Recover a module from the surface... BG parts haven't helped me - can they be made to work?

[Neilski]

Before my recent purchase of BG, I had tackled a few "surface recovery" contracts and had sworn off them. The way I approached them, it was just so damn painful to hover a craft with a Klaw above the module and try to land on it. What I really wanted was a way to lower a craft onto the module and then take off.

Once I bought BG, I took the next surface recovery contract I was offered and had a go. I tried two approaches with BG parts: a wheeled rover, with the wheels on alligator hinges so it could lower its body (+ Klaw) onto the module, and a modified version of the rover with the Klaw on a piston to just lower the Klaw directly onto the module.

Outcome: both approaches failed miserably, because either the whole craft blew up, or the Klaw appeared to engage (and the PAW offered me a "release" button) but the module didn't move with the rover. Very very frustrating. Many attempts, and not a single success. See pic below, if it works, for a flavour of things looked.

Has anyone made these BG parts work for picking stuff up?

(PS: the "Insert image from URL" function won't work for me. This forum is just plain odd :-))

https://imgur.com/a/kmOGybA

Edited January 23, 2021 by Neilski

[lemon cup]

Might not be the answer you are looking for but I’ve come to avoid using the robotic parts from Breaking Ground completely nowadays for the exact reasons you mentioned: they are buggy, wobbly, and hard to control. 

[InfernoSD]

I've found hovering above surface objects equally challenging, especially on those tiny moons. In retrospect I should have used RCS and treated it like docking.

I have used a rover with wheels on hinges and a claw on a hinge. With it I was able to pick objects up and drive around with them pretty smoothly. I haven't tried doing the same thing with a recovery mission, but I don't see why that would be any different.

Your rover looks pretty good. It sounds like your problem is perhaps less to do with the robotic parts and more to do with the claw not working correctly. When is your ship exploding?

[Neilski]

12 hours ago, InfernoSD said:

I have used a rover with wheels on hinges and a claw on a hinge. With it I was able to pick objects up and drive around with them pretty smoothly. I haven't tried doing the same thing with a recovery mission, but I don't see why that would be any different.

Your rover looks pretty good. It sounds like your problem is perhaps less to do with the robotic parts and more to do with the claw not working correctly. When is your ship exploding?

OK, wow it's good to know that it's (or at least was) possible to make it work - were these successes in 1.11 or earlier? I'm thinking of trying my craft on an earlier version just to see if something broke in 1.11.

Most of the time it doesn't explode (just acts like it grabbed, but the module doesn't stick to the Klaw despite offering me a release button) but when it does, it happens right at the point of contact. I have formed the impression that if the contact arises from the Klaw being moved into contact by the hinge/piston, it won't work (failure to grab, or bang). If the Klaw comes into contact from the ship itself moving, it's all good

[king of nowhere]

i have had multiple bugs related to robotic parts being too close to a docking port (and a claw works similarly). so i suggest you try the same without the piston. yeah, those parts are buggy. but they can be made to work

[InfernoSD]

1 hour ago, Neilski said:

OK, wow it's good to know that it's (or at least was) possible to make it work - were these successes in 1.11 or earlier? I'm thinking of trying my craft on an earlier version just to see if something broke in 1.11.

Playing on PS4 so it's a little older version.

The worst case of docking I've had was with my rover on Eve. The issue there was that the rocket I was connecting to was much heavier than the rover itself. The rocket's weight would instantly travel into the rover wheels and damage if not destroy them, then shake the rover around violently. I'm sure you're not dealing with that much weight, though. Maybe the best thing to do would be to look at the flight log to see what the first parts that break and expode are.

It's also worth saying that I've never tried grabbing an object from above as you have. The surface of planets is very solid, and clipping objects into that surface is an easy way to make them explode. It's possible that in the moment of contact you're exerting too much downward force and clipping that object into the ground for a brief moment.

[Wobbly Av8r]

19 hours ago, Neilski said:

Has anyone made these BG parts work for picking stuff up?

(PS: the "Insert image from URL" function won't work for me. This forum is just plain odd :-))

First off I commiserate with you about surface recoveries. Second, yes, absolutely using BG parts for recovery is very possible - your solution parallels my own and others I've seen and I can attest to their effectiveness (and level of frustration, so there's that too...)

I can't quite venture to say why your Klaw would say it was engaged but not picking up the object, but I would offer that there is a thin line between object collection and object collision, which is a large part of the problem here - I navigate this issue by making sure that before engaging the Klaw that it is as DIRECTLY above the object to be recovered as possible; if you are not right above, the object collision is triggered rather than the connection. Whereas you use wheels to establish such as position, I took the "economical" strategy and "asked" one of the Kerbals on board to go out and push the object until it was right underneath the Klaw'd recovery vehicle. (Those snacks aren't gonna pay for themselves! We worked out a deal...)

I would add, if you haven't discovered it already, that when you recover a part which has reaction wheels built in that you disable them before attempting to maneuver, and that your recovery vessel command pod has a higher priority than default or occasionally after you connect, you will have a new orientation / control point and that will definitely make the trip more, uh,... "memorable".

[Edit: Oh! And the way to the get the URL embedded is to remove the html formatting - just the url location itself will allow it to be posted as an image in your post rather than a link...]

Edited January 24, 2021 by Wobbly Av8r

[Neilski]

5 hours ago, king of nowhere said:

i have had multiple bugs related to robotic parts being too close to a docking port (and a claw works similarly). so i suggest you try the same without the piston.

Actually the very first craft just had the hinged wheels and no piston, and I couldn't make that one work either.

4 hours ago, InfernoSD said:

It's possible that in the moment of contact you're exerting too much downward force and clipping that object into the ground for a brief moment.

Yeah, certainly possible, but the weird thing is that the version of that craft that I used before buying BG was actually successful - it had no wheels and so it was a total bugger to get it to hover and land right on top, but when I got the alignment right, it just worked. No explosions, no "fake" grabs...

2 hours ago, Wobbly Av8r said:

you will have a new orientation / control point and that will definitely make the trip more, uh,... "memorable"

Oh yes, this has bitten me several times already and it'll probably bite me again because I never seem to remember to edit the priority in the VAB!
Thanks for the tip about the image URL - will try again next time.

[vv3k70r]

On 1/23/2021 at 7:01 PM, Neilski said:

The way I approached them, it was just so damn painful to hover a craft with a Klaw above the module and try to land on it.

Roll. Land and roll.

On 1/23/2021 at 7:01 PM, Neilski said:

I tried two approaches with BG parts: a wheeled rover, with the wheels on alligator hinges so it could lower its body (+ Klaw) onto the module, and a modified version of the rover with the Klaw on a piston to just lower the Klaw directly onto the module.

Landing legs helps to get elevetion. Rest is on hydraulic actuators similiar way You  describe.

 

[Neilski]

On 1/25/2021 at 9:05 AM, vv3k70r said:

Landing legs helps to get elevetion. Rest is on hydraulic actuators similiar way You  describe.

Ah, cool! I'm struggling to make sense of your picture but was the Klaw deployed vertically downwards on a piston? And was this in 1.11?
I'm wondering what's fundamentally different between your ship and mine...

[vv3k70r]

10 hours ago, Neilski said:

but was the Klaw deployed vertically downwards on a piston? And was this in 1.11?

It was done before 1.11.

Claws are deployed down by pistons.

10 hours ago, Neilski said:

I'm wondering what's fundamentally different between your ship and mine...

Vernier thrusters for side movements. My ship can hover on those four engine and land over the spot extending landing legs then takieng up cargo using pistons when it is landen (or even hover).

My works and cerried lot of stup around da Mun and up to orbit.

Now is at Kerbin orbit to change those crap robotic to radial mounts.

[InfernoSD]

Looking at this again, you have hinges in both designs, no? Have you tried locking the hinges before the grab? Hinges like to create huge phantom forces. It might make the difference.

You might also try grabbing a free floating object in space just to see if anything weird happens there.

[Neilski]

11 hours ago, vv3k70r said:

Vernier thrusters for side movements.

Yeah, I have them too, though I don't really need 'em cos of the wheels. Very handy for translation while hovering though, indeed.

7 hours ago, InfernoSD said:

Looking at this again, you have hinges in both designs, no? Have you tried locking the hinges before the grab? Hinges like to create huge phantom forces. It might make the difference.

You might also try grabbing a free floating object in space just to see if anything weird happens there.

Ahh, good ideas on both fronts there. Must check!

[vv3k70r]

8 minutes ago, Neilski said:

Very handy for translation while hovering though, indeed.

It is my main way of traveling precise on short distance.

You set docking mode for thrusters and pulse ignite engine by z/x to get hower by maine engines.

[Neilski]

Update: I've now tried a similar craft in 1.9.1, 1.10.1 and 1.11.1.

Outcome: things work perfectly in 1.9.1 and 1.10.1; they don't work AT ALL in 1.11.1.

I suspect that all surface recovery missions are currently impossible until this is fixed.
I will report it as a bug on the tracker shortly (and add a link here).
Thanks for the assistance, folks!

Edit: bug is now on the tracker here

Edited January 30, 2021 by Neilski
added bugtracker link