Search Results

Both humans and onboard radiosensitive systems (electronics, materials, payloads and experiments) are exposed to the deleterious effects of the harsh space radiations found in the space environment. The purpose of this paper is to present the space radiation environment extended to deep space based on environment models for the moon, Mars, Jupiter, and Saturn and compare these radiation environments with the earth's radiation environment, which is used as a comparative baseline. The space radiation environment consists of high-energy protons and electrons that are magnetically “trapped” in planetary bodies that have an intrinsic magnetic field; this is the case for earth, Jupiter, and Saturn (the moon and Mars do not have a magnetic field). For the earth this region is called the “Van Allen belts,” and models of both the trapped protons (AP-8 model) and electrons (AE-8 model) have been developed.

A dual-membrane gas trap is currently used to remove gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). The gas trap consists of concentric tube membrane pairs, comprised of outer hydrophilic tubes and inner hydrophobic fibers. Liquid coolant passes through the outer hydrophilic membrane, which traps the gas bubbles. The inner hydrophobic fiber allows the trapped gas bubbles to pass through and vent to the ambient atmosphere in the cabin. The gas trap was designed to last for the entire lifetime of the ISS, and therefore was not designed to be repaired. However, repair of these gas traps is now a necessity due to contamination from the on-orbit ITCS fluid and other sources on the ground as well as a limited supply of flight gas traps. This paper describes a novel repair technique that has been developed that will allow the refurbishment of contaminated gas traps and their return to flight use.

An automated system drills the outer moldline holes on a military aircraft wing. Currently, the operator manually checks countersink diameter every ten holes as a process quality check. The manual method of countersink inspection (using a countersink gauge with a dial readout) is prone to errors both in measurement and transcription, and is time consuming since the operator must stop the automated equipment before measuring the hole. Machine vision provides a fast, non-contact method for measuring countersink diameter, however, data from machine vision systems is frequently corrupted by non-gaussian noise which causes traditional model fitting methods, such as least squares, to fail miserably. We present a solution for circle measurement using a statistically robust fitting technique that does an exceptional job of identifying the countersink even in the presence of large amounts of structured and non-structured noise such as tear-out, scratches, surface defects, salt-and-pepper, etc.

A study was conducted to investigate the impacts of obstacles on pilot performance, workload, and perceptions of safety in a visual flight rule (VFR) obstacle-rich environment (ORE). The study was conducted using a piloted simulation of a single-rotor, multi-engine helicopter operating in a highly detailed urban visual scene database. The database contained multiple obstacle types, with variable obstacle heights and densities. Nine pilots completed the approaches and departures into and out of a heliport located in the center of the generic urban environment. Two flight routes offered unique presentations of terrain and obstacle types. Obstacle height/density and time of day/lighting parameters were systematically manipulated. A multi-dimensional data collection methodology employing the simultaneous collection of direct aircraft state, pilot performance data, pilot physiological data and pilot subjective responses was employed.

The characteristics of the friction materials used in aircraft brakes are extremely important to the performance and safe operation of transport airplanes. These characteristics can change during exposure to environmental effects in the duty cycle, which can lead to problems, such as abnormally low friction, or brake induced vibration. Water vapor in the atmosphere produces a direct lubricant effect on carbon. Observed transition temperatures within the range of 140°C to 200°C, associated with increases in friction and wear of carbon brake materials, are attributed to water vapor desorption. Friction and wear transitions in the range of 500°C to 900°C may be associated with oxygen desorption.

An air quality simulation and assessment (AQSA) model was developed to simulate/evaluate the integrated system performance and obtain air quality characteristics and air contaminants inside the habitable compartments. This model applies both fixed control volume and quasi-steady-state approach for a multi-volume system to assess system performance, operating constraints, and capabilities. The model also integrates a state-of-the-art probabilistic analysis tool, UNIPASS, to compute failure probability due to the uncertainties of variables. In addition, this integrated model also predicts the most likely outcomes for analyzing risks and uncertainties as well as for quantitative toxicological evaluation. This model has been successfully and independently corrected/verified by NASA/JSC to be a very effective, reliable, and accurate tool, while providing savings in both the cost and time of the analysis.

For new aircraft production, initial production typically reveals difficulty in achieving some assembly level tolerances which in turn lead to non-conformances at integration. With initial design, tooling, build plans, automation, and contracts with suppliers and partners being complete, the need arises to resolve these integration issues quickly and with minimum impact to production and cost targets. While root cause corrective action (RCCA) is a very well know process, this paper will examine some of the unique requirements and innovative solutions when addressing variation on large assemblies manufactured at various suppliers. Specifically, this paper will first review a completed airplane project (Project A) to improve fuselage circumferential and seat track joins and continue to the discussion on another application (Project B) on another aircraft type but having similar challenges.

Currently, the Aviation industry uses traditional methods of communication, coordination, & human interaction to give disposition to resolve any kind of nonconformance occurrences which occur during manufacturing or operation of commercial or defense products. This involves increased in-person interaction and additional travel, especially to address the nonconformance issues arising at supplier plants or airports around the globe. During Covid and post-Covid environments, human interactions for the transfer of detailed information at different & distant manufacturing plant locations has been difficult, since support engineering teams (Example: Liaison, Product Review, Quality, Supplier Quality, and Manufacturing Engineering, and/or Service Engineering) have been working remotely.

The trend of moving towards model-based design and analysis of new and upgraded aircraft platforms requires integrated component and subsystem models. To support integrated system trades and design studies, these models must satisfy modeling and performance guidelines regarding interfaces, implementation, verification, and validation. As part of the Air Force Research Laboratory's (AFRL) Integrated Vehicle and Energy Technology (INVENT) Program, standardized modeling and performance guidelines have been established and documented in the Modeling Requirement and Implementation Plan (MRIP). Although these guidelines address interfaces and suggested implementation approaches, system integration challenges remain with respect to computational stability and predicted performance over the entire operating region for a given component. This paper discusses standardized model evaluation tools aimed to address these challenges at a component/subsystem level prior to system integration.

A highly modified F/A-18 aircraft is being used to demonstrate that aeroelastic wing twist can be used to roll a high performance aircraft. A production F/A-18A/B/C/D aircraft uses a combination of aileron deflection, differential horizontal tail deflection and differential leading edge flap deflection to roll the aircraft at various Mach numbers and altitudes. The Active Aeroelastic Wing program is demonstrating that aeroelastic wing twist can be used in lieu of the horizontal tail to provide autonomous roll control at high dynamic pressures. Aerodynamic and loads data have been gathered from the Phase I AAW flight test program. Now control laws have been developed to exploit aeroelastic wing twist and provide autonomous flight control of the AAW aircraft during Phase II. Wing control surfaces are being deflected in non-standard ways to create aeroelastic wing twist and develop the required rolling moments without use of the horizontal tail.

The desire to operate rotorcraft in icing conditions has renewed the interest in developing high-fidelity analysis methods to predict ice accumulation and the ensuing rotor performance degradation. A subset of providing solutions for rotorcraft icing problems is predicting two-dimensional ice accumulation on rotor airfoils. While much has been done to predict ice for fixed-wing airfoil sections, the rotorcraft problem has two additional challenges: first, rotor airfoils tend to experience flows in higher Mach number regimes, often creating glaze ice which is harder to predict; second, rotor airfoils oscillate in pitch to produce balance across the rotor disk. A methodology and validation test cases are presented to solve the rotor airfoil problem as an important step to solving the larger rotorcraft icing problem. The process couples Navier-Stokes CFD analysis with the ice accretion analysis code, LEWICE3D.

ESA and NASA agencies agreed to run an interface compatibility test at the EADS facility between the Columbus flight module and a duplicate ground unit of a currently on-orbit US International Standard Payload Rack, the Human Research Facility (HRF) Flight Prototype Rack (FPR). The purpose of the test was to demonstrate the capability to run US payloads inside the European ISS module Columbus. One of the critical aspects to be verified to ensure suitable operations of the two systems was the combined performance of the hydraulic controls resident in the HRF and Columbus coolant loops. A hydraulic model of the HRF FPR was developed and combined with the Columbus Active Thermal Control System (ATCS) model. Several coupled thermal-hydraulic test cases were then performed, preceded by mathematical analysis, required to predict safe test conditions and to optimize the Columbus valve configurations.

The Selective laser sintering (SLS) process offers unique capabilities for production of complex, thin-walled geometries with internal features, integral attachments and flanges. The benefits of SLS have been realized on a variety of Boeing military platforms for a number of years. However, applications on commercial aircraft have been limited by material flammability requirements. To address this gap, Boeing, in cooperation with Advanced Laser Materials, developed a flame retardant polyamide material that is now commercially available (ALM FR-106). This paper introduces the general advantages of laser sintering as applied to the manufacturing of flight hardware and a description of the development of the flame retardant material in use.

This study was designed to answer what percent of “required” traffic pilots acquire visually using the current “visual acquisition system” of windows, eyes and the Traffic Collision Avoidance System (TCAS). “Required Traffic” was defined as Air Traffic Control (ATC) calls to the research aircraft, TCAS Traffic Alerts and/or TCAS Resolution Advisories. The results of the approximately 40 hours of flight were that the majority of (“required”) traffic was NOT visually acquired (39% visually acquired; 61% not visually acquired). When traffic was identified to the pilots by more than one source, the visual acquisition rate was 58%. For validation purposes, an additional 10 hours of flight observations were made during revenue flights with a major airline. Flight test and airline observations were found to be comparable.

The aircraft lifecycle involves thousands of transactions and an enormous amount of data being exchanged across the stakeholders in the aircraft ecosystem. This data pertains to various aircraft life cycle stages such as design, manufacturing, certification, operations, maintenance, and disposal of the aircraft. All participants in the aerospace ecosystem want to leverage the data to deliver insight and add value to their customers through existing and new services while protecting their own intellectual property. The exchange of data between stakeholders in the ecosystem is involved and growing exponentially. This necessitates the need for standards on data interoperability to support efficient maintenance, logistics, operations, and design improvements for both commercial and military aircraft ecosystems. A digital thread defines an approach and a system which connects the data flows and represents a holistic view of an asset data across its lifecycle.

A family of water-based sol-gel coatings has been developed as an environmentally-friendly alternative to traditional aerospace finishing materials and processes. The sol-gel hybrid network is based on a reactive mixture of an organo-functionalized silane with a stabilized zirconium complex. Thin films of the material self-assemble on metal surfaces, resulting in a gradient coating that provides durable adhesion for paints, adhesives, and sealants. Use of the novel coating as a surface pretreatment for the exterior of commercial aircraft has enabled environmental, health, and safety benefits due to elimination of hexavalent chromium, and flight test and early fleet survey data support the laboratory observations that the sol gel coating reduces the occurrence of “rivet rash” adhesion failures. Modifications of the basic inorganic/organic hybrid network have yielded multifunctional coatings with promise for applications such as corrosion control and oxidation protection.

Every aircraft produced today contains hundreds of thousands of fastened joints. These joints and the fasteners that connect them are perhaps the most common source of failure in aircraft structure. Therefore, it is imperative that advancements in fastener materials and designs be given the utmost consideration and attention to achieve increased joint performance and integrity. This paper presents the results of development efforts relating to an advanced processing technique and its effect upon selected mechanical properties of certain metallic alloy materials that are deemed appropriate or important for potential fastener applications.

Fastening metallic structure for aerospace applications is relatively straightforward and has been done for some time. Dealing with advanced composites, though, requires a significantly different technological approach, especially primary structure. Although composite material utilization has increased enormously in civil and military aircraft in recent years, the application of composite materials to primary aircraft structure has not kept pace and is still greeted with some skepticism in the aerospace community. In particular, no major transport manufacturer has yet employed composite components for fuselage or wing primary structure. This appears to be changing rather rapidly with the introduction and the evolution of new airframes such as the 7E7 and Blended Wing Body (BWB) concepts.

The Boeing Company has recently developed a portable positioning system based upon its patented flexible vacuum track technology, in support of its commitment to lean manufacturing techniques. The positioning system, referred to as Mini Flex Track, was initially developed as an inexpensive drilling system that minimizes machine setup time, does not require extensive operator training due to its simple user interface, is general purpose enough to be used in varying airplane applications, and meets strict accuracy requirements for aircraft manufacturing. The system consists of a variable length vacuum track that conforms to a range of contours, a two-axis numerically-controlled positioning carriage that controls machine motion, an additional rail perpendicular to the vacuum rail that provides transverse motion, and an end effector that can perform various tasks.

The current dual-membrane gas trap is designed to remove non-condensed gases (NCG) from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). To date it has successfully served its purpose of preventing depriming, overspeed, and shutdown of the ITCS pump. However, contamination in the ITCS coolant has adversely affected the gas venting rate and lifetime of the gas trap, warranting a development effort for a next-generation gas trap. Design goals are to meet or exceed the current requirements to (1) include greater operating ranges and conditions, (2) eliminate reliance on the current hydrophilic tube fabrication process, and (3) increase operational life and tolerance to particulate and microbial growth fouling.