One of the most important tasks of any project manager is to manage change requests. If your team is constantly shooting at a moving target, it’s unlikely the goals of the project will be “hit.” Change control is the way you prevent the moving-target syndrome.
When the folks at NASA and the Jet Propulsion Laboratory were preparing the Mars mission, they had a hard deadline because there were only certain times the rocket could be launched when the planets were properly aligned for the mission. During the course of the project, the team creating the landing system discovered they’d underestimated the actual weight of the Mars vehicle (designed by a different team) and had to go back to the drawing board to redesign a landing system that could accommodate the weight of the vehicles.
They didn’t have a choice about making this change nor did they have a choice about the schedule. In their case, the schedule was the least flexible item, and quality was a close second because it wouldn’t do to meet the deadline and have the Mars vehicle crash and burn as it landed on the surface of Mars. Their team raced against the clock to get the project completed.
Another team responsible for the software systems had the launch and landing software tested and ready to go, but were unable to complete the surface navigation software in time. However, they knew that they had a small window