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Technical Paper

Calculations of Ice Shapes on Oscillating Airfoils

2011-06-13
2011-38-0015
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.
Technical Paper

Expanded Accommodation Technique with Application to Maintenance Environment

2011-04-12
2011-01-0521
This paper presents a PC based mathematical and rapid prototyping technique for anthropometric accommodation in a maintenance environment using the principle of simulation based design. The developed technique is capable of analyzing anthropometric data using multivariate (Principal component Analysis) approach to describe the body size variability of any given population. A number of body size representative cases are established which, when used properly within the constraints of the maintenance environments, will ensure the accommodation of a desired percentage of a population. This technique evaluates the percentage accommodation of a given population for the environment using the specific manikin cases as boundary conditions. In the case where any member of a maintenance crew cannot be accommodated, the technique has the capability of informing the designer of the environment why the member(s) is/are not accommodated.
Technical Paper

Ejection Seat Cushions Static Evaluation for Three Different Installation Rail Angles

2011-04-12
2011-01-0806
Jet fighter missions have been known to last extended period of time. The need for a comfortable and safe seat has become paramount considering that fact that uncomfortable seats can lead to numerous health issues. Several health effects like numbness, pressure sore, low back pain, and vein thrombosis have been associated with protracted sitting. The cushion, and of late the installation rail angle are the only components of the ejection seat system that can be modified to reduce these adverse effects. A comprehensive static comfort evaluation study for ejection seats was conducted. It provides comparison between a variety of operational and prototype cushions (baseline cushion, honeycomb and air-cushion) and three different installation rail angles (14°, 18°, and 22°). Three operational cockpit environment mockups with adjustable installation rail angle were built. Ten volunteer subjects, six females and four males, ages 19 to 35, participated in the seat comfort evaluation.
Technical Paper

A Reduced-Order Enclosure Radiation Modeling Technique for Aircraft Actuators

2010-11-02
2010-01-1741
Modern aircraft are aerodynamically designed at the edge of flight stability and therefore require high-response-rate flight control surfaces to maintain flight safety. In addition, to minimize weight and eliminate aircraft thermal cooling requirements, the actuator systems have increased power-density and utilize high-temperature components. This coupled with the wide operating temperature regimes experienced over a mission profile may result in detrimental performance of the actuator systems. Understanding the performance capabilities and power draw requirements as a function of temperature is essential in properly sizing and optimizing an aircraft platform. Under the Air Force Research Laboratory's (AFRL's) Integrated Vehicle and Energy Technology (INVENT) Program, detailed models of high performance electromechanical actuators (HPEAS) were developed and include temperature dependent effects in the electrical and mechanical actuator components.
Journal Article

Disturbance of Electronics in Low-Earth Orbits by High Energy Electron Plasmas

2009-07-12
2009-01-2339
Electrical disturbances caused by charging of cables in spacecraft can impair electrical systems for long periods of time. The charging originates primarily from electrons trapped in the radiation belts of the earth. The model Space Electrons Electromagnetic Effects (SEEE) is applied in computing the transient charge and electric fields in cables on spacecraft at low to middle earth altitudes. The analysis indicated that fields exceeding dielectric breakdown strengths of common dielectric materials are possible in intense magnetic storms for systems with inadequate shielding. SEEE also computes the minimal shielding needed to keep the electric fields below that for dielectric breakdown.
Journal Article

Analysis of Convective Heat Transfer in the Orbiter Middeck for the Shuttle Rescue Mission

2009-07-12
2009-01-2550
The paper presents the results of a CFD study for predictions of ventilation characteristics and convective heat transfer within the Shuttle Orbiter middeck cabin in the presence of seven suited crewmember simulation and Individual Cooling Units (ICU). For two ICU arrangements considered, the thermal environmental conditions directly affecting the ICU performance have been defined for landing operation. These data would allow for validation of the ICU arrangement optimization.
Journal Article

A Fresh Look at Radiation Exposures from Major Solar Proton Events

2008-06-29
2008-01-2164
Solar proton events (SPEs) represent the single-most significant source of acute radiation exposure during space missions. Historically, an exponential in rigidity (particle momentum) fit has been used to express the SPE energy spectrum using GOES data up to 100 MeV. More recently, researchers have found that a Weibull fit better represents the energy spectrum up to 1000 MeV (1 GeV). In addition, the availability of SPE data extending up to several GeV has been incorporated in analyses to obtain a more complete and accurate energy spectrum representation. In this paper we discuss the major SPEs that have occurred over the past five solar cycles (~50+ years) in detail - in particular, Aug 1972 and Sept & Oct 1989 SPEs. Using a high-energy particle transport/dose code, radiation exposure estimates are presented for various thicknesses of aluminum. The effects on humans and spacecraft systems are also discussed in detail.
Technical Paper

Liquid Water Content and Droplet Size Distribution Mass Fractions for Wind Milling Engine Fan Blade Ice Accretion Analysis

2007-09-24
2007-01-3291
A procedure for calculating the engine inlet diffuser section liquid water content and mass fractions of liquid water content associated with the water droplet size distribution for wind milling engine ice accretion analysis is presented. Critical fuel reserve calculation for extended twin-engine operation requires the determination of drag increase due to ice accretion on inoperative wind milling engine fan blade and guide vane.
Technical Paper

A Comparison of the Radiation Environments in Deep Space

2007-07-09
2007-01-3114
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.
Technical Paper

Improvement of Risk Assessment from Space Radiation Exposure for Future Space Exploration Missions

2007-07-09
2007-01-3116
Protecting astronauts from space radiation exposure is an important challenge for mission design and operations for future exploration-class and long-duration missions. Crew members are exposed to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR). If sufficient protection is not provided the radiation risk to crew members from SPEs could be significant. To improve exposure risk estimates and radiation protection from SPEs, detailed evaluations of radiation shielding properties are required. A model using a modern CAD tool ProE™, which is the leading engineering design platform at NASA, has been developed for this purpose. For the calculation of radiation exposure at a specific site, the cosine distribution was implemented to replicate the omnidirectional characteristic of the 4π particle flux on a surface.
Technical Paper

The Personal Computer Transport Analyzer Program

2006-07-17
2006-01-2050
Since flight requirements often necessitate last-minute re-analysis, it became crucial to develop flexible and comprehensive transport phenomena analysis software that would quickly ensure all vehicle and payload requirements would be satisfied. The software would replace various mainframe-based software, such as the Thermal Radiation Analyzer System (TRASYS) and the Systems Improved Numerical Differencing Analyzer (SINDA). The software would need to have the flexibility to employ models that could be developed and modified as vehicle systems change. By use of event files which contain simple, intuitive commands, the characteristics of individual missions could be built as inputs to the model. By moving the Environmental Control & Life Support (ECLS) system model to the PC environment, each analyst would have execution, storage, and processing management control. And of course, software portability would be greatly increased.
Technical Paper

Microbial Characterization of Internal Active Thermal Control System (IATCS) Hardware Surfaces after Five Years of Operation in the International Space Station

2006-07-17
2006-01-2157
A flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUs) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 ± 0.5.
Technical Paper

Integrated Ceramic Composite Firewall

2005-10-03
2005-01-3430
This white paper will outline the material and processes, which have been developed for the fabrication and application of an integrated composite firewall primary structure for use in military and commercial aircraft. Military and commercial aircraft have requirements to protect occupants from fire. One specific fire protection requirement is to contain a (1100°C/2000°F) flame for 15 minutes. This protection on composites is usually provided by a metallic firewall attached to the composite structure. The integrated ceramic composite firewall is an improvement over existing metallic firewall technology. This technology reduces cost, part count, weight, and manufacturing complexity of composites, which require fire protection. The integrated ceramic composite firewall material and process incorporates ceramic fabric and film adhesive into one unique material.
Technical Paper

Fuel Tank Safety on Airplanes

2005-10-03
2005-01-3428
There have been 17 fuel tank ignition events on commercial airplanes since 1959 that have resulted in 542 fatalities and 11 airplane losses. On the military side there have been 12 airplane losses on military version of the B-707 and the B-52 airplanes. The Most notable accident was the TWA 800 in July 1996 on the Boeing 747 which caused loss of 230 lives. This paper looks at the potential root causes of fuel tank explosions and the corrective actions that industry can undertake to minimize the hazard of fuel tank explosions. Fuel tank flammability and ignition sources are considered. The areas looked at are design, installation, and maintenance. Compliance to Federal Airworthiness Regulation are reviewed.
Technical Paper

System Software Safety Assessment Process for Certification of Commercial and Military Aircraft

2005-10-03
2005-01-3390
For the next 10 years new world-wide communication, navigation, and surveillance (CNS) requirements are being incrementally imposed upon military aircraft avionics, and upon the Air Traffic Control community, by the Aviation Administrations of most nations, including the FAA and the JAA. These requirements are the result of a decade of study by the United Nations' International Civil Aviation Organization (ICAO) to improve aviation safety and efficiency. In 2001 the USAF mandated compliance to the CNS requirements for its military aircraft, which is called Navigation Safety (NS) GATM by the USAF. By complying with these requirements, the military aircraft can maintain their ability to fly internationally without CNS restrictions. The FAA requires that flight software be assessed, developed and/or verified (proven) with a methodology recommended by the RTCA document called DO-178B for software based systems.
Technical Paper

Centrifuge Accommodation Module (CAM) Cabin Air Temperature and Humidity Control Analysis

2005-07-11
2005-01-2801
The Centrifuge Accommodation Module (CAM) is designed to be one of the modules of the International Space Station (ISS) for performing on-orbit science experiments over an extended period of time. The common cabin air assembly (CCAA) is utilized as the hardware for air temperature and humidity control (THC) for the CAM module cabin. The CCAA unit contains a variable speed fan, heat exchanger, temperature control valve, water separator, temperature sensor, and electrical interface box. A temperature and humidity simulation model was developed to perform the THC analysis for the CCAA unit inside the CAM. This model applies both fixed control volume and a quasi-steady-state approach for computing critical information for evaluating/assessing CCAA system performance and capabilities.
Technical Paper

International Space Station Mobile Dosimetry Unit: A Comparison of Flight Measurements With Model Calculations

2004-07-19
2004-01-2277
Space radiation measurements were made on the International Space Station (ISS) with the Bulgarian Liulin-E094 Mobile Dosimetry Units (MDU) during 2001. The Liulin-E094 was part of the Dosimetric Mapping experiment lead by Dr. G. Reitz, DLR. Four MDUs were placed at fixed locations: one unit in the ISS “Unity” Node-1 and three units were located in the US Laboratory module. Space radiation flight measurements were obtained during the time period May 11 – July 26, 2001. In this paper we discuss the development of an MDU shielding model using combinatorial geometry and 3-D visualization and the orientation and placement at the four locations within the ISS. Four shielding distributions were generated for the combined ISS and MDU shielding models. The AP8MAX trapped proton model was used to compute the daily absorbed dose for the four MDUs and are compared with the flight measurements.
Technical Paper

Depth Dose Exposures in the Magnetosphere of Jupiter at the Icy Moons: Callisto, Ganymede, and Europa

2004-07-19
2004-01-2326
The highly successful Galileo mission made a number of startling and remarkable discoveries during its eight-year tour in the harsh Jupiter radiation environment. Two of these revelations were: 1) salty oceans lying under an icy crust of the Galilean moons: Europa, Ganymede and Callisto, and 2) the possible existence or remnants of life, especially on Europa, which has a very tenuous atmosphere of oxygen. Galileo radiation measurement data from the Energetic Particle Detector (EPD) have been used (Garrett et al., 2003) to update the trapped electron environment model, GIRE: Galileo Interim Radiation Environment, in the range of L (L: McIlwain parameter – see ref. 6) = 8–16 Rj (Rj: radius of Jupiter ≈ 71,400 km) with plans to extend the model for both electrons and protons as more data are reduced and analyzed.
Technical Paper

Selection of an Alternate Biocide for the ISS Internal Thermal Control System Coolant - Phase II

2004-07-19
2004-01-2472
The ISS (International Space Station) ITCS (Internal Thermal Control System) includes two internal coolant loops that utilize an aqueous based coolant for heat transfer. A silver salt biocide had previously been utilized as an additive in the coolant formulation to control the growth and proliferation of microorganisms within the coolant loops. Ground-based and in-flight testing demonstrated that the silver salt was rapidly depleted, and did not act as an effective long-term biocide. Efforts to select an optimal alternate biocide for the ITCS coolant application have been underway and are now in the final stages. An extensive evaluation of biocides was conducted to down-select to several candidates for test trials and was reported on previously.
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