What are two methods for attaching rotor blades to the rotor disks in a turbine engine?

The correct answer reflects common methods used in turbine engines for securing rotor blades to the rotor disks. The "lock and key" method, often referred to in the context of mechanisms that ensure the blades are securely fitted and can transfer loads effectively, utilizes a specific shape or design to ensure a good fit and retention during operation. The "fir tree-type" attachment is another widely used mechanism; it is designed to accommodate the high stresses that rotor blades experience, especially during high-speed operation. This attachment method provides a significant surface area for load distribution, which is vital for performance and safety in a turbine environment.

The other methods mentioned, such as welded and riveted or tapered and bolted attachments, are less commonly associated with rotor blade attachment in turbine engines. These alternatives might be more relevant in different contexts or components but do not provide the same reliability or efficiency required for rotor assembly under the high-stress conditions encountered in turbine operations. Dovetail and bulb methods, while used in various mechanical applications, do not match the specific needs for rotor blade attachment in turbine engines, making them less suitable in this context.