How do I solve this build issue?

[Rus-Evo]

Hi Guys,

I am currently trying to build a heavy transport jet which is designed to have wheeled cargo pods roll on and roll off (as part of a silly big challenge I set myself).

The jet is problematic and will do a redesign but I needed to do a proof of concept of the cargo transportation.

What I did was to build a jet that had a loading ramp that could be driven on to.

The cargo pod has a grappler (stock) up front.

I drive on to it no problems

It attaches to the front of the cargo area just like I wanted and THEN!!!!!!

Upon creating one new craft the cargo literally falls through the floor attached only by the grappler!!!

Its like the physics change when its one vehicle.

Does anyone have some tips on how to make this work? My master plan will have big problems if I cant operate a roll-on roll off system of cargo moving!!

http://i2.photobucket.com/albums/y32/RusEvo/2014-11-14_00001_zps26ef5085.jpg' alt='2014-11-14_00001_zps26ef5085.jpg'>

[capi3101]

Hmm......this is a tough one. May I ask what kind of setup you have for your stock grappler?

I might suggest a series of docking ports for the plane - one forward, one on each side, and one on the ramp - with corresponding ports on the vehicles. You'd have to drive the vehicle in such a way that all four ports connected simultaneously, and it'd have to be set up so that the vehicle's mass doesn't shift the plane's CoM too far aft (or you'll wind up with an uncontrollable plane). Best I can come up with for a stock option.

To make this idea as realistic as possible, I might suggest you install KAS, if you're not adverse to mods.

[Rus-Evo]

I am adverse to mods!! But maybe it cant be done without it.

As I sit here thinking I wonder if I could mount 2 grapplers in a plane, arm them, and then lower the plane by retracting some gear. The issue with that is whether both grapplers would register as attached!!

[capi3101]

To know for sure, I need to re-ask the question: what kind of setup do you have for your stock grappler?

[Rus-Evo]

I am not sure. All I did was arm it. I don't imagine it would make a difference if I locked the gimbal (though I would have before take off).

Are there further set up options?

[The_Rocketeer]

Seriously respect projects like this. After the 'rocket-to-the-moon' side of KSP, making your own challenges and overcoming them is what I think the game is really about.

Your problem is single crafts do not collide with themselves (hence why clipping parts don't explode under normal circumstances), and using the grappler changes the two separate objects into one new craft, the same as docking.

I'm also aware of glitching problems when two grapplers are attached, i.e. deployed, on one ship:

Without using a mod like KAS, your only real option may be using multiple docking ports, as capi suggested.

Something worth trying though, would be to have the grappler grab the heaviest part of your rolling vehicle radially, in this case the Jumbo tank from the top, bottom or side. That should reduce the 'bendiness' of the cargo overall and could solve your problem.

[cantab]

A craft in general will not collide with itself. Expecting the floor of your cargo bay to take the weight is thus doomed to fail. The claw isn't up to the job of holding that big orange tank by the end, it droops down as you see.

Using multiple claws is extremely prone to bugs, I don't advise it.

You could try mounting a docking port on the floor of the cargo bay, and another on the belly of the payload well-aligned with its centre of mass. Line them up then retract the payload's landing gear to allow it to drop and dock in place.

Or have a look at Overfloater's AstroLiner range, he does cargo spaceplanes a lot.

[Rus-Evo]

I think you guys have confirmed my fears and the direction of solution.

With some experimentation the grand airlift to the inland ksc will be feasible!

Thanks

[Stratzenblitz75]

I built these a while ago that are designed around the idea of grabbing cargo with a Klaw. The trick is to have the Klaw grab the cargo from above, rather than the side. To do this, set up your landing gear so that when you lower them, the Klaw grabs the cargo.

Also, I don't recommend using regular docking ports. They are way too flimsy for heavy cargo; the Klaw is way stronger and makes a much more rigid connection. Don't use multiple klaws either, they are buggy and one klaw is enough to lift all the cargo you need anyways.

If you're not against mods, another solution I've found to work quite well is to use a KAS winch to raise your cargo after it sinks through the floor. The only disadvantage to this is that you need Kerbal to set it up.

Edited November 14, 2014 by Stratzenblitz75

[Hodo]

The easiest thing to do is to just attach struts to the rear of the cargo load that you have there so it is supported at the back. Otherwise it will fall through and or wobble everywhere making the craft nearly impossible to control.

[capi3101]

...so, I feel kinda stupid at the moment. I'd had forgotten about the existence of the Advanced Grabbing Unit and it didn't register that it was the "grappler" you were talking about.

I still stick to my advice about the docking ports; they're probably going to be your best bet for what you want to do in stock. As far the overall design of the plane itself is concerned, I might suggest you take a look at DocMoriarty's KSP Space Plane Construction and Operation Guide; it's a discussion of transporter spaceplanes and VTOLs in the stock game with stock aero. It's definitely helped me out with my own spaceplane-as-launch-vehicle exploits. Definitely some principles there that could be applied to what you're wanting to do.

[Claw]

I am adverse to mods!! But maybe it cant be done without it.

This particular post may not be the most helpful, but I recall that there might be a way to do this. Normally parts on the same ship will clip through each other when bending. However, I believe there is a part (or maybe a couple parts) that will support pieces of the same ship.

I think it might be in the stock construction thread somewhere, but I can't remember. It might also be in the challenge somewhere that was for a fully reusable space program, where you had to take a returned SSTO, refuel it, reload cargo, and launch it again without using the VAB/SPH.

I will try to dig around and see where this was from, but I do think it's possible. I remember it being a piece like a round fuselage section or something like a roller. That being said, your craft will probably be more stable using multiple docking ports as has been suggested.

Good luck,

~Claw

Edited November 15, 2014 by Claw

[MarvinKitFox]

I can think of 4 possibilities:

1) Mount the grappler pointing up, directly above your cargo's CoM. Let it *hang*.

2) Multiple docking ports. If all are aligned, then can all attach. Hint: have the decoupling on an action group.

3) do NOT join the cargo+plane into one entity. Physically restrain it with suitable parts. Landing legs work just fine. Caveat: this flies fine, but do *not* timewarp. The cargo will simply phase through its restraints, and then through your plane. Timewarping like this is a very... intriguing way of launching your cargo once on orbit though!

or, do it right.

4) Use KAS

I am adverse to mods!! But maybe it cant be done without it.

As I sit here thinking I wonder if I could mount 2 grapplers in a plane, arm them, and then lower the plane by retracting some gear. The issue with that is whether both grapplers would register as attached!!

Nope, sorry.

A grappler will only attach to *another* object. As soon as the first one links, the second is trying to join to itself and fails. (it goes through the motions, but no actual link is formed)

Edited November 15, 2014 by MarvinKitFox

[Yakky]

You could try mounting a docking port on the floor of the cargo bay, and another on the belly of the payload well-aligned with its centre of mass. Line them up then retract the payload's landing gear to allow it to drop and dock in place.

Another option is to have the docking port overhead near the middle of the cargo and drive under it at close range. Either way, using a single docking port that is positioned to support the payload near its center of mass, rather than cantilevered at one end, is probably your best all-stock solution. Multiple docking ports are very, very tricky to line up simultaneously.

[Voculus]

I am adverse to mods!! But maybe it cant be done without it.

As I sit here thinking I wonder if I could mount 2 grapplers in a plane, arm them, and then lower the plane by retracting some gear. The issue with that is whether both grapplers would register as attached!!

In my humble opinion, you're doing yourself a huge disservice, by shunning mods, particularly when there's one out there that will solve this problem you're having.

It's called Quantum Struts, and is a very low profile, easy to use mod. Slap two of them onto the free-hanging end of your rover/vehicle, and you're done. You don't have to turn them on, assign action groups, or anything. You simply dock your vehicle, and forget about your problems.

[The_Rocketeer]

In my humble opinion, you're doing yourself a huge disservice, by shunning mods, particularly when there's one out there that will solve this problem you're having.

The stock game is hard partly because of it's forced limitations. Overcoming those is a game in itself. Using mods that solve problems like this could be viewed as cheating. After all, modifying config files in many games would be an out and out hack, let alone adding 'special' guns in a shooter (remember the Golden PP9?) or supercars in a racer.

It's not that I think all mods are cheating, but I am very selective about which mods I adopt because I don't want to play in cheatmode.

Edited November 15, 2014 by The_Rocketeer

[BudgetHedgehog]

TI think it might be in the stock construction thread somewhere, but I can't remember.

Inline docking port.

[Wyre311]

http://forum.kerbalspaceprogram.com/threads/96406-The-Arcadia-series-and-the-Zeus-Ships?highlight=Arcadia

My Zeus can do it.. Tested and verified.. If you wish I can send pictures. PM me your email, download the mods mentioned in my thread and i will send the craft files to you.

Edited November 16, 2014 by Wyre311

[Claw]

Inline docking port.

There you go. That's exactly what I was remembering. Thanks Obsessed.