Intercepting an asteroid

[Moustache]

I find it very diffucult to intercept asteroids with the tools available in game. I been trying over and over, passed by so close that i could see it with my eyes but no way to reach it. I finally got frustrated and quit the game angry swearing i ll never play this game again lol. I just feel i dont have the tools to do that. i think it just a matter of luck.

Alright..i feel better now...i ll just let those rock crash on Kerbin

[cookii]

It's not that hard. I actually did it on my second try, just be sure you know how to dock first.

[petero9]

Do you know how to rendezvous and dock with another ship?

[Xacktar]

I did it kinda by accident today. >.> I just wanted to look at it, ended up bringing it home.

A lot of practice with rendezvous, docking and interplanetary hops will give you the experience to grab one. Play around and don't forget that F5 is a quicksave.

[Langkard]

It is definitely the hardest rendezvous maneuver you're going to make. Practice making a rendezvous with an orbiting vessel first, in some high orbit. Work on matching the orbital inclination of the target, so that you catch up to it from behind on the same general trajectory. Then practice docking with it.

Once you get the hang of making that sort of maneuver, find an asteroid that makes a Kerbin encounter close enough that its orbit is warped some but not too steeply or too shallowly. This type of encounter will be much easier to change into an actual orbit. You want to intercept the path of the asteroid before it reaches its periapsis with Kerbin, going in the same direction and with an inclination as close as possible to the path of the asteroid. You'll boost your way up to it, dock with it - usually from the front of the asteroid, in relation to its trajectory. Then you want to thrust against the asteroid's trajectory, retrograde, slowing it down until it achieves an orbit around Kerbin. From there you can thrust more to de-orbit it.

Scott Manley's demo video of an asteroid redirect is a good one to watch for general clues on what to do. Don't worry about being as minimalist on fuel and rocket design as Scott usually is. Take enough fuel and thrust to overdo it. Worry about efficiency later.

http://www.youtube.com/watch?v=SdF-ftRnt50

[siztem]

There's also Mechjeb, a mod that will handle a lot of the maneuvers for you (i.e. an autopilot). And even if you don't want an autopilot, it has tools that allow you to create and edit maneuver nodes numerically and with incredible precision (which is very, very handy for deep space randezvous).

And if you ask me, I think a numerical editor for the maneuver nodes should be made a part of the game, and not just the mod

[Hellespont]

I rammed my first attempt into the astroid near its periapsis, it slowed it enough to leave it in the gravity well ^-^

[rich0000]

I find the most difficult of this aspect planning the launch. The game provides little information on inclinations/etc so it is not straightforward determining when I should launch and into what trajectory to minimize the cost to approach.

Most of the tutorials I've seen involve just putting a ton of delta V into the rocket. I haven't found any which go over planning how to intercept an asteroid in career mode for minimal cost. But, I'm relatively new to the game so I could have missed them.

[flying diomedea]

Please find here ( forum.kerbalspaceprogram.com/index.php?/topic/68613-asteroid-rendezvous-outside-of-kerbins-soi/ ) an excellent guide to Asteroid R/V, covering all required to make a correct launch. Should something still be unclear, let me know.

[puct]

I did it on my first try :D

Match inclination during launch, have orbit lines touch at one point, boost at contact point to get encounter, profit.

[rich0000]

Potato eredeti hozzászólása:

I did it on my first try :D

Match inclination during launch, have orbit lines touch at one point, boost at contact point to get encounter, profit.

What was your total Delta V though? It isn't hard to intercept something. I want to do it efficiently.

I'd seen that tutorial, but it still ends up using a lot of Delta V. It also only works if the asteroid enters the Kerbin SOI. If there is no hyperbolic orbit to line up it won't work, and I really don't like manually tweaking my launch in map mode. I'd prefer to have an initial launch time and heading/inclination.

I ended up eyeballing one from an equtorial orbit and getting the Delta V down to maybe 1300 or so, but it is still hard to launch into the right inclination.

Part of the issue is that KSP generally avoids numbers.

[rich0000]

RoofCatA eredeti hozzászólása:

If it's outside Kerbin SOI, go for it like you would for Duna.

Sure, but how would you do that, launching into the correct inclination/etc? And without using any online calculators, since those online calculators don't work for randomly-generated asteroid orbits?

I get that you can brute force your way there, and that will obviously work. I'm just trying to find the most efficient way to do it.

The main issue with intercepting them inside Kerbin's SOI is that they're moving towards Kerbin and you're moving away from it, so that basically guarantees a maximum delta-v to intercept. If you want to capture it you'd need to do so before it reaches Pe, otherwise you're stick waiting for a full Kerbin solar orbit to direct it back.

Now, it does seem fairly straightforward to do an efficient intercept if you're willing to wait a few years, since you can efficiently do a plane change and transfer to the asteroid, then do another plane change and transfer back to Kerbin. It will just take a VERY long time that way.

Don't get me wrong, I appreciate the suggestions/etc. I'm just trying to figure out if there is a more efficient way to go about it.

[rich0000]

RoofCatA eredeti hozzászólása:

Quickest solution is to intercept asteroids at 180° as soon as they enter Kerbin SOI. Your speed may be less than 100 if done in advance or 200..300m/s for "last minute" 8 day trip. Asteroid will enter at 400m/s or so. Which isn't much to burn up there. It's a bit harder to make mirrored interception, as game doesn't like it much. But I guess everything is hard the first time.

Hmm, I hadn't thought about that. So far out from Kerbin the velocities would tend to be lower, so it isn't quite as expensive and I am probably thinking. Even if you burn 900m/s at Kerbin Pe you're not going to be going nearly that fast by the time you hit the edge of the SoI.

I'll admit I've been a bit of a glutton for punishment. I just started playing and started on Career mode, and have been staying mostly in the Kerbin SoI so far. I figured I'd challenge myself a bit since I've played Orbiter before. That game gave you more in the way of numbers, but you still needed mods to do interplanetary stuff well, and I've yet to see a game that does a good job of making it easy to discover windows/etc. The maneuver nodes in KSP are actually pretty nice.

[George Kerman]

I'll give you a very simple, shallow and lazy method, for those moments when you'd rather not think. This is done in Kerbin orbit at high altitudes (50 000km ish).
a) Is the asteroid's trajectory more polar or more equatorial? Launch equatorial if asteroid has a more equatorial trajectory and polar if it's more polar
b) Setup a 950(ish) m/s burn in the direction of the asteroid. You might wanna add some normal component / slightly change the burn position until you get some encounter, no matter the distance. If you don't get an encounter but the trajectory intersects (at least sort of), that will do.
The critical thing is that the asteroid doesn't surpass you when you reach the intended intersection point.
c) Even one day before the estimated intersection point, set the navball to target and align the retro vector with the anti-target, just like you'd do with a normal rendez-vous. At such high altitudes, the gravity is not so significant and all your normal and radial burns are pretty efficient. Basically, where you burn is (almost) where you'll go. You wanna correct this from time to time, maybe 30 mins before the interception. While doing the burn, check the rendezvous distance. If it increases, stop the burn and do it closer to that point.

If you go with nukes and add a decent amount of fuel, you got like 4km/s dV "by default", which is more than you'll ever need for this lazy method. This method should take you 2-2.5k depending on the losses you have for that velocity vectors alignment. Obviously you have to add the dv needed to achieve LKO to this. Enjoy!