So it occurs to me that the readings of a single-axis accelerometer represent the sum of thrust acceleration and drag acceleration, regardless of the rocket's orientation in the sky. The accelerometer is, in a perverse perspective, unaffected by gravity.
When the rocket is on a horizontal table, the instrument registers 0. When it is vertical on a table, the instrument registers 1 g. The g that it registers is the result of the force from the table, which equals its earthly weight. If this were imposed on the rocket in outer space, then the rocket would indeed accelerate at the rate of
1 g, which is what the instrument registers.In free fall, the instrument registers 0 g (in zero drag).The problem with accelerometer data is not that they are affected by gravity, but that they are not affected by gravity, and the rocket is. Thus, orientation data are required to derive the rocket's motion.
If that is all given, then it is possible to *infer* angular data from semi-empirical analysis. That is, 2-Dimensional simulation formulas can be written in such a way that only the reading and the acceleration of gravity are needed at each interval. One infers the effect of gravity on the rocket's trajectory without measurement. That part is filled in theoretically. The other acceleration data re filled in from readings - empirically.
One must know the length of the launch rod, because the trajectory formulas are different there. If you assume a different launch rod and launch angle, you get a different trajectory.
Reasonably calm days are required.
What Think?
-Larry (Calm days at high altitudes? It don' work in the stratosphere!) C.