Docking training is extremely difficult to complete!!!

[Xannari Ferrows]

Docking is one of those fields where, when it hits you, it hits hard. A few dockings later, you'll wonder how you got around without it.

[magimix]

On 15/05/2015 at 4:33 PM, Sonny_Jim said:

I think the main problem is that it has bugs, it wouldn't let me click the next button until I had created a new blank manuever node, even though I had already created one and burned until my closest approach was under 1km.

The other problem is that in my opinion, it asks you to match velocities way to early, rather than 60km distance you should start matching at something like <10km.

After bashing away at the docking tutorial for far too long, I found my way into this thread after Googling, "kerbal docking tutorial bad".  Most of the tutorials aren't what I'd call great, but this one is egregiously awkward to follow at times.  Doesn't help that the the manner in which next steps get triggered seems very fragile.  I want to focus on the quoted post in particular, because it nailed the two things I was most getting bogged down by; the tutorial just plain getting stuck, and the tutorial seemingly mis-leading me on the 'close rendezvous' portion.

Following the quoted advice, as opposed to doing what the tutorial text said, I could keep the tutorial unstuck, and I got a nice, close rendezvous on the first try.  To be sure, things fell apart at the end when the tutorial saw fit to vomit confusing text all over me for the final 'actually dock' bit, but at least I'm able to *reach* that bit now.

[Plusck]

Yes, the docking tutorial is a bit of a mess.

• The instructions don't actually fit the starting conditions, so if you follow them to the letter you will end up doing the opposite to what the previous "orbital 101" tutorial told you to do.
• It's a bit buggy about what you need to do to get the "next" button to come up. At one point you have to drop a 0 m/s node somewhere just to prod the tutorial into moving on.
• You should close the gap much more before reducing relative velocity to zero, not at a vast distance like the tutorial tells you. What you should instead do is use the "pushing the marble" technique to reduce relative velocity in stages. By pushing the retrograde marker over the "anti-target" marker, you necesarily reduce relative velocity. Do this a couple of times with main engines and you end up approaching dead on at a reasonable speed.
• You should not use RCS to reduce velocity by such a huge amount. Main engines are meant for that. If you learn to dock efficiently, you can build ships with very little monopropellant on board, which vastly reduces weight (monoprop tanks are heavy).

I gave a long, long answer to doing the docking tutorial here: http://forum.kerbalspaceprogram.com/index.php?/topic/128472-105-training-tutorials-are-bleeped/&do=findComment&comment=2334006

 

[Snark]

The good news is that the tutorials are getting a major overhaul in 1.1, so hopefully this will be a whole lot better Real Soon Now.

[Champ]

On 15/5/2015 at 5:26 PM, WeirdCulture said:

Pecan said:

And just because no-one has said it yet ... docking isn't easy! It becomes easy (or at least easier) with practice but it took NASA a long time to work it out too :-)

Stick with it.

Buzz Aldrin wrote his thesis for Doctorate of Science in Astronautics about docking in space.

I think you are wrong : it was about orbital rendez-vous, not about docking.

At least that is what wikipedia says.

[sal_vager]

Ahh, this tutorial, yes there's a small but significant issue with it.

You're told to make your first manoeuvre node at the descending node, but this puts you in front of the target ship so you cannot get an encounter without waiting several orbits, using the orbit advance button (+) or using a very elliptic orbit with too high a relative velocity at closest approach.

Tip: make your plane change manoeuvre at the ascending node, it's the first one you reach anyway and you have plenty of time to read the tutorial text and make the manoeuvre node.

This ensures you're well behind the target so when you make your second manoeuvre node to intercept it you have plenty of time.

The intercept can end up on the night side, but you can see the vessel labels and you can just wait for the sun to come up before you try to dock.

Hope this helps!

[Wemb]

On 15/05/2015 at 4:26 PM, WeirdCulture said:

Pecan said:

And just because no-one has said it yet ... docking isn't easy! It becomes easy (or at least easier) with practice but it took NASA a long time to work it out too :-)

Stick with it.

Buzz Aldrin wrote his thesis for Doctorate of Science in Astronautics about docking in space.

Yup, even the bit you need to do before you're able to dock is not trivial either - rendezvous was first attempted by manouervre in Gemini IV and the pilots (well, and NASA) got it all horribly wrong and failed completely.  It's not intuitive, and it's not easy to do the first time.  

I think the key here is taking it one step at a time and doing it slowly, and doing it right.  

• Get into a stable orbit.
• Get your orbits circularised (if possible)
• Getting co-planar with the target
• Intercepting as close as possible (and 4-5 km out is not nearly close enough - aim for less than 1km) 
• Matching orbits / velocity
• Final approach
• Orientation
• Docking

All of these are probably best approached, by the newbie, as discrete steps, and all require getting the previous one done right. None of them are automated in the game; and all of them require practise. 

The only two-penneth I'd add which I'm not sure has already been said is that remember you're docking two ships - so don't hesitate to switch between the two ships and point their docking ports at each other if it helps.  Sometimes the trickiest bit - especially if you're not got tonnes of monoprop to spend - is if you approach the target and realise their docking port is on the other side. If you get trouble doing the final steps, do what you can to avoid having to deal with translational and rotational movements, and concentrate on the translational aspect.  (this is the only step where I do often use MJ - the PAR+/- SmartASS assist will keep you two ships aligned axially, which can be a big help)

The good bit, though, is that (for me at least) - my first docking was and is my proudest moment playing KSP - way beyond that of my first Mun landing[1]. 

Wemb
[1] Direct Ascent, of course - Werner was right, it is the least difficult way to do it

[HebaruSan]

(The above are all good tips, so I only have a few tidbits to add. Also I haven't tried the tutorial or watched the cited videos yet, so some of this may still be redundant.)

Rendezvous is getting into the exact same orbit as another craft, which can be thought of in two steps: Matching the position of your target, and then matching its velocity.

To match position, I try to set up the closest close approach possible in advance, often 0.0 km in the map. Set a maneuver node opposite your current closest approach and pull gently on each direction in turn, reversing any change that increases the closest approach distance. Eventually you can develop intuition about which adjustments are needed. Install the PreciseNode mod for fewer UI irritations. Larger distances are best reduced via additional orbits as already mentioned.

I don't match planes as a separate step before approach (unless some special circumstance makes it advantageous, such as already having an unusually high apoapsis). Rather, I just move the AN or DN (whichever starts out closest) to the point of closest approach. The plane change can be incorporated naturally into pushing the marble and zeroing out relative velocity when close.

The Kerbal Alarm Clock mod has alarms for closest approach, which are quite nice for both multitasking and error-free time warping. I usually warp till 2-3 minutes before closest approach.

After coming out of time warp, it's time to match velocity. I like to watch the map view and thrust to keep the closest approach distance around 0.1 km and time around 45 seconds while pushing the marble. If I start to deviate from this, I adjust throttle and/or rotate the craft till I find an angle that puts me back on track. Keeping the time-to-approach constant means our relative speed decreases naturally till we're in RCS-maneuvering territory, with no risk of collisions.

With large craft that rotate slowly, it can be handy to pre-align them to point target-retrograde long before you're in range. To accomplish this, I place a maneuver node at my optimal point of closest approach, then fiddle with it till the post-maneuver Ap and Pe markers match and overlap those of my target. This gives me the final rendezvous burn needed to zero out relative velocity, so I point the ship that way before time warping. It also shows me approximately how long that burn needs to be, which can be combined with the time to closest approach to determine when to start burning (but this is only to inform efforts at pushing the marble--I still would not recommend a "suicide rendezvous" except as its own form of fun).

[Plusck]

4 hours ago, HebaruSan said:

...I still would not recommend a "suicide rendezvous" except as its own form of fun).

... but doing a suicide rendezvous with a large (class D or E) asteroid is the next-biggest thrill to getting your first docking done. You plan for it, your set your nodes, you line up and you see this thing approaching at a ridiculous speed. The green dot on the screen shows it's at 25, 20, 15 kilometres and then you burn just right and it's suddenly stationary 200m away.

[WeirdCulture]

On 25/01/2016 at 11:04 AM, Champ said:

I think you are wrong : it was about orbital rendez-vous, not about docking.

At least that is what wikipedia says.

well you are right.. but for docking the rendezvous is 95% of the work, at least here in KSP, and the OP have troubles even to rendezvous in space

 

Edited January 27, 2016 by WeirdCulture