Asteroid Capture Techniques

[mpk10]

I'm Curious whether there are a lot of different methods that folks have used for capturing asteroids. Back in 0.24, I was trying to land them at KSC with a sky crane, but have had better luck now just loading them up with parachutes.

Does anyone have any asteroid getter creations that work well for all sizes? Is there another thread that you know that has a lot of different types of Asteroid Getters?

This is my best current working Asteroid Getter bringing back an Asteroid named Asimov. All my asteroids are named after science fiction authors

It landed about 2km from KSC at about 9m/s. No mechjeb, just a few F9s.

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[Rune]

I don't bring them all the way home like you did there, but my Modular Propulsion System can tug really large asteroids:

The Klaws, like the engines, are independent pods, and the front end is an adaptor so you can position one centred on the opposite side of the engines. So you can actually attach the other one to the opposite end of the asteroid to have good RCS placement for attitude control, while pulling (instead of pushing) in a very stable manner very big loads. Not much RCS fuel, though... I am very conservative with it.

Rune. It is one my most ignored posts, but I still think the design is awesome: the drive pods, for example, are a 11 part subassembly that can draw fuel from its three ports without fuel lines.

Edited November 30, 2014 by Rune

[mpk10]

Looks good. Yeah, that RCS on the opposite sides of the asteroid thing was such a time-saver once I figured it out. You can move E-Class Asteroids with that?

[Rune]

Looks good. Yeah, that RCS on the opposite sides of the asteroid thing was such a time-saver once I figured it out. You can move E-Class Asteroids with that?

...Kinda. Or drop them into the sun, if you bunched enough of them side by side. You see, it is modular as I said:

So you could put as much fuel as you need into a single stack. On the other hand, I usually rendezvous on solar orbit, and from them it's only a couple dozen m/s usually to get an aerocapture pass, so most of the delta-v in the mission is actually to raise the periapsis after capturing, and that is usually only high if you want to park in a low orbit. At the end, you end up using more fuel to get to the asteroid than to tow it into stable orbit! All in all, you could move an asteroid into a stable orbit with just a couple hundred m/s, and this should give, with just the two tanks that you get into orbit on the single launch, about as much delta-V as needed to capture 'roids of up to 1000-2000mT, if I have worked Tsiolkovsky right and you manage to only need about a couple hundred meters per second once you grab it.

Rune. But you know, still perfectly possible to tug an E-class to Jool if need be, if you have the computer to move the parts.

[Laie]

not many pics to share, but I've written up some lessons learned in another thread. Might as well repeat my post here:

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I think you forgot to lock thr pivot. It would explain what you are experiencing.

When locked, it provides resistance to bending and will (absent any other forces) return to it's set position; but the claw is the weakest link and will act as pivot even when locked. This becomes ever more apparent the bigger the rock and vessel is (not a great insight: stronger forces make it bend more, who'd have thunk?).

In order to give you and idea of the kind of forces I'm dealing with, see this picture. That's a lot of thrust and a long lever -- of course I'm having problems.

You might also find it helps to turn off SAS and RCS on the engine section. Let the separate pods turn the asteroid and the asteroid turn the engines.

This helped a lot, and here's why:

It's not necessary to turn off all SAS on the pusher: leaving some of it active still makes the whole thing more maneuverable. But the rock should have more torque than the pusher.

Important hint: If your asteroid redirect mission as flexible as mine, and the whole assembly is yawing left, you should turn off some engines on the right. This will swivel the pusher relative to the CoM, so that the whole pusher acts as a gimbal and brings the rock around in the direction you want it to go.

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Edit to add (I'm just tossing in everything I notice while doing this, for the sake of anyone who finds this thread):

As of this writing, the claw is still a powerful magnet for bugs and glitches. I've encountered a few during my mission. Save early, save often, make use of named savegames. The more friendly bugs will destroy your craft then and there; there's also more insidious one where the orbit of your vessel is no longer updated properly. When your orbit changes without your input, you caught one of these. Most of the time, the problem will go away when you quit and restart the game, but I had a variant that was peristent between savegames.

[Rune]

snip

This post, while very informative, show the clear advantage of puller systems: they are dynamically stable with non-rigid objects.

Rune. The difference between pushing a piece of rope and pulling it.

[mpk10]

This post show the clear advantage of puller systems: they are dynamically stable with non-rigid objects.

.

That is true, but pulling only works if your engines are sufficiently far from the asteroid. Or if they're tilted to aim around it. If the engine propellant washes right towards the asteroid you're pulling, it cancels out all the thrust you're trying to make.