ahs@burl.UUCP (Spinks Albert H. ) (02/04/86)
Can anyone explain why during assent the orbiter flies upside-down? I remember reading somewhere that it was necessary for the crew to see the earth's horizon during assent and that it is difficult to do that with a normal attitude because the tank and boosters would be in the way. With todays guidance control systems, it has been hard for me to buy that argument completely. Does anyone know the true poop on this subject? -- Albert H. Spinks
bl@hplabsb.UUCP (Bruce T. Lowerre) (02/07/86)
> Can anyone explain why during assent the orbiter flies upside-down? > I remember reading somewhere that it was necessary for the crew to > see the earth's horizon during assent and that it is difficult to do > that with a normal attitude because the tank and boosters would be > in the way. With todays guidance control systems, it has been hard > for me to buy that argument completely. Does anyone know the true > poop on this subject? A rocket's thrust line must go through its center of mass, otherwise it will tumble. The center of mass for the shuttle structure at launch is located within the ET. The three main engines on the shuttle are offset and are pointing upwards toward the rear when viewed setting on its wheels. Thus, during ascent, the shuttle must be on its back so as to allow the engines to lift the center of mass of the entire launch vehicle.
greg@nmtvax.UUCP (Greg Titus) (02/07/86)
> Can anyone explain why during assent the orbiter flies upside-down? > ... > > Albert H. Spinks I believe I recall something about the antennas on top of the shuttle needing to be able to "see" the ground, without the shuttle body and ET in the way. This is not for sure, though. greg -- Greg Titus ..!ucbvax!unmvax!nmtvax!greg (uucp) NM Tech Computer Center ..!cmcl2!lanl!nmtvax!greg (uucp) Box W209 C/S greg@nmt (CSnet) Socorro, NM 87801 greg.nmt@csnet-relay (arpa) (505) 835-5735 ======================================================================
dave@quest.UUCP (David Messer) (02/09/86)
> Can anyone explain why during assent the orbiter flies upside-down? > I remember reading somewhere that it was necessary for the crew to > see the earth's horizon during assent and that it is difficult to do > that with a normal attitude because the tank and boosters would be > in the way. With todays guidance control systems, it has been hard > for me to buy that argument completely. Does anyone know the true > poop on this subject? The shuttle does indeed fly upside down so the pilot can see the horizon. I think you are probably right about todays guidance systems (if a system failure was so complete as to create a need to 'eyeball it', I don't think it would matter), but American manned spacecraft have always flown upside down for that reason. I think the bottom line is that there is now reason to pick any other attitude, so they might as well choose one that provides some marginal safety advantage. -- David Messer UUCP: ...ihnp4!quest!dave ...ihnp4!encore!vaxine!spark!14!415!sysop FIDO: 14/415 (SYSOP)