Engineering is often a choice between competing good things.

More safety can add mass. More redundancy can add complexity. More capability can increase cost and schedule. Systems trades compare alternatives against the mission objective.

• Which option best serves the mission?
• What does each option cost in mass, time, money or complexity?
• Which risks are reduced or introduced?
• Which choice remains robust when assumptions change?

A good trade is not the option with the most features. It is the option whose compromises best fit the mission.