B4-2 EnginesThe Estes B4 2 engine is a strong choice for your classroom, camp, or youth program when you want safe, repeatable flights that help students understand the fundamentals of model rocketry. With a total impulse of 5. 00 N sec and a 2 second delay, the B4 2 delivers clear, easy to observe flight behavior that supports hands on learning. Because the B4 2 provides consistent thrust and dependable ignition, you can run group launches with confidence. This