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At least 55 records · Page 3

Space Shuttle Thermal Protection System Repair Flight Experiment Induced Contamination Impacts

NASA s activities to prepare for Flight LF1 (STS-114) included development of a method to repair the Thermal Protection System (TPS) of the Orbiter s leading edge should it be damaged during ascent by impacts from foam, ice, etc . Reinforced Carbon-Carbon (RCC) is used for the leading edge TPS. The repair material that was developed is named Non- Oxide Adhesive eXperimental (NOAX). NOAX is an uncured adhesive material that acts as an ablative repair material. NOAX completes curing during the Orbiter s descent. The Thermal Protection System (TPS) Detailed Test Objective 848 (DTO 848) performed on Flight LF1 (STS-114) characterized the working life, porosity void size in a micro-gravity environment, and the on-orbit performance of the repairs to pre-damaged samples. DTO 848 is also scheduled for Flight ULF1.1 (STS-121) for further characterization of NOAX on-orbit performance. Due to the high material outgassing rates of the NOAX material and concerns with contamination impacts to optically sensitive surfaces, ASTM E 1559 outgassing tests were performed to determine NOAX condensable outgassing rates as a function of time and temperature. Sensitive surfaces of concern include the Extravehicular Mobility Unit (EMU) visor, cameras, and other sensors in proximity to the experiment during the initial time after application. This paper discusses NOAX outgassing characteristics, how the amount of deposition on optically sensitive surfaces while the NOAX is being manipulated on the pre-damaged RCC samples was determined by analysis, and how flight rules were developed to protect those optically sensitive surfaces from excessive contamination where necessary.

Smith, Kendall A.↗

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density polyurethane foam, BX-250. Challenges in modeling the RCC include its extreme brittleness, the differing behavior in compression and tension, and the anisotropic fabric layup. These effects were successfully included in LS-DYNA Material Model 58, *MAT_LAMINATED_ COMPOSITE_ FABRIC. The differing compression and tension behavior was modeled using the available damage parameters. Each fabric layer was given an integration point in the shell element, and was allowed to fail independently. Comparisons were made to static test data and coupon ballistic impact tests before being utilized in the full scale analysis. The foam's properties were typical of elastic automotive foams; and LS-DYNA Material Model 83, *MAT_FU_CHANG_FOAM, was successfully used to model its behavior. Material parameters defined included strain rate dependent stress-strain curves for both loading and un-loading, and for both compression and tension. This model was formulated with static test data and strain rate dependent test data, and was compared to ballistic impact tests on load-cell instrumented aluminum plates. These models were subsequently utilized in analysis of the Shuttle leading edge full scale ballistic impact tests, and are currently being used in the Return to Flight Space Shuttle re-certification effort.

Carney, Kelly↗

NASA advanced aeronautics design solar powered remotely piloted vehicle

Environmental problems such as the depletion of the ozone layer and air pollution demand a change in traditional means of propulsion that is sensitive to the ecology. Solar powered propulsion is a favorable alternative that is both ecologically harmless as well as cost effective. Integration of solar energy into designs ranging from futuristic vehicles to heating is beneficial to society. The design and construction of a Multi-Purpose Remotely Piloted Vehicle (MPRPV) seeks to verify the feasibility of utilizing solar propulsion as a primary fuel source. This task has been a year long effort by a group of ten students, divided into five teams, each dealing with different aspects of the design. The aircraft was designed to take-off, climb to the design altitude, fly in a sustained figure-eight flight path, and cruise for approximately one hour. This mission requires flight at Reynolds numbers between 150,000 and 200,000 and demands special considerations in the aerodynamic design in order to achieve flight in this regime. Optimal performance requires a light weight configuration with both structural integrity and maximum power availability. The structure design and choice of solar cells for the propulsion was governed by the weight, efficiency, and cost considerations. The final design is a MPRPV weighting 35 N which cruises 7 m/s at the design altitude of 50 m. The configuration includes a wing composed of balsa and foam NACA 6409 airfoil sections and carbon fiber spars, a tail of similar construction, and a truss structure fuselage. The propulsion system consists of 98 10 percent efficient solar cells donated by Mobil Solar, a NiCad battery for energy storage, and a folding propeller regulated by a lightweight and efficient control system. The airfoils and propeller chosen for the design were research and tested during the design process.

Elario, David S.↗

Solar powered multipurpose remotely powered aircraft

Environmental problems such as the depletion of the ozone layer and air pollution demand a change in traditional means of propulsion that is sensitive to the ecology. Solar-powered propulsion is a favorable alternative that is both ecologically harmless as well as cost effective. Integration of solar energy into designs ranging from futuristic vehicles to heating is, therefore, beneficial to society. The design and construction of a Multipurpose Remotely Piloted Vehicle (MPRPV) seeks to verify the feasibility of using solar propulsion as a primary fuel source. This task has been a year-long effort by a group of eight students, divided into four teams, each dealing with different aspects of the design. The aircraft was designed to take off, climb to the design altitude, fly in a sustained figure-eight flight path, and cruise for approximately one hour. This mission requires flight at Reynolds numbers between 150,000 and 200,000 and demands special considerations in the aerodynamic design to achieve flight in this regime. Optimal performance requires a lightweight configuration with both structural integrity and maximum power availability. The structural design and choice of solar cells for the propulsion were governed by weight, efficiency, and cost considerations. The final design is an MPRPV weighing 35 N that cruises at 7 m/s at the design altitude of 50 m. The configuration includes a wing composed of balsa and foam NACA 6409 airfoil sections and carbon fiber spars, a tail of similar construction, and a truss structure fuselage. The propulsion system consists of 98 12.5 percent-efficient solar cells donated by Mobil Solar, a NiCad battery for energy storage, and a folding propeller regulated by a lightweight and efficient control system. The airfoils and propeller chosen for the design were researched and tested during the design process.

Source record↗

Composite sandwich construction with syntactic foam core - A practical assessment of post-impact damage and residual strength

An account is given of an inspection method that has been successfully used to assess the postimpact damage and residual strength of syntactic (glass microspheres in epoxy matrix) foam-core sandwich panels with hybrid (carbon and glass fiber-reinforced) composite skins, which inherently possess high damage tolerance. SEM establishes that the crushing of the microspheres is responsible for the absorption of most of the impact energy. Damage tolerance is a function of the localization of damage by that high impact energy absorption.

Hiel, C.↗

STS-114: Discovery Return to Flight: Langley Engineers Analysis Briefing

This video features a briefing on NASA Langley Research Center (LaRC) contributions to the Space Shuttle fleet's Return to Flight (RTF). The briefing is split into two sections, which LaRC Shuttle Project Manager Robert Barnes and Deputy Manager Harry Belvin deliver in the form of a viewgraph presentation. Barnes speaks about LaRC contributions to the STS-114 mission of Space Shuttle Discovery, and Belvin speaks about LaRC contributions to subsequent Shuttle missions. In both sections of the briefing, LaRC contributions are in the following areas: External Tank (ET), Orbiter, Systems Integration, and Corrosion/Aging. The managers discuss nondestructive and destructive tests performed on ET foam, wing leading edge reinforced carbon-carbon (RCC) composites, on-orbit tile repair, aerothermodynamic simulation of reentry effects, Mission Management Team (MMT) support, and landing gear tests. The managers briefly answer questions from reporters, and the video concludes with several short video segments about LaRC contributions to the RTF effort.

Source record↗

Impact Testing on Reinforced Carbon-Carbon Flat Panels with Ice Projectiles for the Space Shuttle Return to Flight Program

Following the tragedy of the Orbiter Columbia (STS-107) on February 1, 2003, a major effort commenced to develop a better understanding of debris impacts and their effect on the space shuttle subsystems. An initiative to develop and validate physics-based computer models to predict damage from such impacts was a fundamental component of this effort. To develop the models it was necessary to physically characterize reinforced carbon-carbon (RCC) along with ice and foam debris materials, which could shed on ascent and impact the orbiter RCC leading edges. The validated models enabled the launch system community to use the impact analysis software LS-DYNA (Livermore Software Technology Corp.) to predict damage by potential and actual impact events on the orbiter leading edge and nose cap thermal protection systems. Validation of the material models was done through a three-level approach: Level 1--fundamental tests to obtain independent static and dynamic constitutive model properties of materials of interest, Level 2--subcomponent impact tests to provide highly controlled impact test data for the correlation and validation of the models, and Level 3--full-scale orbiter leading-edge impact tests to establish the final level of confidence for the analysis methodology. This report discusses the Level 2 test program conducted in the NASA Glenn Research Center (GRC) Ballistic Impact Laboratory with ice projectile impact tests on flat RCC panels, and presents the data observed. The Level 2 testing consisted of 54 impact tests in the NASA GRC Ballistic Impact Laboratory on 6- by 6-in. and 6- by 12-in. flat plates of RCC and evaluated three types of debris projectiles: Single-crystal, polycrystal, and "soft" ice. These impact tests helped determine the level of damage generated in the RCC flat plates by each projectile and validated the use of the ice and RCC models for use in LS-DYNA.

Melis, Matthew E.↗

Compression After Impact Strength Comparison of Rohacell Foam and Aluminum Honeycomb Core Sandwich Structure

This Technical Memorandum is a follow-on study to a previous one1 that examined the compression after impact (CAI) strength of carbon fiber sandwich structure with aluminum honeycomb core and Rohacell foam core with barely visible impact damage (BVID). In this current study a wider range of impact energies were utilized and the CAI strength assessed with these different damage severity levels. This was done to provide a more complete database for the two types of sandwich structure tested in these studies. In addition, the honeycomb sandwich specimens were tested with both the ‘L’ and ‘W’ directions aligned with the axis of compression loading. As in the study examining CAI strength with BVID1, the results were normalized by the mass of the sandwich structure. The results showed that the CAI strength did differ depending on the orientation of the core during testing and that when tested in the W-direction, the honeycomb core sandwich structure had about the same CAI strength as the foam core sandwich structure when normalized by the mass of the sandwich structures.

Sandwich Structure↗

Return to Flight Resource Reel 1 of 2

A video presentation detailing the tests performed on the Space Shuttle Discovery in preparation for its return to flight is shown. The tests include: 1) Reinforced Carbon-Carbon (RCC) Impact Test Article; 2) RCC Foam Impact Testing; 3) Thermal Protection System (TPS) Ice Impact Testing featuring Justin Kerr, Project Engineer; 4) Wing Leading Edge Wireless Sensors featuring Karl Kiefer, President and CEO of Invocon, and Kevin Champaigne of Invocon; 5) TPS Repair Testing KC-135 Zero-G Environment featuring Soichi Noguchi, Mission Specialist; 6) TPS Extravehicular Activity Tool Demonstration; 7) TPS Repair Testing Vacuum Glove box; 8) TPS Repair Testing Human Thermal Vacuum Chamber; 9) TPS Reentry Testing Atmospheric Reentry Materials and Structures Evaluation Facility; 10) TPS Alternative Repair Concept; 11) Lora Bailey Lead Engineer for EVA Tools; 12) Reinforced Carbon-Carbon ATK Thiokol Plug Repair Animation; 13) 3-Percent Model Build-Up; and 14) Wind Tunnel Testing RCC Aging Research Ballistic Testing.

Source record↗

Process for the manufacture of low density bis-maleimide-carbon microballoon composites

A process for the preparation of composite laminate structures of glass cloth preimpregnated with polybismaleimide resin and adhered to a polybismaleimide-glass or aromatic polyamide paper honeycomb cell structure filled or partially filled with a syntactic foam consisting of a mixture of bismaleimide resin and carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic microballoons and subsequently bonded using a 2% bismaleimide solution. The laminate structures are cured for two hours at 477.degree. K. and are adhered to the honeycomb bismaleimide adhesive using a pressure of 700 kN/m.sup.2 pressure at 450.degree. K. The laminate composite is then post-cured for two hours at 527.degree. K. to produce a composite laminate having a density in the range from about 95 kilograms per cubic meter to 130 kilograms per cubic meter.

Kourtides, Demetrius A.↗

Low density bismaleimide-carbon microballoon composites

A process is described for the preparation of composite laminate.structures of glass cloth preimpregnated with polybismaleimide resin and adhered to a polybismaleimide glass or aromatic polyamide paper honeycomb cell structure that is filled or partially filled with a syntactic foam consisting of a mixture of bismaleimide resin and carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic microballoons and subsequently bonded using a 2% bismaleimide solution. The laminate structures are cured for two hours at 477 deg K and are adhered to the honeycomb bismaleimide adhesive using a pressure of 700 KN/sq m pressure at 450 deg K. The laminate composite is then post-cured for two hours at 527 deg K to produce a composite laminate having a density in the range from about 95 kilograms per cubic meter to 130 kilograms per cubic meter.

Kourtides, D. A.↗

Development and Evaluation of Stitched Sandwich Panels

This study explored the feasibility and potential benefits provided by the addition of through-the-thickness reinforcement to sandwich structures. Through-the-thickness stitching is proposed to increase the interlaminar strength and damage tolerance of composite sandwich structures. A low-cost, out-of-autoclave processing method was developed to produce composite sandwich panels with carbon fiber face sheets, a closed-cell foam core, and through-the-thickness Kevlar stitching. The sandwich panels were stitched in a dry preform state, vacuum bagged, and infiltrated using Vacuum Assisted Resin Transfer Molding (VARTM) processing. For comparison purposes, unstitched sandwich panels were produced using the same materials and manufacturing methodology. Test panels were produced initially at the University of Utah and later at NASA Langley Research Center. Four types of mechanical tests were performed: flexural testing, flatwise tensile testing, core shear testing, and edgewise compression testing. Drop-weight impact testing followed by specimen sectioning was performed to characterize the damage resistance of stitched sandwich panels. Compression after impact (CAI) testing was performed to evaluate the damage tolerance of the sandwich panels. Results show significant increases in the flexural stiffness and strength, out-of-plane tensile strength, core shear strength, edgewise compression strength, and compression-after-impact strength of stitched sandwich structures.

Stanley, Larry E.↗

Test and Analysis Correlation of Form Impact onto Space Shuttle Wing Leading Edge RCC Panel 8

Soon after the Columbia Accident Investigation Board (CAIB) began their study of the space shuttle Columbia accident, "physics-based" analyses using LS-DYNA were applied to characterize the expected damage to the Reinforced Carbon-Carbon (RCC) leading edge from high-speed foam impacts. Forensic evidence quickly led CAIB investigators to concentrate on the left wing leading edge RCC panels. This paper will concentrate on the test of the left-wing RCC panel 8 conducted at Southwest Research Institute (SwRI) and the correlation with an LS-DYNA analysis. The successful correlation of the LS-DYNA model has resulted in the use of LS-DYNA as a predictive tool for characterizing the threshold of damage for impacts of various debris such as foam, ice, and ablators onto the RCC leading edge for shuttle return-to-flight.

Fasanella, Edwin L.↗

Simulation of Foam Impact Effects on Components of the Space Shuttle Thermal Protection System

A series of three dimensional simulations has been performed to investigate analytically the effect of insulating foam impacts on ceramic tile and reinforced carbon-carbon components of the Space Shuttle thermal protection system. The simulations employed a hybrid particle-finite element method and a parallel code developed for use in spacecraft design applications. The conclusions suggested by the numerical study are in general consistent with experiment. The results emphasize the need for additional material testing work on the dynamic mechanical response of thermal protection system materials, and additional impact experiments for use in validating computational models of impact effects.

Fahrenthold, Eric P.↗

Development of the International Space Station (ISS) Fine Water Mist (FWM) Portable Fire Extinguisher

NASA is developing a Fine Water Mist Portable Fire Extinguisher for use on the International Space Station. The International Space Station presently uses two different types of fire extinguishers: a water foam extinguisher in the Russian Segment, and a carbon dioxide extinguisher in the US Segment and Columbus and Kibo pressurized elements. Changes in emergency breathing equipment make Fine Water Mist operationally preferable. Supplied oxygen breathing systems allow for safe discharge of a carbon dioxide fire extinguisher, without concerns of the crew inhaling unsafe levels of carbon dioxide. But the Portable Breathing Apparatus (PBA) offers no more than 15 minutes of capability, and continued use of hose based supplied oxygen system increases the oxygen content in a fire situation. NASA has developed a filtering respirator cartridge for use in a fire environment. It is qualified to provide up to 90 minutes of capability, and because it is a filtering respirator it does not add oxygen to the environment. The fire response respirator cartridge does not filter carbon dioxide (CO2), so a crew member discharging a CO2 fire extinguisher while wearing this filtering respirator would be at risk of inhaling unsafe levels of CO2. Fine Water Mist extinguishes a fire without creating a large volume of air with reduced oxygen and elevated CO2. From a flight hardware design perspective, the fine water mist fire extinguisher has two major elements: (1) the nozzle and crew interface, and (2) the tank. The nozzle and crew interface has been under development for several years. It has gone through several design iterations, and has been part of more than 400 fire challenge and spray characterizations. The crew and vehicle interface aspects of the design will use the heritage of the CO2 based Portable Fire Extinguisher, to minimize the disruption to the crew and integration impacts to the ISS. The microgravity use environment of the system poses a set of unique design requirements specifically for the tank. The nozzle requirements drive a tank pressure that is 2-5 times higher than any commercially available water mist systems. Microgravity requires deliberate separation of gas and water, facilitated by a bladder, a diaphragm, a piston, or separate tanks. This paper will describe the design details of the tank and the nozzle, and discuss the trade studies that informed the decisions to select the tank and nozzle configuration.

Clements, Anna L.↗

Developing Standards to Qualify a Fine Water Mist Fire Extinguisher for Human Spaceflight

NASA is developing a Fine Water Mist Portable Fire Extinguisher for use on the International Space Station. The International Space Station presently uses two different types of fire extinguishers: a water foam extinguisher in the Russian Segment, and a carbon dioxide extinguisher in the US Segment and Columbus and Kibo pressurized elements. Changes in emergency breathing equipment make Fine Water Mist operationally preferable. Supplied oxygen breathing systems allow for safe discharge of a carbon dioxide fire extinguisher, without concerns of the crew inhaling unsafe levels of carbon dioxide. But the Portable Breathing Apparatus offers no more than 15 minutes of capability, and continued use of hose based supplied oxygen systems increases the oxygen content in a fire situation. NASA has developed a filtering respirator cartridge for use in a fire environment. It is qualified to provide up to 90 minutes of capability, and because it is a filtering respirator it does not add oxygen to the environment. The fire response respirator cartridge does not filter carbon dioxide, so a crew member discharging a CO2 fire extinguisher while wearing this filtering respirator would be at risk of inhaling unsafe levels of CO2. Fine Water Mist extinguishes a fire without creating a large volume of air with reduced oxygen and elevated CO2. Compared to the carbon dioxide based Portable Fire Extinguisher, the flight qualification of Fine Water Mist systems requires special care. Qualification of the CO2 based Portable Fire Extinguisher began with the assumption that any fire on ISS would be extinguished if the air in the fire environment reached a critical concentration of CO2. Qualification of a CO2 based system requires the developers to make assertions and assumptions about vehicle geometry and the ability of the extinguisher to deliver CO2 in different geometric configurations, but the developers did not need to make assertions or assumptions about the size of the fire, the temperature, or the heat generation rate. Fine Water Mist systems extinguish a fire predominantly by removing heat -- so qualification standards must evaluate geometry, but also temperature, heat transfer, and heat generation rate. This paper outlines and describes the methods used to develop standards used to qualify Fine Water Mist systems for a human spaceflight environment.

Graf, John↗

Development of the International Space Station (ISS) Fine Water Mist (FWM) Portable Fire Extinguisher ICES Abstract

NASA is developing a Fine Water Mist (FWM) Portable Fire Extinguisher (PFE) for use on the International Space Station. The International Space Station presently uses two different types of fire extinguishers: a water foam extinguisher in the Russian Segment, and a carbon dioxide extinguisher in the US Segment and Columbus and Kibo pressurized elements. Changes in emergency breathing equipment make Fine Water Mist operationally preferable. Supplied oxygen breathing systems allow for safe discharge of a carbon dioxide fire extinguisher, without concerns of the crew inhaling unsafe levels of carbon dioxide. But the Portable Breathing Apparatus (PBA) offers no more than 15 minutes of capability, and continued use of hose based supplied oxygen system increases the oxygen content in a fire situation. NASA has developed a filtering respirator cartridge for use in a fire environment. It is qualified to provide up to 90 minutes of capability, and because it is a filtering respirator it does not add oxygen to the environment. The fire response respirator cartridge does not filter carbon dioxide (CO2), so a crew member discharging a CO2 fire extinguisher while wearing this filtering respirator would be at risk of inhaling unsafe levels of CO2. FWM extinguishes a fire without creating a large volume of air with reduced oxygen and elevated CO2. The following paper will discuss the unique functional and performance requirements that have been levied on the FWM PFE. In addition, the NASA ISS specific fire standards will be described which were developed to establish acceptable extinguisher performance. The paper will also discuss the flight hardware design. The fin e water mist fire extinguisher has two major elements: (1) the nozzle and crew interface, and (2) the tank. The nozzle and crew interface have been under development for several years. They have gone through several design iterations, and have been part of more than 400 fire challenge and spray characterizations. The crew and vehicle interface aspects of the design will use the heritage of the CO2 based Portable Fire Extinguisher, to minimize the disruption to the crew and integration impacts to the ISS. The microgravity use environment of the system poses a set of unique design requirements specifically for the tank. The nozzle requirements drive a tank pressure that is 2-5 times higher than any commercially available water mist systems. Microgravity requires deliberate separation of gas and water, facilitated by a bladder, a diaphragm, a piston, or separate tanks. This paper will describe status of the project to date, the design details of the tank and the nozzle, and discuss the trade studies that informed the decisions to select the tank and nozzle configuration.

Clements, Anna L.↗

Development of the International Space Station (ISS) Fine Water Mist (FWM) Portable Fire Extinguisher

The National Aeronautics and Space Administration (NASA) is developing a Fine Water Mist (FWM) Portable Fire Extinguisher (PFE) for use on the International Space Station (ISS). The ISS presently uses two different types of fire extinguishers: a water foam extinguisher in the Russian Segment, and a carbon dioxide extinguisher in the United States Orbital Segments, which include Columbus and Kibo pressurized elements. Currently, there are operational concerns with the emergency breathing equipment and the carbon dioxide extinguisher. The toxicity of the carbon dioxide requires the crew members to have an oxygen supply present during a fire event, therefore inherently creating an unsafe environment. The FWM PFE extinguishes a fire without creating a hazardous breathing environment for crew members. The following paper will discuss the unique functional and performance requirements that have been levied on the FWM PFE, identify unique microgravity design considerations for liquid and gas systems, as well as discuss the NASA ISS specific fire standards that were developed to establish an acceptable portable fire extinguisher s performance.

Rodriquez, Branelle↗