This working Heron steam engine is propelled by the same pneumatic principles that powered Heron of Alexandria's original steam turbine in the first century AD. A precursor to the jet engine, Heron's steam turbine was the first of its kind to extract thermal energy from pressurized steam and convert it into rotary motion. The desktop steam turbine is powered by an alcohol burner that heats a sphere boiler holding 2/3 oz. of water, evoking the metal cauldron that heated Heron's original aeolipile. When steam is generated, it is expelled through two nozzles on the sphere pointing in opposite directions, generating thrust that rotates the sphere on its axis up to 2,500 rpm. The steam turbine is made from solid brass and black anodized aluminum, two extremely durable and scratch-resistant metals that withstand the high temperatures and torque created by the engine. The boiler is easily refilled through a top-mounted valve using the included plastic syringe. 5 3/4" L x 4 1/2" W x 4 1/2" H. (9 3/4 oz.)