Recent advances in vibroacoustics
Numerous vibroacoustics advances and problems in the aerospace industry have occurred over the last 15 years. This article addresses some of these that developed from engineering programmatic task-work at the NASA Glenn Research Center at Lewis Field.
Review of pyroshock wave measurement and simulation for space systems
Abstract Numerous pyrotechnic devices are used in aerospace vehicles to accomplish initiation, release, severance/fracture, jettison, valving, switching, time delay, and actuation process. The initiation of these devices generates severe shock, which has been overlooked as a potentially damaging environment in many equipment specifications. This severe shock is referred to as pyroshock which is characterized by transient high acceleration and high frequencies. Since pyroshock can cause the failure of electronic components, many researchers have attempted to develop an effective method to analyze the generation and propagation of shock waves. The simulation and characterization of shock waves in ground tests are necessary to ensure equipment integrity in this phase. We review the measurement and characterization of pyroshock, requirements for various experimental simulations, excitation and measurement techniques, data acquisition, and an overview of numerical simulation.
Microwave source with enhanced radiation power based on orbitron MASERs
We have proposed the design of high power microwave source in a vacuum tube based on the theory of negative mass instability. The proposed source does not operate based on a slow-wave structure but instead makes use of accelerated charged particles. In our structure, an electron emitter injects the charged particles into to the cavity. Emitted particles move around the anode, which leads to electron acceleration and emission of electromagnetic waves with a specific frequency. In this paper, we have enhanced the output power and frequency of microwave source by variation of particles initial energy and the number of anodes incorporating their specific arrangement and applied voltages. Working at room temperature, compactness, wide bandwidth, and tunability of output frequency are among the advantages of the proposed source.