Technical Support Packages

Hydrodynamic Drag Force Measurement of a Functionalized Surface Exhibiting Superhydrophobic Properties

With superhydrophobic properties being extended to a variety of metallic substrates through the process of ablation due to femto-second laser surface processing (FLSP), it is important to understand the hydrodynamic benefits of such a material, as well as its resiliency. This research focuses on the skin friction drag effects of a superhydrophobic flat plate compared to an untreated flat plate of the same material and geometry. The resiliency of this material will also be tested through the use of an accelerated corrosion fog chamber using both treated and untreated aluminum samples.

Posted in: Briefs, Aerospace, Lasers, Metal finishing, Aluminum alloys, Corrosion resistant alloys, Materials properties

High-Power Broadband Multispectral Source on a Hybrid Silicon Chip

For applications in manufacturing, remote sensing, medicine, military, and fundamental science, an ideal laser would have high output power and a diffraction-limited beam. The figure-of-merit to describe this property is the brightness, which scales proportional to output power and inverse to the beam quality factor M2.

Posted in: Briefs, Aerospace, Integrated circuits, Lasers, Waveguides, Silicon alloys

Stimulated Brillouin Scattering (SBS) Suppression and Long Delivery Fibers at the Multikilowatt Level with Chirped Seed Lasers

One obstacle in the scaling of high-power fiber lasers arises because of nonlinear effects (e.g., stimulated Brillouin scattering [SBS]) due to the large intensity times length product. Efforts to raise the power threshold include:

Posted in: Briefs, Aerospace, Fiber optics, Lasers, Performance upgrades

Erbium Doped GaN Lasers by Optical Pumping

The main objective of this research was to construct an optical pump system that would allow the study of Er:GaN materials under 980 nm resonant excitation to be carried out. The results obtained from the optically pumped studies could then be utilized to guide crystal growth and laser design.

Posted in: Briefs, Aerospace, Lasers, Optics, Materials properties, Refractory materials, Pumps

New Class of Excimer-Pumped Atomic Lasers (XPALS)

The focus of this research program was the investigation of XPAL properties, and new pumping schemes, as well as modeling, and measuring critical photoionization and excited state-excited state reaction rates in order to improve the performance of XPALs.

Posted in: Briefs, Aerospace, Lasers, Research and development, Pumps

Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

Structural analysis of solid rocket motors is challenging for several reasons, but the most important of these is the complex behavior of the propellant. The mechanical response of a solid propellant is time and temperature dependent. The complexity of the mathematical analysis of the propellant depends on the loading conditions, but for some loading situations, the linear viscoelasticity assumption is reasonable. In particular, linear viscoelasticity is perhaps the most appropriate material behavior description for use in the simulations of stresses related to storage conditions. Typically, simulations use a viscoelastic model in the form of a Prony series and a Williams–Landel–Ferry (WLF) equation. The parameters in these models are derived from stress relaxation experiments, making the stress relaxation experiment a key viscoelastic test, analogous to the tensile test for linear elastic materials.

Posted in: Briefs, Aerospace, Defense, Fluid Handling, Propulsion, Solid propellants, Spacecraft fuel, Performance tests

Combustion Characteristics of Hydrocarbon Droplets Induced by Photoignition of Aluminum Nanoparticles

In the study of combustion characteristics of liquid rocket fuels, it is customary to either study the combustion of liquid fuel droplets or the combustion of fuel sprays. However, the two are closely related to each other, because in a typical rocket combustion chamber, the burning of droplets, droplet clusters, and fuel sprays occur simultaneously.

Posted in: Briefs, Aerospace, Defense, Propulsion, Test & Measurement, Spacecraft fuel, Aluminum, Combustion and combustion processes, Liquid propellant rocket engines

Vapor Pressure Data and Analysis for Selected Organophosphorous Compounds: DIBMP, DCMP, IMMP, IMPA, EMPA, and MPFA

Knowledge of the physical properties of materials is critical for understanding their behavior in the environment as well as in the laboratory. Vapor pressure is an important physical property for a wide variety of chemical defense-related applications, including estimation of persistence, prediction of downwind time-concentration profiles after dissemination, generation of controlled challenge concentrations for detector testing, evaluation of toxicological properties, and assessment of the efficiency of air filtration systems.

Posted in: Briefs, Aerospace, Defense, Emergency management, Chemicals, Materials properties, Hazardous materials

Coupling of Coastal Wave Transformation and Computational Fluid Dynamics Models for Seakeeping Analysis

This research focused on depth-integrated modeling of coastal wave and surf-zone processes in support of computational fluid dynamics (CFD) simulation of ship motions. There were two components of the project. The first was the development of a numerical dispersion relation for a family of Boussinesq-type equations commonly used in modeling of coastal wave transformation. The relation depicts numerical dissipation and dispersion in wave propagation and provides guidelines for model setup in terms of temporal and spatial discretization. The second component was an extension of existing depth-integrated wave models to describe overtopping of coastal reefs and structures along with a series of CFD and laboratory experiments for model validation. The basic approach utilizing the HLLS Riemann solver performs reasonably well and produces stable and efficient numerical results for practical application.

Posted in: Briefs, Aerospace, Defense, Computational fluid dynamics, Marine vehicles and equipment

Assessment of Non-Traditional Isotopic Ratios by Mass Spectrometry for Analysis of Nuclear Activities

The objective of this work is to identify isotopic ratios suitable for analysis via mass spectrometry that distinguish between commercial nuclear reactor fuel cycles, fuel cycles for weapons grade plutonium, and products from nuclear weapons explosions. Methods will also be determined to distinguish the above from medical and industrial radionuclide sources.

Posted in: Briefs, Aerospace, Defense, Nuclear energy, Identification, Test procedures