[Tutorial] Orbital Rendezvous Made Easy

[Kosmo-not]

I'm going to be jumping right into orbital rendezvous. There are two important things to know before getting started: orbital plane change maneuver and circularizing orbit. I won't be covering how to do these two tasks, so you will have to look those up on your own.

Let's pretend we have a space station sitting in a circular orbit of 100km. Our plan is, of course, to rendezvous with it. All of the tutorials I have seen on rendezvous involve a lot of guessing. This is because we have very basic instruments to guide us. But, there is one piece of information that we have that can tell us almost exactly when to initiate our intercept burn: distance to target. You can get this distance by hovering your mouse over the target diamond in your main view.

For the purposes of this tutorial, launch will be timed to insert into a parking orbit of 80km, ending up a little behind the station. After achieving a circular 80km, we wait to catch up to the point of intercept burn initialization. The question is: how do we know when to do our intercept burn?

The math is not hard to understand. We start out with both craft at the same point, and work backwards to the intercept burn point. We know how much time it takes to go from the burn point to intercept, and can determine the position of the target at that time. We can then solve for the relative distance between the two objects.

Attached is a table I made with the distance to target you have to wait for (any distance above 100km, and you won't see it due to the visibility limit). In the case of this tutorial, the distance we need it 50.4km (680km row, 700km column. Kerbin's radius is 600km). When we come within 100km range, the target diamond will appear and we watch the range until 50.4km is achieved. Then we burn prograde, raising our apoapsis to 100km to match our target.

You then just need to wait half an orbit. We watch as the space station passes overhead and then approaches from behind. Burn at apoapsis to complete the rendezvous maneuver. That wasn't so bad, was it?

The table is also the same for Mun orbits from 480km to 600km (Mun's radius is 200km).

Table:

Download rendezvous table spreadsheet here.

*New*

I have decided to attach the spreadsheet I used for the rendezvous table.

*Even newer*

Here's a video tutorial:

Edited October 10, 2014 by Kosmo-not

[Zephram Kerman]

Oh this is a gold nugget. Thank you!

[Kosmo-not]

Just to give people an idea on how accurate this method is:

I intercepted my space station (the one at 100km) from a 120km orbit. After the maneuver was complete, I was 300m away from the station.

Going from 80km to 100km, I came within 600m, but was off plane a little. It would probably be similar to the other result if I was more on plane.

I can\'t wait for docking now.

[VincentMcConnell]

Can you make a guide showing where our target vehicle should be when we launch our docking vessel?

I have a space station in a 200KM orbit with a docking vehicle in a 190KM orbit. I\'m waiting until they are 25.4 Kilometers away from eachother to make the intercept burn.

[Kosmo-not]

Can you make a guide showing where our target vehicle should be when we launch our docking vessel?

I have a space station in a 200KM orbit with a docking vehicle in a 190KM orbit. I\'m waiting until they are 25.4 Kilometers away from eachother to make the intercept burn.

The best method I can think of so far is to time how long it takes to get to orbit, and the angle you\'re at compared to the launchpad at that time. Then you can calculate the angle the station moves through during that time.

[VincentMcConnell]

Just got within a few hundred meters of my space station, and like I said, orbital rendezvous is kind of boring. I was fine controlling with the RCS, it took too long and I just got bored.

Unfortunately, right now, there\'s NO payoff for rendezvous. You can\'t dock yet, so basically all you can do is wave hello to the target. That\'s what started boring me about Mun landings.

[rustymcclintock]

Just got within a few hundred meters of my space station, and like I said, orbital rendezvous is kind of boring. I was fine controlling with the RCS, it took too long and I just got bored.

Unfortunately, right now, there\'s NO payoff for rendezvous. You can\'t dock yet, so basically all you can do is wave hello to the target. That\'s what started boring me about Mun landings.

maybe make your target thin and cylindrical and put landing legs on your rendouvous vessel, use the legs to 'grab' it. gonna test that soon.

[VincentMcConnell]

The image can no longer be viewed.........

[Kosmo-not]

The image can no longer be viewed.........

Lovely server migration. Thanks for letting me know. Fixed now.

[VincentMcConnell]

Lovely server migration. Thanks for letting me know. Fixed now.

Thanks Kosmo-not.

[Kosmo-not]

I have attached the excel spreadsheet for all to use. This makes it easy for you to make rendezvous tables to your own custom scaling (for example: if you want a table for low mun orbit rendezvous).

I\'m continuing to work on a more general case for rendezvous.

[VincentMcConnell]

Yes, you did indeed make it easy. That\'s my second rendezvous in two days. One late last night and this one right when I got home. I had no trouble. 200KM above Kerbin for anyone who\'s wondering.

[the_bT]

maybe make your target thin and cylindrical and put landing legs on your rendouvous vessel, use the legs to 'grab' it. gonna test that soon.

Intresting Idea... if the standard Lander Legs do not work, maybe a custom part could be made... (one part to grab, and some 'legs/arms' to actually grab it)

Edit: Seems to work, see this:

Three modified lander lags grab a single full fuel tank+decoupler:

Press G again it\'s gone =P

Note, this was done while under full throttle in athmosphere, but should work in orbit just as well right?

I kinda messed up the 'legs' rotating though, need to fix that.

I\'ll make a thread in addon release after that, its kinda off topic here...

[Endeavour]

This is great. Thanks for figuring this out and posting it Kosmo-not. Helped me finally be successful

[White Owl]

Of all the guides and tutorials I\'ve looked at for this orbital rendezvous deal, this chart is by far the simplest and easiest to use. Very nice work.

[Motorsheep]

I finally managed a Kerbin-orbit rendezvous, thanks to your chart, Kosmo-not

[White Owl]

You know what would be great? A simple mod to display this chart on the screen when desired.

[Kosmo-not]

Alrighty! I said I would make a tutorial video, and I did. Have a look at the first post to see it.

[Zephram Kerman]

I really liked that touch near the end; the most efficient way to close a small error. Burning prograde and a bit inwards to catch up makes sense to me, now, but I wouldn\'t have thought of that on my own.

[VincentMcConnell]

I do not have excel, so I was wondering if someone could give me the distance from the target at the time of intercept burn with regards to an orbit of the Mun.

My target will be in a 30KM orbit and my LM will be in a 28KM orbit. What distance must I be from the target at the time I make the intercept burn?

[Kosmo-not]

I do not have excel, so I was wondering if someone could give me the distance from the target at the time of intercept burn with regards to an orbit of the Mun.

My target will be in a 30KM orbit and my LM will be in a 28KM orbit. What distance must I be from the target at the time I make the intercept burn?

5.1km

I would recommend having the LM at a lower altitude. 48.8km distance at 10km altitude. Also, the catch-up rate is 10x faster.

If you want a picture of a custom table, just PM me.

[VincentMcConnell]

5.1km

I would recommend having the LM at a lower altitude. 48.8km distance at 10km altitude. Also, the catch-up rate is 10x faster.

If you want a picture of a custom table, just PM me.

I will PM you. I changed my desired rendezvous altitude to 100KM above the Lunar surface. CM is orbiting at 98. I would do the other way around, but I forgot to bring RCS on my LM APS.

[VincentMcConnell]

5.1km

I would recommend having the LM at a lower altitude. 48.8km distance at 10km altitude. Also, the catch-up rate is 10x faster.

If you want a picture of a custom table, just PM me.

None of my PM\'s seem to be going through, man.

If you didn\'t get them, I changed my desired altitude to a 120KM above the Mun rendezvous. My docking vehicle is at 100KM and my target at 120. That\'s really the only measurement I need.

[VincentMcConnell]

Apollo Lunar Orbit Rendezvous. Command Module and Lunar Module.

First, to prove I came from the surface...

Lunar Module on the ground:

Lunar Module Lifting into Lunar Orbit

Command Module first catches sight of the Lunar Module\'s icon.

Very close:

Rendezvous!

[Kosmo-not]

That was from a 100km parking orbit to the 120km orbit?