Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!tut.cis.ohio-state.edu!sppy00!cjs From: cjs@sppy00.UUCP (SCHALLER CHRIS) Newsgroups: sci.space.shuttle Subject: Re: Shuttle Status for 04/22/91 (Forwarded) Message-ID: <1207@sppy00.UUCP> Date: 26 Apr 91 16:24:20 GMT References: <1991Apr22.234907.29805@news.arc.nasa.gov> Organization: Online Computer Library Center, Dublin, Ohio. Lines: 27 In article , rose@beowulf.ucsd.edu (Dan Rose) writes: > yee@trident.arc.nasa.gov (Peter E. Yee) writes: > > > The countdown clock entered the T-11 hour planned built-in > > hold this morning at 4:45. The clock will continue to hold until > > resuming the count at 4:45 p.m. today. > > This may be a naive question, but . . . Why do they have these planned > countdown holds? Maybe "countdown" has a more specific meaning to > NASA than it does to me, but it seems like there's no sense in starting > a countdown until it's, well, time to count down. > -- The purpose of the built in countdown holds are to give the various launch teams, time to catch up, coordinate, and syncronize. At any time during a launch countdown, there seems to be a million things going on at once. If youve ever watched a launch on Nasa select TV, you can listen to the conversations between the people in the lauch control room talking to the astronauts on the shuttle, the payload people, the weather people, the people at mission control, the people feuling the ET etc, ect. You get the idea that theres a hell of alot going on. At some point there might be a function that is taking a little more time than usual, if you are on a strait countdown, you couldnt allow for that extra needed time. The built in hold gives everyone time to complete operations to a point where the groups (teams) can be polled one by one to verify their readyness to proceed with the count.