  In order to address the need for an affordable reduced gravity test platform,
this work focuses on the analysis and implementation of atmospheric
acceleration tracking with an autonomous aerial vehicle. As proof of concept,
the vehicle is designed with the objective of flying accurate reduced-gravity
parabolas. Suggestions from both academia and industry were taken into account,
as well as requirements imposed by a regulatory agency. The novelty of this
work is the Proportional Integral Ramp Quadratic PIRQ controller, which is
employed to counteract the aerodynamic forces impeding the vehicles constant
acceleration during the maneuver. The stability of the free-fall maneuver under
this controller is studied in detail via the formation of the transverse
dynamics and the application of the circle criterion. The implementation of
such a controller is then outlined, and the PIRQ controller is validated
through a flight test, where the vehicle successfully tracks Martian gravity
0.378 G's with a standard deviation of 0.0426.
