Docking Encounter Tips

[Anders_]

Hi,

I recently docked for my first time in KSP and it was pretty fun, but I was wondering if anyone had any tips for me. Once I get an encounter I am actually pretty good at the rest (probably because I use the Matt Lowne lazy docking method), so tips for getting the first encounter would be very helpful but any tips would be helpful.

Thanks!

P.S. If you want to know how bad I am at getting the encounter... %95 of the time when I get an encounter my periapsis is so low that I get destroyed by re-entry heating before I can even get to the encounter.

[king of nowhere]

35 minutes ago, Anders_ said:

Hi,

I recently docked for my first time in KSP and it was pretty fun, but I was wondering if anyone had any tips for me. Once I get an encounter I am actually pretty good at the rest (probably because I use the Matt Lowne lazy docking method), so tips for getting the first encounter would be very helpful but any tips would be helpful.

Thanks!

P.S. If you want to know how bad I am at getting the encounter... %95 of the time when I get an encounter my periapsis is so low that I get destroyed by re-entry heating before I can even get to the encounter.

so, you have your ship you want to reach in orbit.

you start by sending your new ship in an orbit inside it, touching it on a point. if your target is on a 80x80 orbit, you want to be on a 80x75 orbit.  of course, fix the orbital plane first (there are ways to skip this, and they save a little bit of fuel, but are harder)

so, the smaller an orbit is, the shorter it takes. the ship in the smaller orbit will slowly gain on the other one. this will let you reach a ship ahead of you - i generally target for this situation when i lauch for a rendez-vous. if instead you are ahead of your target and you need it to catch up, just increase your orbit a bit, still touching your target. in this example, an 80x85 will do.

here is an example. i am commanding the space station and want to reach the plane. i am a bit ahead of it, so i put myself in a slightly larger orbit, so the plane will reach me in a few orbits.

keep this difference small, the greater the difference in the orbits, the more fuel you'll have to use to equalize the two vessel's speed

ok, so here we see the orange marker for the next close encounter. the plane will still be behind me. we set up a manuever node just after the close encounter

now that we set up the manuever node, the game calculates the closest approach after the node. this means in the next orbit. so in the next orbit the plane will be closer, but still behind us. so we right-click on the manuever node and shift it ahead by one orbit

now the manuever node is 2 orbits from now, and it says that in the third orbit, the plane will be slightly ahead of us.

that's just what we want! now we only have to make sure that instead of being ahead of us, it just reaches us perfectly.

to do so, we must accelerate just a bit, enough to cover those 29 km that the plane will have made past our position.

and to accelerate, we need to burn retrograde. our orbit gets smaller, and we accelerate and gradually catch up to the plane again, until we have a near perfect encounter

you don't even need a manuever node; just burn retrograde very slowly, and you'll see the close encounter marker gradually shift.

 

i hope that was helpful.  the  key is to have the two orbits intersect in one point, and then burn in that point, prograde or retrograde depending on whether you need to go slower or faster.

[DeadJohn]

1 hour ago, Anders_ said:

my periapsis is so low that I get destroyed by re-entry heating before I can even get to the encounter

You might be trying to do too large of a burn to get that encounter. Regardless of heating, the encounter display assumes zero drag, so if you skim the atmosphere even a little your encounter will change. Keep your Pe above 70km on Kerbin.

Assuming you need to catch up with your target, and are already in a slightly lower orbit than your target, wait a few orbits to reduce the distance before doing the maneuver burn to get a very close intercept. You won't have to lower the periapsis as much by waiting.

 

 

[Spricigo]

6 hours ago, Anders_ said:

P.S. If you want to know how bad I am at getting the encounter... %95 of the time when I get an encounter my periapsis is so low that I get destroyed by re-entry heating before I can even get to the encounter.

In that case the most useful tip probably is: don't rush it.

Notice you don't want only to get to the same position your target is, ou also  want to match velocities  when you get there. That is a lot easier if you take your time to do as many small adjustment as needed  to get closer and closer to it.

6 hours ago, king of nowhere said:

you start by sending your new ship in an orbit inside it, touching it on a point.

That was precise to the point.* The means already matching  the velocity direction. If you know your closest encounter lies several orbits ahead, you can reduce the magnitude diference with gradual adjustments every time you pass that point.

 

*...and to the pun. NO REGRETS!

[Caerfinon]

It you use mods, then Navball Docking Alignment Indicator CE-2 helps with docking a great deal by helping you visualize the alignment during the docking.

 

[Anders_]

Thanks so much for all your tips! I will try them out later today and tell you if they work!