Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!spool.mu.edu!uunet!stanford.edu!eos!aio!vf.jsc.nasa.gov!kent From: kent@vf.jsc.nasa.gov Newsgroups: sci.space.shuttle Subject: Re: Shuttle computers break down during glide tests Message-ID: <1991Apr26.111139.1@vf.jsc.nasa.gov> Date: 26 Apr 91 17:11:39 GMT References: <1593@philtis.cft.philips.nl> Sender: news@aio.jsc.nasa.gov (USENET News System) Distribution: sci.space.sghhuttle Organization: NASA Johnson Space Flight Center Lines: 35 In article <1593@philtis.cft.philips.nl>, munk@cft.philips.nl (Harm Munk) writes: > My question: what happened with the computers during that first (?) > glide test. I will give this one a shot, One General Purpose Computer (GPC) failed and the others quit listening to its inputs ( as they are programed to do). Three GPC's all run the same software and compare results to assure one is not sick. > Along the same tracks: during the landing of one of the later tests, the > shuttle made a rather bumpy landing. The commentator remarked that this > was caused by the inexperience of the pilot, but I recall reading > somewhere that is was caused by the computers being to busy with other > things that they could not constantly attend to the bussiness of landing > the ship, thereby inducing quite some roll. Is this true, or was the > commentator right ? It was not caused by the computer being too busy. It was most likely a pilot induced ocsolation. The computers sample the input from the pilot X times a second. The computer then chews on the input and sends commands to the control surfaces. There is a delay built into the command/action. If the pilot is not aware of the delay it can cause an oscolation. He commands down and does not see the resoponse so he commands down even more..... The computer, issues the down commands and the issues the larger command as well. the pilot see there is too much command down and commands up even more..... the cycles get larger and larger....... I believe some changes were made to the shuttle software to minmize the effect. Also the Pilots are trained extensively to be aware of the effect. -- Mike Kent - Lockheed Engineering and Sciences Company at NASA JSC 2400 NASA Rd One, Houston, TX 77058 (713) 483-3791 KENT@vf.jsc.nasa.gov