🔍 Key Concepts
• Relationship between prime mover (diesel, steam turbine, gas turbine, electric motor) and the propeller
• How quickly shaft speed and direction can be changed with each system
• Which systems allow frequent, rapid reversals without stressing the main engine
💭 Think About
• For each drive type, ask: can the main engine itself safely and quickly change RPM and reverse direction often, or is that slow and limiting?
• Which system allows the propeller to reverse thrust very rapidly while the main power source keeps running in a favorable, steady direction?
• Think about which arrangement is commonly used on ships needing very fine speed control (e.g., tugs, dynamic positioning, frequent docking).
✅ Before You Answer
• Identify which option uses electric motors on the propeller shaft, independent of the prime mover speed/direction
• Consider which drives (diesel/geared, steam turbine, gas turbine) normally run in one direction at nearly constant RPM
• Verify which drive system is known for excellent low‑speed control and rapid thrust reversal.