Time is the time passed since launch. In the simple case of a spacecraft in vaccum, the duration of the thrust is arbitrarily set at one hundred seconds. A rocket going to low earth orbit will usually burn for about two hundred and thirty seconds. In the trajectory table, ten equally spaced time intervals are displayed, ranging from zero to the last time inclusively, for a total of eleven rows.

In more detailed analysis, the duration is calculated from the empty mass ratio, exhaust velocity, liftoff acceleration and payload ratio.

duration = exhaust velocity / liftoff acceleration * ( 1.0 - ( 1.0 + payload ratio ) / empty mass ratio )
 

This is used in astropolis, spacecraft in vacuum, atmospheric spacecraft, multi stage spacecraft, and spacecraft cost.
 
 

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