Rendezvous

[Anonymous49]

In the last question (Name: Science) was kinda solved when I am running out and I couldn't do a mun flyby. But then I found out I already have  a exploration contract - Explore Kerbin. I'll need to rendezvous 2 capsules together to finish it. I obviously cannot do that by myself as I suck at it and don't understand the tutorials so I relied on Mechjeb. I need cargo for my one-segment (should be 2 but the second one wasn't launched yet) space station - there wasn't solar panels. Right, I loaded up my needed cargo and used mechjeb. Everything was good at first, good staging and stuff like that. But then it started to get off course - it wasn't in a circular orbit. But it is still a good orbit - Still enough to rendezvous. So I went into the next step - Rendezvous. It automatically got under a 250km distance but then suddenly went on a large suborbital trajectory - 500km apogee and -500km perigee. And splashdown! Nothing, didn't rendezvous with the station! [Snip]

Edited January 15, 2021 by James Kerman
Redacted by a moderator

[James M]

So first off, let's learn how to rendevous and dock before we start using automatic tools. 

Assuming you know how to orbit already, position your first segment in a large orbit to give yourself wiggle room when trying to rendezvous later. (recommend 85-100km orbit)

Now, when launching your second segment, timewarp on the pad (Preferably connected to a launch clamp to keep power flowing to your rocket) until your first segment is flying above the KSC in space, then launch your segment on the pad into an orbit with your Apoapsis (AP) up at the altitude your first segment is at then circularize once you get there.  Once there, set Segment one as your target in the map screen.

Now that you're on the same plane as your first segment, all you need to do is figure out, "Do I need to catch up to it because it's in front of me or fall back because it's behind me?" Once that question is answered then you do this... 

Plot a maneuver node that has you either accelerate prograde to slow down and let segment one catch up to you (As you'll be further from Kerbin therefore slower) OR accelerate retrograde (AKA deaccelerate so you're closer to Kerbin and moving faster relatively to segment one). It's at this point you need to be paying attention to the orange markers on the orbital line as these will tell you how far you will be (Relative distance) and how fast you will be moving (relative velocity) relative to segment one. 

If all goes well, you'll get the two orange markers lined up veeery closely, and you can of course take extra time and make extra maneuvers to get them closer. (In other words getting relative distance lower and velocity lower). Tbh Distance is more important than velocity as you can slow down quickly once you get to segment one, but closing distance will always happen over time because.. Orbital Mechanics just works like that. 

Once you execute the maneuver, and get segments one and two close together, this is when RCS comes into play. Using all your tools available, you'll want to position the docking ports pointed toward each other and then target the segments docking port you want to connect to. At the same time, you'll want to right click the docking port on the segment you're flying and select "Control from here". This will alter your navball to show it's perspective. 

Now we're on to docking. Accelerate slowly in the direction of the docking port (Even if your docking port isn't pointed directly at it) as what you really need is for the prograde marker to line up with the target marker. Remember, Prograde is where you are going, and you want to go to the target. So as long as the prograde marker is on top of the target indicator, then you're going to your target. Even if it takes a little while. If you take your time and keep the indicators aligned, you should dock and you will be free to breathe again. 

Good luck!

Edited January 15, 2021 by James M

[Anonymous49]

Ok but I have no rcs

I don't need to dock, it's a crewed cargo resupply mission

I don't need to send my second segment but has it ready in the VAB. 

I don't need to send my second segment but has it ready in the VAB.  I need to rendezvous and not dock. i checked a lot but they mainly talk about docking

[James M]

4 minutes ago, Anonymous49 said:

Ok but I have no rcs

I don't need to dock, it's a crewed cargo resupply mission

I don't need to send my second segment but has it ready in the VAB. 

So it's a crewed resupply to a station, with no RCS, and you ALSO have a second segment in the VAB?

Edited January 15, 2021 by James M

[Anonymous49]

yes

i have no plans to launch the second segment

yes and i made sure they all have EVA jetpacks

[James M]

Firstly, RCS isn't mandatory, it's just nice to have. Secondly, you say you're having trouble rendezvousing, or docking? I gave instructions for both. Other than that, all anyone can do for you is try to fix MJ. If that's what you need I can't really help you there  I've never needed it. 

Post question: Is the crewed ship that's DOING the rendezvousing already in orbit? 

Edited January 15, 2021 by James M

[Anonymous49]

https://imgur.com/a/jjlxdvJ

3 minutes ago, James M said:

Firstly, RCS isn't mandatory, it's just nice to have. Secondly, you say you're having trouble rendezvousing, or docking? I gave instructions for both. Other than that, all anyone can do for you is try to fix MJ. If that's what you need I can't really help you there  I've never needed it. 

Post question: Is the crewed ship that's DOING the rendezvousing already in orbit? 

it was but eventually splashed down

[Anonymous49]

i did it again, putted it into orbit

[James M]

Sorry I had a thing. I'm back now. Delta V left?

[Anonymous49]

2391m/s upper stage, infinite fuel cheat on

[James M]

Just now, Anonymous49 said:

2391m/s upper stage, infinite fuel cheat on

You've got enough to go all the way to minmus, orbit, and come back. You don't need the cheat. Can you show me a picture of the orbits of both crafts you're trying to rendezvous? I'll see what I can do to help you.  

[Anonymous49]

reverted to VAB cuz I forgot to load on all my cargo. Coming into orbit

[James M]

Lol been there xD All good.

[Anonymous49]

https://imgur.com/a/sB2rbF0

[Gargamel]

Lots of good stuff in this thread that will help you out:

 

[Anonymous49]

I DON'T NEED TO DOCK!!!

[Gargamel]

5 minutes ago, Anonymous49 said:

I DON'T NEED TO DOCK!!!

But to dock, you need to rendezvous, and there's some good stuff in that thread on it.    Did you try reading it?  

 

[James M]

26 minutes ago, Gargamel said:

But to dock, you need to rendezvous

Thank you c:

In that picture, you would need to burn prograde and slightly anti normal to get the orange indicators closer to one another. 

Edited January 15, 2021 by James M

[VoidSquid]

31 minutes ago, Gargamel said:

there's some good stuff in that thread on it

@Snark also made an excellent docking guide: 

 

[Daveroski]

You have two ships in orbit and you want to bring them close enough together that a kerbal can jetpack over from one to the other.

A ship you are going to. 'The Target'

A ship going to meet it. 'Your Ship'

When you are getting two ships together it is much easier to do it if they both have close to the same 'inclination.'
The further apart their inclinations, the further apart will the ships be on 'closest approach'

It is better if the target is in the lower orbit. This gives Your Ship a little more room to manoeuvre.
I suggest that you always endeavour to have your target in the lower orbit.

The Higher Ship will be travelling more slowly than the Lower Ship.

This means that the Lower Ship is ALWAYS getting closer to the Higher Ship.
It will get to 'closest approach' and once it passes the Higher Ship, it will eventually catch up again and again...

When you set the ship you are going to as 'Target Vessel' you will be able to see a lot of useful information.

Its lowest point or periapsis. (Pe)
Its highest point or apoapsis.(Ap)
Its ascending node (AN)
Its descending node (DN)

The AN and DN are where the ships inclinations cross each other and from either of these two points you can make your inclinations the same by using either Normal or Anti-Normal  directions in a course correction burn.

Now we assume you have made your inclinations the same. (it takes a little practice and you may feel you need the hands of a surgeon)

Prograde points in the direction your ship is travelling.
Retrograde   points in the opposite direction to the one your ship is  travelling.

 

As you pass your targets' Ap point your ship Prograde and fire the engines until your Ap is about 50km higher than the target's Pe.
Your Pe should be close to the target's Ap.
Your Ap should be about 50km higher than the targets Pe.

At your Ap burn Retrograde  until your Pe overlaps the target's Ap. Making your Pe the same as your targets Ap.
It is ok if your Pe is a couple of Km lower than your targets Ap

Now place a manoeuvre node a little behind Your Ship.

Just having a node will show you the closest you get to your target in this orbit.
At this point Right Click the one that gives you 'closest approach' distance and relative velocity at 'closest approach.
When you look at the node marker, you will see just below it a greyed out - and an available + button.
Without changing any of the directions advance the orbit with the + button and watch the 'closest approach' marker.click the + as many times as you need to get the 'closest approach' as close to '0' as possible. If you overshoot use the now ungreyed - button to go back an orbit.

The closer you can get it to '0', the better.

Now you can slightly adjust the direction markers to bring you closer. On the map gizmo very slowly rotate the mouse-wheel and see what affects it has on your 'closest approach' using a little ,,,, and can refine your approach.
You are aiming for a figure between 0 and 5km.  Again closer to '0' is always better. '0' itself is brilliant but not always quickly attainable in Kerbins' orbit.

While you  are doing all this Your Ship is still going around Kerbin and could pass the node where you are working and throw out your plot.
Knowing about the + and - buttons is a good thing now you need one less orbit.

So you have your course plotted and it is a number of orbits in the future.
Point your ship at the manoeuvre node in your Nav-ball.

You can use the 'warp to node' feature and it will eat up the time for you.

It is a good idea to have the time to burn percentage set to 50% so that when you start your burn at '0' seconds, you will do half of the burn before the node and half of it after giving balance to the overall burn.

Now that you are on your way to the rendezvous you might want to give yourself a braking node.

Make sure your Nav-ball is set for Target and not Orbit or Surface
Click exactly on the closest approach or very slightly before (a hair) and create a node. When you use retrograde, you should see that your 'relative velocity' decreases. Again as close to '0' as possible is good but getting '0' is unlikely.

Once you have it 'close enough' (a popular engineer's phrase) aim for the node in the navball and you can safely warp to the node but once the warp ends set your SAS to retrograde and concentrate more on bringing your relative velocity to '0'

Once your relative velocity is 0 you will possibly be close enough for your crew transfer.

If not. Aim at your target and give a full burn until the Retrograde marker on the SAS becomes available.
Should be just a second or two.

Then select retrograde on the SAS and wait until you are close enough and gently come to a stop.

Perform your crew transfer.

I would like a reply to this post even if it is just to inform me I have wasted an hour of what little life I have left.

D.

 

[king of nowhere]

3 hours ago, Anonymous49 said:

I DON'T NEED TO DOCK!!!

before you dock two ships, you necessarily need to rendez-vous them. so, any docking guide will also start with rendez-vous.

the theory for rendez-vous is quite simple: the larger your orbit, the more time it takes. so, make sure the two spaceships orbits touch each other; then make one of them longer or shorter (in this last case, without crashing into the planet) to coordinate the time and make both ships arrive in that segment of the orbit at the same time.

besides that, there is nothing else i can add that others haven't said already

anyway, you should learn docking too. you will need to assemble ships in orbit, and to recover your landers. basically, you will need it for all the complex missions.

[Anonymous49]

14 minutes ago, king of nowhere said:

before you dock two ships, you necessarily need to rendez-vous them. so, any docking guide will also start with rendez-vous.

the theory for rendez-vous is quite simple: the larger your orbit, the more time it takes. so, make sure the two spaceships orbits touch each other; then make one of them longer or shorter (in this last case, without crashing into the planet) to coordinate the time and make both ships arrive in that segment of the orbit at the same time.

besides that, there is nothing else i can add that others haven't said already

anyway, you should learn docking too. you will need to assemble ships in orbit, and to recover your landers. basically, you will need it for all the complex missions.

well yes so you are telling me to dock without rcs

I could rely on mechjeb until the intercept course

[king of nowhere]

1 minute ago, Anonymous49 said:

well yes so you are telling me to dock without rcs

where do you get this?

I am not telling you to dock, with rcs or otherwise. perhaps you miss the meaning of the two words?

rendez-vous: bring the two ships close, and with similar speed.

docking: join the two ships together

I am telling you that before you join the two ships, you need to bring them close, so a docking guide will also discuss rendez-vous.

 

Anyway, if you also want to try docking (which i suggest, after you rendez-vous you may as well try), i also suggest you start docking small ships without rcs. rcs is an unnecessary complication, small ships dock perfectly without it and i never even felt the need for anything more while i was limiting myself to the 10-ton range. Now I am routinely docking 200-ton ships to 4000-ton motherships, and for those, rcs is needed. but it's an additional set of commands to learn, you may as well wait.

[Echo__3]

I don't know what tutorials you have seen, but maybe this one will help explain things for you.

 

[James M]

8 hours ago, Anonymous49 said:

well yes so you are telling me to dock without rcs

I could rely on mechjeb until the intercept course

Like I said earlier. While having RCS isn't technically mandatory, it would certainly make things easier. It's only really used however during the 'docking' portion of your missions so it's not at all necessary if all you intend to do is rendezvous. 

Also yes. You could rely on mechjeb again technically until the two craft intercept, but that's of course if you understand how to rendezvous first before you try programming it to do so. All is for naught however if you lack the prerequisite knowledge.