Chapter 7 - Functions and Graphs - 7.2 Domain and Range - 7.2 Exercise Set - Page 459: 54

$$ \text{All numbers that are greater than or equal to zero.}$$

We know that the domain is all possible inputs into the function. Since it would not make sense to measure the height of the safety flare at negative times (before it is launched), the domain is: $$ \text{All numbers that are greater than or equal to zero.}$$