[KAS] A better way?

[capi3101]

Good morning, all. This will be the first time I ask a question regarding usage of a specific mod, and regretfully I will be doing this without access to either screenshots or craft files for now. If y'all will bear with me, I can have both available later this evening (probably after 02Z).

So, I've installed KAS, and for my first task I've been attempting to build a combination tow cart / refueling tanker for my Auk VIII spaceplane. I do have some screenies of that craft:

The second shot is an updated version of the craft, one where I'd ironed out most of the kinks in its original design (i.e. the first screenie). I have since made one addition to the craft, and its for KAS - I've added a radial connector port on the aft RCS tank centerline, below the central engine.

Now, my tow cart design is based on a Jumbo-64 tank. I've added a probe core for primary control and a Mk1 Lander Can for Jeb to climb in and out of (figured out early on that I had to have a Kerbal present in order to actually plug in the cables if I wanted to do actual fuel transfer). It has a series of I-beams on the top with a winch and electromagnet on the end; this is meant to serve for towing. On the underside is another winch; this one is meant to act as the refueling cable. The idea is that after the plane lands from making a delivery, the tow cart puts it back at the beginning of the runway and refuels it to full, then gets out of the way. The plane then takes off for another mission. I realize I could just "recover flight" and go from there; I'm mainly just doing this for the lulz.

The problem I'm experiencing is that inevitably when I attempt to tow the plane anywhere, the plane inevitably tips up onto its engines and knocks off the rear RCS tank, rear fuel tank and centerline engine. I'm not sure why it's doing this, and I'm concerned it has something to do with how I'm attempting to tow it.

I guess my question is - for towing purposes, is it better to push or pull? And how would you go about pushing with KAS? And is there someway to fix the length of the winch cables so they hold tension?

Is there a tool that is better for towing than the electromagnet? For reference, I'm attempting to put it on the orange tank just forward of the rear engine/RCS ballast assembly. The I-beam assembly is long enough that it does have the reach it needs.

I suppose while I'm at it, is a Kerbal strictly necessary for plugging in cables and "docking" two craft together?

Any help would be greatly appreciated here.

[Geschosskopf]

I guess my question is - for towing purposes, is it better to push or pull? And how would you go about pushing with KAS? And is there someway to fix the length of the winch cables so they hold tension?

Is there a tool that is better for towing than the electromagnet? For reference, I'm attempting to put it on the orange tank just forward of the rear engine/RCS ballast assembly. The I-beam assembly is long enough that it does have the reach it needs.

I suppose while I'm at it, is a Kerbal strictly necessary for plugging in cables and "docking" two craft together?

Any help would be greatly appreciated here.

Well, last question first. Instead of using a Kerbal, you can put a grappling hook on the winch, take careful aim, and fire it at the ship to be towed using the "eject" function.

I've never had much luck going with cables. Physics gets wonky around them, even if the connected ships AREN'T moving. All kinds of phantom forces build up in the cable. I've therefore found it better to do it in a series of drags. That is, connect the cable at 50m, park the towing vehicle, and retract the cable to drag the towed vehicle to the tow truck. Disconnect, drive the tow truck forward 50m, repeat. And all this is more trouble than it's worth.

In general, KAS is good for making fuel connections and adding struts to wobbly assemblies. It's also good for anchoring things to the ground and hoisting. But not so much for towing 1 thing with another.

A better option is to make an actual wrecker-type tow truck using Infernal Robotics. Make an arm that can grab the nosewheel strut and lift it slightly off the ground. Allow the wheel strut to rotate within the grabber. Now you can tow the thing quite well. You'd still need KAS to refuel it, though, and it's advisable to do these operations entirely separately. Also, you might want to use the KAS pipes instead of a winch because physics doesn't hate rigid pipes as much as flexible cables.

[Streetwind]

Mod support requests should go over here, for the record: http://forum.kerbalspaceprogram.com/forums/13-Add-on-Requests-and-Support

[capi3101]

Well, last question first. Instead of using a Kerbal, you can put a grappling hook on the winch, take careful aim, and fire it at the ship to be towed using the "eject" function.

<snip>

Also, you might want to use the KAS pipes instead of a winch because physics doesn't hate rigid pipes as much as flexible cables.

So something grabbed with the grappling hook counts as "docked"? I'll have to try that; it'd be a time-saver.

Can you disconnect a pipe once it has been connected? How does that work? I haven't played around with the pipes much yet.

I'll give the Infernal Robotics mod some consideration.

Mod support requests should go over here, for the record: http://forum.kerbalspaceprogram.com/forums/13-Add-on-Requests-and-Support

Noted for future reference - may I have a moderator please move this thread to the correct location?

[Cerberus738]

I've used KAS for a while now. The cables are nice but i don't use them in DOCKED mode. they get reeeeaaally wonky and explode stuff lots. For fuel transfer i always use the pipes. you have to have a pipe end point on each craft. use your kerbal right click an endpoint and select link. then right click the other end point and link again. it connects the 2 ships together. if your kerbal is in the way of where the pipe will be once the ends are connected (or any other parts) you will get an explosion. once you are done use your kerbal and right click the endpoint and unlink. bingo!!!

as for towing... like Geschosskopf said... parking your towing vehicle and winching the payload closer is the best way to go. i expect your plane is flipping backwards because you are pulling from the bottom. it gives it a bit of upward force and its probably enough to tip it back on the landing gear.

i prefer the electromagnet. i always have problems getting the grapple to detach. then once its detached i can't get it locked back on the winch to eject it again. just annoying so i never use them. they are very nice for anchoring stuff to the ground though!! also the electromagnet you can set to a action group to have it turn off and release your payload. remember you need power for it... also for the winched to work.

[capi3101]

Pipes seem to have done the trick.

The plane had tipped up onto its engines prior to this shot; I was able to use the electromagnet to straighten it out and I left it connected while I hooked up the pipe. Refueled the Auk, then began the process of towing it back to the near end of the runway. I did have to disconnect long enough to reorient both plane and tow cart when they got to the center of the runway proper - lousy steering, and then later when I was towing it back I got going too fast. Damn near lost Jeb when the tow cart rolled and started exploding, and of course the back engine assembly fell off. I probably could've still made orbit but the ballast for the launch would've been off.

So...next questions. I'm assuming at this point that it'd be better for me to tow then refuel, instead of the other way around. Inertia and all that. I'm also wondering if I'd benefit from switching from the ruggedized wheels to the big ones considering the mass of the tow cart when it's full of gas. Any other critiques (read: scathing criticisms) of the tow cart design would be welcome.

[Lazro]

Generally, the ruggedized wheels are better than the really super hugeâ„¢ wheels, unless you're planning to build a mobile launchpad or are Whackjob. Your design as it stands seems alright.

[PUNiSH3R]

Well, last question first. Instead of using a Kerbal, you can put a grappling hook on the winch, take careful aim, and fire it at the ship to be towed using the "eject" function.

The same can be done with an electromagnet; I haven't used grappling hooks much, can they be removed and reused once 'embedded' in something?

A better option is to make an actual wrecker-type tow truck using Infernal Robotics. Make an arm that can grab the nosewheel strut and lift it slightly off the ground. Allow the wheel strut to rotate within the grabber. Now you can tow the thing quite well.

I'm a big fan of this method, however my end effector of choice is a winch with an electromagnet. activate the magnet and attach it to your target, then retract the cable until the connector locks into the winch. at that point you can move it around with your 'arm' and the only nastiness to deal with is the momenta of the object (which can be significant for a long arm).

The "Wrecker" method:

The "Arm" method:

[Geschosskopf]

So...next questions. I'm assuming at this point that it'd be better for me to tow then refuel, instead of the other way around. Inertia and all that. I'm also wondering if I'd benefit from switching from the ruggedized wheels to the big ones considering the mass of the tow cart when it's full of gas. Any other critiques (read: scathing criticisms) of the tow cart design would be welcome.

There's another option to move the plane around on the ground: have it taxi itself. This eliminates the need for the winch cable and its wonky physics, so all you need is a fuel truck, not a tow vehicle.

The ideal in taxiing is to have wheels with rover motors in them, which both move and steer. And most importantly, move in reverse, too. That way, if the plane has a huge turning radius, you can back and fill as needed to maneuver in tight spaces, or just reverse along the runway.

The problem with stock rover wheels, however, is that they can't tolerate the high landing speeds of planes. Thus, you have to mount them so they're clear of the ground until the plane stops. It's possible to do this by putting the rover wheels on the sides of the fuselage beside the nosewheel mounted on the bottom, then retract the nosewheel to lower the nose onto the rover wheels. Or you can mount the rover wheels on Infernal Robotics pivots and swing them down. Problem, of course, is the extra weight of having 2 sets of wheels.

There are also mods that add new landing gear parts that have rover motors built in. Thus, you only need 1 set of wheels. I know Firespitter does this, maybe B9 these days as well, although I don't think that's ever been updated to 0.23.

Another method is to use the thrust reverser parts from the Boat Parts mod. These allow you to taxi in reverse with the main jet engines.

[PUNiSH3R]

There are also mods that add new landing gear parts that have rover motors built in. Thus, you only need 1 set of wheels. I know Firespitter does this, maybe B9 these days as well, although I don't think that's ever been updated to 0.23.

the 0.22 version of B9 does have powered and steerable gear and it does work for me with 0.23.