How to intercept asteroid?

[ThinkOutsideTheHangar]

I'm the worst person you could go to for docking, so I'm naturally confused at this. How do I intercept asteroids?

[dbmorpher]

If you select the asteroid you can target it. Once targeted in the map view look at the arrows labeled Ascending Node or Descending Nodes. Make a Maneuver node at one of these points and pull on one of the purple triangles until it reaches zero. Next try to create a prograde node that extends your orbit close to the asteroid. After you make that burn make another node at your apoapsis to circularize your orbit. Once your orbit is close to the asteroid's, use your rcs to get near it. If you need practice with that try the rendezvous tutorial on ksp.

[Hyomoto]

Let me ask this, can you reach the Mun? Yes? You already have half the skills need to do this. So, let's simplify a bit, shall we?

The basic idea is the same no matter what your target is. You need to intercept the asteroid, planet, ship or whatever. Since small bodies like ships and asteroids don't have gravity, however, you'll need to make an educated guess on your own. Instead of trying to intercept its sphere of influence, you are simply trying to find the closest point at which you intercept your target, think of it like picking a desired altitude to approach a planet at. However, instead of the SOI marker, you want to pay attention to the closest intercept markers and you want a very low altitude. I strongly recommend you try to get them to less than 3km, though less than 10 is pretty workable. Now, just like meeting the Mun, you need to wait.

Once you get within range, make sure your target is selected. If you click on your speed display above the navball you'll see you have an option called 'target'. Notice that when this is selected, your retrograde and prograde markers move and your speed changes. This is because it is displaying the difference in speed between you and your target, instead of you and the planet you are orbiting. Now, all you need to do is burn prograde until your speed is low, below 1m/s is fine. Then, orient your ship towards the target marker and burn again. If you look at map mode, you can watch your intercept markers move. Once again, try for the closest intercept you can. You can just repeat these two steps until you get as close as you need to be. All you are doing here is closing the gap on your target. The reason is because you aren't travelling in a straight line, and being in different orbits you are going to reach a point where they overlap as close as they can before you start getting further away again. So you just zero out your speed in relation to your target, and then burn towards it again.

Sound hard? Let's look at it in steps:

1. Plot intercept course.

2. Upon intercept, switch to target speed display, burn prograde and zero out speed.

3. Burn towards target.

4. Upon intercept, burn prograde to zero out speed.

5. Repeat 3 and 4 until you are in the desired range.

I hope that makes it sound easy, because it really is once you know how to use the target speed readout on your navball. Give it a try with something in orbit! Once you can do that, there is really very little left to learn in KSP.

Edited April 8, 2014 by Hyomoto

[Collin Cutler]

Here is a video that explains it really well.

Hope it works for you!

[Nukem950]

Sound hard? Let's look at it in steps:

1. Plot intercept course.

2. Upon intercept, switch to target speed display, burn prograde and zero out speed.

3. Burn towards target.

4. Upon intercept, burn prograde to zero out speed.

5. Repeat 3 and 4 until you are in the desired range.

I hope that makes it sound easy, because it really is once you know how to use the target speed readout on your navball. Give it a try with something in orbit! Once you can do that, there is really very little left to learn in KSP.

I just captured my first asteroid following Hyomoto's advice. It worked! I want to add some things to what was said though:

1. What is the size of the asteroid you are going to capture? Size matters. My class C asteroid weighs 120t.

2. Try to grab the asteroid near its center. This is important because of having to point your ship at the center of it's mass.

3. Once you dock with it, right click on the asteroid and click "target center of mass."

4. Right click on your advanced grabbing unit and click "Free Pivot."

5. Move your ship around until your navball aligns with the asteroid's center of mass.

6. Right click on your grabbing unit and lock it.

7. Now you should be able to do things like circularizing its orbit around Kerbin.

[Rus-Evo]

What I did was the following:

1, Launch in a manner that puts you into an orbit which is aligned with the path of the asteroid (might need to wait until Kerbin spins round to the right spot).

2, Get into a tight orbit (say 100 x 100).

3, Refine your orbit to align more closely if neccessary.

4, Set asteroid as target and monitor how fast it is coming in.

5, When it gets closer set a maneuver node on the opposite side of the planet to the asteroids periaps and set it to expend to the orbit of the asteroid.

6, Look at the distance to target, if it is very far, then cancel the node and do another orbit, then set out another node as above, it should be closer. Repeat as neccessary until you get a reasonable intercept (I got 80kms first time).

The reason I stick in a close orbit is that it gives me more refined timing for when I burn out to the roid, bigger orbits would mean less windows for burning out to it.

7, When you get close to the asteroid you may find you need to cancel out 700ms or more of mutual velocity, so be ready for that.

8, Cruise in as with any other intercept.