Thrusters are the item that can be installed in a diamond-shaped1 slots in ships. They determine how fast a ship moves in combat.

Thrusters have "TYPE thruster", fit only in special thruster slots, and just do the one thing; but in most other ways they are very similar to systems.

Ships can only have one thruster installed at a time. Thrusters don't need the "nomulti" FLAG, but automatically behave as if they had it.

Codes and Commands

The code structure of the .ini files of a thruster include the following elements, in this order:

Nested / second-level entries on that list are flags or values that follow the first-level code before them. For example, you must have a line that reads "TYPE thruster", but you wouldn't have a line that just says "TYPE" or just says "thruster".

Things in bold are ones all main-game items have in common. It's highly likely you'll need them in your items' .ini file in order for it to function properly.

PAR0 and thruster Speed

Thrusters have exactly one stat that determines how well they perform. That stat is "PAR0". PAR0 is a numerical value that controls thruster speed4. It seems to work roughly like a percentage, which is applied to the MOVE stat of the hulls of ships. So, a ship with a Reactionless Thruster (PAR0 210) moves about double the speed of an identical ship with a Fusion Tube Thruster (PAR0 100).

Correlation between PAR0 and COST

This chart sums up the entries for that stat in the main game, along with a side-by-side comparison of the costs/values of the thrusters.

Thruster PAR0 COST
Pulse Detonation Thruster 66 67
Fusion Tube Thruster 100 126
Ion Impulsor Thruster 145 361
Reactionless Thruster 210 1000

As you can see, a relatively short range of variance in PAR0 results in a wide range of variance in cost or value.
Also of note is that the Reactionless Thruster is tied for the highest value of any treasure in the game. So, if you want to make a thruster that exceeds a rating of 210 in PAR0, you'll probably need to downgrade the value of the Reactionless Thruster.5

Experiments with High Values of PAR0

Starting with the 2.0 version of my Drives'R'Us Mod, I began playing with thruster values above 210. What I found was that much higher speed values start to mess with the AI programmed into the game. Ships are programmed to dodge at a certain distance, and to move toward the enemy if any of their weapons aren't in range. Anecdotal evidence suggests these behaviors are programmed to kick in for a certain amount of time. Putting a really fast thruster on a ship messes with those calculations. If PAR0 gets too high, ships will dodge when there's no chance of an enemy hitting them, and travel right out of weapon range when they do dodge. It can get pretty weird.

Thruster Slots in Hulls

Where the thrusters reside on a ship is defined by the THRU entry in the (hull).ini files. As mentioned above, ships can only have one thruster installed at a time. Even a ship with 3 or four THRU lines only takes one thruster at a time, and that one thruster will fill all the slots at once.

Casual experimenting suggests that the location of the thruster on the hull sprite doesn't really matter. I've created ships with thrusters way over on one side of the hull, and if it results in them handling differently at all, it's too subtle for me to notice.

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