Title:
Projectile linear theory for aerodynamically asymmetric projectiles
Projectile linear theory for aerodynamically asymmetric projectiles
Author(s)
Dykes, John William
Advisor(s)
Glezer, Ari
Costello, Mark
Costello, Mark
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Abstract
Currently, there are few analytical tools within the ballistics community to aid
in the design and performance evaluation of aerodynamically asymmetric projectiles.
The scope of this thesis is to (1) create analytical tools that are capable of quantifying
aerodynamically asymmetric projectile performance, (2) demonstrate the ability of
these models to accurately account for aerodynamic asymmetries, and (3) gain insight
into the flight mechanics of several aerodynamically asymmetric projectiles. First, a
six-degree-of-freedom (6 DOF) flight dynamic model, which uses a point-force lifting-surface
aerodynamic model, was developed to replicate flight characteristics observed
from measured results of common projectiles. A quasi-linear flight dynamic model
was then created using the machinery of Projectile Linear Theory (PLT). From this,
flight dynamic stability models were developed for linear time-invariant (LTI) and
linear time-periodic (LTP) systems. Dynamic simulation and stability trade studies
were then conducted on asymmetric variants of 4-finned, 3-finned, 2-finned, and hybrid
projectile configurations. First, stability of symmetric projectiles are validated
and show that the classical and extended PLT model yielded identical results. Results show that aerodynamic asymmetries can sometimes cause
instabilities and other times cause significant increase in dynamic mode damping and
increase/decrease in mode frequency. Partially asymmetric (single plane) configurations
were shown to cause epicyclic instabilities as the asymmetries became severe,
while fully asymmetric (two plane) can grow unstable in either the epicyclic modes or
the roll/yaw mode. Another significant result showed that the LTP stability model
is able to capture aerodynamic lifting-surface periodic affects to evaluate dynamic
stability requirements for asymmetric projectiles.
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Date Issued
2011-11-01
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Thesis