The Force of Gravity

Newton’s law of universal gravitation describes the force of attraction between two bodies at non-relativistic velocities: proportional to each mass relative to the distance each way.

In gr_4Xity, ships travel to other star systems by “jumping” into the target star’s “gravity well”. Plotting a course requires sufficient gravitational attraction between the ship and destination star (m₁ and m₂), which diminishes with the squared distance between them (d²) because gravity reaches in both directions, dependent on the power of the ship’s gravity drive (G).

As a result, the distance (in light years) your ship can jump is the geometric mean of the masses of your ship and target star, scaled by the power your ship’s gravity drive (G) relative to the required force (F) to plot a course.

In future posts, we’ll detail the travel mechanics—as well as apply Albert Einstein’s theory of relativity to travel at the speed of light.

Here, we’ll start by asking and answering the most important question:

Where’s the Fun?

Newton’s equation is about trade-offs, and these have interesting consequences for navigating the map as designed and implemented in gr_4Xity:

• Bigger ships can reach farther stars, all else equal. gr_4Xity‘s Arkships are built from the solar system’s largest asteroids—mined hollow for valuable resources, with leftover regolith dumped on the surface to maintain mass and provide shielding, then spun up for artificial gravity and lit up for habitation by nuclear power.
• “Star lanes” emerge from the stellar distribution of the procedurally-generated galaxy. Larger stars may be critical transit hubs but may be more hostile to life.
• “Star lanes” are directionally asymmetrical. You may be able to jump from a small star to a larger one, but it may not be possible to return the same distance to the smaller mass—without finding an alternate route or improving your technology.
• As technology (G) advances, newer, smaller ships can keep up or even surpass legacy Arks in range but not carrying capacity. While it’s common in 4X games for technology to determine unit movement distance, gr_4Xity’s legacy units can increase their value as their role in your interstellar empire changes over time—making them riper targets in conflict!
• There are diminishing returns to the technological power of your ship’s gravity drive (G). It takes four times as much power to double your jump range (d), so consider the focus of your technological development carefully.
• While all Arkships move at the same speed (the speed of light), higher-tech ships can take more direct routes with fewer stops, all else equal. Anticipate enemy ship movements and head them off at the pass!
• Spending time and resources to upgrade the gravity drive on legacy units can change the developmental course of your empire. That old “stagecoach stop” critical early on to making it from one side of your space to the other can become a ghost town, while industrialized planets developed mid-game around a network of “train depots” can become a source of late-game internal instability as they “rust” in the face of more efficient competition.

Navigation in gr_4Xity is a tactical challenge!

Choose your course and your stops wisely to execute your strategic goals:

• eXplore: Take different routes, risking unknown hazards to uncover new opportunities in deep space?
• eXpand: Transport colonists to settle on alien worlds or military units to establish outpost stations?
• eXploit: Transport and exchange resources to support growth at home and across your colony worlds?
• eXterminate: Defend or embargo star lanes? Deliver invading armies or spend time to siege vulnerable colonies into submission?

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