Move rotating service structure to "park" position.This built-in hold varies between 13 to 14 hours. Close out the tail service masts on the mobile launcher platform.Resume orbiter and ground support equipment close-outs.Fill launch pad sound suppression system water tank. Begin final preparations of the orbiter's three main engines for main propellant tanking and flight.Demate the orbiter's midbody umbilical unit.This built-in hold typically lasts four hours, but may be extended if PRSD offload is required. Begin operations to load cryogenic reactants into the orbiter's fuel cell storage tanks.Image above: After rollback of the rotating service structure on Launch Pad 39A, space shuttle Endeavour waits for launch on the STS-127 mission. Begin loading cryogenic propellants into orbiter's power reactant storage and distribution (PRSD) system.Clear launch pad of all non-essential personnel.This is the first built-in hold and typically lasts four hours. Complete flight deck preliminary inspections.Complete preparation to load power reactant storage and distribution system.Remove middeck and flight deck platforms.Load backup flight system software into the orbiter's general purpose computers.Review flight software stored in mass memory units and display systems.Begin final vehicle and facility close-outs for launch.The Shuttle Test Director performs the traditional call to stations and the countdown clock is activated. Note: Event times and lengths are approximate and subject to change. Here are some of the key events that take place at each milestone after the countdown begins. For the space shuttle countdown, built-in holds vary in length and always occur at the following times: T-27 hours, T-19 hours, T-11 hours, T-6 hours, T-3 hours, T-20 minutes, and T-9 minutes. Pauses in the countdown, or "holds," are built into the countdown to allow the launch team to target a precise launch window, and to provide a cushion of time for certain tasks and procedures without impacting the overall schedule. On this page, you'll learn how the countdown operates, and what milestones to watch for during our live launch coverage. The countdown clock is one of the most-watched timepieces in the world. Image above: Spectators gather on the grounds in front of the countdown clock during a space shuttle launch.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |