Homeworld Effects Manual: setDeltaLength()
setDeltaLength(float value)
Legal values: all real numbers
Default value: 0
setDeltaLength() has no effect if there is a setScale(1) active at the same time.
setDeltaLength() causes the Length attribute for the current object to change by value each second. A positive value makes the object grow longer, and a negative value has the opposite effect. Unless, of course, Length is negative to begin with, then everything is switched.