[quote]What I was getting at in the first post was the way in which hovercraft turn, they kind of slide sideways and turn into the slide…doesn’t make much sense unless you’ve seen it…
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Ah, ok. I know what you’re talking about. See, I was assuming multiple thrust vectors instead of a single rear thrust vector. i.e. All the thrusters on the bottom would “tilt” to provide forward, lateral, and reverse momentum. Combinations of tilt could produce vehicle rotation. What you’re referring to is simply redirecting the rear thrust in a way that produces rotation.
This is complicated, because the hovercraft spins only because the power transfer from one end to another is incomplete. As you said, a tensor field. It also wouldn’t work as well in a vacuum, because the air provides a certain amount of resistance that helps “push” against the opposite end of the vehicle.
I think you may be able to get a reasonable approximation by “guessing” the rotation imparted on the vehicle when the thrust is redirected. You can continue to treat the rear thrust as a vector, and simply redirect the vector with the thrust. Then impart an amount of rotation based on the angle of the thrust. The result would be that when you turn, you will start to spin and slide to the side. As soon as you complete your spin, you can redirect the thrust back the other way to stabilize your trajectory right before you re-center the thrust to provide maximum forward power.
That being said, I can’t imagine that any engineer in his right mind would design a hovertank like a traditional hovercraft. It simply isn’t stable enough as a weapons platform, and would be hellaciously hard to control. (That’s a lot of mass you’re pushing around!) Instead, I think an engineer would take the approach of using various directed thrusters to maneuver the tank in much the same way as the OHMS system maneuvers the space shuttle.
Our mythical engineer would probably install four lateral thrusters which would allow the tank to slide sideways (fire both on the same side) or rotate on its axis (fire one on each side, at opposing ends of the tank). The hovering would then be achieved with a set of shielded thrusters at the bottom which provide enough thrust to hover the vehicle, but keep enough in reserve to adjust their thrust to cancel out any roll motion produced during strafing maneuvers. Forward thrust would be provided by either tilting the bottom thrusters, or by having thrusters in the rear. Reverse thrust (also braking) would be provided by tilting or forward mounted thrusters.
The proper way to then control such a vehicle is two joysticks. (Anyone remember Atari Battlezone?) Centered sticks would produce thrust only for hovering. Both sticks forward would produce thrust from the rear for forward motion. Both stick to the side would provide lateral motion (i.e. strafing). One stick forward and one stick back would activate the side thrusters whereby the forward stick would activate that side’s forward thruster, and the back stick would activate that side’s rear thruster. Both sticks back would activate the thrusters on the front of the vehicle.
Such a design becomes very easy to calculate for. You have a vector for weight (down), a vector for hovering thrust (up), and a vector for each thruster mounted on the sides, front, and back of the tank. Take the tank’s current vector and add all of those to it. Then take air resistance as a percentage of the vector to subtract. The only special case is then rotation which can then be set to any value that “feels” correct.
Does that help at all?