Hovercraft Mechanics

When creating the hovercraft, I wanted invoke a sleek and tight feeling to driving the hovercraft. My imagination would compare it to formula racing, where racers would pull out of turns and seamlessly accelerate as if riding on clouds. I also wanted to invoke feelings of true hovercraft physics, where the the hovercraft reacts to what is beneath it instead of feeling attached to guiding rails. Because of this, my design revolved around applying 5 different forces to the hovercraft, consisting of the hover balance forces, main thruster force, forward counter-force, the sideways counter-force, and the rotational turn force.

Balance Forces

Four different forces come together to create the balance forces, each one placed at their respective corner of the hovercraft. Each force operates as a basic spring, pulling and pushing each corner closer to their ideal distance from the ground.

Due to wanting a fast response, all variables in the calculation are quite high. The goal was to achieve the ideal distance within half a second and having no more than one oscillation from over-shooting the distance. Due to these constraints, heavy testing was required to achieve the fast steady-state distance. For achieving the limited oscillation, I found the ratio of spring force to be 1-3.5ish. Then I cranked the numbers up until the balancing correction felt instantaneous, which immediately broke the true hovercraft feeling. Then I brought the numbers slightly down until the instantaneous feeling disappeared. What I was left with was a balancing model that felt snappy when transferring between different ground angles, but still maintained the believability of a real world hovercraft.

Main Thruster and Counter Forces

The main thruster force was a pretty simple implementation. All that was needed was to apply a force to the hovercraft at the center of mass in the direction of the forward vector. Most of the balance associated with the main thruster came along with the forward counter-force. The counter-force applies a force opposite the thruster based on the current velocity in the forward direction, seen in the picture below.

These two forces were then balanced to allow for a fast acceleration to max speed. To achieve the driving model I wanted, a high main thruster force was paired with a sharp forward counter-force curve to quickly reach max speed.

The side counter-force existed to help achieve higher cornering speeds and simulate how wheeled cars round corners. By simply calculating how perpendicular the hovercraft’s velocity is with its current forward vector gives a good coefficient for the sideways force. When multiplied by a balanced constant, the hovercraft is able to quickly make tight turns while achieving a slight drift when pulling out of a turn.