Impulse command

The IMPULSE command sets a ship's requested sublight speed and may also set a new course. The ship accelerates and turns over subsequent movement updates; the command does not move it instantly.

Syntax

Classic Galactic Empire and ge-next both accept a relative turn:

IMPULSE speed [relative-turn]

Impulse speed ranges from 0 through 99. It is displayed as a fraction of warp speed: impulse 5 is warp 0.05, impulse 50 is warp 0.50, and impulse 99 is warp 0.99.

The relative turn must be from -180 through 180 degrees. Positive values turn to starboard (right), while negative values turn to port (left).

ge-next additionally accepts an absolute galactic heading:

IMPULSE speed @heading

The @heading form is only available in ge-next. Classic Galactic Empire does not recognize @ with the IMPULSE or WARP commands. In classic, use ROTATE @heading, allow the ship to finish turning, and then issue IMPULSE without a heading.

Examples:

IMPULSE 5
IMPULSE 10 5
IMPULSE 20 -25
IMPULSE 50 @140
IMPULSE 0

These request impulse 0.05 without a new turn, impulse 0.10 with a five-degree starboard turn, impulse 0.20 with a 25-degree port turn, impulse 0.50 on absolute heading 140 in ge-next, and a complete stop.

The classic help file gives 355 as an example of a five-degree port turn. The actual classic validation accepts only -180 through 180, so the working form is -5.

Requested speed and heading

The command stores a target speed and target heading. Acceleration and rotation then proceed independently toward those targets. A ship may therefore be turning while it accelerates, and its path curves until the requested heading is reached.

Acceleration is determined primarily by ship class. Deceleration occurs at twice the normal acceleration rate. ge-next may further modify acceleration through system damage and the acceleration-booster upgrade.

Omitting the heading behaves differently between versions:

In classic, IMPULSE speed acts as a relative turn of zero from the ship's current heading. This replaces the pending target heading and cancels a turn already in progress.
In ge-next, omitting the heading preserves the existing target heading. A turn already in progress continues while the ship changes speed.

A damaged helm refuses the command because it cannot accept either the speed or heading order. ge-next's STOP command can still initiate an emergency stop when the helm is damaged.

Issuing a valid IMPULSE command while orbiting a planet breaks orbit and cancels any planetary maintenance in progress.

Normal space only

Impulse engines cannot be commanded while the ship is in hyperspace. Use WARP 0 and wait for the ship to return to normal space before issuing an impulse order. See Impulse travel#Systems available at impulse for ship systems available at impulse and Orbit for the separate speed requirements of planetary operations.

Movement and energy

An impulse order sets the target speed; the ship's actual speed changes over subsequent movement updates. For distance-per-update formulas and examples, see Impulse travel#Distance per movement update. Impulse propulsion consumes no flux in classic GE. ge-next charges one unit per movement update while the ship is holding speed or accelerating toward its target, with automatic pod loading when needed. See Impulse travel#Flux for the full energy model and what happens when the ship runs out.

Differences from WARP

Impulse has no class-specific maximum below 99 and does not cause overspeed damage. It does not enter hyperspace, switch phasers to hyper-phaser behavior, or impose the combat-system restrictions associated with warp travel.

IMPULSE 0 and WARP 0 both request a normal stop when the helm works and the ship is already in normal space. ge-next's STOP command is the alternative when helm damage prevents either navigation command from being accepted.

Comparison

Behavior	Classic Galactic Empire	ge-next
Relative turn with `IMPULSE`	Yes	Yes
Absolute `@heading` with `IMPULSE`	No	Yes
No heading supplied during an existing turn	Cancels the pending turn	Preserves the pending turn