Equipment Bay Research Articles

Aerodynamic noise analysis of the skirting board under an ultra-high-speed train based on bidimensional empirical mode decomposition

ABSTRACT The grille located in the lower part of the train often forms a grille-cavity structure in the equipment bay’s surface. The issue of flow-induced sound of this structure becomes more significant at high speeds. In this study, we focus on a skirting board with a grille, that is simplified as a grille-cavity structure. We use DDES in combination with modal decomposition, to analyze the fluidization mechanism of the structure. The results indicate that the shear oscillation at the opening of the cavity is more pronounced at ultra-high speed. Moreover, it has been shown that both POD and BEMD can accurately separate and identify coherent structures in the flow field. BEMD has higher accuracy. And the flow is primarily dominated by low-frequency acoustic oscillation. Finally, when we compare three grille configurations (V, ᴖ), we find that the grille’s presence mitigates the cavity’s aerodynamic noise, especially when using a -shaped grille.

Flow Simulation-Based Methodology for Reducing The Risk of Fuel Fire In An Aircraft’s Fuel System Enclosure

ABSTRACT This study applies advanced computational fluid dynamics (CFD) simulations to enhance the safety of an aircraft’s fuel system by striving to minimize the risk of on-board fire hazards. Employing a detailed flow simulation model, this research assesses the efficacy of newly designed measures within a fuel system, designed for a modified radial engine on a test-bed AN 2 airplane. The model simulates internal airflow, droplet particle flow, the formation of Eulerian Wall Film, and the vaporization process from the fuel film within the enclosure of the aircraft’s equipment bay. By exploring both the original and modified geometries of this fuel system enclosure, the simulations provide insights into the flowpaths of leaking fuel, the spatial and temporal distribution of fuel vapor concentrations, and the overall effectiveness of design modifications aimed at rapid removal of hazardous substances. Structural improvements, including the addition of strategic ventilation inlets and outlets, are proposed based on the simulation results to ensure rapid dispersion of vapors and minimal residual fuel, effectively reducing the potential for vapor ignition. This study thus underscores the potential of precise CFD modelling in identifying risks and developing robust fire hazard mitigation strategies in aviation fuel systems.

Ariane 5 Fairing Preparations for the James Webb Space Telescope (JWST)

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The Ariane 5 payload faring (PLF), interior and Vehicle Equipment Bay membranes received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels.Investigation of PLF cleanliness began early in the JWST program to test the Fairing Acoustic Protection (FAP) panels. Initial PLF cleaning was performed at RUAG in Switzerland prior to shipment to the launch site in collaboration with NASA and ESA. The cleaning procedure used at RUAG premises was based on heritage of the PLF cleaning procedure for ESA/Herschel-Planck and NASA/Mars2020 missions on an Atlas V launcher. The Ariane 5 fairing was packaged in a clean manner and inspected and cleaned upon arrival to CSG. Silicon wafers and particle fall out (PFO) plates were used to monitor the internal fairing cleanliness prior to encapsulation. Just after encapsulation, PFO plates and calcium fluoride (CaF2) crystals were placed inside the fairing on a specific tool door for monitoring the cleanliness inside the fairing during the ventilation phase. The fairing itself was specially sealed to protect the inner environment with just a small, doored porthole accessible via diving board for final closeout of the purge interface. Fairing cleanliness was achieved and mitigated contamination distribution upon launch.

Analysis of hypervelocity-impacted thin films for space applications

Exposure to the harsh space environment and hypervelocity impacts from micrometeoroids and small orbital debris can affect space operations through long-term degradation of spacecraft materials, surfaces, or systems. Multi-layer insulation (MLI) and coated polyimide films are spacecraft materials commonly found on the external surfaces of spacecraft for thermal control and protection. Characterizing the damage to these exposed materials with in situ and laboratory measurements can better inform spacecraft designers and operators in understanding and mitigating surface or system degradation. In this paper, we examine flown Hubble Space Telescope (HST) Equipment Bay 5 MLI and coated polyimide hypervelocity ground tested articles to characterize hypervelocity impact damage. Impact feature cavities are inspected to identify damage, which can validate long-term degradation models, improve thermal management systems, or improve accuracy of damage predictions. An overview of the impact characterization using optical microscopy, narrow-band spectroscopy, and Scanning Election Microscopy/Energy Dispersive X-ray (SEM/EDX) of the two materials is presented. Observations of robustness in the space environment, as well as a detailed assessment of cratering and penetration statistics for the space-exposed sample, are also discussed.

Scoring Approach to Assess Maintenance Risk for Aircraft Systems in Conceptual Design

Ease of maintenance can significantly contribute to reducing aircraft operational cost. Maintenance risk is defined as the opposite of maintenance ease; it is impacted by many factors, most of which are decided upon during the aircraft’s conceptual design. This paper proposes a novel method to assess the maintainability risks of aircraft systems by combining various aspects on the component level, intercomponent level, bay level, and aircraft level. For each level, all contributing factors to maintenance risk are analyzed and integrated into several scores. These maintenance risk scores can be used to assess the various aspects contributing to maintenance risk, using input parameters available during the conceptual design phase. This paper presents the validation of the scores using different components and aircraft equipment bays, such as avionic racks, the nose cone, and a complex aft equipment bay of a business jet. The proposed maintenance risk scoring method will enhance multidisciplinary tradeoff studies during aircraft conceptual design, considering competing design aspects such as system placement, thermal aspects, impact on aircraft balancing, or even the overall aircraft shape. Therefore, this new conceptual design capability enables designing novel aircraft configurations featuring unconventional system component placement or component bay shapes while considering maintenance aspects upfront.

Pressure measurement inside non-sealed equipment bay of the geostationary spacecraft

Pressure measurement inside non-sealed equipment bay of the geostationary spacecraft

Improving aircraft conceptual design through parametric CAD modellers – A case study for thermal analysis of aircraft systems

Aircraft manufacturers strive to improve their efficiency and effectiveness of the development processes. Increasing maturity and implementing more disciplinary analyses in the conceptual design are key enablers to reduce costly design iterations in later design stages. Therefore, the aircraft's conceptual design employs more and more multidisciplinary design analysis and optimization (MDAO) frameworks, which require automation of the involved disciplinary analysis. Recent aircraft conceptual MDAO frameworks integrate geometrical modellers, but these are generally limited to represent external aircraft geometry. Computer-Aided Design (CAD) software enables the generation of three-dimensional (3D) models that can provide geometrical parameters to most of the disciplines involved in aircraft conceptual design. Moreover, using an advanced CAD system early in conceptual design allows a seamless transition to more detailed design phases. For novel aircraft configuration and more electric, hybrid electric, and fully electric aircraft architectures, systems integration in the conceptual design is essential. To integrate aircraft systems and subsystems analyses within the MDAO frameworks, aircraft geometric or CAD modellers need to follow suit. This paper proposes a framework to describe CAD modellers' integration into MDAO environments for use in the conceptual design phase. This paper also formalizes the interactions between the disciplines and a CAD modeller within MDAO workflows and provides requirements for automated systems and subsystems analyses. Therefore, the presented work enables integrating novel disciplines, such as thermal, maintenance, safety, and electromagnetic compatibility (EMC) analyses, into the aircraft conceptual design phase. A case study covering the thermal analysis of an aircraft equipment bay demonstrates the effectiveness of the proposed MDAO framework.

Ventilation considerations for an enhanced thermal risk prediction in aircraft conceptual design

The capability to assess thermal aspects early in aircraft design is a crucial enabler for unconventional, more-electric, hybrid-electric, or all-electric aircraft configurations. This paper presents an extended version of a so-called thermal risk assessment approach for aircraft conceptual design. The assessment of thermal risk and the definition of a suitable cooling strategy during the conceptual design phase enables the anticipation of changes in the design process within a multidisciplinary design and optimization framework. In a previous paper, the authors propose applying dimensionless numbers to assess the thermal environment of a considered aircraft zone and predict the systems' thermal risk with a limited number of inputs. This research paper investigates the relations between the aircraft systems' locations within an equipment bay and the characteristics of the ventilation sources. The concept of mainstream flow is introduced, and new dimensionless numbers are established. The streamwise and the cross-stream numbers help to assess the closeness of a system to a ventilation source, while the heat removal potential assesses the cooling effectiveness due to the closest ventilation source for a particular system in an equipment bay. Two aircraft equipment bays with different configurations demonstrate the effectiveness of the thermal risk assessment methodology. The results are validated using computational fluid dynamic simulations. The enhanced thermal risk assessment approach will enable a more accurate definition of thermal requirements for aircraft systems within the aircraft conceptual design phase and reduce potential thermal issues later in the design process.

Thermal risk prediction methodology for conceptual design of aircraft equipment bays

Early thermal analysis is becoming increasingly important, in particular for more electric, hybrid electric or all electric aircraft in combination with novel vehicle concepts. Traditionally, aircraft thermal analyses are performed later in the design process, when the aircraft system architecture is already defined, which can lead to costly modifications and delays late in the design process. Thus, assessing thermal risk during the conceptual design phase represents a way to anticipate changes in the design process. This research paper presents an innovative approach using dimensionless numbers to predict system thermal risk for the conceptual design of aircraft equipment bays. The article presents two realistic case studies, a business jet aft equipment bay and a rotorcraft nose equipment bay. The validation with computational fluid dynamic simulations demonstrates novel the capabilities of this thermal risk assessment. In summary, the proposed approach will improve the definition of thermal requirements during the aircraft conceptual design phase and will reduce the risk of potential thermal issues later in the design process.

Physiologic Strain of SCBA (Maze) Training Compared to Circuit Training and Live Fire Training

Firefighting is a dangerous occupation and even training carries substantial risk. In fact, about 10-12% of firefighter line of duty deaths occur in training–most due to sudden cardiac death. Self-contained breathing apparatus (SCBA) maze training (also known as SCBA confidence courses) are a common training exercise, and it is often assumed that this type of drill is less physically taxing because there is no “live-fire”. However, little is known about the physiologic strain associated with SCBA maze training. PURPOSE: To compare the physiological strain of SCBA maze training to live fire training and circuit training among cadets at a training academy. METHODS: Cadets (N=40) wore physiologic status monitors to assess heart rate (HR) and estimated core temperature (ECT) during circuit training, live fire training and SCBA maze training. SCBA maze training occurred in full personal protective equipment (PPE) and took place in an air conditioned building. Live fire training occurred in a specialized training structure, and the circuit training workout occurred in a large equipment bay. Age-predicted maximum (APM) HR was calculated using the 220-age formula. Data were analyzed using repeated measures ANOVA and Bonferroni post-hoc. RESULTS: Data from 40 cadet firefighters (31±3 yrs. old) were analyzed. No significant difference (p>0.05) was observed between SCBA maze training and live fire training for HR or ECT (see Table 1). However, HR and ECT differed significantly between circuit training and both SCBA maze training and live fire training. CONCLUSIONS: Even though SCBA maze training was performed under controlled environment it involved a physiological strain above circuit training and as high as live fire training, reaching age predicted maximum HR. SCBA maze training should be considered as physiologically stressful as live fire training of similar duration.Table 1: Physiologic characteristics of academy training among cadets (N=40)Supported by FEMA AFG Grant EMW-1015-FP-00731

Study of Influential Factors of the Vibration Modal of the Rocket Equipment Bay and Structural Improvement Based on Finite Element Analysis

In this paper, the study focuses on influential factors of the vibration modal of the equipment bay of a carrier rocket and the structural improvement of the equipment bay by using finite element modal analysis. The finite element analysis focuses on the influences of the mass of the inertial bracket, the thickness of parts of the inertial bracket, and the stringer thickness on the first modal frequency of the equipment bay. As the analytical results show, the vibration displacement of mounting panels can be greatly reduced when the equipment bay is added with mass, and the vibration of the equipment bay with mass mainly occurs on the inertial bracket (without mass, the maximum vibration displacement occurs on the mounting panel); the top surface thickness of the inertial bracket has the maximum influence on the first modal frequency of the equipment bay, the stringer thickness and the side thickness of the inertial bracket have relatively high influence on the first modal frequency, the rib thickness of the inertial bracket has relatively low influence on the first modal frequency, and the beam thickness of the inertial bracket has the minimum influence on the first modal frequency.

Aerodynamic Characteristic Analysis of Flow Structure around the High-Speed Train Equipment Bay

An improved train model, which contributes to obtain the aerodynamic characteristic of the high-speed train equipment bay, is established. By building a VEB (vehicle equipment bay) model in it, this improved model can demonstrate air flow around the VEB. The result shows that pressure fluctuation appears around the VEB, which gives visible difference from the classical train model. Applying the spectral analysis, the influence factors (include position and train speed) of the pressure fluctuation is studied.

Modular MEMS-based optical cross-connect with large port-count

We describe and demonstrate a modular microelectromechanical systems (MEMS)-based optical cross-connect (OXC) architecture. The OXC port count increases modularly by adding new optical modules, and a maximum cross-connectivity of /spl sim/ 350 /spl times/ 350 can be achieved in the current design. Each optical module has 16 ports with closed-loop servo-controlled MEMS mirrors. Using a prototype OXC system, mounted in a standard telecommunications equipment bay comprising optical modules, folding mirrors, and other optical elements, we demonstrate switching times of less than 10 ms, excellent optical power stability of less than /spl plusmn/ 0.15-dB variation, and immunity to stochastic vibrations. An automatic power peak-up process is performed when the power falls below 0.5-dB off the maximum coupled power for any connection.

Vibration Confinement in a Generic Launch Vehicle

A controller design for vibration control and alignment maintenance at critical location is developed in a generic launch vehicle whose equipment bay (EB) houses the main inertial platform. The controller uses active control to reduce the attitude disturbance in the attitude at the EB due to elastic deformation. The vibration energy is redistributed by the technique of vibration confinement, which enables the response at the EB to reach its steady state faster in the remaining portion of the structure. (AIAA)

A use of case-based reasoning technique in building expert systems

Matra Marconi Space France and Aramiihs (Action de Recherche et Application Matra Irit en Interaction Homme Système) laboratory have used and evaluated Case Based Reasoning (CBR) techniques in two projects: • - The first project is about the development of a system dedicated to help satellites AIT/AIV (Assembly Integration and Test/Validation) test engineers to cope with incidents occurring during test activities. The project is funded by the EGSE System Section of ESTEC (European Space Research and Technology Centre.). • - The second project is related to the building of a knowledge-based system for diagnosis assistance in AIT/AIV activities of Ariane4 Vehicle Equipment Bay (VEB). The project is financed by internal funding of MMS-F. In the two projects, CBR technique is neither used the same way nor with the same purpose. In the first project, CBR technique is used to find out or suggest the cause of an anomaly when an incident appears. Confronted with the occurrence of an incident, the system will refer to its characteristics (test context, symptoms…) that are considered as relevant to retrieve previous similar incidents. In the second project, CBR technique is combined with Rule Based Reasoning and Model Based Reasoning ones to form the reasoning core of a Hybrid Knowledge Based System. When an incident occurs, the system proposes to test engineers a diagnosis approach based on the combination of different knowledge (coded into rule, cases and models). Aramiihs is a research unit where engineers from MMS and researchers from the IRIT (Institut de Recherche en Informatique de Toulouse) CNRS (Centre National de la Recherche Scientifique) collaborate on problems concerning new types of man-system interaction.

Composite patch reinforcement of cracked aircraft upper longeron: analysis and specimen simulation

The use of composite patches on cracked portions of metallic aircraft structures is an accepted means of improving fatigue life and attaining high structural efficiency. As more and more advanced composite materials are beng developed, the wider use of the repair technology is anticipated even for the reinforcement of primary aircraft structure. The objective of this work is to illustrate how the composite patch repair technology can be successfully applied to restore the structural integrity of cracked components. The Phosphoric Acid Anodize (PAA) surface treatment on aluminum when applied in conjunction with the AVI13/HV998 adhesive were essential for achieving the appropriate patch bonding strength. Such a process was done without immersing the component into the PAA tank; dismantling the component from the aircraft was not necessary. Boron/epoxy and carbon/epoxy patches were applied at room temperature to the 7075-T6511 cracked specimens and tested under fatigue simulating the load spectrum for the upper longeron attached to the access door of the electronic equipment bay. Considerable improvement in the fatigue life was observed after the repair. Equivalent flight test hours were increased from approximately two thousand hours at which the component fractured completely when not repired to twelve thousand hours when the repair was made with only a small amount of crack growth. A six times increase fatigue life is obtained. The laboratory developed technique has been applied to several in-service aircraft which have now been flown for more than 700 h without detection of crack growth.

Physical and mathematical modeling of wave propagation in the ariane 5 VEB structure

The separation of the lower stage of the ARIANE 5 Vehicle Equipment Bay (VEB) Structure is to be done using a pyrotechnic device. The wave propagation effects produced by the explosion can affect the electronic equipment, so it was decided to analyze, using both physical and numerical modeling, a small piece of the structure to determine the distribution of the accelerations and the relative importance of damping, stiffness, connections, etc. on the response of the equipment.

Measurements of ozone in the Antarctic atmosphere during August and September 1987

Mixing ratios changed dramatically for ozone in the austral polar stratosphere during August and September 1987. Data were obtained with an ultraviolet photometer mounted in the equipment bay of an ER‐2 aircraft. Measurements were made between the latitudes of 53° and 72°S at pressure altitudes (U.S. Standard Atmosphere (1976)) up to 21 km in a series of flights from Punta Arenas, Chile, over the Palmer Peninsula. Additional data were obtained between 37°N and 53°S on the ferry flights leaving from and returning to Moffett Field, California. The sample‐collecting system and the analytical techniques are described. In September the mixing ratios for ozone at pressure altitudes above 15 km in the southernmost part of the flights over the Palmer Peninsula were significantly lower than values for mid‐latitudes. The various latitudes of the ER‐2 aircraft's encounters with the boundary of the region of depleted ozone lie between 59° and 71°S. Near the 425 K potential temperature surface and well within the vortex, the measured mixing ratio of ozone declined from about 2 parts per million by volume (ppmv) to about 0.6 ppmv during the period of the ER‐2 flights. The distributions of ozone as a function of altitude indicate the presence of layering of ozone.

Rectangular thermal doublers of uniform thickness

An infinite series solution is developed for the steady temperature field in a thin, rectangular region exposed to a piecewise continuous heat flux and losing energy from exposed surfaces either by linearized radiation or true convection. The geometry and environmental conditions approximate a spacecraft application in which a finlike plate (thermal doubler) is used to enhance the radiating area of an energy-dissipating electronic component mounted in an equipment bay. A numerical example, based on typical spacecraft power and environmental conditions, is used to show how the closed-form solution may be used to investigate geometrical influences. Both direct (i.e., specified thickness, unknown temperature) and design (i.e., specified temperature, unknown thickness) problems are examined to show how temperature and doubler thickness depend on the shape of the heated area (''footprint), the shape of the doubler, and the location of the footprint within the doubler boundaries. The numerical results indicate that the two-dimensional solution for a case with double symmetry is bounded by the one-dimensional solutions for a circular footprint/circular doubler and a simple Cartesian geometry. The present formulation will be useful both for the trade studies leading to a preliminary design and as an exact solution for calibrating nodal models.

Some practical applications of Bayesian reliability measurements for aerospace-electronic systems

An attempt has been made to highlight the applications of Bayesian techniques for estimating the reliability parameters for aerospace-electronic systems. Both the exact form of Bayesian exponential estimation and its normalised form are discussed. A method of quantifying the prior density parameters from the pre-test knowledge, such as reliability prediction etc., is also hinted at. To illustrate the methodology, two practical examples, namely, of (i) a sequencer and (ii) an equipment bay, are given.