Vehicles: ships, submarines, balloons

Skill ferret-physics-vehicles · download all skills · SKILL.md

When to use#

Anything that floats, dives, flies on gas, or is pushed by a screw or a sail.

The model#

A Vessel (VesselSpec) is one body with parts: hull (cells), tanks, compartments (flood through breach and doors), envelopes, thrusters, surfaces (rudders, foils, sails). Draft = mass / (ρ × waterplane area). stability() gives the metacentric height gm: positive rights itself, negative rolls over.

Steps#

1. Size the hull so mass matches displacement; set cog low.
2. Add hullDamping and angularDamping, addedMass 0.1–1.
3. Submarines: fill/blow tanks; neutral fill = (displacement − dry mass) / tank capacity; crushDepth.
4. Drive by vessel.thrust, rudders, sails (sailPolar).
5. Commands: vessel.add|info|state|fill|thrust|breach|blow|surface.

Check afterwards#

Light and loaded drafts follow Archimedes; gm is positive; a breach floods the named compartment.

What usually goes wrong#

• Floats too high or low: mass and hull do not match.
• Rolls over: gm negative; lower cog, widen, empty part-filled tanks.
• Never settles: no damping.
• Passes through the shore: light kernel or body: false; use Havok.
• vessel.breach refused: unknown compartment name.

Files#

• reference/vehicles.md — A vessel is one body with parts: a hull that displaces water, ballast tanks, flooding compartments, gas envelopes, thrusters, rudders and sails. How to build one, drive it and read its stability.
• reference/api-physics-vehicles.md — every export of @ferret/physics-vehicles with signature and doc comment
• reference/commands.md — 7 commands of these packages with their arguments
• recipes/water-and-boats.md — Six recipes: tanks that equalise, a U-tube of two liquids, a wave that slows on a beach, a boat that sinks deeper with cargo, a wing that stalls, a ball that curves.