Search Results

To improve the fatigue properties of additive manufactured (AM) titanium alloy Ti6Al4V, cavitation abrasive surface finishing (CASF) was proposed. With CASF, a high-speed water jet with cavitation, i.e. a cavitating jet, was injected into a water-filled chamber, to which abrasives were added. Abrasives accelerated by the jet created a smooth surface by removing un-melted particles on the surface. Simultaneously, cavitation impacts induced by the jet introduced compressive residual stress and work hardening into the surface, similar to cavitation peening. In this study, to demonstrate the improvement of the fatigue properties of AM Ti6Al4V owing to CASF, Ti6Al4V specimens manufactured through direct metal laser sintering (DMLS) and electron beam melting (EBM) were treated using CASF and cavitation peening, and tested using a plane bending fatigue test.

Titanium’s high strength-to-weight ratio and corrosion resistance makes it ideal for many aerospace applications, especially in heat critical zones. Superplastic Forming (SPF) can be used to form titanium into near-net, complex shapes without springback. The process uses a machined die where inert gas is applied uniformly to the metal sheet, forming the part into the die cavity. Standard titanium alpha-beta alloys, such as 6Al-4V, form at temperatures between 900 and 925°C (1650-1700°F). Recent efforts have demonstrated alloys that form at lower temperatures ranging between 760 and 790°C (1400-1450°F). Lowering the forming temperature reduces the amount of alpha case that forms on the part, which must be removed. This provides an opportunity of starting with a lower gauge material. Lower forming temperatures also limit the amount of oxidation and wear on the tool and increase the life of certain press components, such as heaters and platens.

The past twenty years have seen tremendous changes in the Avionics display and flight deck lighting due to the application of solid-state LED (light emitting diode) light sources and LCDs (liquid crystal displays). These advances significantly benefit the customer and pilot users when integrated correctly. This paper discusses recommended practices and guidance given in SAE ARP 4103 for modern Avionics flight deck lighting systems to satisfy the end user and obtain certification. SAE ARP 4103 Flight Deck Lighting for Commercial Transport Aircraft has recently been revised to keep up with the Avionics state-of-the-art and add clarification where needed. ARP 4103 contains recommended Avionics flight deck lighting design and performance criteria to ensure prompt and accurate readability and visibility, color identification and discrimination of needed information under all expected ambient lighting and electrical power conditions. For additional details, see the actual ARP 4103.

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.

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.

Environmental Control Systems (ECS) ducts on airplanes are primarily fabricated from aluminum or thermoset composites, depending on temperature and pressure requirements. It is imperative to fabricate lightweight, cost effective, durable, and repairable systems with minimal tooling. It is also important that the duct systems are easy to assemble even with alignment issues resulting from structural variations, tolerance accumulation, variation from thermal expansion of different materials, and inherent duct stiffness. These requirements create an opportunity and need for a technology that can address all of these issues, while increasing performance at the same time. This report provides a background on current ECS ducting systems.

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.

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.

The objective of this study is to evaluate ventilation efficiency regarding to the International Space Station (ISS) cabin ventilation during the ISS assembly mission 1J. The focus is on carbon dioxide spatial/temporal variations within the Node 2 and attached modules. An integrated model for CO2 transport analysis that combines 3D CFD modeling with the lumped parameter approach has been implemented. CO2 scrubbing from the air by means of two ISS removal systems is taken into account. It has been established that the ventilation scheme with an ISS Node 2 bypass duct reduces short-circuiting effects and provides less CO2 gradients when the Space Shuttle Orbiter is docked to the ISS. This configuration results in reduced CO2 level within the ISS cabin.

The International Space Station (ISS) requires stores of Oxygen (O2) and Nitrogen (N2) to provide for atmosphere replenishment, direct crew member usage, and payload operations. Currently, supplies of N2/O2 are maintained by transfer from the Space Shuttle. Following Space Shuttle retirement in 2010, an alternate means of resupplying N2/O2 to the ISS is needed. The National Aeronautics and Space Administration (NASA) has determined that the optimal method of supplying the ISS with O2/N2 is using tanks of high pressure N2/O2 carried to the station by a cargo vehicle capable of docking with the ISS. This paper will outline the architecture of the system selected by NASA and will discuss some of the design challenges associated with this use of high pressure oxygen and nitrogen storage in the human spaceflight environment.

The International Space Station (ISS) Payload Engineering Integration (PEI) organization has developed the critical capabilities in dynamic circuit modeling and simulation to analyze electrical system anomalies during testing and operation. This presentation provides an example of the processes, tools and analytical techniques applied to the improvement of science experiments over-voltage clamp circuit design which is widely used by ISS science experiments. The voltage clamp circuit of Science Rack exhibits parasitic oscillations when a voltage spike couples to the Field-Effect Transistor (FET) in the clamp circuit. The oscillation can cause partial or full conduction of the shunt FET in the circuit and may result in the destruction of the FET. In addition, the voltage clamp circuit is not designed to detect the high current through the FET, and this condition can result in damage to surrounding devices. These abnormal operations were analyzed by dynamic circuit simulation and tests.

The rising cost of fuel prices, in part due to the perception of diminishing supplies of common fuelstocks, as well as worldwide attention to reducing emissions has pushed the need to explore the use of many alternative fuels. The aviation industry has been under recent scrutiny due to its contribution of greenhouse gas emissions (GHG). Current contribution of GHG by airplanes is relatively small, 2% of the total GHG emissions, but world air traffic is anticipated to continue to grow and may have a corresponding increase in emissions. Both commercial and government aviation sectors have efforts to seek ways to lower fuel consumption through efficiency and reduce emissions. Development of a suitable alternative fuel that can be seamlessly used in place of conventional jet fuel is desirable. A strategy to enable this goal is to be fuel flexible; utilizing an array of fuels from bio-diesel to current jet fuel.

The new materials and material combinations such as composites and titanium combinations used on today's new airplanes are proving to be very challenging when drilling holes during manufacturing and assembly operations. Orbital hole drilling technology has shown a great deal of promise for generating burr free, high quality holes in hard metals and in composite materials. This paper will show some of the orbital drilling development work Boeing is doing with Novator to overcome the obstacles of drilling holes in a combination of both hard metals and composites. The paper will include a new portable orbital drilling system designed for these challenging applications as well as some test results achieved with this system.

Estimates of the effectiveness of the high-hydrogen containing materials, sodium alanate and ammonia borane, are made by calculating dose and dose equivalent for the 1977 solar minimum and 1970 solar maximum galactic cosmic ray spectra and for the large solar particle event spectra from the space era event of August 1972 and comparing their shielding effectiveness with that of polyethylene.

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.

This paper summarizes the first seven plus years of on-orbit operation for the Major Constituent Analyzer (MCA). The MCA is an essential part of the International Space Station (ISS) Environmental Control and Life Support System (ECLSS). The MCA is a mass spectrometer instrument in the US Destiny Laboratory Module, which provides critical monitoring of six major atmospheric constituents (nitrogen (N2), oxygen (O2), hydrogen (H2), carbon dioxide (CO2), methane (CH4), and water vapor (H2O)). These gases are sampled continuously and automatically in all United States On Orbit Segment (USOS) modules via the ISS Sample Delivery System (SDS). Continuous readout of the partial pressures of these gases is critical to verifying safe operation of the Atmosphere Re-vitalization (AR) system, Atmosphere Control System (ACS), and crew safety for Airlock Extravehicular Activity (EVA) preparation.

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.

The Carbon Dioxide Removal Assembly (CDRA) is a part of the International Space Station (ISS) Environmental Control and Life Support (ECLS) system. The CDRA provides carbon dioxide (CO2) removal from the ISS on-orbit modules. Currently, the CDRA is the secondary removal system on the ISS, with the primary system being the Russian Vozdukh. Within the CDRA are two Desiccant/Adsorbent Beds (DAB), which perform the carbon dioxide removal function. The DAB adsorbent containment approach required improvements with respect to adsorbent containment. These improvements were implemented through a redesign program and have been implemented on units on the ground and returning from orbit. This paper presents a DAB design modification implementation description, a hardware performance comparison between the unmodified and modified DAB configurations, and a description of the modified DAB hardware implementation into the on-orbit CDRA.

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.

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.