Microwave Photonic Notch Filter

Helps Ensure Critical Mission Success

Interference mitigation is crucial in modern radio frequency (RF) communications systems with dynamically changing operating frequencies, such as cognitive radios, modern military radar, and electronic warfare (EW) systems. To protect sensitive RF receivers in these systems, frequency agile RF filters that can remove interferers or jammers with large variations in frequency, power, and bandwidth are critically sought. Unfortunately, an RF bandstop or notch filter that can simultaneously provide high resolution, high peak attenuation, large frequency tuning, and bandwidth reconfigurability does not presently exist. Microwave photonic (MWP) filters are capable of tens of gigahertz tuning and have advanced in terms of performance, but most are limited in stopband rejection due to the challenge in creating a high-quality-factor optical resonance used as the optical filter. To achieve MWP filters with similar performance to state-of-the-art RF filters in terms of isolation bandwidth and rejection is still very challenging, especially in compact integrated photonic chip footprint.

Posted in: Articles, Aerospace, Defense, Radar, Telecommunications systems, Waveguides, Radar, Telecommunications systems, Waveguides

Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

New testing technique requires less material, gives more accurate results.

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, TSP, Aerospace, Defense, Fluid Handling, Propulsion, Solid propellants, Spacecraft fuel, Performance tests

Combustion Characteristics of Hydrocarbon Droplets Induced by Photoignition of Aluminum Nanoparticles

Test methodology allows analysis of combustion dynamics for subscale rocket injectors under super critical conditions.

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, TSP, 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

Determining the thermophysical properties of chemical warfare agent simulants can help evaluate the performance of defensive equipment.

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, TSP, Aerospace, Defense, Disaster and emergency management, Emergency management, Chemicals, Materials properties, Hazardous materials

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

New analytical tools improve understanding of vessel operating environments in the littorals.

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, TSP, Aerospace, Defense, Computational fluid dynamics, Marine vehicles and equipment

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

Technique can be used to distinguish between commercial nuclear reactor fuel cycles, fuel cycles for weapons grade plutonium, and products from nuclear weapons explosions.

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, TSP, Aerospace, Defense, Nuclear energy, Identification, Test procedures

The Rapid Rise of Beryllium-Aluminum Alloys in Aerospace

Enhanced performance operating envelopes for aerospace platforms continue to challenge industry limits. Aerospace platform operators demand extreme performance in harsh environments from the aircraft, UAVs, and satellites they deploy today: lighter weight, greater strength, superior fuel efficiency and operational range, vibration-mitigated platforms, low coefficients of thermal expansion, better corrosion resistance — the list goes on.

Posted in: Articles, Aerospace, Defense, Aircraft structures, Aluminum alloys, Beryllium, Materials properties

New Products: August 2017 Aerospace & Defense Technology

Rugged Data Recorders

DTS’ (Seal Beach, CA) ultra-small SLICE MICRO and NANO data recorders are rugged and designed to embed directly in the test article – even small drones. The NANO has a footprint of just 26 × 31 mm. The standalone systems include a microprocessor, excitation, full signal conditioning, and sample up to 500,000 sps/channel.

Posted in: Products, Aerospace, Defense

Aeroacoustic Simulation Delivers Breakthroughs in Aircraft Noise Reduction

Aircraft manufacturers face increasingly stringent standards for reducing community noise. Conventional aircraft development methods based on engineering experience, past designs and flight testing will not suffice to meet future noise reduction targets. Computational Fluid Dynamics (CFD) software based on so-called Reynolds-averaged Navier-Stokes (RANS) methods has revolutionized aerodynamics engineering, but is insufficient for high-fidelity aeroacoustic simulation. However, the Lattice-Boltzmann-based technology of Exa Corporation’s PowerFLOW software provides aeroacoustic simulation accuracy comparable to wind tunnels and flight testing.

Posted in: Articles, Aerospace, Defense, Computational fluid dynamics, Noise pollution, Acoustics, Acoustics, Aircraft

Thermoelectric Cooling: How Does It Work? Why Should You Choose It?

There are many places one can go to get an outline on the pros and cons of different methods for enclosure cooling. Although we will briefly touch on them here, this is really an in-depth article on how to choose a Peltier (thermoelectric) air conditioner, once you have committed to the technology.

Posted in: White Papers, White Papers, Electronics & Computers