it,lights may be a good investment.
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* [[Docking]] two craft together
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** Assembling a [[space station]]
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** Interplanetary craft
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** In-orbit refuelling
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** Transfering a more experienced [[Scientist]] to an orbital [[Mobile Processing Lab MPL-LG-2]]
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* Grabbing an [[asteroid]] with the [[Advanced Grabbing Unit]]
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* Rescuing [[Kerbonaut|kerbonauts]] on [[EVA]] stranded in orbit
  
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-RCS,A reaction control system is required for docking, to move your ship in place and to get it to the other port, Remember to conserve, docking can take alot of monopropellant so if you're using an RCS to stabilize your ship keep track of your reserves One time I was ready to dock and I realized I had no RCS system, don't be like me.
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====[[Encounter]]====
  
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== Completing the rendezvous ==
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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.   
  
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It looks intimidating, but just read through, re-read whatever you have a hard time understanding, quicksave often, and I'm sure you'll be fine. it's a good idea to read this as you do the procedure, notjust read this all the way then take it from the top.
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Often only one craft does the orbital maneuvers and the other object is passive and does not change its orbit.
  
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Assuming you've gotten yourself into a stable orbit somewhat the same size as your target's, it's ready to pick a meeting place. First click the target and select "Set target", this will cause a whole variety of symbols to appear. such as your target's Ap and Pe, the Ascending and Descending nodes, your next encounter, and the next encounter after that. If your target is at an inclined orbit then add a maneuver at either the Ascending or Descending nodes and move the purple symbols (which are normal and anti-normal) until your orbits are within a 5-10° inclination of each other. All you have to do now is add a maneuver somewhere on your orbit and fiddle around with it until either the purple arrows or orange arrows come within 20km of each other. You can tell how close they are by hovering over them. A docking can really be done with them as far as 40 or 50 but I never settle for more than 15 myself. A good way of doing this is often to add a maneuver at the orange arrow on your orbit and burn prograde until either sets of arrows match up, and if that doesn't work, do the same with the purple arrow. These may not work at all, and you might need to just add burns at random places until you meet the target. Every meeting can be done with only 1 burn, adding another might just decrease your accuracy so try not to use 2 or more. Another rule of thumb is to keep the fuel use under 500m/s, remember, all the fuel your using now you'll need to use again to stop (relative to the target) so keep it as low as possible.
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====Velocity Matching====
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Once you have completed the burn and are now on your way to the meeting point you have to get ready to do some maneuvers so you don't fly right past the target. once you get close to the target your speed indicator will automatically switch to show your speed relative to the target. You may note that once you get within ~2 minutes of the meeting your speed relative to the target is very close to the speed you needed to set the rendezvous in the first place. Once you are between 50-70 seconds of the meeting make sure your speed is measured relative to the target (It will be displayed just above the Nav Ball as normal) and burn retrograde until your speed is at about 100m/s. As you burn you will notice that the meeting point moves away from you, and the distance displayed by it is changing. They will either get closer together or farther apart, if they start out getting closer, they will soon begin to go farther apart. As you burn more and more, and the meeting gets farther and farther away, the change in distance will accelerate very rapidly. if you burn for to long the meeting distance (The distance between you and the target at the next encounter, not the distance between you and the encounter, although that increases rapidly as well) can become extremely large, so if the distance between you and the meeting point are about 2 minutes away, stop burning and wait to get closer to prevent the meeting distance growing to fast. Continue this until you are within 3 km of your target. At this point you should have around 0.0 - 1.0m/s speed relative to the target. Now it's time to go manual. You will no longer be needing the map view for this, so go into the staging view and point at your target, which you will be able to see at this point. If your target is relatively large you may even see some of its structures. Now, pointing at the target, which on the Nav Ball is represented be a pink dot inside of a pink circle, increase throttle. if you are 1-3km away it's safe to point straight at the target, however if you are closer you should point off to the side a little to avoid ramming your target. You should go fast enough to get their in a reasonable time but not so fast that you fly past it. I usually go at 10m/s for every km I am from the target. so at 3km I would go at 30m/s. Make sure to turn as soon as you get done accelerating as missing your target is a huge waste of fuel. Repeat this until your are within 100m of your target. Now it is time to dock. Most people go into docking mode for this but I don't because it changes many controls. Just know that WASDQE changes attitude and IJKLHN changes position (with RCS thrusters). So activate your RCS and orient yourself to the position you need to be in to dock, THEN start moving towards the target. Things move slow and you may need to use time warp for the approach but don't go above 5x, once you are very close, approach the docking port and slowly move towards it. Face the entire thing from the side, and adjust yourself to be perfectly lined up, then face from a 90° angle to that, making sure you can still see both ports, you may notice that although from the other angle you looked dead-on, from this angle you do not. So adjust this one until you look dead-on again and switch back to the other view angle. keep switching and adjusting the angle until you dock. You don't have to be perfect, just close. Once you get close the automatic magnetic docking thingy will activate, you'll notice that once you're very close to the target, you'll start accelerating towards it quickly until your ports hit each other. If you weren't to good then the ports will slide back and forth a while so if that happens, just be patient, a failed docking is very rare. It may dock instantly as well, if so, good job! Either way, you just docked. Cool right?
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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]).
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====[[Tutorials#Orbital Rendezvous|Tutorials]]====
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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.
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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.
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* [[Tutorial:Orbital Rendezvous|Orbital Rendezvous]]
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* [[Tutorial: Orbital Docking with the Kergena Target Vehicle|Orbital Docking with the Kergena Target Vehicle]]
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* A detailed discussion on [[Tutorial: How to meet objects in orbit|how to meet objects in orbit]], including how to synchronize orbits/phases
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* [[Tutorial: Orbital Rendezvous|In depth tutorial for an orbital rendezvous and docking]] by It's Just Rocket Science
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== Gallery ==
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<gallery>
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File:Kerbal Space Program Enhanced Edition 20220117205015.jpg|A small docking craft rendezvouing with a satellite.
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</gallery>
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[[Category:Maneuvers]]

Latest revision as of 12:48, 10 May 2022

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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.

Usages

Possible usages of orbital rendezvous include:

Encounter

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.

Velocity Matching

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]).

Tutorials

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.

Gallery

  • A small docking craft rendezvouing with a satellite.

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