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Docking tutorial - *insert random curseword*


Unigo

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Hello fellow Kerbonauts,

I'm playing KSP for a while now, with passion. Usually focusing on building planes, lately i'm getting more and more into rockets. I've been to the Mun, been to Minmus, brought a (one piece) spacestation into orbit, onwards to the next chapter: docking.

KSP has a very 'handy' docking tutorial in the game itself. But, i can't complete it! In short, what i DO manage to do:

-correct the inclination of my ship with my target
-burn prograde till i have an intersection below 5 km.

Now where it gets funny: KSP tells me to, (when within 60 km of my target) burn retrograde till my relative speed towards my target drops below 50 m/s. All fine and dandy, and i can manage that, but the result is that my orbit and my target's orbit don't intersect anymore, creating around +- 50 km's of distance between us. Some internet research tells me that i then have to burn towards my target (don't have the fuel for it)...

Anyone who has completed this training mission? 

 

Thanks for the help!

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This thread caused me to do something I never thought I'd do.

Follow a KSP in-game tutorial :D

It's... okay. It's a difficult concept and they're trying to introduce multiple things at once. I'd personally break it up into 3 steps and have each be their own tutorial. Rendezvous, getting a close approach within - say - 10km. Then Approach, getting next to the target and stationary with respect to it. And finally Docking.

Did I say I would do that? I mean I did. Almost 2 years ago. :D

Rendezvous:

Spoiler

 

Approach:

Spoiler

 

Docking:

Spoiler

 

 

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On 12/20/2015 at 10:43 AM, Unigo said:

In short, what i DO manage to do:

-correct the inclination of my ship with my target
-burn prograde till i have an intersection below 5 km.

Now where it gets funny: KSP tells me to, (when within 60 km of my target) burn retrograde till my relative speed towards my target drops below 50 m/s. All fine and dandy, and i can manage that, but the result is that my orbit and my target's orbit don't intersect anymore, creating around +- 50 km's of distance between us. Some internet research tells me that i then have to burn towards my target (don't have the fuel for it)...

Anyone who has completed this training mission?

I've never bothered with any of the training missions, so I can't help specifically there.  However, if you have the skillz to get your craft on a rendezvous trajectory that takes you within 5 km or so of the target, then here's an illustrated docking tutorial I put together which you may find useful.

...it's designed to take you from the "Okay, I'm on a rendezvous course" to "docked".

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Have you tried downloading and playing THIS stock scenario by Blizzy?:

Blizzy's In-Game Rendezvous Scenario

and then there's also a separate docking scenario:

Blizzy's In-Game Docking Scenario

Here's the thread that goes with them:

Blizzy's Launch, Rendezvous & Docking Tutorial

 

Edited by Stone Blue
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You do approach burn when closest to target. 60km is faaar away. Like they say, fire when you see whites of their eyes :-) Hint: you can plan it as any other maneuver. Place maneuver node at closest approach point and plan an orbit that matches your targets orbit. You don't actually use it – it's not precise enough - but it should tell you aproximate ETA and burn time. For actual rendezvous you just watch target distance and relative velocity. Target distance is decreasing - you wait and do nothing. Target starts to get away, you burn relative retro until relative speed is zero to stop it running away. This takes you on "almost matching" orbit, paralel to target but slightly faster/slower. So you do transfer orbit again - if you can get within 10km you just burn at target and repeat.

Other hint: imediately after first transfer burn align your ship to cardinal axes, open map view, turn on RCS and try giving it slight push in all directions and see where it pulls approach point. I am usualy able to get within 1km and can get visual from there.

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I had a crack at the training mission just now, and yeah, it seems a little rough.

My first problem was with the scenario instructing to burn at the Descending Node to align orbital planes. By then, your vessel in the lower orbit has caught up too much with the stranded one and it's really hard to set up a good intercept (without waiting several more orbits to overtake and come up from the rear again). Instead, burn at the Ascending Node. It's only about 6-7 minutes away when you start the scenario, so you'll have to be quick. But you'll have a lot more freedom to set up a good transfer orbit straight away. Here's the maneuver I was able to set up. The first intercept is about 2.5km, which is a good target to aim for. And if all goes well after setting up this orbit you should still have around half a tank of fuel.

kvuLYe2.png

The tutorial's directions to slow down while you're still 60km away seem kind of janky. For the above transfer orbit, doing that pushed my closest intercept from 2.5km out to >20km, which is very counterproductive. Instead, change your navball to target mode as the tutorial instructs, wait until you're less than 10km away, and burn retrograde to lose almost all of your speed.

Once your relative speed is below 50m/s you'll be able to click forward through the tute, which will tell you to carry on and burn retrograde until your speed is 0m/s. From there the tutorial directions look to me to be good enough to let you complete the docking.

Docking is one of the harder things to do, and it's definitely worth trying the other scenarios and tutes people have put together here as well.

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The mission text is poorly written. 60km burn is what you use to intercept asteroids when either the intercepting ship has low acceleration or the dV between ship and asteroid is huge, usually is, and I mean HUGE, like around 1000m/s.

start your burn, much, much closer, test the distance, plus, when you have a dV of, say, 10m/s to target, stop burning, make sure your ship keeps retrograde to target and wait until target passes ABEAM your ship. When it does, burn the last 10m/s

 

never bothered with these training missions, anyway.

but they are useful when starting to play, or they should, if the mission profile was properly done, that is...

 

Docking the easy way?

select docker, select a docking port, control from here, select target, preferably select a DOCKING PORT on target, if you can at the given distance, if not select one when close enough.

point the ship towards the target (pinky circle with pink dot in center on the navball). Thrust rcs forward. No more than 5m/s if it is your first docking

When close enough (50m) make sure ship keeps moving exactly prograde (pointing to the yellow circle on navball) and reduce dV between you and target to 0m/s.

point ship to target again.

go to target, select the docking port you selected as target, from the docker, and control from here. Point target to docker.

 

now both ports should be aligned.

get back to docker, move forward with rcs at no more than 1m/s. Keep ship nose on pink ring and keep yellow circle prograde on pink ring too (all aligned). When yellow circle tries to move away from center use side rcs's to bring it back gently to center.

10m or so from touch, reduce speed to 0.5 and then 0.2 m/s

touch and dock.

 

:)

good luck.

 

this method is the easiest for almost ANY 2 vessels but for the most huge space stations and capital ships, so it should be enough for a long time and by then you shall have figured out how to dock the big ones yourself ;)

 

 

Edited by Jaeleth
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I am having the EXACTLY same experience as Unigo.  Following the instructions on the tutorial gets me (on a VERY good day) to within about 50m of the target vessel... then I start drifting away again, even when it says I am approaching at about 5m/s.  I follow all the instructions to a T.  I get well within the parameters it says are good.  Still, no go.

It is a nightmare tutorial that makes me frustrated to the point of having to walk away for a day or so.

I think next attempt when I feel up to it, I may scrap what the tutorial instructs and follow someone else's guide.  Snark's guide helped with some 'missing' concepts and explanations that the tutorial didn't go over as well as hoped.  So... maybe tomorrow.

I feel like an idiot, though.  Like if I don't get an almost input by input, step by step, screen by screen hand-holding I am hopeless at docking.  Sigh.

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5th Horseman, you are one of my new heroes for KSP!!!

Holy Kerbaltastic!  I DOCKED!
 

*does the Kerbal happy dance*

I docked! I docked! I docked!

Oh, to be sure, it was ugly as all get out.  And *nervous laughter*, there were a few moments of bumper cars in space (very slow, so no harm done).

And *cough cough blush*, this was after getting a little antsy to try things out and making another attempt after only getting through the second video (which was an GI-NORMOUS help!).  This may be the 'beginner' way (as you stated in the video), but it helped me get my approach slow and tight so that I was able to make small corrections... and my yo-yo-ing around wasn't as wild as usual.  Of great help, especially, was the part where you described turning sideways to the target and using that as a reference to judge 'braking'.  Haven't quite mastered it yet, but it definitely was an improvement.

*feeling chuffed*

 

Where I was very frustrated and discouraged before, now I am excited to keep trying and get better and better at docking until I almost look like I know what I am doing!

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Congratulations. Learning to dock is easily the hardest thing I had to figure out in KSP. I also finally figured it out by reading lots of tutorials and then doing the in-game one.

The technique I use nowadays is something like this:

  1. Plot an intercept. Try to get it within 2 km or so. I aim for less than 1 km but it's not always feasible. For very low-grav bodies (Minmus-sized or smaller) the distance can be more without it getting seriously expensive.
  2. Assuming I have sufficient relative speed, I keep the target retrograde markers aligned using target retrograde burns. If not, I fire prograde to speed up, aligning the prograde markers.
  3. Down to 5 km distance, I keep the speed > 50 m/s (accelerating if necessary), then I start slowing down until I'm at about 10 ... 30 m/s at 1 km, 5-10 m/s at 500 m, 2-5 m/s at 100 m, 2 m/s at 50 m, 1 m/s at 20 m, and then keep it at that until I bring it down to 0.3...0.5 m/s for actual contact.
  4. Once within 100 metres/2-5 m/s or so, I point my craft at the port and switch to RCS: I keep the craft pointed at the port, and use IJKL to keep the prograde marker on it, and HN to accelerate/decelerate.
  5. I periodically switch to the other craft, which I "control from" the target docking port, and keep that pointed at the moving craft's docking port.

Also, on elliptical orbits I try to dock closer to the apoapsis (easier, less drifting), and by daylight (although this is less important as the navball is quite sufficient for it).

I also don't find it too hard to dock even without RCS using this technique. The only difference is that my contact velocity will be about 1...1.5 m/s, and I hit that about 20-30 m to the target, at which point I point the approaching craft at the docking port, and switch between the two repeatedly to keep the ports aligned. It makes a bigger klunk but works well enough. That's why I sometimes leave out RCS altogether when mass saving really is extremely important, e.g. on interplanetary return missions.

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I read through this thread and only now just figured out how old it is. I hope that @Unigo figured it out eventually. Also, it makes me wonder how long it took Buzz Aldrin considering he did his PhD thesis on orbital rendezvous.

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