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Stock Helicopter

VincentLaw

By VincentLaw
in KSP1 The Spacecraft Exchange

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VincentLaw

VincentLaw

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Picture first, then details. Download link here: https://www.dropbox.com/s/3d7caiivkv993na/Light%20Helicopter.craft

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(Prototype variant. Different tail and lacks ejection system.)

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I was just messing around with stock helicopter designs to see if the pylon bug is still there in the new update. Unfortunately it is, but I managed to come up with a more reliable rotor design. With this design scheme the rotors get stuck on mission start much less frequently. I'm still not exactly sure why this "workaround" works at all. Mostly just trial and error. I recommend quicksaving before spooling up, then if it does get stuck just reload and it should work the second time. You are free to modify/redistribute but I don't guarantee it will work properly if you change anything.

Max speed ~55 m/s (level flight)

Controls are mostly like you would expect them to be for a helicopter, except it uses throttle instead of collective, which makes the response time terrible. Just remember that lift depends on rotor rpm, not engine rpm or throttle. Hover is around 30% throttle with full tanks. The SAS helps stabilize a little, but it is mostly there for ballast. I have not tested landing with empty fuel tanks, so more ballast may be necessary for that. Be somewhat gentle on the roll controls, and don't try doing barrel rolls or rotor failure may occur. The limiting factor here that causes rotor failure is the angle between the rotor disk and the mast. The larger the angle becomes, the more undesired torque occurs at the hub.

The first stage is engines, the second stage ejects the rotor blades, the third stage ejects the cockpit (zero-zero capable), and the fourth stage is a parachute. If you try to blend the second and third stages, then the blades won't eject, and launching yourself into blades is generally a bad idea.

Improvements over my previous design:

Higher speed

Vastly less prone to rotor failure

More fuel (range)

More stable

This design is mostly just for flying around for the fun of it. I may do a cargo helicopter later.

Edited by VincentLaw
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VincentLaw

VincentLaw

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Is it possible to do this with wings instead of I-Beams?
Yes, wing parts can be used for the structural elements, but it's more difficult to get good symmetry using only wing pieces, and wings are less structurally sound for various reasons. Also, wing pieces near the center of the rotor disk are much less efficient than wing pieces near the rotor tips, so those end up mostly producing drag except under precise circumstances.

(I just updated the craft file to remove some garbage like unconnected struts and fuel lines.)

Edited by VincentLaw
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VincentLaw

VincentLaw

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Since RocketscientistV expressed interest, here is a cargo helicopter. (cargo not included). Again, I recommend quicksaving before spooling up, and if the rotors get stuck, quickload and it will probably work the second time. This one also sometimes has a problem with unbalanced torque which I have not figured out. I blame KSP inconsistent physics bugs.

helicopter download link here: https://www.dropbox.com/s/scfpgat6ocw1n32/Heavy%20Helicopter.craft

(warning, 304 parts)

It can lift the equivalent mass of about one orange fuel tank, so basically anything you can drive into the cargo bay is liftable. Press 1 to open and close the gate on the back. Raise the landing gear while on the ground to make it easier to drive cargo in.

Cargo used in the screenshots is MeticulousMitch's Delorean DMC 12, available here: http://forum.kerbalspaceprogram.com/threads/49670-Cars-by-MeticulousMitch?highlight=delorean

Screenshots:

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Edited by VincentLaw
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VincentLaw

VincentLaw

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Post some picture of the cargo-copter flying

Okay, Here it is flying around with the world's ugliest bus.

(Also, I just updated the file to remove the canards. They were causing undesired pitching.)

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Edited by VincentLaw
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VincentLaw

VincentLaw

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I never quite understood how to make a stock helicopter before

I can never figure out how to make axels for the rotors that rotate and don't blow up

It relies on a physics exploit. It used to work really well, but now (since 0.21) there is a bug that makes it hit and miss. Basically, all parts are wobbly to a certain degree, but decouplers are extra wobbly. Certain combinations of parts make them even more wobbly (to the point of being able to rotate indefinitely), but now there is a bug that makes some parts completely rigid some of the time for no reason. It seems that certain combinations of parts make the new bug happen less frequently, but I honestly don't understand the new bug.
Waaaaaaaaaaaaaaaaaaaattt~!~!~!

SSTO Helicopter!?~!@~!~!~#

Where where where!?!?!?!?!?

I must see!!

No download link because it is not compatible with this 0.22. It could only barely make it into orbit, but I could probably do a better design now. Obviously it is a hybrid helicopter, so it stowed the rotors for minimum drag and went into space like an airplane. It was capable of transition between helicopter and airplane modes during flight.

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VincentLaw

VincentLaw

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VincentLaw... that is awesome... My next mission is to make an SSTO Helicopter....

I will need to take apart your helicopter to understand how the rotors work xD

This should help as long as you are not color blind. If you are colorblind an unable to decipher these, let me know and I might number them or something.

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For first image:

  • The red angle gives pitch authority to the rotor blades. The higher the angle, the more pitch authority, but at the cost of lift. I am guessing getting the angle backwards will invert your pitch controls, but I have not tested it.
  • The cyan angle is the angle of incidence of the blade. This is necessary to generate lift. for wing parts, the ideal angle is probably around 20 degrees for hovering. Steeper angles increase power required to hover, but increase max speed. (I'm not sure if control surfaces can stall in KSP, so steeper angles may be better. Maybe someone can confirm this.)
  • The green control surfaces give yaw authority. They also act as stabilizers, but reduce max speed.
  • The yellow circle is a micronode. These are very strong joints, so it helps keep the engine from breaking off.
  • The blue strut increases engine efficiency. Without it, momentum will cause the engine to point at an angle.

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For second image:

  • The cyan strut reduces axial loading on the rotor hub and keeps the rotor blades inline. Without it, they will bend around wildly.
  • The green vertical decoupler allows the rotor blades to rotate relatively freely around the mast. Being connected to an I-beam seems to mitigate (but not eliminate) the new sticky bug. It acts like a periodic torsion spring, so really lightweight rotor blades will get stuck easily at low throttle.
  • The red horizontal decouplers are attached using symmetry so that they are equal distances from the axis of rotation. They allow rotation of the rotor disk relative to the mast to reduce out of plane torque on the rotor hub. Without it, rotor failure is inevitable. If you want to eject the rotor blades for some reason, these are the best decouplers to use since they will be flung away from the craft.

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For third image:

  • The red distance determines roll authority. The larger the gap, the stronger roll controls will be. Left roll input increases the lift on a counterclockwise spinning rotor and decreases the lift on a clockwise spinning rotor. Right roll input does the opposite respectively. For this reason, the left rotor should always spin clockwise and the right rotor should always spin counterclockwise (when viewed from above and behind). If you get it backwards, then your roll controls will be inverted.
  • The blue stack separator is not necessary, but it absorbs some of the shock between the rotors and the fuselage.
  • I'm not actually sure if the green decoupler does anything. It might mitigate the sticky bug, or it might not do anything useful.

As you can see, there is complete three axis control from the rotors themselves, and the contrarotation cancels torque. so RCS, SAS, reaction wheels, etc. are not necessary. If you are trying to make an SSTO, you might actually want to take all controls off of the rotors and just use wing parts on them, since control input may cause them to rotate at speed. If you are going high speed and the rotor tries to rotate, it will most likely be ripped off. You can also see how I put vertical stabilizers on one end of the rotor blades on my SSTO to help keep them from rotating.

Tip: the center of lift of the swept wing part is at the root of the wing, so it's actually better to mount them from the outside of the rotor disk pointing in.

Edited by VincentLaw
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VincentLaw

VincentLaw

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One question,

it is possible to make a single rotor helicopter stable cause in my short experience with helicopters they always seem to spin no matter how many reaction wheels there are

It is possible, but there is a reason I use contra-rotating rotors in my helicopters. Reaction wheels provide only a tiny fraction of the torque that the jet engines produce, which is why I called them "ballast" in the first post, They are not very effective for counter torque. RCS works if you give it a long enough moment arm, but it runs out of fuel quickly. mounting a jet engine sideways like a tail rotor works, but jet engines have too much thrust, so they have to be mounted on a short arm to provide the correct torque, which causes a large side force. using a small rocket engine has the same problem as RCS of bad fuel efficiency. One thing I have not tried is more fins at the rotor tips to control yaw enough for counter-torque. It would not make sense for that to work, but sometimes KSP doesn't make sense, so it can be worth trying ideas that seem illogical.

Another problem with a single rotor design is there is no way to control roll with a single rotor in KSP (unless you mount the cockpit vertically, then the controls act differently) so you would either need a ton of reaction wheels, or RCS for roll control. As you can see in one of my posts on page 2, roll input basically works like a collective that depends upon the direction of rotation, so if the rotor is mounted at the center of mass, it doesn't induce roll.

The main advantages of a single rotor design would be lower part count, and lower chances of the sticky bug affecting the rotor (it seems to affect parts randomly, so less rotors means less chances of sticking).

Edited by VincentLaw
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The14th

The14th

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That bird is terrifying to fly! :D

A fantastic way to Kerbal outside the box!

I almost made it to the island runway. I pitched awkwardly at the last moment and clipped the ground with one of the rotors.

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Still, very fun to try out :D

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