In this activity, learners create a "Jam Jar Jet" based on Francois Reynst's discovery of a pulsejet engine, which uses one opening for both air intake and exhaust. Learners will be amazed at the deep blue, noisy flame that grows and shrinks and "breathes" fire in the jar. Learners can add salt or boric acid crystals to change the color of the flames. Use this activity to explore combustion and/or aerospace engineering. This resource includes step by step instructions with helpful photographs, trouble-shooting tips, and resources. This is an advanced project that should only be undertaken with appropriate safety precautions. Follow all directions carefully.