KrakenDrive with Adjustable Thrust [Stock, 1.4.3]

[sgt_flyer]

Hello, i scratched my head for some time for rebuilding an effective stock KrakenDrive, within the current limitations of the game,

notably that wheels don't collide with the same craft - you need a separate part for the landing gear to press upon for that.

Second problem, is getting a mean to redock this separate plate after use, for warp time or for saving games.

for that, i started playing around with Airbrakes to give the pressure plate enough spacing from the docking port, to get it to redock once the airbrakes retracts.

So the basics is simply having a moving part applying various levels of pressure on the wheel, with rail guides to prevent the moving part from escaping.

 

One incredible bonus in having this kind of setup, was that it was possible to change on the fly the amount of pressure applied on the landing gear, simply by varying the airbrakes authority slider.

The result, is that it was now possible to control the KrakenDrive's thrust within both Hover and Thrust modes !

one thing i realised that changed though, was Krakensbane (pre 1.0, the transition speed was at roughly 700 m/s speed)

During hover mode with High G manoeuvers, the thing sometimes transitionned on it's own from hover mode to thrust mode - within atmosphere !

once in thrust mode, it was easy to get the thing to orbit on it's own

 

Tested various form factors for the engine, and i could miniaturize it enough (though, it's a bit less stable) to fit within a single CRG-08 MK2 bay !

 

Here's the video of the drive in operation :

Here's the full mission album  :

https://imgur.com/a/SJtQn0o

 

Here's the .craft files (Dropbox)

KAT 25 (2.5 m form factor) :

https://www.dropbox.com/s/3ie9xeimhq2xk0b/KAT 25.craft?dl=0

 

KAT MK2 (MK2 form factor) :

https://www.dropbox.com/s/0h2tdzzu1ct80vy/KAT MK2.craft?dl=0

 

mods / DLCs i had during this KrakenDrive's devellopment :

Making History KER, RCS Buildaid, EVE and Planetshine.

While i have Making History, i didn't used any part from MH within those two drives, so a stock install should be able to launch them.

i didn't use any of the new decouplers either, though i don't know how it will react in other versions of the game

 

 

Operations :

Pin down the AIRBRAKES, and use the slider to change pressure. the KrakenDrive effect threshold is roughly around 54% slider.

For the KAT 25, press AG 1 to toggle on and off the KrakenDrive. it will redock on it's own when turned off.

For the KAT MK2, press AG 1 to turn on the KrakenDrive, and press AG 2 to turn it off (a reverse pair of AIRBRAKES will then push back the pressure plate to redocking range)

note : if you  incorporate the MK2 within a spaceplane, you'll need to keep the cargobay slightly opened (1% in clamped mode) else the airbrakes will not move within a fully closed cargo bay.

In Hover mode, the speed can vary between slightly negative descend speed (between 0m/s and -1 m/s) (though you're really at minimum effect), and + 20m/s of vertical speed (the krakendrive can't get higher vertical speed in hover mode, once reached, it's not necessary to continue to increase the airbrakes authority further)

Transition : seems the transition speed seems to be between 60 and 100 m/s, the krakendrives can achieve transition during High G manoeuvers in hover mode, (though, generally, you have a really high airbrake setting at this point, the thing will be nearly uncontrollable until you dial back the krakendrive to a lower thrust setting, generally by 57 / 58% of the AIRBRAKE slider)

Thrust mode in air :

within atmo, you will be limited by the Krakendrive's drag, don't expect to be able to break the sound barrier with it while under 10000 m. (throttle back the krakendrive to keep a steady speed near 300m/s while under 10000m)

above 10000m, the acceleration of a given setting will gradually increase as atmospheric density decreases. feel free to throttle back further to get a steady ascent (plus, it will protect the KrakenDrive from atmospheric heating)

 

once in orbit, you can circularize with classic Kdrive operations. (and with thrust control on the kdrive, it's easy to get into low G thrust, the deactivation of the kdrive is nearly instantaneous when you hit the button (in ship mode though ^^, actiongroups won't respond in map view)

In thrust mode in space, i've seen the krakendrive go from roughly 0.5G of acceleration to above 35Gs ! thankfully the thing is built like a tank

so, there's nearly nowhere you can't get with those !

 

Limitations from my test :

The number 1 limit for these KrakenDrive seems to be the Wheel Stress. the faster you go, (above 20000/30000 m/s of speed) the faster the Wheel Stress rises during operation. (and it's hard to brake if you're too fast, the stress still increases while braking)

once wheel stress reach 100%, the gear's damper breaks, and krakendrive stops working.

Other Limitation :

the krakendrives don't seem to like aerodynamics. aircrafts with active KrakenDrive onboard are very hard to control

from the few tests i made, an open ended MK2 bay at the rear of a plane can be moderatly controlled. trying to place the KDrive near the COM seemed to help to if the Kdrive was embedded within the plane.

Getting to hover mode while in space : not really recommanded possible (slow down to near 0 orbital speeds), but can have side effects (can break the Airbrakes), that said, managed to land the KAT 25 on Mun once, all on it's own

 

Have Fun playing with it,

i expect KrakenDrive researchers can get new ideas from it (at least, the few KDrive researchers that weren't lost in the Kraken's belly for abusing it's powers .... the Kraken's behind me isn't it ? ^^

[sgt_flyer]

Added the video of the KrakenDrive in operation to the post

https://www.youtube.com/watch?v=DFNXb2aaxA4

 

Edited May 21, 2018 by sgt_flyer

[Rune]

This looks very, very awesome. Will DL and investigate!

 

Rune. The power of the kraken propels you!

[Lego_Prodigy]

Tbh, Im considering turning to kraken drives for better boosters.the engines are too fuel hungry, the tanks too heavy, and just don't help me.

[Windspren]

The pusher plate often disappears without warning when the drive is on, even when using it for 0.5 g thrust. Surrounding the drive with structural panels has no effect on this.

[sgt_flyer]

it's kraken based technology it can be unpredictable by nature

though, it's seems the further away from kerbin (or planet), the faster the wheel stress rises.

when i tried braking after entering jool's orbit with low thrust, wheel stress rose instantly to 100% and broke the dampener.

i guess it could still be used to send things on an interplanetary transfert, then you detach the drive and send it back to kerbin for the next payload

Edited June 2, 2018 by sgt_flyer

[FleshJeb]

You know, I haven't played with Krakentech since 0.18 or so. This looks very nicely engineered, I'm going to give it a shot.

It occurs to me that you could control this with KRPC (and probably KOS). That might help prevent the runaway and breakage problems. I think these are the relevant items:

https://krpc.github.io/krpc/python/api/space-center/parts.html#SpaceCenter.ControlSurface.authority_limiter

https://krpc.github.io/krpc/python/api/space-center/parts.html#SpaceCenter.Wheel.stress_percentage

[sgt_flyer]

ok, tested a few things with a rebuilt the mk2 version.

(tightened the slides, rebalanced the wheel position to limit reaction wheels needs)

(note : i play with max physics delta time per frame set to 0.03, guess it helps taming the kraken a bit :p - he has less time to try to wreak havoc on physics ^^)

from those tests, seems the wheel stress changes based on distance from the orbited body, instead of the speed of the craft.

from early measurements made from a 100x100 save, seems like at 6500 km above kerbin the wheel stress rises to 95% when the k-drive is operationnal.

note : quicksaving and quickloading before engaging the drive reduce a bit the stress at a given altitude, but it's a bit random

From 100x100 orbit around Kerbin, with various saves :

(the last save and load is made at the previous altitude) - ko means the wheel stress broke the dampener

Stress     Altitude
1.9           400km
2.3           500km
4.8           1000km
12.8         2000km
24.5         3000km
40.1         4013km
100/ko    7000km
100/ko    8000km

Here, there was a quicksave and a quickload just before engaging the k-drive.

Stress     Altitude

1.0           400km
0.8           500km
2.1           1000km
10.5         2000km
10.5         3000km
15.3         4013km
30.0         7000km
100/ko    8000km

in this last table, all tests with the last save and loads made from a 100x100, the orbit was then extended to an orbit with a 100km periapsis and an apoapsis at the edge of the body's SOI. no save before each test. :

Kerbin    Duna    altitude
                60        2870km
40           100      4000km
59.1                    5000km
82.2                    6000km
95                       6500km

 

It seems the wheel stress increases faster on a body with a smaller SOI.

 

The tests were all done with the prototype seen here, which did make the flight from Kerbin's Airstrip to duna, with no rocket engines nor RCS !

Propulsion : 2 whiplashes (for takeoff and accelerating up to transition speed), 1 MK2 KrakenDrive

 

the transition is real smooth with jet engines to bring the kdrive above 100 m/s

simply set the authority to 56 / 57.

Take off on jet engine, and accelerate to 100 m/s, engage the k-drive, then shut down the jet engines, the K-Drives do the rest.

(throttling down the k-drive a bit during high altitude acceleration phase helps not burning ^^)

 

now, for the flight to duna, i managed to make my transfer with a 1000 km periapsis around duna directly from LKO, as i had no mean to correct the trajectory (because of the behaviour shown above).

I guess a more complete prototype with small rocket engines for course corrections would make the best use of this KrakenDrive.

 

i'll try to test various SOI's to get to know the safe operation altitudes for the engine

 

 

 

 

 

Edited July 7, 2018 by sgt_flyer

[MR L A]

Sorry, despite a few thousand hours of gameplay this sort of KSP engineering is a little out of my depth. Can somebody explain what in the name of Jehovah is going on here?

The thing defies game physics right? Creates ludicrous thrust from almost nowhere? Any good videos of one in action?  

[KerbalChamp2006]

Wow! Nice glitch abuse!

[sgt_flyer]

6 hours ago, MR L A said:

Sorry, despite a few thousand hours of gameplay this sort of KSP engineering is a little out of my depth. Can somebody explain what in the name of Jehovah is going on here?

The thing defies game physics right? Creates ludicrous thrust from almost nowhere? Any good videos of one in action?  

Well, you can see it in action in the video in the first post  

https://www.youtube.com/watch?v=DFNXb2aaxA4&ebc=ANyPxKqVZYu5H479wuEP15RcuIyBzHIeaKqpTwmSbzWOvc-K-89UahjnIOkpCMUmRLWf9UayNIDA

As for the how, basically when the wheel dampeners try to extend after having been compressed, the force is only applied to the craft the wheel is a part of (instead of also applying to whatever the wheel is pressed on).

Normally there's no problems (wheels usually press on a planet's or moon's surface), It's simp'y a computing simplification for limiting the resources used by the physics engine of the game.

But here, when it's the same craft that press on the wheel, the wheel only impart force in one direction (instead of two), resulting in net thrust.

Before the game swithed to unity 5, the wheels could interact with the same craft, so you never needed a separate part

since unity 5, wheels can't interact with the same craft, so you need a separate intermediate part.

Basically, you get :

1) Part A wheel's dampener is compressed by part B.

2) Part A wheel's dampener try to extend back, pushing part A away from part B (but imparting no force on B, while in real life it would impart force on both sides) 

3) because the part A also pushes on B (but B get's no return force from the wheel), you get a net thrust.

It's like that magnet troll physics meme

Now, for the two modes of operation (hover mode vs thrust mode) it is thought it's because Krakensbane steps into action (Krakensbane is a piece of code added by the devs to prevent kraken attacks (which worsened the faster / farther you went), but this code only steps into action after you went faster than a specific speed

 

Now for the pure mechanical in this craft (outside the troll physics), the objective was to have a reliable sliding mechanism with redocking for part B within part A. 

Using the airbrakes authority limiter allows to control the movement of part B, pressing it more or less on the wheel, controlling in return the amount of force applied by the wheel on the craft

When the airbrakes retract, they pull part B to redocking range  (in te 2.5m model)

[MR L A]

This is incredible stuff! I think I'm going to build one into a interplanetary ship - its a bit like an Alcubierre drive... crazy physics but works!  Is there a reason for having so many reaction wheels on your design though?

[sgt_flyer]

@MR L A

basically, it's because the wheel's position has to be extremely precise to prevent offset thrust (the dampener force is not exactly lined up with the wheel's visual model) - even then, when using maximum pressure, the part bend slightly worsening the offset. (And it's even worse with a center of gravity far away from the drive)

the reaction wheels are basically there to compensate the resulting torque

now, be careful on long range missions, you can basically only use the drive from lower orbits in planets SOI, as the wheel stress rises the further away you are from the planet you're orbiting. If stress reach 100% the dampener breaks and the drives stops working. (On kerbin near 7000 KM stress is near 100%, on duna it's 4000 km) so you need very precise transfers (or classic engines to do course corrections) :p

it's doable though, managed to get my mk-2 version from kerbin's surface to duna's low orbit with only jet engines (for getting above krakensbane speed) and the mk-2 krakendrive for getting into orbit, make the transfer, and braking near duna