Flight Model
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Overview
Jumpgate Evolution (JGE) uses a semi-Newtonian model to simulate space flight. Translational motion of a ship obeys Newton's Three Laws of Motion. Ship dynamics are govern by a Thrust Force and a Drag Force. Angular momentum is not modeled. A stationary ship rotates at the same rate no matter the equipment load-out or cargo.
- As of June 3rd, 2009, Newtonian drift had aparently been turned up significantly as compared to previous builds. Ben Kuchera of Ars Technica, who tested both at GDC and at E3 said: "The controls are likewise tricky to get used to; inertia is a big issue as you fly around the level."
History
The JGE flight model is inherited from Jumpgate Classic (JGC). The JGC flight model was called DANCER. Per JOSSH FAQ: "DANCER (Drag And Near-true-physics Combined to Engineer Reality) is NetDevil's proprietary physics engine that makes space flight in Jumpgate so interesting and fun. Using Newtonian physics, your ship will continue to travel in a straight line once you accelerate, even if you rotate your vessel - this means you can be facing a completely different direction than you are moving."
- "Netdevilās D.A.N.C.E.R engine remains the core of flight behavior. Most of our changes are being made at the user interface level, not at the flight physics level."
-- Steve "Istvan" Hartmeyer (NetDevil Developer) Source
Physics
This section provides a mathematical description of the JGE flight model. Readers are assumed to understand the concept of a Vector.
Thrust Force
Thrust is generated by ship engines. Without lateral control inputs, the direction of the Thrust Vector is the direction the ship is facing. The magnitude of the Thrust Vector is controlled by the throttle setting.
Drag Force
A Drag Force acts against a ship in motion. The direction of Drag is always opposite the current Velocity Vector. The magnitude of Drag is the Coefficient of Drag (Cd) times Velocity squared. Jumpgate ships each have a Cd attribute.
- The Dampener flight control is based on changing the magnitude of the Drag Force.
- The Jumpgate Drag Force equation is similar to the atmospheric drag equation used to determine orbital perturbations on low orbit spacecraft. Both have Velocity squared elements. The Jumpgate Drag equation lacks the exposed surface area element in the real perturbation drag equation. Jumpgate Drag is the same for both when the ship nose is facing or when the ship belly is facing the Velocity Vector.
Equation of Motion
The equation of motion for Jumpgate is Mass times Acceleration = Thrust Vector plus Drag Vector.
- A ship will stop accelerating when Thrust = Drag. The constant speed of a ship can be calculated by the equation: Velocity = square root of Thrust divided by Coefficient of Drag.
- During a linear acceleration burn, Drag acts against Thrust. During a linear braking burn, Drag acts with Thrust to stop the ship.
References
- Quote from Steve "Istvan" Hartmeyer. Darkspace Dispatch Special Report 1
- Hermann Peterscheck - Codemasters Forums 1, 2
- JGC information portal. JOSSH FAQ
- Donald T Greenwood (1988). Principles of Dynamics, Second Edition, New Jersey US: Prentice-Hall, INC, sections 1 to 4. ISBN 0137099819
- P. Fortescue & J. Stark (1992). Spacecraft Systems Engineering, West Sussex UK: John Wiley and Sons, section 4.5.2. ISBN 0471927945