When an engine is ignited, it produces thrust and boosts the rocket into the sky. After the propellant is used up, delay is activated, producing tracking smoke and allowing the rocket a brief coast.
infirmary (plural infirmaries) 1  A place where sick or injured people are cared for, especially a small hospital; sickhouse. 2  A clinic or dispensary within another institution.
Polio, or poliomyelitis, is an infectious disease that can elicit no symptoms, or can lead to paralysis and even death. The word âpolioâ derives from the Greek, and means âgreyâ in reference to the spinal cord. â-Itisâ refers to inflammation. History.