The University of Kentucky has been working with ILC Dover, manufacturers of space suits and inflatable space structures, to develop inflatable wings that can be used on future space exploration aircraft. Extensive experimentation has been done at UK regarding the aerodynamic performance of the inflatable wings made by ILC Dover. Through the use of computational fluid dynamics thorough testing of different profiles with different bumpy configurations can be analyzed. This can lead to the optimization of an ideal wing for a specific application without the wasteful process of building and analyzing, experimentally, non-ideal wing geometries. Current simulations of the Eppler 398 profile are being done to validate the unstructured based, incompressible code UNCLE for inflatable wing analysis applications. Validation is being done with experimental results obtained by Arvind Santhanakrishnan from the University of Kentucky's Fluid Mechanics Lab. Once the results are verified, different geometries can be tested to help ILC Dover and experimental fluid dynamists interested in this field of research.
The wings that they have provided for analysis include straight Eppler 398 based profile inflatable wings that possess the ability to become rigid when exposed to UV rays. These wings are packaged with a light-curing resin that hardens upon exposure to UV rays in the upper atmosphere. The success of the BIG BLUE Project in May of 2004 demonstrated these capabilities. Below are pictures of wind tunnel testing done by Arvind Santhanakrishnan and x-component velocity contours by Daniel Reasor of the UK CFD Group.
Rigidizable Inflatable Wing with Bumpy Eppler 398 Profile
Re=54,000, α=7o Numerical Results were obtained with UNCLE (SST Turbulent Model, Transient)
ILC Dover has also provided NACA 4318 based tapered wings that include a two piece construction; the interior is a polyurethane bladder while the exterior is composed of excess Vectran from the construction of the crash bags used on the Mars Rover. The polyurethane/Vectran composition of the wings make them relatively heavy for their size and also require an operating inflation pressure of 15-18psi (gauge). High pressure inflation makes these wings extremely rigid but also making deformation and warping difficult. Each pair of the Vectran wings, also known as FASM wings, are handmade making mass production difficult. Each pair of the FASM wings also has a unique bolt pattern at the root chord requiring experimentalists to fabricate unique test fixtures for each set of wings. Below are pictures of a torque testing experiment performed by the Dynamic Structures and Controls Lab. The FASM wings were used in BIG BLUE IV where they flew a lifting body test bed at ~39lbs with a 4.5hp 50cc engine.
FASM Wing with Bumpy NACA4318 Profile
The most recent wings that ILC Dover have provided to UK for analysis are called MIAV wings. These wings are made of rip-stop nylon and possess the capability of being mass produced. These wings also use the NACA 4318 profile. These wings are not only easily produced, but are relatively light and operate at an inflation pressure of 6-8psi (gauge). The lower pressure makes these wings more applicable to wing deformation/warping methods for roll control. Below are pictures of different sizes of MIAV wings available and some preliminary testing of trailing edge deflection through the use of a servo.
MIAV Wing with Bumpy NACA 4318 Profile
**Pictures of experimental setup pictures courtesy of Arvind Santhanakrishnan, Andrew Simpson and Jon Rowe at the University of Kentucky. **
Arvind Santhanakrishnan and Andrew Simpson are members of the UK Fluid Mechanics Lab. Arvind Santhanakrishnan primary research involves boundary layer control through the use of plasma actuators and Andrew Simpson's primary research is in roll control through the use of wing warping. Jon Rowe is a member of the UK Dynamic Structures and Controls Lab where he focuses on the Finite Element Analysis of FASM wings and inflatable structures.
Relevant Publications:
Reasor, D. A., Lebeau, R. P., Smith, S., Jacob, J. D., "Flight Testing and Simulation of a Mars Aircraft Design Using Inflatable Wings", Accepted to 45th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 2007.