Make a *stable* skycrane challenge *hinge + rope in thread*

[Barie]

So, i made a skycrane mechanism(using DamnedRobotics and Mumechlib)

it worked perfectly, the only problem is that it is incredibly hard to make a working and stable desigh for the rover/crane

Some pics of the crane at work:

As you see, when i tried controlling it it didnt work out that well

^ this happened a couple times

The Challenge:

Make a Working skycrane that can deliver a rover(something with wheels) to a planet(kerbin,mun,minmus)

the skycrane must extend the rope atleast a couple of meters and then decouple and fly away when the rover is on the ground.

All mods allowed, must use these 2 skycrane parts.

in the download there is a cylinder(extendable rope) and a hinge(so it can swing and is not fixed)

Assembly, attach the hinge onto your skycrane and the cylinder to the hinge, then attach the rover to the cylinder. see the pics

-use fuellines for the rope, they look like real rope's-

NOTE:

when the command pod it on the crane and not on the rover , the rope is turned around, the original bottom side of the rope should be directed at the pod

i will keep a list of all skycrane's created here

the parts: http://www.sendspace.com/file/3pa0pa

-working skycrane #1 completed by joepinball

-working skycrane #2 completed by ExtraPlanetal, with 2 command pods -

Hardcore mode:

have your command pod attached on the rover (this makes controlling a LOT harder)

-Joepinball completed the hard mode challenge with one of the most epic things i have ever seen in ksp! -

Edited August 10, 2012 by Barie

[Joe Pinball]

For some strange reason the "rope" (modded cylinder) doesn't display correctly for me either in the VAB or at launch.

Nevertheless I carried on, knocked up a simple crane of MechJeb pod, 2 RCS tanks (never got around to adding RCS jets tho!), 4 small tanks, with 4 of those boob-shaped engines hung off each tank.

underneath is a skycrane hinge, 'rope' part, and an IRII escape decoupler (could have used a normal one I guess, but this one is triggered by a hotkey instead). underneath that I slung a stock cart to simulate the rover probe.

I went to launch, and then tested I could lower the cart to the launch pad base, and then wound it back close to the SKyCrane Mk 1

I pressed space to launch, and dialled up minimum thrust on the motors, then used TranslaTron's KEEP VERT function with Kill H/S (Horizontal Speed) also selected, dialled in 1 m/sec, and pressed execute.

Once MechJeb had cranked the throttle past 1/3, I pressed space to fire the decouplers, and gently sailed majestically skywards!

After that, I waited until i was slightly above the VAB, and then dialled in 0 for vert speed so was now hovering, and then nudged the skycrane slooowly until it was hovering perfectly above the VAB, and then lowered the cart until it was almost above the VAB, and activated the decoupler.

Huge Success! \o/

alas, the force of the jets as I moved away from the VAB then made the cart fall off and land on the pad below!

having proven the point that it worked (this was a quick first run, I haven't even added RCS jets, this is completely stable when flown as above) I then dialled in -1 on the KEEP VERT to gently descend next to the slighlty dented Rover.

Album below:

http://imgur.com/a/plOR8#0

also, I have attached the .craft file. the only non-stock item is the IRII escape decoupler, feel free to substitute it with a stock one however, and add it as a stage above the launch clamps!

Joe

Edited August 7, 2012 by Joe Pinball

[Barie]

Joepinball awesome,good job on making a fully usable skycrane! nasa would be proud of you!

nice design ,but your rover cant do anything, it has no command pod i'll add a hardcore mode to the challenge

after trying it, you should add some boosters when decoupling the cart for extra awesomeness

Edited August 7, 2012 by Barie

[ExtraPlanetal]

I took a different approach to this - instead of choosing between having the command pod be the sky-crane or the rover, I put on in both.

I was planning to have some docking mechanism hang from the skycrane and connect the rover to it by using it, but I couldn't find any good ones in the add-on section (please tell me if there are). So I made a cage that the rover could drive into. This cage has doors on opposite ends of the platform to allow safe access to the rover and to keep said rover in the cage. the cage itself can be lowered or lifted by the skycrane hydraulic system.

I must unfortunately admit that this model has a few 'teething problems', but I am pretty sure that they can be solved. Also - the solid rocket boosters are only there to achieve flight, they could in all likelihood be removed and replaced. Here come the screenshots!

1 - Rover driving into Skycrane

2 - Skycrane/rover combo right before take-off

3 - Take-off (at least sort of)

Also, here is the .craft of the Skycrane

https://dl.dropbox.com/sh/wnpb6v3v7klnxze/3HbOCwVI9b/Skycrane%20V2.craft?dl=1

[Yogui87]

Why making a challenge with my skycrane mod? For your challenge, why did you remove the winch? It's already stable with my "stock-mod" parts.

It would be nice tell me about it before making this challenge. If someone is interested in the full mod go check: http://kerbalspaceprogram.com/forum/showthread.php/12106-0-16-Lionhead-Aerospace-Inc-Solar-Rover-v3-6-New-update-01-08

[ExtraPlanetal]

But where's the fun in using a purpose built mod

Edited August 8, 2012 by ExtraPlanetal

[Barie]

Why making a challenge with my skycrane mod? For your challenge, why did you remove the winch? It's already stable with my "stock-mod" parts.

It would be nice tell me about it before making this challenge. If someone is interested in the full mod go check: http://kerbalspaceprogram.com/forum/showthread.php/12106-0-16-Lionhead-Aerospace-Inc-Solar-Rover-v3-6-New-update-01-08

Well the challenge is that this isnt stable , its an extendeble rope hanging on a freely moving hinge

[Barie]

ExtraPlanetal, that is epic, driving the rover into the crane, didnt think of that for a docking mechanish, i suggest Damnyoujapan's claw

[Rage Baneblade]

About the Hardcore challenge:

Would having a MechJeb on the rover constitute a command pod?

Because most of my rovers were actually separate vehicles from the main assembly that were left on the Mun once the mission was over. Due to MechJeb, they could still drive around.

Or by command pod do you mean the primary command module?

[ExtraPlanetal]

ExtraPlanetal, that is epic, driving the rover into the crane, didnt think of that for a docking mechanish, i suggest Damnyoujapan's claw

I tried it, but it ended up either crushing my rover, dropping it or ripping it apart on take-off.

Also - I dare anyone who has enough mad skillz to actually land a rover on the Mun with my Skycrane. You are allowed to make minor alterations (reworking the robotics and swapping out the propulsion system, but the entire lift thing must stay).

Good luck >

Edited August 9, 2012 by ExtraPlanetal

[togfox]

What part is the 'rope' and what is the IRII escape decoupler?

[Joe Pinball]

you make the "rope" yourself using fuel line. there are 2 parts: the hinge and the cylinder. the cylinder is what would be the rope (but it only shows up as 2 flat squares)

a quick search for IRII escape decoupler will reward you with:

http://kerbalspaceprogram.com/forum/showthread.php/7678-Plugin-Part-KSP-0-14-Escape-Decoupler-Alpha

note: it was designed for .14 but still works perfectly with .16.

Joe

I have now switched myself to the stock decoupler, as so few folks seem to know where it is!

P.S. I'm still struggling to do the hardcore part of the challenge with any reliability...

Edited August 9, 2012 by Joe Pinball

[Joe Pinball]

This is (I hope) a decent "tester" craft for my hardcore attempt:

The hardcore problem:

Putting mechjeb/control/command pod on the lander adds some difficulties.

Firstly, as the capsule is the top-level "parent" part, the SkyCrane assembly has to go "above" it, which usually means a capsule with an attachment point rather than a MechJeb pod, so we're dealing with live Kerbals here!

Also, any attempt to control descent is being effected by the SkyCrane, but the 'target' for such control is at the end of a slightly springy "tether" and wobbling like a pendulum.

MechJeb tends to eventually get into a tizzy and the result can be a smooth descent marred by utter chaos and a crash at the last minute. if you manage to actually get the lander within 5 to 10 metres of the ground and not moving too fast horizontally, decouple quickly! controlling it manually leads to pretty much the same lack of control also!

My attempt at a solution:

This craft's basic premise is to lob the entire SkyCrane & Lander assembly high enough up, so that it returns on a decent ballistic trajectory at high speeds, which is close enough to simulate a proper terminal phase of a re-entry profile.

I found through experimentation that without struts, the entire SkyCrane assembly will just flop over & destroy the rocket on the pad the moment it gets unpacked: as the tether's "floppy" behavior is intended, we need lots of struts make it a rigid part of the rocket but also have the ability to get rid of these struts when we want to do the final SkyCrane part.

This meant adding a stage with struts and some ballast at the bottom, however I can easily pretend it's the heat-shield part of the martian lander stage!

I also decided to add in a chute, even though it would be discarded before it unfurled, to add a touch of drag & also replicate that step in the martian lander.

The next problem is how to smoothly migrate from "rigid with struts to stop it falling to bits" to "no struts and still smoothly in control" - I decided the best strategy was to establish a smooth almost vertical descent before decoupling the strut/stiffener bottom stage, so that natural drag would (hopefully) keep the tether taught before the chute would fire to help with increased drag from the top.

This approach works, with the added minor issue that the decoupled strut/strengthener stage has LESS drag than the SkyCrane & payload, so tends to remain stuck underneath during cart descent instead of falling away like I wanted it to, so I stuck 4 upside-down engines on it which use the handy small amount of liquid fuel in DYJ's Crew Tank (used as ballast to hekp keep the entire assembly upright during descent).

This (usually) blasts this stage clear...

After that, the the 'chute is decoupled and the SkyCrane stage is fired, usually using only KILL ROT and keeping it vertical (or trying to when closer to the ground!)

Then, use the SkyCrane engines to drift slowly downwards, pay out the tether, keep everything as smooth and as vertical as you can and then decouple when safe & close enough to do so. If you get it right the rover will plop down intact onto the surface and the Skycrane, now freed of it's payload weight, will rise and gently soar overhead just like in the Curiosity landing animations, to crash nicely, from a few hundred meters away to several km.

I have attached the craft file for you to have a play with. This one is 100% stock parts except for the following:

MechJeb: in AR-202 case on capsule

SkyCrane: hinge and 'cylinder'

HSTW carts: Large cart

Damned Robotics: 1 metre truss

Operation:

Once the rocket has unpacked, DO NOT use the SkyCrane controls to adjust the tether length! as it is held in place with struts, you will put huge forces on it and possibly break the rocket.

Use SmartASS KILL ROT function, wind up to 100% throttle and launch.

Leave the rocket pointing straight up, all the way until it runs out of fuel.

When the lifter stage is empty decouple it: enjoy a minute or 2 of weightless as you coast to ApoKee, which should be around 55km. Now dial up 2/3 throttle, ready for when you need thrust later.

As you begin to descend, try & keep the craft vertical with KILL ROT still.

At around 15 km, deploy chute. (it has little effect but what the hey, it adds a bit of realism)

Once down to around 200 m/s and/or 3km altitude, fire the retro engines for the ballast & strut stage, and then immediately stage it (I tried to do this all in one but it decouples before the engines fire, and so wont work as intended). Hopefully this will shoot away and veer off to one side.

As soon as the ballast & strut stage is cleanly descending, decouple the chute; and then stage again to fire the SkyCrane engines.

If you remembered to pre-set the throttle to 2/3, this should gently bring your vertical speed down to something manageable.

Now it's up to you to get a nice slow descent speed, and pay out the tether enough.

I suspect the way the SkyCrane 'drives' is dependent largely on how much you pay out the tether: too long and it will be almost impossible to manage.

When close enough to the ground, a final decouple should allow the SkyCrane stage to soar up and overhead, gently keeling over in a nice satisfying long arc to end in an excellent medium-sized explosion a few hundred metres or more away, and your cart/lander safely on Kerbin!

staging:

Stage 0 - capsule and Cart (could be lander/probe ofc)

Stage 1 - final SkyCrane decoupler

Stage 2 - Skycrane proper, 4 engines 5 small tanks 2 RCS tanks + RCS thrusters + SAS

Stage 3 - 'chute decoupler

Stage 4 - Strut & ballast stage decoupler

Stage 5 - ballast tank & 4 retro rockets, struts to keep SkyCrane rigid.

Stage 6 - 'chute deploy

Stage 7 - lifter stage decoupler

Stage 8 - main lifter stage

---------------------------------------

Enjoy!

Joe

Edited August 10, 2012 by Joe Pinball

[ExtraPlanetal]

Damn Joe, freaking nice ship you built there, way better than mine anyway XD

[Claes]

Ok, done.

I made a stable lander. It will MechJeb-autoland and MechJeb-autohover. The trick seems to be that the entire stack´s center of gravity must be *above* the center of thrust for MechJeb to work properly. When I attached the boosters too high, or made the stack parts above the hinge lighter than the parts below the hinge, the stack just somersaulted off the launchpad.

The solution was to have a lander that was (a lot) heavier than the rover, and had the center of gravity above the center of thrust, and had thrst-vectoring engines. I also concur on the above observation that having the MechJeb below the hinge, and thus being pendulumed (?) around, confuses MechJeb, and the cartwheeling starts again. I believe (this is a guess) that MechJeb assumes the entire stack is pointing in the same direction as MechJeb. Now, if MechJeb were to get thrust vectors from the actual engine pods, that would maybe remedy this issue.

My stack is attached as a .zip below. Operate as follows:

Set MechJeb ascent autopilot as described in image 1 (orbit alt 5 km, turn end at 18 km, ascent profile slider 75% to the right, inclination 140 deg.)

Start enginges

Release "launch clamp"

When stack reaches ~4500 meters, disengage ascent autopilot

Release drogue chute (press space)

When stack has almost stopped pendulum-ing (seriously, what's the proper term?) engage MechJeb autoland

Release drogue chute (press space)

At [your desired altitude, I suggest ~100m] disengage MechJeb autoland

Engage Rotatron Keep Vert, set to 0, and Kill Horiz. Stack will now hover, stable. Move sideways with wasd.

To release rover: (this is manual & tricky, would it be possible to make a Autom8 LUA-script for this? "When Altitude < 5m Coupler.X.Disengage and Booster.Y.SetPower(100%)") (i can't code LUA, but something like that?)

Lower rover wheels (press g)

Select MechJeb autoland (0.1 m/s touchdown speed)

When at < 5m, deselect MechJeb autoland, set full throttle, release rover ½ second later (press space)

Congratulations to all others who made it.

Thanks to Barie for the challenge and to KSP dev for exercising my brain.

Now, off to do it again, with Lionhead parts and some aesthetics.

Safe landings!

/Claes

[Gefrierbrand]

Hi! I wanted to try out Joe Pinballs rocket, but I'm missing "DRCylinder2" and "Crewmodule". Where can I get these parts?

I have installed all listed plugins/parts, or at least I thought so...

[Claes]

The modded hinge (works as intended, as far as I could see) and invisible piston (displays incorrectly on my installation, but functions as a regular piston, which does the job anyway) are found in this link:

the parts: http://www.sendspace.com/file/3pa0pa

Safe landings

/Claes