Novel Tilting Ducted-Fan Aerial Vehicle Configurations

There has been recent renewed interested in ducted-fan, powered-lift vertical takeoff and landing aircraft vehicles for
uninhabited aerial vehicle and urban aerial mobility aerial applications. Early work was conducted in the 1950’s to
the late 1980’s into ducted-fan vehicles, especially at the time for military missions. The focus of ducted-fan research
began to shift to UAV’s and personal air transportation in the 2000’s. Work in the early 2000’s fostered interest into
ducted-fan aerial vehicles for vertical lift planetary aerial vehicle missions, especially for missions to Titan, a moon
of Saturn. For example, early work at NASA Ames conducted the first known investigation into oval ducts (with
internal tandem fans) to be used for these aerial vehicles. The use of twin oval ducts (with internal tandem fans)
allowed the use of quadrotor-style rotor rpm control for vehicle trim (in hover, for transition to high-speed forward
flight the addition of a tilt-actuator to pitch the twin oval ducts forward to be aligned with the freestream needed to be
added to the control approach. This current study explores open-rotor, single isolated ducted-fan, and full vehicle
configuration aerodynamic performance for hover, transition, and cruise regimes for novel tilting ducted-fan aerial
vehicle configurations. The objective of this study is to better understand the design aerodynamics trade space for
noncircular tilting ducted-fans. The primary analysis tool used in this paper is the mid-fidelity computational fluid
dynamics RotCFD tool. Several interesting and largely unexplored rotor-on-rotor (or fan-on-fan), duct-on-rotor, rotor-
on-duct, and duct-on-airframe are examined in this paper. Many of these aerodynamic interactions are the key to
overall aerial vehicle performance. Limited parametric sweeps of rotor-to-rotor spacing (and, therefore, sizing and
shape of the enveloping ducts) for the various duct configurations will also be performed. The trade-offs between
duct thrust augmentation in hover versus improved transition controllability versus improved cruise L/D will be
discussed for various novel duct configurations. These ducted-fan configurations include oval ducts, ‘figure-eight’
ducts, and ‘B-shaped’ ducts, among others.