AI War:Engines and Speed (including Tractor Beams and Gravity Effects)

This page is up to date for game version 5.033 and should still be correct.

Speed

A ships base speed is found in white text on the third line of the text description box as "Speed: 48" in white text.
While ships do not instantaneously accelerate and decelerate, the rates of acceleration and deceleration are so fast that most ships effectively move at either their current top speed or are stopped. In practice one notices this acceleration only for very fast ships like scouts.
If a ships current effective top speed is different then its base speed then the ships current speed will be displayed in yellow text in the first line of a ships description box next to the ships name.

Speed Boosts

There is a universal doubling of speed in friendly territory as all Human Command Stations double the speed of all human ships. The Logistics Command Station offers a substantial speed increased above and beyond the speed doubling all Command Stations offer.

Speed boosts in unfriendly territory are much rarer and require something like the Speed Booster to accompany your fleet.

Speed Reduction

A ships speed can be reduced in three different ways.

Engine Damage

Ships with the Ability: Engine Damage damage a targets engines with each shot.
The amount of engine damage done is a flat number that is subtracted from the target ships Engine Health, which is also a flat number.
When a ship takes engine damage, its speed is modified in a linear progression.
So if a ship takes 25% engine damage, its base speed is now 75% of what it was.
At 50% engine damage, its base speed is now cut in half.
Note that a mobile ship always has a base speed of at least 1, even if its engine health is reduced to 0.

Ships with 'Engine Health: Inf' can not take engine damage and just ignore the engine damage. Other effects of the shot, such as health damage, are not ignored.
Stationary structures are given 'Engine Health: Inf' even though they are stationary so the game is not wasting processing power trying to compute engine damage for a structure that can not move.

Tractor Beams

Tractor beams, such as those emitted by the Tractor Beam Turret, grab a ship and hold it in place until the tractor beam emitter is destroyed.
While this is technically a speed stop and not a speed reduction, a ships speed is effectively 0 for as long as the tractor beam lasts.
Mobile tractor beam emitters, such at the Etherjet, hold ships grabbed in their tractors relative to them as they move.
Ships stuck in a tractor beam always in range of the the emitter that is holding them even if the emitter would normally be out of range.
If the tractor beam emitter is in some other way untargetable, such as being cloaked, the ship stuck in the tractor beam can not attack the ship holding them.
Unlike attacks, tractor beam emitters do not suffer any penalties for being protected by a force field, in fact it is recommended that you place a forcefield over your tractor beam emitters so they stay alive longer.

Gravity Effects

Ships caught in a gravitational field, such as the one emitted by a Gravitational Turret have their maximum speed reduced to what the gravitational field limits them to.
Gravitational effects are applied after speed boosts so even a ship with so many speed boosts it should be traveling at a speed of 500 will have its speed reduced to 8 when caught in the gravitational field of a Gravitational Turret Mk I.<br/

Gravity Drills are a special planet-wide equivalent, although they affect all ships. The Grav Driller AI will use these to reduce all ship-speeds to 8 on affected systems, which can result in extremely slow gameplay, including exo-waves.

Ships not being slowed

The Immunity: Speed Boosts, Tractor Beams, and Gravity Effects all do exactly what they say and render a ship immune to those effects.
A ship with 'Engine Health: Inf' is effectively immune to engine damage.

One surprise that can allow multiple ships to bypass your tractor beams or gravity effects is the Fleet Mechanic.
The Fleet Mechanic is most commonly found on Hybrids or Exo-waves and can be recognized when a major ship is escorted by a small fleet.
Because these fleets often warp in several systems away from the human territory, the escorting fleet does not move as normal, rather they hold position on the major ship leading their fleet.
When an escort ship is holding position on their fleet leader, its speed is boosted or reduced as necessary to stay next to its fleet leader and the fleet leader shares its immunities with its escort fleet.
So a Missile Frigate that normally has a speed of 44 when part of an escort fleet for a Hybrid Hive would have its speed boosted to 100 to match the Hybrid Hive and would gain the Immunity: Tractor Beam that the Hybrid Hive has.
Once the Hybrid Hive is destroyed, the Missile Frigate will go back to being a normal ship and lose both the speed boost and the extra immunities.

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