How to rendezvous/intercept properly?

[Unknow0059]

I don't have problems with the actual process of intercept, the biggest problem for me is, when i come close to the craft, it passes by my ship too fast, so i can't reach it, any tips?

Edited November 5, 2014 by Unknow0059

[Master Tao]

Many, though a video tells a million words:

. The intercept portion takes the first 6 1/2 minutes, but the link should skip those. You might also check out this list of tutorials.

[Norpo]

Target the thing you're trying to rendezvous with.

Click the velocity indicator on the navball (the thing that says orbital, surface etc.) Click it until it reads Target.

When you get close, e.g, when you think you'll rendevous with it in 7 or so seconds is a good rule of thumb, turn to the retrograde, and start your engines, Keep burning retrograde until it turns away, and mess with this until the velocity indicator reads 0.0m/s (or very close to it) This means you're going the same speed around the body (e.g Kerbin) as the thing you're rendevousing with, this is good.

The pink circle with the dot in the middle is the target prograde, if you aim there and use your engines, you'll go towards it. Te pink thing with the 3 lines going away from the dot is the TARGET retrograde, if your prograde is on it, you're going away from it.

I reccommend doing this with quicksave to try it out, as this involves a lot of trial and error, especially for the first time doing it.

EDIT: Also, see the videos/tutorial lists in the above post, in case this doesn't explain things (I'm not very good at making tutorials or describing things, but I hope this post helps! )

[Starman4308]

I don't have problems with the actual process of intercept, the biggest problem for me is, when i come close to the craft, it passes by my ship too fast, so i can't reach it, any tips?

Target the, well, target. Watch your closing velocity (click the velocity meter to show target velocity) as you close in, and just before going past, burn target retrograde until you hit 0 m/s relative velocity. To have the velocity killed at absolute closest approach, you will want to burn for time t, and begin the burn at 1/2*t before closest approach: so if it would take 8 seconds to kill your relative velocity, start your burn 4 seconds before closest approach.

One thing to watch for is that you need to be pretty close to judge what relative velocity will be: if you're far away, the relative velocity is dominated by the phase angle*.

*For example, if you've got two spacecraft in 2.3 km/s circular orbits, 180 degrees away from each other, their relative velocity will be 4.6 km/s, because they are going 2.3 km/s in opposite directions relative to the center of Kerbin. This goes down to 0 as the phase angle goes to 0.

[Kryxal]

I'd suggest giving yourself somewhat more time before closest approach, and ease off the throttle some ... that way, you have more room to play with things if you think you'll overshoot. Still, closing at 100 m/s with you being capable of .5 g is only 20 seconds of burn all told, so starting at maybe 15 seconds, 3/4 throttle shouldn't be a problem.

[Friend Bear]

The biggest thing...when you are within 10km (I think), your pro/retrograde becomes relative to the target. burn retro until you are at 0 orbit, relative to the target (it will show 0 m/s) and then aim at the circlular red target, burn, burn retro as you close in...rinse - repeat.

[Scarecrow88]

When getting close to actual rendezvous, you're navball should be in target mode, and the speed indicated will be relative to your target. As you get closer, you need to burn retrograde to bring that speed down, preferably to zero. If it's nowhere near zero, then you are going to go whizzing past, as you have discovered.

If you can get to zero relative velocity, but are still a little way off your target, point yourself towards the pink target marker and burn to get yourself closer; how fast this burn neds to be will be governed by how far away from your target you still are. As you get closer, repeat from the step above until you are actually close enough to dock.

[Zylark]

What I do (when not lazy and let MJ do it all), is to get the intercept as close as comfortable, between 100 and 500 meters is fine. Before estimated closest approach, I turn the vessel to target retrograde. Then at estimated closest approach, burn until relative velocity to target is +/-0.1 m/s. Then I turn vessel to target, setting up so that I get to a good position for final approach and docking. Speed for approach depends on distance to target. Rule of thumb being distance (in meters) divided by 100 is the closing speed I aim for. So if 500 meters out, initial approach speed is 5m/s. During the approach - and if available on my vessel - I reduce speed as I close using RCS. Again following the 1m/s per 100 meter distance to target guideline. If RCS is not available, I turn the vessel to target retrograde again, and use main engines to reduce speed as I get closer.

Keeping such low speed during approach assures no unfortunate collisions, and makes it easy to make minor course corrections to line up properly to the docking port I'm aiming for.

Actual docking is done by using MJ SmartASS target Par- autopilot to keep my vessel aligned to the docking port, and do the approach using Docking Port Alignment mod. Unless it is some small nimble vessel, where MJ does a good job of docking for me. Larger vessels have to be done manually, as MJ gets very wasteful with monoprop - and I don't usually have much of that on my ships.

[Higgs]

i am going to be short and sweet with you on this. get mechjeb. do not listen to the naysayers and negative nellies when they bemoan my suggestion. The truth of the matter is: no tutorial video or written how-to can properly explain things. Reason is simple: they are not using a craft YOU built. Mechjeb will take the craft YOU built <so long as you place mechjeb onto the craft> and fly it into orbit, then with the use of the proper options once in orbit, will fly a rendezvous, and then, can dock with your target vessel. so long as: you have matching docking ports on each craft, target your desired port, and tell mechjeb to control from the desired port you wish to dock with <this time, this port is the one on the vehicle that is approaching the docking target>. mechjeb, such a vital tool, yet so wildly hated, yet, is such a vital tool. use it, and use it proudly.

[Scarecrow88]

The truth of the matter is: no tutorial video or written how-to can properly explain things. Reason is simple: they are not using a craft YOU built.

That is perfectly true, but the principles of rendezvousing are the same no matter what craft you are flying. One of the greatest satisfactions I achieved in this game was mastering rendezvousing and docking. Until I did it all seemed like a black art. I too experienced the same problem the OP is having; getting close only to just go whizzing past. When it all finally clicked, and I worked out where I was going wrong and what I needed to do, to say I felt really chuffed would be an understatement. If I had given in and let MechJeb do all that, I wouldn't have experienced that same level of elation and the sense of a job well done.

[Zylark]

@Higgs: Whilst MJ certainly is useful, very much on my 'must have' mod list, it is also a bit of a crutch. And quite often, not as good, efficient or precise as doing it yourself.

I view MJ as a tool for doing the routine. Much as pilots use their autopilot. Whilst it can do certain jobs very well, it requires constant monitoring and is no replacement for a proficient pilot doing it manually. What makes MJ essential however, is all the nice data panels and the Maneuver Node Editor. From designing the ship to flying it manually, all that information and fine control of the MNE is vital to doing a good job of it.

What the autopilot is good for is executing nodes you've set up, getting stuff to a desired orbit and landing stuff (*NOT* Spaceplanes) at a desired spot. Everything else is a matter of convenience, as MJ tends to do them very inefficiently. But if you got fuel or monoprop to spare, then by all means go ahead.

[ElWanderer]

One thing I do after performing a burn to set-up an intercept is to place a manoeuvre node on the intercept point. That alone can be used to set a Kerbal Alarm Clock alarm so I don't accidentally time warp past the intercept, but it can also be used to estimate the delta-v and burn time that will be needed to match speed with the target: fiddle with the node until your predicted orbit closely matches that of the target. So far I it's never been accurate enough to burn as per the node, but it's useful as a guide.

[Higgs]

@zylark mechjeb is not a crutch at all. I consider it a flight computer and autopilot, both of which are EXACTLY what it is. I think it is something that should if not MUST become stock. When it comes to learning as the OP seeks, mechjeb simply cannot be beaten.

[magnemoe]

I don't have problems with the actual process of intercept, the biggest problem for me is, when i come close to the craft, it passes by my ship too fast, so i can't reach it, any tips?

Ok so you can get close intercepts but is not able to stop?

The problem is that you can see the closest intercept point and time in map mode but not in normal mode.

First find how long time you will use to do the burn. orient ship so you point away and stay in map mode, start the burn, then speed get low go to normal mode and see distance.and if you should continue burning or not.

Another option is to make an node who make your orbit simlar to target, do this and then adjust.

[Unknow0059]

Sorry i forgot to change the thread to Answered :C

Anyway guys thanks for the help!