Asteroid Capture Tutorial.

[mike9606]

So I plan on capturing the C class asteroid shown Here. It's periapsis is at 10,464,769m.

With this Craft.

The issue is, I don't know how to capture an Asteroid. There is a tutorial in-game, but in that the asteroid is already in Kerbin Orbit. So the things I want to know are 1. Does the craft have enough DeltaV to get to the asteroid and capture it. 2. How would I do it? Mechjeb does not have an autopilot to reach target that is on an escape trajectory.

Edited August 11, 2014 by mike9606

[Specialist290]

You might find this tutorial handy

[Wanderfound]

Treat it like orbital rendezvous; you need to get close to it and match speed and velocity before attaching. Match inclination and direction (or launch into the correct inclination to start with), use a lower orbit to catch up to it or a higher orbit to let it catch up to you.

It doesn't take too much ÃŽâ€V to get there (relatively speaking; you need enough for the inclination match and to then boost to escape velocity), but it will take a fair bit to capture it. After you've attached, the mass of your craft effectively becomes the mass of the rocket plus the mass of the asteroid. High efficiency engines (LV-N, LV-909, Poodle) are advisable.

[cantab]

There's a tutorial on the forum about intercepting asteroids in solar orbit, but the key "trick" is to leave Kerbin's SOI in the direction the asteroid is predicted to enter. For some reason that naturally gets you a close encounter.

You've certainly got ample delta-V to rendezvous with the asteroid unless you really hash it up. Depending on how picky you are about your final orbit, aerocapturing it shouldn't require that much delta-V - you just need a small correction shortly after you grab it to adjust periapsis, make the aerocapture, then a small burn to raise periapsis for a stable orbit. Off the top of my head a C-class asteroid should mass about 100 tons, and you ought to have plenty of delta-V with it in tow. I captured a 500-ton D class with about the same amount of fuel as you have there.

Where your design has problems I think isn't power but control. I don't see any reaction wheels and it looks like there might be no RCS either. You're never going to claw the asteroid perfectly so you need to be able to handle a slightly off-centre mass and not end up spiralling, and you'll probably prefer to be able to rotate the asteroid for burns rather than having to unclaw, fly round, and reclaw. (The latter is often necessary for heavy E classes, but C's and below definitely shouldn't need it with a well designed tug).

[mike9606]

There's a tutorial on the forum about intercepting asteroids in solar orbit, but the key "trick" is to leave Kerbin's SOI in the direction the asteroid is predicted to enter. For some reason that naturally gets you a close encounter.

You've certainly got ample delta-V to rendezvous with the asteroid unless you really hash it up. Depending on how picky you are about your final orbit, aerocapturing it shouldn't require that much delta-V - you just need a small correction shortly after you grab it to adjust periapsis, make the aerocapture, then a small burn to raise periapsis for a stable orbit. Off the top of my head a C-class asteroid should mass about 100 tons, and you ought to have plenty of delta-V with it in tow. I captured a 500-ton D class with about the same amount of fuel as you have there.

Where your design has problems I think isn't power but control. I don't see any reaction wheels and it looks like there might be no RCS either. You're never going to claw the asteroid perfectly so you need to be able to handle a slightly off-centre mass and not end up spiralling, and you'll probably prefer to be able to rotate the asteroid for burns rather than having to unclaw, fly round, and reclaw. (The latter is often necessary for heavy E classes, but C's and below definitely shouldn't need it with a well designed tug).

I do have RCS on there, and the Reaction Wheel is actually at the bottom insase I want to put something on the bottom docking port (the reaction wheels extends the docking port downward a little).

[Targa]

You can use MechJeb (mostly). Follow this post I just made in another thread: http://forum.kerbalspaceprogram.com/threads/90206-General-questions-about-asteroids?p=1345779#post1345779

[Claw]

There's a tutorial on the forum about intercepting asteroids in solar orbit, but the key "trick" is to leave Kerbin's SOI in the direction the asteroid is predicted to enter. For some reason that naturally gets you a close encounter.

Because that's where it's coming from.

-Claw

[mike9606]

Well as of this writing ehcjeb is time warping to a maneuver node tha twill bring me 19.4 km away from the asteroid. Sadly I am only at 100km so it is ages to do so.

[cantab]

Timewarp in the tracking station instead?

[Monger]

As always: test it and practice with it before it gets serious.

Put some garbage in the orbit of Kerbin. Launch your grabber ship, try to rendezvous with it, then try to deorbit it and put it back into a stable orbit. See if this feels safe and precise. Also take a look at how much RCS fuel you are burning. Learn from this, improve your ship, try again. Repeat this a couple of times until you are satisfied. Fortunately, when you discover Asteroids there are usually many days away from impact, so there is still some time to prepare.

When you want to intercept an asteroid, try to take a step back, and look at the bigger picture. The asteroid usually has a stable orbit around Kerbol, it just unfortunately happens to cross Kerbin. It is extremely unlikely that an asteroid hits Kerbin, and if you nudge it just a little early enough, it will miss Kerbin and probably never encounter it again. So, try to ignore the impact for a second, and think how you would rendez-vous with an object on a similar orbit around Kerbol. This works very similar like a rendezvous with Duna or Eve, just make sure that your rendez-vous happens BEFORE impact, and not after it.

When the ARM patch was released, I was kind of shocked. I knew that preventing an asteroid from hitting earth is difficult, but I never imagined that it might be next to impossible, depending on how "benign" the asteroid's orbit is, and how early you can detect it. The problem is not nudging it somehow, but getting there in the first place. In KSP the asteroids are kind of designed so they can be captured easily, but in real life I could imagine trajectories where even detecting an asteroid a year in advance, even if you had your spaceship ready at launch it would not suffice.

[magnemoe]

My favorite is to intercept inside Kerbin SOI, perfectly you want launch in pretty much the same plane as the astroid and intercept it between minmus and Mun while falling towards kerbin.

You don't want too high intercept speed as it burns too much of your fuel.

Typical deep space intercept tend to be far more expensive, exception if you have long time to intercept, benefit is that its pretty easy to lower Pe and even change plane and this can save fuel later.