Engineering a spin launcher for Ortus City | KSP 1.11.2

as a civilization expands into space it begins to use the same gravitational pathways over and over again for our deer kerbals here this pathway is to minmus the second moon of kerbin from low curb in orbit there is no celestial body that is easier to reach land on and refuel on voyages out to further destinations for this reason minmus will be essential for the further expansion of kerbals into space but we need infrastructure to make this happen and thankfully the people of a community colonization project the upsilon initiative have delivered their creation is ortis city a large refinery colony built on the minmus flats it features an artificial gravity hub refinery monorail observatory space port shipyard [Music] train station [Music] solar field and many other impressive structures in total this city has over 6 600 parts which to my knowledge makes it the largest community colony in ksp history their work is a testament to the creativity and skill of the ksp community and is worth exploring in its own right i've linked some videos made by the organizer of the project knight of saint john and the contributors of the city if you want to see more of it [Music] while impressive and fully capable of housing a self-sufficient population this colony just needs one more thing an efficient way to return its produced fuel back to low curb in orbit this will be my contribution to the project after some thought and some failed ideas i arrived on the idea of making a reusable spin launcher the basic idea behind a spin launcher is that you place a payload at the end of a long arm spin that arm up using electric motors and then release it to give your payload a large boost in velocity by building one of these you could reduce or eliminate the use of propellant which in turn lets you deliver more payload to your destination for a giving starting mass now i've built spin launchers in the past but they've all suffered from the same problem rapid disassembly turns out releasing the incredible internal forces in the spin launcher just does not end well if we want to reuse this system around our populated space colony we need something a little less catastrophic one way we can improve the chances of our spin launcher working is to eject a counterweight at the same time as the payload by doing this we can balance the forces out which will hopefully keep everything intact this is an obvious solution to the problem and indeed totally valid however i don't like it so much because of all the resources you need to expend to get it to work in a typical spin launcher setup you're ejecting a mass equal to your payload mass which is a lot of resources to expend because of this i decided to take a different direction my solution was not to have a counterweight at all i know it does look quite strange not to have a counterweight you'd think that the unbalanced forces would cause a lot of problems for this but as you can see it's perfectly stable even through the payload release i'll talk a bit more about the engineering of this later but for now this launcher is not much use on kerbin this pesky atmosphere here is inhibiting our speed let's get this off to minmus where it can really shine i think you know the drill by this point it's time to slap an excessive number of mammoth-powered boosters on and blast this 38 000 ton monstrosity off into space i know it's not pretty but it gets the job done one thing to note here this ascent is finicky due to the large amount of drag created by the motor assembly up top we need to keep this pointed close to prograde in order to stop it from flipping over now that we are in orbit the next step is to transfer over to minmus and to do that we need to turn this monstrosity around since the stock rcs thrusters are way too small for this i've attached mammoth engines in two rcs clusters at the top and bottom of the craft i'm using a mod called throttle control avionics to then use these mammoth engines as rcs thrusters once we're pointed the right direction we can get off on our transfer to minimus we don't need to drop any more stages from here one of the nice things about building these large crafts is that they use a lot of mark iii fuel tanks in their structure which means we have a ton of fuel available to us just on the craft after a quick hop over to midness the final step in our journey is to land the spin launcher at our designated landing site since this craft is so large and cumbersome to turn we're going to come down straight over our target it's not the most efficient way to land but it doesn't matter so much because minimus has low gravity and we have plenty of excess fuel [Music] okay as we're approaching the city the city itself poses some lag related issues as i mentioned earlier it's composed of over 6 000 parts and it's split across multiple separate crafts as a result as you approach it loads these crafts one at a time which can painfully drag out the approach to get around this i'm making a bit of a risky play as i get closer to the 2.5 kilometer loading distance i'm going to slow down switch to the tracking station let the spin launcher fall a bit so that it gets within range of all the buildings and then switch back to it this way the city can be loaded all at once which saves us some time i know i've been talking about how the city creates a lot of lag so why does this video here look so smooth well i always speed up my videos to remove the game lag this section here actually took me well over 30 minutes speaking of landing there we have it not quite aligned the way i want it i'll shift it around until it's just right i'll spare you that laborious process with it in position now all that's left is to jettison the landing thrusters this process can disturb the crack in a bit so we need to jettison everything and then immediately switch to the tracking station doing this locks the launcher in place and allows the engines to fall to the ground and be deleted harmlessly our spin launcher is now operational let's fire it up here we have a 150 ton fuel tanker to load the launcher we just drive the payload onto this loading elevator here the elevator will take the payload 200 meters above the ground to the arm why 200 meters well this is the physics loading range in ksp crafts inside this range will have physics applied while those outside this range will not by lifting the craft up 200 meters we can guarantee the payload will never get within 200 meters of anything on the ground which helps us reduce lag once we're at the top the claw at the end of the arm will grab the payload and we can return the elevator to the surface all right payload is loaded solar panels are deployed all systems are go let's release the clamp and get this thing spinning [Music] an array of 48 mark iii wheels on the motor assembly up here provide the torque needed to rotate the arm in total these wheels consume 672 electric charge per second that's quite a lot of power enough to drain the largest battery in the game in less than 10 seconds we can't feasibly power this with batteries so that's why we have these solar panels up here in the center the solar panels are attached to these unpowered dlc motors so they can stay in a fixed position while the arm rotates remember at the start how i mentioned the center of mass is not balanced on this you would expect this thing to violently shake as it rotates like a brick thrown into a washing machine but as you can see it's staying perfectly stable the reason comes back to the physics range i mentioned the spin launcher is actually two separate crafts one craft is the arm which is what we're controlling the other craft is the tower the root part of the tower is located at the very top here in the center of rotation since the root part of the arm is located over 200 meters away the tower is actually out of physics range and is not pushed by the imbalanced force yet despite this we can still interact with the colliders the base to keep the arm attached a lovely quirk of ksp we still have a bit of time before the payload reaches the velocity we want so let's take a closer look at the bearing while we wait the bearing is made of two parts the large landing gear on the arm and these onion re-entry modules the re-entry modules seem like a strange choice i know but they have a very unique property a large spherical collider this allows for smooth rotation unlike most of the parts in ksp which have much more crude colliders the combination of the heavy landing gear with these re-entry modules allows the arm to support the immense centrifugal force while remaining stable [Music] speaking of immense centrifugal force we have now reached our desired angular velocity at an angular velocity of 0.9 radians per second our payload has a tangential velocity of 340 meters per second this corresponds to a centripetal acceleration of 30 g's which exerts a force of over 4 000 tons on the arm with just the press of a button the payload is off the spin launcher handled the huge shift and center of mass wonderfully we can now slow down the rotation and lock the arm back in place with these air brakes it is now ready to be used again now back to the payload we not only gave it enough velocity to enter mimi's orbit we gave it enough to escape mimus entirely and return back to kerbin let's just check our trip oh wait a minute um actually no i appear to have gotten the direction mixed up instead of returning it back to kerbin i appear to have ejected it into interplanetary space uh let's rewind that and do it correctly this time okay there we are now that's properly going back to carbon the payload can then aerobrake to low carbon orbit and then deliver its fuel or whatever else it needs to do okay so returning payloads back to kerbin is one potential application of the spin launcher but that's not all we can do with it our payload was quite heavy what if we got something lighter how fast can we throw it well let's take this cargo plane here with a mass of 35 tons it's less than a quarter the mass of our first payload let's load it up and see what we can do it's got a bit of a wide profile so we need to swing the arm out of it first before we can take the elevator back down once we get that out of the way we can get spinning and as expected the acceleration is much higher while the original payload took about 20 minutes of in-game time to spin up that was three hours for me when you add the game lag this one will get up to speed in about 3 minutes we're getting past 1 radian per second now which is faster than the original payload this corresponds to a launch velocity of about 370 meters per second we're not done yet though let's keep going our goal is to get up to 2 radians per second here despite the fact that this payload is less than a quarter the mass of the first payload it's actually starting to exert a similar amount of force at this rotation rate this is because centrifugal force is a factor of velocity squared so in other words if you go twice as fast you quadruple the force once we're up to speed we can just let it go and there we have it the spin launcher has actually survived launch number two and our payload is off at 780 meters per second this is more than enough to escape kerbin as you saw last time and not only that it's enough to take us all the way out to duna that's right this thing has wings for a reason with this mode of transportation we can deliver all the delicious minimus ice cream you want to arrow keen city [Music] sadly we shouldn't use it to take kerbals with us at 2 radians per second the centripetal acceleration was over a hundred and sixty g's which the kerbals probably wouldn't enjoy that said i'm not your boss i just designed the thing do what you want speaking of things you probably shouldn't do we have one last application of the spin launcher and i'm sure some of the more sadistic of you might have noticed this as well due to an unforeseen change in plans for this design the spin launcher itself got positioned in a way so that it could deliver payloads back to the city i guess if your citizens ever get out of line you can show them who's boss or um uh i guess you can leave them running for the hills whatever unruly dissenters are probably not a problem anymore probably well with that that's all i have to show thanks for sticking around until the end and i hope to see you in the next video which hopefully should not take this long to produce next time alright see ya [Music] you

Channel: Stratzenblitz75

Views: 1,308,718

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Id: vS74SsBd3eQ

Length: 17min 22sec (1042 seconds)

Published: Mon Dec 27 2021