For operations limited by the casting speed, or for steel grades more sensitive to centcrline rather than surface defects, the control of metallurgical length is very important. Operations designed to reduce ccntcrlinc defects, such as soft reduction, are affected greatly by transient changes in the metallurgical length. This work explores the potential of using open-loop spray- cooling control methods to minimize deviations in the metallurgical length from its desired location, during casting speed changcs under temperature setpoint constraints. This objective essentially reduces to motion planning, i.e. apriori generation of spray flow rate commands that when applied to the process make the latter exccutc the motion that carries out the above task in the shortest time possible. The results show that there is only a small potential to maintain metallurgical length during speed changes in a 221mm thick slab caster. By changing spray water flow rates between their greatest and smallest conditions, it is possible to accommodate casting speed variations from 1.7 to 1.5 m/min, while maintaining a constant metallurgical length of 22.29 m during steady casting. For a sudden speed drop, however, a dip in metallurgical length is unavoidable. Bang-bang control was the best method investigated to manage water sprays during the transition. This control method can lessen the dip JFEin metallurgical length from over 2m (with no control), to less than lm.