What is the main purpose of the motor liner and O-ring seals in a solid rocket motor?

The main purpose of the motor liner and O-ring seals in a solid rocket motor is to keep hot gases from damaging the motor case. The motor liner is typically made of materials that can withstand high temperatures and pressures generated during combustion. It acts as a barrier between the burning propellant and the structural integrity of the motor casing. This is crucial because if hot gases escape through the motor casing, it could lead to structural failure or catastrophic failure of the rocket.

O-ring seals play a vital role in providing a tight seal at critical junctions, ensuring that the high-pressure gases produced during combustion do not escape into areas where they could compromise the motor's integrity. This sealing prevents hot gas leakage, which could damage the rocket motor and potentially lead to unsafe conditions.

The other options focus on aspects not directly tied to the primary function of the motor liner and O-rings. While enhancing thrust and ensuring a steady burn of propellant are important features of rocket performance, they are not the primary functions of these specific components. Similarly, preventing overheating is a broader concern that involves various design elements beyond just the motor liner and O-rings.