Utilizing equivalent circuits to describe the strain- and temperature-dependence of electromagnetic metamaterials

Electromagnetic metamaterials have demonstrated unique and unprecedented behaviors in a laboratory setting. They achieve these novel properties by utilizing geometry and structure, as opposed to a strict reliance on chemical composition, to dictate their interactions with electromagnetic (EM) radiation. As such, metamaterials significantly expand the toolkit from which engineers can draw when designing devices that interact with EM waves. However, the flexibility afforded by these structures also implies environmental sensitivities not seen in traditional material systems. Some recent efforts have borne this out, demonstrating significant strain- and temperature-dependence in metamaterial samples. To date, little has been done to fundamentally understand the mechanisms driving these dependencies. This understanding is crucial for developing engineering-quality predictions of the EM performance of metamaterial structures in a relevant environment, a crucial step in transitioning this technology from laboratory novelty to fielded capability. This study leverages equivalent circuit models to understand and predict the strain- and temperature-dependent EM properties of metamaterial structures. Straightforward analytic expressions for the equivalent circuit parameters (resistance, inductance, capacitance) detail the strain-induced changes in geometry as well as the temperature-dependence of the metamaterials constituent materials. These expressions are initially utilized to predict the strain-dependent shift in resonant frequency, a key descriptor of the metamaterial\u27s EM behavior. These same expressions are then utilized to describe the metamaterial\u27s strain- and temperature-dependent EM constitutive properties (permittivity, ε, and permeability, μ), which are critical for solving Maxwell\u27s equations and performing EM simulations within the material. This study focused on the Electric-LC (ELC) resonator, a design commonly used to provide a tailored response to the electric field of the EM wave. However, the author believes that the same process, and similar analytic expressions for the circuit parameters and constitutive properties, could be used to successfully predict the strain- and temperature-dependence of other metamaterial structures, to include Split-Ring-Resonators (SRRs), a design commonly used to provide a tailored magnetic response to EM waves.\u2

Multiple Payload Adapters: Opening the Doors to Space

In order to increase the number of satellites that can be flown with reduced costs, Multiple Payload Adapters (MPAs) are needed to take advantage of excess payload capability on launch systems. This paper will discuss the development of several MPAs at the Air Force Research Laboratory Space Vehicles Directorate in support of current and future Air Force and Department of Defense requirements. The adapters are being designed using state-of-the-art manufacturing processes, launch vibration isolation, and low-shock separation technology that can accommodate multiple satellite configurations. The MPAs can deploy multiple satellites, in a large range of sizes (15 kg to 1000 kg), depending on the design configuration. The MPAs are being developed to support the Minuteman and Peacekeeper derived space launch vehicles, the Evolved Expendable Launch Vehicle, and the Space Shuttle. The successful development of these adapters will greatly reduce the cost of launching satellites into orbit by allowing for the efficient use of currently unused payload margins. These MPA concepts maximize the opportunity for low-budget satellites to be manifested for launch, and are being proposed to fly as early as 2003. Additionally, work has begun to standardize adapter configurations and connections across multiple launch vehicles to provide reduced flight integration costs and greater opportunities for inclusion of small experiments on larger missions

Structural Health Determination and Model Refinement for a Deployable Composite Boom

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77171/1/AIAA-2009-2373-948.pd