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Unread 30-11-2013, 15:29
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Re: SpaceX launch live coverage

Quote:
Originally Posted by wireties View Post
FYI - the countdown is not supposed to be a linear temporal scale. It is more of a reverse progress indicator (lower number = more progress towards lift-off) . Certain activities occur at each point in the countdown and there is little correlation to clock time. At least that is how NASA did things.
You are thinking of the "T-" clock vs the "L-" clock. NASA, ULA, etc use both clocks and use T- is the context you describe with built-in holds. However the L- clock represents time from planned engine ignition.
SpaceX did away with the T- clock and uses only the L- (and calls it T-). Although events are sequenced based on clock times, there's no scheduled clock holds and the clock really should be treated like time left until nominal ignition.
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