[geocentrism] Re: acceleration calcs

Allen D
I don't wish to delay nor to complicate your departure but perhaps you would 
take this query with you and respond at your convenience.
An accelerometer is in essence a mass suspended between two springs and 
constrained to move only along the axis of its construction. Yes I'm aware that 
a practical device involves a great deal more than that -- amplifiers, feedback 
loops, damping networks, sensors, electromagnetic compensators, computer 
processing and probably more but that is irrelevant to the basic concept. An 
inertial guidance system as I understand it consists, in part, of three 
accelerometers -- one in each axis. That they function well is attested to by 
the fact that airliners once relied upon them for successful navigation as did 
nuclear submarines and the Apollo space vehicles including the Luna missions. 
In the latter service, they were touted as being sufficiently accurate as to 
permit unassisted return to Earth from any point in the mission should ground 
updates for any reason cease.
However, I do not believe that the accelerometers provide any input to the 
navigation system if a SEPARATE and EXTERNAL force is NOT acting on the vehicle 
to which they are rigidly mounted ALONE. I specifically do not believe that the 
mass in an accelerometer will move relative to the vehicle to which it is 
rigidly connected if both it -- the mass -- and the vehicle are uniformly 
accelerated. This latter condition is satisfied when both (could hardly be 
otherwise!) are in free fall such as in orbit eg the Earth orbiting the Sun or 
in a body outside Earth's atmosphere falling toward Earth.
Paul D


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