A built-in hold is a period in a launch countdown where the countdown clock is stopped. The hold serves as a milestone in the countdown and may be of a fixed or variable duration. Criteria for exiting that hold and restarting the countdown may be based on a fixed time, the completion of a checklist of work items, or a go/no-go decision from mission management. [1]
For example, space shuttle launch countdowns included seven holds at T-27 hours, T-19 hours, T-11 hours, T-6 hours, T-3 hours, T-20 minutes, and T-9 minutes. [2]
References
- ^ Evans, Ben (2009). Escaping the bonds of Earth : the fifties and the sixties (Online-Ausg. ed.). Berlin: Springer. ISBN 978-0-387-79093-0.
- ^ "NASA - Countdown 101". Archived from the original on 2020-01-26. Retrieved 2011-06-29.
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