Vector movement

Introduction

Space combat games are typically played on black hexgrids with no terrain features at all. Some games add asteroid fields, planets, nebulas, electric storms etc and some even try to incorporate the gravity field around planets. This is at least something we know, real planets do have gravity fields around them and climbing up the gravity well takes serious effort; just look at how big the Saturn V needed to be in order to send three guys to the moon and back.

What can we say about gravity then? Well, it pulls you back toward planets, a ship can remain indefinitely in orbit without thrusting, the higher above the planet a ship orbits the longer it takes; 1.5 hours in low orbit, 24 hours in Clarke orbit and a whole month per lap when you are as far away as the moon. We also know that if a ship has enough speed it can escape the gravity of a planet, this speed is called escape velocity for obvious reasons. Orbits don’t have to be circular either, they can be elliptical with one part getting real close to the planet and the other part taking it back further out, these orbits are also stable and require no thrust to maintain.

Prior examples

The first boardgame I came across that used vector movement was also the first that tried to depict gravity in a sensible manner, that game was Mayday. Mayday borrowed its gravity rules from Triplanetary and the mechanics where simple: If your vector, including its endpoint but excluding its startpoint, intersected one or more hex adjacent to a planet its future position would be affected. Another game with gravity rules was a game called Orbit war that was published in the Space gamer and then became a full blown boardgame.

Intercept version

In Intercept we want to do more than just being in orbit or not. Having several stable orbits with different periods allow us to model low tech orbital warfare with limited endurance fission/fusion rockets and spotting limited by the horizon. We can do elliptical orbits but that is something that just happen to work, free chrome one could say.

How do you do gravity in Intercept then? If your ship is inside a planet’s gravity well (6 squares for Earth) check what arc of the
planet you are in and adjust your drift in the direction of your current position towards the planet. Yes, gravity pull is based on the
position of your ship versus the planet but applied on the drift of your ship. If your ship is on the planet itself you do not adjust for
gravity (what direction would that be?).

That is all folks; if the ship is inside the gravity well but not on the planet you note the direction towards the planet and move your drift in that direction.

Scenario: Fission duel

This is a simple scenario with two equal ships battling it out in orbit above a planet. the ships start in the same orbit on opposite sides of the planet knowing where the opponent is but they cannot track him because the planet blocks LOS. The ships are 1G fission thrusters with 8 turns of thrust endurance and they are armed with a single small missile turret. You must carefully maneuver your ship close enough for your missiles 2G range single turn range. The ship has a crew of two; 1 pilot and 1 gunner/sensor op, there is no repair crew so there can be no repairs. Use the orbit from the image, ship A starts at x=0, y=-1, ship B starts at x=0, y=1 with the drift positions as shown. As I said earlier, this scenario is especially suited for deterministic play.

Gentlemen, start your fission drives, let the duel commence!

Major victory: Your opponent is a mission kill (incapable of firing and incapable of maneuvering) and you manage to land on the planet.

Minor victory: Your opponent is a mission kill and you are not.

Draw: Both ships incapable of maneuvering  and in such orbits that they will never get within 2G of a missile shot.

Make your own TL 8 Fission thruster equipped ships, equal or custom designed by each player. 100 MCr each is my suggestion for price.

This entry was posted on May 13, 2010 at 13:31 and is filed under Boardgames, Design system, Intercept, Other vector movemet systems, Scenarios. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.