Note that this method analyzes single-axis accelerometer data alone to

produce two-dimensional trajectories. It does not use altimeter data to

find the vertical component of velocity.Inertial data can be reconciled

with altimeter data after the fact, however, and facilities (Graphs,

statistics, and optimization) are provided for that purpose.

The program is called OVAA.xls. It is available free of charge in the

PC downloads section of

formatting link

See description below.

-Larry Curcio

OVAA.XLS VERSION 2.0

Copyright 5 August 2006

Larry Curcio

WHAT IT DOES

OVAA stands for Off-Vertical Accelerometer Analysis. It exploits the

observation that accelerometer data are unaffected by gravity. (See

explanation below.) Thus, to a good approximation, accelerometer data

measure the sum of thrust and drag accelerations along the longitudinal

axis of the rocket. Vertical accelerometer analyzers plug these

readings into a 1-dimensional trajectory simulator to produce a

rendering of the trajectory, based on the assumption that the

rocket's ascent is entirely vertical. OVAA plugs the readings into a

two-dimensional trajectory simulator to cover off-vertical flights. For

vertical flights, OVAA is entirely equivalent to a one-dimensional

accelerometer analysis program.

OVAA.xls is a Visual Basic macro application in Microsoft Excel=99. It

takes advantage of the Excel's spreadsheet, graphing, and optimizing

facilities to provide a versatile environment for trajectory analysis.

OVAA.xls is specifically designed for flight computers that take

simultaneous inertial and barometric readings.

OVAA.xls has the following functions:

1) Finds altitude, throw distance, velocity, acceleration at each

point;

2) Temperature-corrects barometric data;

3) Extracts thrust/time tables from inertial data;

4) Extracts drag coefficient/speed tables;

5) Evaluates goodness of fit between inertial and barometric altitudes;

6) Can find the launch angle that yields the best such fit

7) Provides a low-pass filter utility to reduce noise in Cd curves; and

8) Has a scratch area for ad-hoc computations and graphs.

OVAA.xls provides the following graphs:

1) Inertial and Barometric Altitudes v Time during ascent

2) Inertial Altitude v Throw Distance during ascent

3) Velocity v Time during ascent

4) Acceleration v Time during ascent

5) Inertial - Barometric Altitude v Time during ascent

6) Thrust v Time

7) Drag Coefficient v Speed

DISCLAIMER

No warranty of any kind is made for this program or the underlying OVAA

method. Indeed, at this writing, the method is not substantiated by any

formal research. The author takes no responsibility for its use.

Decisions made on the basis of its output are made at the risk or the

user alone. Off-vertical flights are also made at the risk of the user.

This program is intended for post-flight analysis, and not in-flight

control. The underlying method may have control applications, but the

author takes no responsibility for experiments based on such

applications.

This program is not intended for use with rockets that are illegally

constructed, transported, stored, or flown.

The author takes no responsibility for copies of this software that may

be infected with viruses. Again, this program is used at the sole risk

of the user.

CONTACT INFORMATION

At this writing, OVAA analysis is brand new. I have precious little

data to work with, and would appreciate hearing from you and sharing

yours. I can be reached at

snipped-for-privacy@verizon.net

Two-dimensional analysis of single-axis data represents a new

technology that can potentially extend the usefulness of existing

products. Even though better technologies are emerging, the existing

technologies are still substantially less expensive.

The development of such new technology is potentially advantageous to

flight computer manufacturers, but the advantage is contingent upon

established validity, and validity must be founded on data. For this

reason, I am asking manufacturers of flight instrumentation to collect

and share off-vertical data with me and with others.

Thanks and regards,

-Larry Curcio