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.
A mouth ulcer (also termed an oral ulcer, or a mucosal ulcer) is an ulcer that occurs on the mucous membrane of the oral cavity. Mouth ulcers are very common, occurring in association with many diseases and by many different mechanisms, but usually there is no serious underlying cause. mucosal ulcer is an ulcer which specifically occurs on a mucous membrane. An ulcer is a tissue defect which has penetrated the epithelial-connective tissue border, with its base at a deep level in the submucosa, or even within muscle or periosteum.