Final answer:
The most common thrust reverser on turbojet engines is the clamshell thrust reverser, with cascade type being another considerable option, depending on engine design and aircraft requirements.
Step-by-step explanation:
In the field of aviation and aircraft design, the most common type of thrust reverser used on turbojet engines is the clamshell (or bucket-type) thrust reverser. This mechanism functions by deploying two bucket-like doors which redirect the exhaust flow of the engine forward. When activated, these doors swing into the exhaust stream, effectively reversing the thrust and aiding in the deceleration of the aircraft upon landing.
Another prevalent type, though slightly less common, is the cascade type thrust reverser. This design uses a series of blocker doors that redirect the exhaust flow through cascading vanes, which then direct the thrust forward. It is often used on high-bypass engines like those on many modern commercial airliners.
The choice of thrust reverser type depends on the engine design and the specific performance requirements of the aircraft. While both are widely used, the simplicity and effectiveness of the clamshell design for certain aircraft models make it a favored option.