Rendevous problems

[Natokerbal]

So I have played ksp for a while but I can't get good at rendvous in kerbin orbit but I can on minmus and Mun and also duna and moho. Any tips or tutorials?

 

[James Kerman]

Greetings @Natokerbal and welcome to the forums.

@Snark has created a great illustrated guide to docking that really helped me.  Section 1 is  what you want.

Is there a particular issue you are having?

[Vanamonde]

The process is exactly the same, though maneuvers cost more dV due to the velocities required by Kerbin's mass an orbital speeds. So what kind of problems are you having at Kerbin? 

[Natokerbal]

The problem is so at that at the time I reach periaphsis the targeted way too far ahead to reach using maneuver nodes. Also when I burn to get a rendezvous I either colloidal or burn so I'm sub-orbital

[Natokerbal]

I think it might be me having too much energy when I exit the atmosphere

[James Kerman]

11 hours ago, Natokerbal said:

I think it might be me having too much energy when I exit the atmosphere

I don't think so - you need to do at least 2250ms to make an orbit.

I think you might be pushing to get a rendezvous instead of waiting for it to get close before adjusting.  If you are in a higher or lower orbit than that of your target you will eventually get a close encounter by doing nothing, just waiting.

One little trick that I use is when I'm pretty close to rendezvous I adjust my orbit to be really close to my targets orbit while still being slightly above if I am in front of the target or slightly below if I'm chasing my target.

 

[Dman979]

15 hours ago, Natokerbal said:

The problem is so at that at the time I reach periaphsis the targeted way too far ahead to reach using maneuver nodes. Also when I burn to get a rendezvous I either colloidal or burn so I'm sub-orbital

Actually, if the target is ahead of you, you'll want to meet it near your apoapsis.

Explanation:

2 hours ago, James Kerman said:

One little trick that I use is when I'm pretty close to rendezvous I adjust my orbit to be really close to my targets orbit while still being slightly above if I am in front of the target or slightly below if I'm chasing my target.

This works because objects in a lower orbit move faster than objects in a higher orbit. If an object is ahead of me, I need to drop my orbit a bit, and if it's behind me, I need to raise my orbit a bit.

[Hodari]

17 hours ago, Natokerbal said:

The problem is so at that at the time I reach periaphsis the targeted way too far ahead to reach using maneuver nodes. Also when I burn to get a rendezvous I either colloidal or burn so I'm sub-orbital

First of all, be patient.  You don't need to make the encounter happen on the first time around or anything.  You can spend several orbits slowly catching up(or letting it catch up to you, as needed).  If the other ship is behind you in the orbit, you normally will want to put yourself in a slightly higher orbit, thus taking longer and allowing the other ship to catch up.  If it's ahead of you, you normally want a lower orbit.  BUT, if that's not possible since any lower orbit would put you into the atmosphere(or worse yet, colliding with the surface), you can go into a HIGHER orbit instead and you'll just have to wait until you circle all the way around and catch up from the other direction instead. 

A lot of times, it will end up being a tradeoff between spending more delta-v in order to get a faster encounter or saving fuel but needed to spend time orbiting the planet several times in order to catch up.  It all depends on how much fuel you have left at that point and how patient you're willing to be, but since(in stock at least) you don't need to worry about stranded Kerbals dying or anything, you can take as much time as you want.

[Ohm is Futile]

1 hour ago, Hodari said:

First of all, be patient.

This is really key, putting the pedal to the metal to get an encounter super fast is incredibly inefficient and will send you through the atmosphere or terrain if you are not careful.

In low orbit around Kerbin, it requires you to be extra patient because of the atmosphere and DeltaV requirements to change your orbit.

Quote

 If it's ahead of you, you normally want a lower orbit.  BUT, if that's not possible since any lower orbit would put you into the atmosphere(or worse yet, colliding with the surface), you can go into a HIGHER orbit instead and you'll just have to wait until you circle all the way around and catch up from the other direction instead. 

This is good advice.

So what do you do to get that perfect encounter? You do what has been stated... normally you can get an encounter within 20km if you are patient just by letting both vehicles orbit. Then, make sure you have targeted the other vehicle and switch your navball to target mode. The trick to closing the distance when you are within those 20km is to "drag" your prograde marker over your target marker on the navball. The way to do this is to burn on the opposite of the target marker from the prograde marker until both circles are on top of each. Then, more patience.

Example:

--v--            O           -o-
Navball        Target        Prograde
Marker         Marker        Marker

^ burn here until it looks like this:

--v--		-O-
Navball     Both Target and Prograde
Marker      markers overlapping

If you do this, when you check your map again, you should get a much closer encounter next. Pay attention to your Navball markers and keep burning if the two markers separate a lot and you are not close enough yet.

 

Finally, when you are closing in to RCS range, make sure the Navball is still on target mode and burn retrograde until the speed meter is less than 1 m/s. Voila!

 

Quote

I think it might be me having too much energy when I exit the atmosphere

Don't shoot for an encounter from the launch pad... you can try to time it to be as close as possible when you get to orbit, but aim to get into orbit first, then you can close the distance.

Edited December 21, 2016 by Ohm is Futile
noticed something else