Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!titan!phil From: phil@titan.rice.edu (William LeFebvre) Newsgroups: sci.space.shuttle Subject: Re: Atlantis misses by a hair Message-ID: <3210@kalliope.rice.edu> Date: 2 May 89 18:36:20 GMT References: <4361@omepd.UUCP> Sender: usenet@rice.edu Reply-To: phil@Rice.edu (William LeFebvre) Organization: Rice University, Houston Lines: 79 This is all from memory, so forgive me if there are a few minor errors. In article <4361@omepd.UUCP> snidely@inteloa.UUCP (David P. Schneider) writes: >Atlantis and Magellan missed their first launch attempt by 31 >seconds... This is something that needs to be cleared up. This "only 31 seconds" jazz is getting to me.... I'm not flaming Mr. Schneider, but I've heard the news people say "with JUST 31 seconds....." as if to say "they came SOOOO close...." So I'll take this opportunity to speak my mind. The problem was actually noticed at about T-1:15, but the hold didn't take place until T-31secs. They have planned times for holds: T-20min, T-9min, T-5min, and T-31sec as well as others. They only go into a hold at those times (although I suppose something real serious would make them stop the clock). If anything happens between T-5min and T-31sec that violates launch criteria, they will continue the count anyway until the T-31sec hold. Then they go into a hold. Why T-31 seconds? Because it is at that point that the automatic launch sequencer takes over and then everything is handled directly by computer, effectively controlled by the on-board computers (GPCs). >Some questions about this: is this one of the pumps that was installed >after Atlantis was on the pad, how was the anomaly noticed, which >desk/function/station announced the hold (it sounded like a woman's voice, >such as had been calling off some checklist items a little before, if that >helps with the identification) Booster would have been the first to notice it, but the woman you heard was probably some sort of overseer or coordinator. That is, she was probably not the person that first noticed the problem---she was probably just relaying the call. (I know a whole lot more about how mission control/JSC works that I do launch control/KSC). >and how big a hold can be dealt with at T - 31 seconds with little >or no rollback of the count? They cannot hold at T-31sec for more than a few minutes, because the Auxiliary Power Units (APUs) are running. Once they are started, launch must happen within something like 15 minutes or they have to roll back the count and recharge the APUs (I believe that takes hours, so it would force them to scrub for the day). >From the sound of things, once the hold was announced, having to scrub was >pretty much automatic because the sequence could not be recovered within >the launch window. And because of the nature of the failure, even if they had tried again, they would have failed. Of course, they didn't know that at the time.... >At least one account I heard was that this was a very smooth countdown up >until T - 31 seconds, best since return-to-flight. I had heard that it was the smoothest countdown in the history of the shuttle program, up until they held for the RSO's computer. >NASA select, though, >had extra polling going on regarding a range safety computer that needed to >brought back on line. The range safety officer (RSO) had to reboot his computer at some point during the morning. That was why the launch was delayed about 5 minutes. Since I didn't tune in until after T-9 minutes, I don't know at what point in the countdown they held for that. I didn't actually hear this happening---I heard about it later. >The boot sequence must not have been as rough as >some other issues, though, enven though it had the potential to scrub the >launch. They will not launch if the RSO doesn't have his computer. Even though the computer is on the ground. William LeFebvre Department of Computer Science Rice University