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.
For other uses, see Atrium. The atrium (plural: atria) is one of the two blood collection chambers of the heart. It was previously called the auricle, but that name is now used for an appendage of the atrium. The atrium is a chamber in which blood enters the heart, as opposed to the ventricle, where it is pushed out of the organ. It has a thin-walled structure that allows blood to return to the heart. There is at least one atrium in animals with a closed circulatory system.