Rendezvous and docking?Slowing down and retro grade engine burn trowed the bottom of Horizon?

[Cloakedwand72]

I got lucky catching up and getting a close visual of my little Agena Gemini style target ship.But i end up deorbiting why?Do i burn retro facing down the horizon?Or just use a Auto pilot mod for the Docking stuff?

[Jarin]

Set your navball to target mode (click speed to change) and once you get close, thrust retrograde to target velocity and reduce relative velocity to zero, then just nudge yourself towards it. Sounds like you were thrusting retrograde to orbital velocity instead.

Edited January 16, 2016 by Jarin

[AlamoVampire]

@Cloakedwand72 i will provide you with the best help possible. get mechjeb, have it teach you. While all the words in the world are fine, there is 0 they can do for you to show you how YOUR craft will fly in those conditions. the same can be said for watching videos. Now, the anti-mechjeb crowd will naysay what I have just said, but, ignore them. The debate on mechjeb is as old as time, and if there is one thing I have learned, it is this: there is no teacher alive that can teach you as well as experience.

[dave1904]

 

Just watch videos to learn and there is no better teacher than scott and trial and error in KSP. Don't watch mechjeb dock 100 times unless you want to waste your life because mechjeb takes forever. Its also a game and you do things yourself instead of a mod doing it for you. Just press F5 and when you love up F9 until you can dock like a pro. 

Download this mod and watch tutorials and in a week you can dock as good as anyone else.

http://forum.kerbalspaceprogram.com/index.php?/topic/40423-10x-docking-port-alignment-indicator-version-62-updated-05042015/

Edited January 19, 2016 by dave1904

[GregA]

I learned docking and rendezvous by watching Mechjeb do it about 100 times, then I started to notice the potentially inefficient things that mechjeb does, so I started to take over here an there.  Now I just do the whole thing because it is just faster and easier if I do it.

It is tough to tell from your description of problem, but it sounds like you were intercepting your target, then didn't burn off your relative velocity in time.  The final intercept requires a burn that can potentially deorbit if the maneuver is not completed in time.

 

[AlamoVampire]

@dave1904 its like i said in my post, and to be honest, i speak from hard won experience, there is nothing that is superior to seeing how YOUR craft does. Watching someone elses craft is fine and all, BUT, watching mechjeb put YOUR craft thru the paces is a far better teacher, as it illuminates where you are strong and where you are weak. No tutorial can do this, no teaching video can do this. only mechjeb acting as your teacher using what you built will. well, that and just flinging things up into space and trying to learn the hyper hard way, but, to each their own.

[Guest]

Mechjeb is good at some things and not so good at others. I realize that statement leads to a lengthy discussion, but really, mechjeb should be looked at as a tool, not a teacher.

[Reactordrone]

You may have adjusted your periapsis down into the atmosphere to get a  close intercept showing for the next orbit. Always keep an eye on your orbit when setting up a rendezvous to avoid dipping into the atmosphere or running into high terrain on airless bodies. You can always go to a higher orbit and let the other vehicle catch up to you if you can't safely drop low to catch up to them.

[Rune]

4 hours ago, AlamoVampire said:

@dave1904 its like i said in my post, and to be honest, i speak from hard won experience, there is nothing that is superior to seeing how YOUR craft does. Watching someone elses craft is fine and all, BUT, watching mechjeb put YOUR craft thru the paces is a far better teacher, as it illuminates where you are strong and where you are weak. No tutorial can do this, no teaching video can do this. only mechjeb acting as your teacher using what you built will. well, that and just flinging things up into space and trying to learn the hyper hard way, but, to each their own.

Actually, since I had a theoretical understanding of what I had to do beforehand, it only took me a couple of tries to learn to dock myself, without installing mechjeb. I see form the "watching mechjeb 100 times doing it" comments, that watching a computer do it without explaining itself at any point, might be a tad more difficult. The real tricky thing about docking IMO is the final alignment and translation, that is a motor skill that you have to develop (or have mechjeb do it for you). The rendezvous and orbit matching until you park within 2kms at less than 10m/s relative velocity? That is something to read about beforehand, because that takes thinking, not muscle memory.

Regarding the original question: by playing with your orbital period (raising, lowering your orbit), you make your orbit intersect the target's with such a period that you will encounter it at that spot (I.E: you get a close encounter indicator of under ~5-10kms). Then, when you get close, it's all a matter of changing the velocity indicator in the navball to "target" mode, and "push" your relative velocity vector so it points to the target (target prograde to velocity prograde, target retrograde to velocity retrograde). Then just slow down as you come in, as late as you dare. And that is rendezvousing in a nutshell! I think that is the part you were having issues with.

Once you are parked next to the target... well, practice flying your ship like it was a kerbal, I do it with the camera in "locked" mode, so up is always up, and both hands on the keyboard, WASD with the left for attitude and left on IJKL for translation.

 

Rune. There are two distinct phases to this, the rendezvous and the proximity ops, and they require vastly different skillsets.

Edited January 16, 2016 by Rune

[tranenturm]

First, no need for mechjeb. If it works for you, use it. But it's not a requirement. I've never installed it and learned docking in just a few tries. 

Read the Kerbal Wiki tutorial on this, very useful. 

Things that helped me:

Use circular orbits if possible. Ellipticals are doable, just an added challenge the farther from circular they are.

Mom your first attempts, be sure to start from a situation where the orbits don't cross. If they are crossing, it's still doable but can take longer and be harder depending upon how in phase they are. 

Select the other craft as your target. You'll see intersection points when your orbits get close enough. So from a  two circular non-crossing orbits use the maneuver node to plan a burn that will take you to just to touching the targets orbit and the intersection markers will appear. Click on the circle of the maneuver node and move it around your orbit until you find a spot with the minimum distance at intersection. You may need to orbit a few times to get this distance to less than 10 km. 

Do the burn and when you get close, the nag ball should automatically switch to target when you're closer than 25 km. Clicking on it will toggle between surface, orbit, and target. 

Click so you're on target, and the retrograde marker now registers relative to the target, not orbit. Prepare to burn retrograde. Get the target vessel in sight and when the distance between ships is no longer going down burn retrograde until you have close to zero speed between targets. You don't need to be exact. Under 2 m/s here is fine. Find the  purple circle on the navball which indicates the direction of the target and burn towards the target. You'll repeat this burn in the opposite direction when you get close so the amount of burn is relative to how much fuel you want to spend and how much time you spend closing the distance. 

When you get close, burn retrograde on the navball and this time get as close to zero as you can get. Switch to the target craft and rotate the craft to have your docking port facing the incoming ship. Switch back to your craft. Make sure you are pointed at the docking port, and burn slowly towards it. With careful piloting on a small craft with ample SAS you don't need RCS. Larger, slower crafts will need RCS. 

[pandaman]

Rendezvous and docking are never 'easy', but they do get easier with practice.

It takes patience setting up your rendezvous, don't be afraid to use multiple orbits to get your closest approach closer each orbit, trying to get it spot on in the first orbit often makes it a lot harder and rusks screwing it up completely.

I never used mechjeb, but try it if you think it will help, Scott Manley's video helped me a lot.   

[Rocket In My Pocket]

This awesome illustrated guide is how I learned to do Orbital Rendezvous/Dock, all props go to the original creator...I have no idea who that is though. 

It's under the spoiler as it's rather large!

Spoiler

 

[Glaran K'erman]

15 hours ago, AlamoVampire said:

@dave1904 its like i said in my post, and to be honest, i speak from hard won experience, there is nothing that is superior to seeing how YOUR craft does. Watching someone elses craft is fine and all, BUT, watching mechjeb put YOUR craft thru the paces is a far better teacher, as it illuminates where you are strong and where you are weak. No tutorial can do this, no teaching video can do this. only mechjeb acting as your teacher using what you built will. well, that and just flinging things up into space and trying to learn the hyper hard way, but, to each their own.

I've had MJ screw up some pretty straightforward docks for me. From MY hard won experience () I will tell you to read, and then most importantly, watch people on YouTube teach you to dock. MJ is definitely a better tool than teacher.

Edited January 16, 2016 by Glaran K'erman

[Raptor9]

Just because Mechjeb is a computer, doesn't necessarily mean it can perform tasks better than a human.  Computers are only as good as the people that program them.  I'm not saying anything bad about the author/programmer of the Mechjeb mod, I'm just pointing out that Mechjeb is not the "expert" pilot that some claim it to be.  I used to use Mechjeb (pre 0.21), but I found after practicing the maneuvers myself, I could do them quicker and with less fuel.  Even reentering the atmosphere and landing at the KSC with an unpowered spaceplane like a Shuttle can be done without Mechjeb or the Atmo-Trajectories mod with a little practice.

Having said all that, I think getting into a Mechjeb vs Non-Mechjeb debate is about as ridiculous as the FAR vs Stock aerodynamics debates.  Bottom line: Do whatever keeps KSP fun for you.

[dave1904]

On 16/01/2016 at 1:53 PM, Rune said:

Actually, since I had a theoretical understanding of what I had to do beforehand, it only took me a couple of tries to learn to dock myself, without installing mechjeb. I see form the "watching mechjeb 100 times doing it" comments, that watching a computer do it without explaining itself at any point, might be a tad more difficult. The real tricky thing about docking IMO is the final alignment and translation, that is a motor skill that you have to develop (or have mechjeb do it for you). The rendezvous and orbit matching until you park within 2kms at less than 10m/s relative velocity? That is something to read about beforehand, because that takes thinking, not muscle memory.

Regarding the original question: by playing with your orbital period (raising, lowering your orbit), you make your orbit intersect the target's with such a period that you will encounter it at that spot (I.E: you get a close encounter indicator of under ~5-10kms). Then, when you get close, it's all a matter of changing the velocity indicator in the navball to "target" mode, and "push" your relative velocity vector so it points to the target (target prograde to velocity prograde, target retrograde to velocity retrograde). Then just slow down as you come in, as late as you dare. And that is rendezvousing in a nutshell! I think that is the part you were having issues with.

Once you are parked next to the target... well, practice flying your ship like it was a kerbal, I do it with the camera in "locked" mode, so up is always up, and both hands on the keyboard, WASD with the left for attitude and left on IJKL for translation.

 

Rune. There are two distinct phases to this, the rendezvous and the proximity ops, and they require vastly different skillsets.

I assumed most expired player use both hands. I've never used the docking controls since and can't even remember the key layout. The docking mod or whatever its called from navyfish and the docking last 20secounds.

[Temstar]

No I don't use both hands. At the start of the docking process I align both ships using the artificial horizon and cardinal direction as the guide and turn SAS on for both ships. Then for the remainder of the docking it's translation only.

[RizzoTheRat]

On ‎16‎/‎01‎/‎2016 at 1:53 PM, Rune said:

Once you are parked next to the target... well, practice flying your ship like it was a kerbal, I do it with the camera in "locked" mode, so up is always up, and both hands on the keyboard, WASD with the left for attitude and left on IJKL for translation.

Locking the camera is the key thing for me (although it now seems to work slightly differently than it used to and slews with my position relative to the target), along with setting the vessel to control from the docking port, and targeting the other ships docking port.  Then it's just a case of flying it on the nav ball.  WASD to keep the nose pointing at the target, and IJKL to keep the prograde vector pointing at the target, or off to onside slightly if you want to straighten up your approach.  Unless it's a big unwieldy station I'm docking with I'll usually switch to the target and rotate it so the docking port faces the ship too.

 

Edited January 19, 2016 by RizzoTheRat

[dave1904]

14 minutes ago, Temstar said:

No I don't use both hands. At the start of the docking process I align both ships using the artificial horizon and cardinal direction as the guide and turn SAS on for both ships. Then for the remainder of the docking it's translation only.

You should give it a try.

[Guest]

Use both sets of keys and learn to read and use the navball.  The navball and a practiced hand are all that are really needed for docking, you can eyeball the approach with ease and line up correctly every time, even with sloppy RCS placement.

[Majorjim!]

 Practice practice practice. If you don't know where to start watch Scott Manely's explanation.

[Temstar]

4 hours ago, dave1904 said:

You should give it a try.

I did when the docking mode first came out, I don't find it any better or faster than my method, Now that SAS no longer waste nearly as much monoprob as during the beta there's even less reason to.

[Tourist]

On 1/16/2016 at 3:41 PM, AlamoVampire said:

@Cloakedwand72 i will provide you with the best help possible. get mechjeb, have it teach you. While all the words in the world are fine, there is 0 they can do for you to show you how YOUR craft will fly in those conditions. the same can be said for watching videos. Now, the anti-mechjeb crowd will naysay what I have just said, but, ignore them. The debate on mechjeb is as old as time, and if there is one thing I have learned, it is this: there is no teacher alive that can teach you as well as experience.

On 1/16/2016 at 2:50 PM, Cloakedwand72 said:

I got lucky catching up and getting a close visual of my little Agena Gemini style target ship.But i end up deorbiting why?Do i burn retro facing down the horizon?Or just use a Auto pilot mod for the Docking stuff?

 

With the greatest respect to AlamoVampire, I disagree that watching Mechjeb dock for you is the best way to learn... the reason being is that Mechjeb will do alot of stuff, but it what it will not explain why it is doing it. That's why watching the videos is better and using its advice to try what they describe.

This is important because you may miss aspects of the process. For instance, you may not notice that the Navball switches modes from orbital speed, to target speed... it usually does this automatically when you get close, but if it doesn't, and you don't change it manually, problems like the kind the you describe can occur.

Also, people are really good at learning by doing, but are generally pretty bad at learning by watching alone. The best example I can give about this is if you have ever been a passenger in a car to a place you have never been before, and which requires some navigating. If you have only been a passenger, the first time you come to drive the route yourself you may have no idea where to go... even if you have been a passenger on that route many times. However you generally only need to have driven the route once or twice before and you will remember how to do it every time after.

Of course, people are different, and how people learn is unique to them.  Some people really are good at learning by watching alone. So, do what works for you.

I do feel I need to add, just because the "is X cheating" plague seems to have flared up today. Even though I don't think its a very good learning tool, I want to be clear that Mechjeb is not cheating, nor anything else that makes the game easier or more entertaining or less frustrating, to the way you play.

[AlamoVampire]

@Tourist I disagree with you. Let us say, for argument sake, you and I make a video each. In this video we both make a docking target vehicle and place it in a parking orbit somewhere between 75km to oh say 350km (why 350km? Why not?) and then design a ship to go dock with it. Standard stuff so far. Are you certain you will cover every single nuance? Every single issue that could happen? I don't just mean the most likely stuff, but, I mean everything. I know I can't. I am statistically reasonably certain you can't either. What I am dead on certain of is, mechjeb CAN. What I am also certain of is this: no two rockets are 100% identical unless every part of the second one, root part INCLUDED comes from either the saved ship or the subassembly doodad. 

Also, seeing YOUR rocket or MY rocket in action is never a good analogue for the students rocket. You said it yourself, mirroring me, no substitution for experience and mechjeb gives it. Videos don't. Written how-to's don't. 

[Temstar]

10 minutes ago, AlamoVampire said:

@Tourist I disagree with you. Let us say, for argument sake, you and I make a video each. In this video we both make a docking target vehicle and place it in a parking orbit somewhere between 75km to oh say 350km (why 350km? Why not?) and then design a ship to go dock with it. Standard stuff so far. Are you certain you will cover every single nuance? Every single issue that could happen? I don't just mean the most likely stuff, but, I mean everything. I know I can't. I am statistically reasonably certain you can't either. What I am dead on certain of is, mechjeb CAN. What I am also certain of is this: no two rockets are 100% identical unless every part of the second one, root part INCLUDED comes from either the saved ship or the subassembly doodad. 

Also, seeing YOUR rocket or MY rocket in action is never a good analogue for the students rocket. You said it yourself, mirroring me, no substitution for experience and mechjeb gives it. Videos don't. Written how-to's don't. 

No I disagree with that sort of thinking. The idea behind rendezvous and docking can be derived from first principle, that's why Buzz Aldrin was able to write a thesis on the subject and became known as "Dr Rendezvous". Specific details relevant to each vehicle (and I mean, there's really only two things that are different: location of docking port and RCS placement) can be trivially compensated for which is the whole reason why a machine like mechjeb can handle it.

Mechjeb doesn't teach you from first principle, rather it rigidly follows algorithms and encapsulates the knowledge away from you. To really get a feel for rendezvous and docking you need to either do it the old fashion way from reading books or watching instructional videos, or do it yourself and get a intuitive feel for it. Looking at mechjeb only teaches you how to mimic mechjeb's algorithm which is much worse than a human pilot.

[Tourist]

@AlamoVampireUnsurprisingly I disagree on a number of points. Firstly, once in orbit, whether it be 75kms or 350kms the specific design of your craft doesn't really matter that much (except for perhaps dodgy placement of RCS ports and compensating for the lower receptiveness of high mass craft.) Also rendezvous and docking is not that hard, there is not that much nuance to it.... the only maneuvers you need to know are plane alignment, setting up a close approach, matching velocity/closing the distance, docking. 

The tools people need to do that is understanding the map screen and the navball. The problem is, Mechjeb does not explain these tools. It doesn't explain why it is burning anti-normal or normal at a specific point in the process, it does not explain why lowing or raising your PE or AP will help you catch up with another craft. These I believe are vital to understanding rendezvous and docking, but MJ only demonstrates by doing, it doesn't explain why. 

However I can see the benefit of mechjeb demonstrating the final docking part.... without mod tools like the docking alignment indicator this can be tricky, but I think most people will understand what its trying to do. 

Although as I noted, everybody learns differently, I may just be describing my own learning process.  

 

Edited January 20, 2016 by Tourist