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Can you design stable ships with moving rotors?

Discussion in 'General' started by SirConnery, Sep 12, 2019.

  1. SirConnery Apprentice Engineer

    Messages:
    155
    So I've always wanted to have ships with rotating spotlights while flying. But even using a small rotor that's rotating slowly while you are flying makes the ship quite unstable, as in it starts to tilt in the direction of the rotor spin while flying.

    Is there some way to design a ship so you can have spindly parts while retaining full maneouvarability? Maybe a counter rotating rotor could work, haven't tried yet.

    I kinda wanted to make a huge ship composed of two rotating huge discs, but seeing that even with a small ship a small rotor causes so much difficulty in manouvering, I might have to abandon that design.
     
  2. Darkheyr Trainee Engineer

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    42
    Subgrids, unlike the main grid, actually make centre of mass and relative mass between grids relevant. I'd first suggest to make sure Share Inertia Tensor is off and that the rotor is attached as close to the centre of mass as possible.

    Otherwise, I even have a ship with rotating engine pods:
    https://steamcommunity.com/sharedfiles/filedetails/?id=1622343858

    It works with this script:
    https://steamcommunity.com/sharedfiles/filedetails/?id=757123653

    I'm not sure if it stabilises without thrusters on subgrids, but you could try!

    I also have a large grid ship with a small grid access elevator mounted on a rotor and pistons that works without scripts, but the elevator mass is minuscule compared to the ship.

    Maybe post a screenshot of what youre trying to do?
     
  3. Malware Master Engineer

    Messages:
    9,510
    @Darkheyr That shouldn't be true anymore since the physics update a good while ago. Motion, however, will still affect the ship
     
  4. Darkheyr Trainee Engineer

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    42
    Really? Nice to know!
     
  5. SirConnery Apprentice Engineer

    Messages:
    155
    Which part of his post isn't true anymore?

    So far I've tried 2 ship designs with rotors. I can post pictures later if needed.
    I've used a small rotor on a small ship it's still flyable if the rotor is on small velocity.
    I've used a large rotor on a large grid which began to tilt the whole ship really badly (although that time the rotor was not on the center of mass).

    @darkhyr
    The rotating engines are operating on a script. And they also don't constantly rotate like the designs I'd like to do.
     
  6. Malware Master Engineer

    Messages:
    9,510
    @SirConnery The center of mass thing. Motion will still affect your ship.
     
  7. SirConnery Apprentice Engineer

    Messages:
    155
    I will have to try with the counter rotating rotor on some small ship, perhaps that balances out the other rotor's velocity? More likely it's gonna just tear itself apart.
     
  8. Malware Master Engineer

    Messages:
    9,510
    Eh, it's more likely that you simply don't get the intuitive behavior than it tearing itself apart.
     
  9. Darkheyr Trainee Engineer

    Messages:
    42
    Nothing I can do about the script, but the ship also doesnt have odd behaviour while rotating midflight. If it did itd be useless to me.
     
  10. Spaceman Spiff Senior Engineer

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    1,360
    My experience is a big, fat "nope" on that idea. One of my ships, Nimbus Freighter, has counter-rotating refinery assemblies and both are of identical mass. The affect is truly wonderful, but the ship is not stable at all; hovering in a planet's gravity well will result in the ship slowly losing altitude at a constant velocity. Here's the ship (the aforementioned refinery assemblies are located at the ship's middle):

    https://steamcommunity.com/sharedfiles/filedetails/?id=1645320568

    [​IMG]

    Even turning off the counter-rotation does no good. Only when I removed the rotors did the ship become stable.

    My most recent build, Triggerfish ( https://steamcommunity.com/sharedfiles/filedetails/?id=1853378028 ) has a single piston. Again, when in a planet's gravity well, Triggerfish has the annoying behavior of pitching (i.e., rotating in the nose-up direction) when ascending or descending. And, once again, the ship becomes stable if I remove the piston.

    That's my experience with rotors and pistons, and these reasons are why most of my blueprinted ship builds do not use them.
     
  11. mojomann71 Senior Engineer

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    1,669
    If your piston or rotor is in close proximity of the main grid (i.e. "brushes" right over it) it can still cause this behavior. For rotors it is a simple action of raising or lowering the rotor head displacement. Pistons on the other hand...yeah still an issue.
     
  12. Stardriver907 Senior Engineer

    Messages:
    2,927
    Here's a short clip of an earlier version of Chilkoot Trail

    The ship's design has changed a bit since that video, but the rotating center carousel remains a feature. Oddly enough, when I set it in motion, the rest of the ship seems to want to rotate in the same direction. If the ship is at rest I can compensate by overriding the gyros. In flight, though, there doesn't seem to be any significant effect, especially if I let the auto-pilot do the flying. Typically I don't rotate the carousel during flight.

    All my stability problems come from subgrids attached to rotors and/or pistons. Those subgrids have to be tightly secured before I attempt to move, else they will try to go their own way. If you want to have a subgrid spinning around while you move, you might try a dedicated gyro as a countermeasure.

    Let me know if that works :)
     
  13. SirConnery Apprentice Engineer

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    155
    "Dedicated counter gyro" sounds so awesome it must work! Will try later.
     
  14. Ronin1973 Master Engineer

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    4,704
    With sub-grids, as stated above, the center of mass of your main grid becomes relative. If possible try to balance any cargo loads to get your center of mass close to center again (assuming you have a symmetrical design). I experienced some heavy yawing a couple of days ago until I realized that my large cargo container full of ice had turned to hydrogen and my cargo was extremely unbalanced.

    In natural gravity, I use a script to keep the ship level. If you have access to scripts, it's always a good idea to have one active. I had a pirate drone explode near my ship and a part landed on top of the defending ship. I had hopped out to explore the pirate base I just took down and looked back. My large ship had listed far enough that the thrusters couldn't compensate and down she went into the planet. That was not a good day.