Help with rendezvous and docking.

[Orc]

HI all

 

I am a noob. I need to learn how to dock to go further in the game (i've landed on the Mun and Minimun and orbited the sun). I am playing the most recent version of KSP (1.1). 

 

I've followed the Docking Tutorial as taught by Gene Kerman. I use the maneuver nodes to get within 1 km of the target, and a velocity difference of 10 to 16 m/s. I am PRETTY SURE I've followed all of the instructions to the letter.

 

So now I'm supposed to try get closer with the RCS, using H and N to speed up to slow down. Problem is the target gets closer and closer and then appears over shoot and I have to start adjusting my speed in the opposite direction. I can do this twisted little dance until the RCS propellant runs out and never get closer than 200 meters and 4 m/s.

 

This is very frustrating. Is this just a symptom of a rookie pilot, or am I obviously doing something wrong? Or is Gene giving me bad (outdated advice)? Or do the Kerbals in the other spaceship NOT want to get rescued?

 

Any help or advice welcome.

 

Thanks, take care

Orc

[Rocket In My Pocket]

Spoiler

Follow this illustrated guide under the spoiler and you shouldn't have any problems!

Also, sounds like you are getting really close on your own, but you are just going too fast and overshooting your target. Remember that in space there is no friction to slow you down, every m/s you gain going forward is a m/s you are going to have to lose by burning in the opposite direction to slow down.

Make sure you click the Navball where it says "orbit" and set it to "target" mode, so that you can see your speed relative to the target, you want to bring this down as close to 0 as you can and then slowly start to move towards the target, I don't personally recommend going any faster than 5m/s. Remember that the direction you are thrusting and the direction you are traveling can be two different things, so you may need to "pull" or "push" your prograde marker over the target marker by aiming "past" it. Keep practicing and you'll get it!

Edited March 29, 2016 by Rocket In My Pocket

[N_Danger]

 That's a very good guide that I used to learn the ropes(just in the past month too). It is showing an alignment mod at the bottom that is not stock but very much worth downloading. It will help get you docked in that last 100 meters.

 And it takes practice, lots of practice to get the first docking but once you get it down it will come naturally to you there after.

[KocLobster]

I would also suggest this thread, it was just recently posted and has a lot of good answers.

I also would suggest NavyFish's Docking Port Alignment Indicator mod. If youre okay with mods, I never leave KSC without it.

Edit: oh sorry I couldn't load that picture. ninja'd. +1 to that pic @Rocket In My Pocket posted then

Edited March 29, 2016 by KocLobster

[Geschosskopf]

4 hours ago, Orc said:

I've followed the Docking Tutorial as taught by Gene Kerman. I use the maneuver nodes to get within 1 km of the target, and a velocity difference of 10 to 16 m/s. I am PRETTY SURE I've followed all of the instructions to the letter.

Given that you've now got some excellent tutorials, I'll just hit a few details here.

That's actually pretty good for doing the rendezvous manually.  It's possible to do better but it takes a lot of frustrating fiddling with the maneuver node and besides, having a few hundred meters of space between you and the target when you're coming in fast and need to burn to match velocities with your engine pointed more or less at the target is a safety measure.

4 hours ago, Orc said:

So now I'm supposed to try get closer with the RCS, using H and N to speed up to slow down. Problem is the target gets closer and closer and then appears over shoot and I have to start adjusting my speed in the opposite direction. I can do this twisted little dance until the RCS propellant runs out and never get closer than 200 meters and 4 m/s.

RCS is for the actual docking once you're right up next to the target.  Use the main engine (gently) to close the last few hundred meters from where you matched velocity at the end of the rendezvous.  What you do is point get into target mode on the HUD and point actual retrograde (not target retrograde) to reduce your velocity relative to the target to 0.  Then point at the target and burn very gently on the main engines until you're going about 5m/s (relative to the target).  Rotate again to true retrograde and be ready to kill your velocity again.  Watch the range to the target and its position and apparent motion relative to your ship.  As you get closer, it will start to slide sideways across the screen.  Kill velocity at that point, then point at and burn towards the target gently again.  You might have to repeat this process several times but eventually you'll be within spitting distance of the target.  At this point, kill your velocity relative to the target one last time and begin the actual docking.

4 hours ago, Orc said:

Any help or advice welcome.

Well, now that you've rendezvoused and are within 100m of the target, you stop using the main engine and do the rest with torque and RCS.

Actually docking consists of 4 main phases, doing which requires either torque, RCS, or both, as follows:

1. Getting on the Correct Side of the Target:  The docking port is on a certain side of the target so can only be approached from that direction.  So if you're not already on that side of the target, you have to get there, either by flying your ship around the target or switching to the target to rotate its docking port at the approaching ship.  If the target is reasonably small and robust, rotating it should be no problem but this usually isn't an option for big, floppy space stations, which means you have to fly around to the correct side.  This is best done with RCS translation, very similar to flying a Kerbal around on EVA, although using the main engine VERY gently also works.
2. Aligning Your Ship with the Docking Port.  Now that you're on the correct side of the target, you need to turn your ship so its docking port is facing the target docking port, and that the line drawn from your port into your ship is parallel with the line drawn from the target's port into the target.  All you're going for here is parallel docking axes.  Use torque to do this.
3. Getting Colinear Docking Axes:  Once your docking axes are parallel, use RCS translation to slide your ship sideways until it's lined up directly with the target docking port.
4. Final Approach:  Now that you're all lined up, just ease ahead slowly with RCS translation (or maybe just a tiny blip of main engine) until the ports come into contact and attach.  Try to make contact doing no more than about 0.1-0.2m/s

The 2 most tricky parts of the above are Steps #2 and #3.  I recommend mods to help with these because the stock game is woefully short of essential instrumentation that you need to perform either step with certainty.  These mods DO NOT fly the ship for you, they just give you helpful information to let you fly it more effectively.

I recommend NavyFish's excellent Docking Port Alignment Indicator.  It makes it MUCH easier to see what you're doing in both steps.

HOWEVER, it won't help much for Step #3 unless your ship has balanced RCS thrust.  If it doesn't, then translating will introduce unwanted rotation, which makes trying to do Step #3 screw up what you've already done in Step #2.  This makes docking very frustrating if not impossible.  Therefore, success in Step #3 really begins in the VAB by building the ship with balanced RCS thrust.  To do this, I recommend the wonderful RCS Build Aid mod.  Using this, you can be sure your ship won't rotate while translating and docking will be MUCH easier.

[Plusck]

5 hours ago, Orc said:

I've followed the Docking Tutorial as taught by Gene Kerman. I use the maneuver nodes to get within 1 km of the target, and a velocity difference of 10 to 16 m/s. I am PRETTY SURE I've followed all of the instructions to the letter.

Very important: do NOT follow the instructions to the letter. Gene tells you to use RCS to reduce your velocity to target which is absolutely wrong. Main engines are meant to do this.

Geschosskopf's advice is sound.

I'd add another point: drop a maneuvre node on the point where you are going to meet your target. This tells you how many minutes away you are. When you're a few minutes away, turn to face the antitarget marker. Make sure the NavBall is in target mode. The target retrograde should be near to the antitarget. Now, point your ship slightly to the other side of the retrograde marker, and gently fire your engines. This should reduce your speed relative to the target and also move retrograde over the antitarget. If you delete the maneuvre node on your map, you should see that the encounter is now a touch further away (in time) and a touch closer (between the two ships).

Drop a node there, guesstimate how much time it'll take you to reduce velocity to zero (judging by what happened in the paragraph above), and wait until you're about that far from the node. Then kill velocity like Geschosskopf said.

[justidutch]

I have gotten into the habit of reducing relative velocity to 0 when I am about 100 meters out, (in other words, coming to a standstill relative to the target).  After I have finished the burn that gets me close (within 7km of the target) I will immediately turn my vehicle around 180 degrees, then time warp until a minute or two before the rendezvous.  When I get back to normal time my ship is more-or-less pointed in the direction it needs to be to kill velocity relative to the target.  When doing so I will push the yellow retrograde target on the navball onto the target, which means I am heading directly at it.  When the target is 1 km away I don't want to be going any faster than 10 or 15 m/s, then I will coast to the 100 meter perimeter and will come to a stop.  From that point on I will manoeuvre my ship to make sure I am lined up perfectly, using RCS (I love using the IKJL keys for translating up/down/left/right), then either a puff of the main engine or the RCS to move towards the target.  By the time the docking ports are 10 meters apart or so, I will be going only 2 m/s; the magnets on the ports will do the rest.

[KocLobster]

49 minutes ago, Geschosskopf said:

The 2 most tricky parts of the above are Steps #2 and #3.  I recommend mods to help with these because the stock game is woefully short of essential instrumentation that you need to perform either step with certainty.  These mods DO NOT fly the ship for you, they just give you helpful information to let you fly it more effectively.

I recommend NavyFish's excellent Docking Port Alignment Indicator.  It makes it MUCH easier to see what you're doing in both steps.

HOWEVER, it won't help much for Step #3 unless your ship has balanced RCS thrust.  If it doesn't, then translating will introduce unwanted rotation, which makes trying to do Step #3 screw up what you've already done in Step #2.  This makes docking very frustrating if not impossible.  Therefore, success in Step #3 really begins in the VAB by building the ship with balanced RCS thrust.  To do this, I recommend the wonderful RCS Build Aid mod.  Using this, you can be sure your ship won't rotate while translating and docking will be MUCH easier.

+1 I'd really like to emphasise this great part of a great post.

Most of us have already recommended NavyFish's docking mod (GET IT), but equally important, in my opinion, is the RCS Build Aid mod. I feel its essential for any docking manuevers. It allows you to make sure you're placing your RCS thrusters in exactly the right spot, which is just as essential for docking. Docking is infinitely more difficult with wrongly placed RCS thrusters, if not impossible.

Also, on approach, make sure you're only moving a couple m/s. When you're very close and using thrusters, you want to make sure you're relative velocity is no faster than 0.3m/s, if that.

Edited March 29, 2016 by KocLobster

[Ser]

I do my approaches until the last several meters with the main engine too. Here's a hint that might help:

On final hundreds of meters when you try to match the target's marker on the navball, applying thrust in any direction "attracts" the prograde marker to your ship's nose and makes retrograde marker "run away" from your nose. And, of course, burning towards prograde increases your speed and burning towards retrograde decreases it. Thus you can move your prograde to match exactly the target marker (or retrograde to match the anti-target) at the exact speed.

At final meters use RCS and go very slowly, 1-2 m/s is enough, you have nowhere to hurry.