Asteroid grabber design

[chd]

What do you all think of this, or something like it, for catching larger asteroids? This idea is to grab the asteroid with the center klaw, then line up with the center of mass and lock the pivot. Once that's done, the four outer klaws (which are mounted on extending hydraulic tubes) can be extended to also grab the asteroid and add rigidity. They were added one at a time, without using symmetry, so I should be able to extend them differing distances to accommodate the asteroid surface.

I'm thinking the center klaw needs to extend farther ahead of the others; the hydraulics extend farther than I thought, so that wouldn't be a problem.

The other problem I haven't figured out yet is delta-v; fully fueled, that has about 6600 m/s, which will drop to like 300 when you grab a class D. So many fueling runs. Maybe used Nervs or Cherenkovs (have NFA), but oh so expensive in career mode.

And a related question; I don't see any real way to put any kind of fairing around the whole girder construction for launch; any suggestions for reducing drag?

Thanks!! :-)

[bewing]

Apologies, but you are about to run into one of the limitations of the game. It's a clever and cute ship, and if it were possible to grab an asteroid in multiple places at the same time, it would probably work fairly nicely.

However, it doesn't really work like that. If you design a couple of craft with docking ports perfectly, and then fly them perfectly, you can get multiple docking ports to attach simultaneously. But klaws never do. And you aren't even trying to get them to attach at the same time. The way the additional arms work will depend on your "self interaction" setting for this craft. Because once the first klaw attaches to the asteroid, then the asteroid becomes just one more part on your craft. And a klaw on a craft will not attach to itself. It'll either pass through itself (meaning the asteroid in this case), or it will just bounce off.

But the reality is that if you want to grab an asteroid and not have the joint bend, then you should just use one klaw and then add an autostrut after you lock the joint.

[chd]

Hm, ok - thanks! Not having tried this before, I had noticed the "same vessel interaction" option for some parts, and kindof assumed that if I toggle this to the correct value I could get my extra klaws to attach to the asteroid even after it's considered part of my ship... maybe not.

Thanks!

[Superfluous J]

If you want the same result without the work, you can replace the 4 outer Claws with... well anything, really, and then turn Autostrut on them to Heaviest part. As soon as you grab the asteroid, they will strut to it.

Or you can use a mod that lets you strut in flight. I did that in this (fairly old but still valid) entry to the Dres Awareness Challenge.

Spoiler

 

 

Edited September 18, 2020 by Superfluous J

[king of nowhere]

10 hours ago, bewing said:

 

However, it doesn't really work like that. If you design a couple of craft with docking ports perfectly, and then fly them perfectly, you can get multiple docking ports to attach simultaneously. But klaws never do. And you aren't even trying to get them to attach at the same time. The way the additional arms work will depend on your "self interaction" setting for this craft. Because once the first klaw attaches to the asteroid, then the asteroid becomes just one more part on your craft. And a klaw on a craft will not attach to itself.

really?

because it happened to me. i was experimenting a robotic arm to lift a rover in and out of a cargo bay, and when the claw touched the wall, it stuck there. both the claw and the cargo bay had the same ship interaction on.

anyway, when that happened, the ship components were scrambled by a kraken, so while it is possible to attach a claw to its ship, i would not want to try it

[Okhin]

You can have several klaws grabbing a roid. I've done it several times already, but you can rarely get all the klaw grabs at the same time (even if I had, at times, two klaws grabbing the same asteroid in one successful harpooning). That is why, in multiple klaws setup, I generally add a piston behind them to allow to throw them at the asteroid one after the other.

I've described the sequence I use here :

It's a bit tedious at time, but then I have 4 klaws linked to an asteroid, and I'm center of mass targeted. And I can move the asteroid easily (given I've packed enough reaction wheels and engines). Short version :

1. Extend the first piston to maximum, grab the asteroid with the klaw on it and unlock (not disarm) the klaw to be able to rotate the ship
2. Keep center of mass targeted, and retract the first piston to half it's extension.
3. Extend the opposite klaw to full extension, unlock and target center of mass.
4. Rince, repeat.

Once done, keep target CoM, lock your klaws, retracts your piston has much as you can, and have fun with your nice asteroid.

And for reducing drag at launch, maybe stick a big stage separator and a 5m rocket nose cone ? Or maybe insert a fairing just above the girder section. You'll add your central klaw to the fairing, and you can use the fairing to cover the girder sections. Once deployed it should be ok.