Momentum - March 2021 - 5

Student Generation

To design COLUMBUZZ, the scoring function
was visualized in MATLAB and indicated that
three CDAs combined with an appropriate ratio
of water bottle and habitat payloads maximizes
score. The 750-Watt power limit on the
mothership constrained takeoff weight, and the
rules limited CDA weight to 9 oz. On both the
mothership and CDA, our objective for 2020 was
reducing drag and weight, devoting savings to
increased payload. Experience from 2019
informed initial sizing and we set a goal to
double payload.
Configuration selection centered on supply
accommodation. Individual payload center of
gravity is limited by the rules to be within 10
inches of the aircraft center of gravity. Chordwise
payload accommodation would require a thick
fuselage, increasing drag and decreasing
propulsion performance. Therefore, a blendedwing body was selected for spanwise payload
distribution. The payload bays accommodated a
modular configuration to optimize the supply
ratio. Oversized control surfaces granted
maneuverability on approach to the drop zone. A
high wing provided for underwing CDA
mounting, and a single boom tail minimized
weight and drag. With the configuration selected,
performance innovation over our 2019 aircraft
began.
Aerodynamic performance improvements
increase the fraction of energy available to carry
payload. Mothership optimizations included
creating custom airfoils in XFOIL and refining
planform in Athena Vortex Lattice, AVL. A custom
central airfoil was generated to accommodate

MOMENTUM

Viktor Hromyk

The Athena Vortex Lattice (AVL) analysis of the COLUMBUZZ aircraft provides a lift distribution to aid in aerodynamic structural design.

Georgia Tech's Advanced and Micro Class teams pose after both placed first at SAE Aero
Design East 2020.
the geometric constraints of the supply payloads. To accomplish this, a
Python script added smooth piecewise-polynomial functions to the upper
and lower surfaces of a starting airfoil to satisfy the payload geometry. XFOIL
analysis showed the modified airfoil performance, and the shape
modification functions were adjusted until the drag polar satisfied the
desired parameters. Mothership analysis in AVL examined the lift distribution
and stability derivatives. CDA aerodynamics were analyzed in CFD to
examine the flow over our " cranked delta " configuration. Through this
method, the glide ratio was doubled from 2019.
Payload fraction improvements were achieved by replacing airframe
weight with payload. On the main aircraft, carbon composites drove weight
reduction in the spar, center ribs, and electro-structural connecters. Spanwise
loading analysis determined the carbon spar could be thinned or eliminated
in areas of low stress. As a result, spar weight decreased by a quarter pound.

March 2021 5

Momentum - March 2021

Table of Contents for the Digital Edition of Momentum - March 2021