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Rivers, H. Kevin

Publications and source records attributed to Rivers, H. Kevin.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Optical Method for Detecting Displacements and Strains at Ultra-High Temperatures During Thermo-Mechanical Testing

An ultra-high temperature optical method incorporates speckle optics for sensing displacement and strain measurements well above conventional measurement techniques. High temperature pattern materials are used which can endure experimental high temperature environments while simultaneously having a minimum optical aberration. A purge medium is used to reduce or eliminate optical distortions and to reduce, and/or eliminate oxidation of the target specimen.

Smith, Russell W.↗
NASA NTRS2007

Portable Microleak-Detection System

The figure schematically depicts a portable microleak-detection system that has been built especially for use in testing hydrogen tanks made of polymer-matrix composite materials. (As used here, microleak signifies a leak that is too small to be detectable by the simple soap-bubble technique.) The system can also be used to test for microleaks in tanks that are made of other materials and that contain gases other than hydrogen. Results of calibration tests have shown that measurement errors are less than 10 percent for leak rates ranging from 0.3 to 200 cm3/min. Like some other microleak-detection systems, this system includes a vacuum pump and associated plumbing for sampling the leaking gas, and a mass spectrometer for analyzing the molecular constituents of the gas. The system includes a flexible vacuum chamber that can be attached to the outer surface of a tank or other object of interest that is to be tested for leakage (hereafter denoted, simply, the test object). The gas used in a test can be the gas or vapor (e.g., hydrogen in the original application) to be contained by the test object. Alternatively, following common practice in leak testing, helium can be used as a test gas. In either case, the mass spectrometer can be used to verify that the gas measured by the system is the test gas rather than a different gas and, hence, that the leak is indeed from the test object.

Rivers, H. Kevin↗
NASA NTRS2006

Advances in Hot-Structure Development

The National Aeronautics and Space Administration has actively participated in the development of hot structures technology for application to hypersonic flight systems. Hot structures have been developed for vehicles including the X-43A, X-37, and the Space Shuttle. These trans-atmospheric and atmospheric entry flight systems that incorporate hot-structures technology are lighter weight and require less maintenance than those that incorporate parasitic, thermal-protection materials that attach to warm or cool substructure. The development of hot structures requires a thorough understanding of material performance in an extreme environment, boundary conditions and load interactions, structural joint performance, and thermal and mechanical performance of integrated structural systems that operate at temperatures ranging from 1500 C to 3000 C, depending on the application. This paper will present recent advances in the development of hot structures, including development of environmentally durable, high temperature leading edges and control surfaces, integrated thermal protection systems, and repair technologies. The X-43A Mach-10 vehicle utilized carbon/carbon (C/C) leading edges on the nose, horizontal control surface, and vertical tail. The nose and vertical and horizontal tail leading edges were fabricated out of a 3:1 biased, high thermal conductivity C/C. The leading edges were coated with a three-layer coating comprised of a SiC conversion of the C/C, followed by a CVD layer of SiC, followed by a thin CVD layer of HfC. Work has also been performed on the development of an integrated structure and was focused on both hot and warm (insulated) structures and integrated fuselage/tank/TPS systems. The objective was to develop integrated multifunctional airframe structures that eliminate fragile external thermal-protection systems and incorporate the insulating function within the structure. The approach taken to achieve this goal was to develop candidate hypersonic airframe concepts, including structural arrangement, load paths, thermal-structural wall design, thermal accommodation features, and integration of major components, optimize thermalstructural configurations, and validate concepts through a building block test program and generate data to improve and validate analytical and design tools.

Rivers, H. Kevin↗
NASA NTRS2005

Thermal Structures Technology Development for Reusable Launch Vehicle Cryogenic Propellant Tanks

Analytical and experimental studies conducted at the NASA, Langley Research Center (LaRC) for investigating integrated cryogenic propellant tank systems for a reusable launch vehicle (RLV) are described. The cryogenic tanks are investigated as an integrated tank system. An integrated tank system includes the tank wall, cryogenic insulation, thermal protection system (TPS) attachment sub-structure, and TPS. Analysis codes are used to size the thicknesses of cryogenic insulation and TPS insulation for thermal loads, and to predict tank buckling strengths at various ring frame spacings. The unique test facilities developed for the testing of cryogenic tank components are described. Testing at cryogenic and high-temperatures verifies the integrity of materials, design concepts, manufacturing processes, and thermal/structural analyses. Test specimens ranging from the element level to the subcomponent level are subjected to projected vehicle operational mechanical loads and temperatures. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of light-weight reusable cryogenic propellant tanks.

Johnson, Theodore F.↗
NASA NTRS2002

Investigations of Control Surface Seals for Re-entry Vehicles

Re-entry vehicles generally require control surfaces (e.g., rudders, body flaps) to steer them during flight. Control surface seals are installed along hinge lines and where control surface edges move close to the vehicle body. These seals must operate at high temperatures and limit heat transfer to underlying structures to prevent them from overheating and causing possible loss of vehicle structural integrity. This paper presents results for thermal analyses and mechanical testing conducted on the baseline rudder/fin seal design for the X-38 re-entry vehicle. Exposure of the seals in a compressed state at the predicted peak seal temperature of 1900 F resulted in loss of seal resiliency. The vertical Inconel rudder/fin rub surface was re-designed to account for this loss of resiliency. Room temperature compression tests revealed that seal unit loads and contact pressures were below limits set to protect Shuttle thermal tiles on the horizontal sealing surface. The seals survived an ambient temperature 1000 cycle scrub test over sanded Shuttle tiles and were able to disengage and re-engage the tile edges during testing. Arc jet tests confirmed the need for seals in the rudder/fin gap location because a single seal caused a large temperature drop (delta T = 1710 F) in the gap.

Dunlap, Patrick H., Jr.↗
NASA NTRS2001

Detection of Micro-Leaks Through Complex Geometries Under Mechanical Load and at Cryogenic Temperature

Polymer Matrix Composite (PMC) hydrogen tanks have been proposed as an enabling technology for reducing the weight of Single-Stage-to-Orbit reusable launch vehicles where structural mass has a large impact on vehicle performance. A key development issue of these lightweight structures is the leakage of hydrogen through the composite material. The rate of hydrogen leakage can be a function of the material used, method of 6 fabrication used to manufacture the tank, mechanical load the tank must react, internal damage-state of the material, and the temperatures at which the tank must operate. A method for measuring leakage through a geometrically complex structure at cryogenic temperature and under mechanical load was developed, calibrated and used to measure hydrogen leakage through complex X-33 liquid-hydrogen tank structure sections.

Rivers, H. Kevin↗
NASA NTRS2000

Carbon-Carbon Piston Architectures

An improved structure for carbon-carbon composite piston architectures is disclosed. The improvement consists of replacing the knitted fiber, three-dimensional piston preform architecture described in U.S. Pat.No. 4,909,133 (Taylor et al.) with a two-dimensional lay-up or molding of carbon fiber fabric or tape. Initially, the carbon fabric of tape layers are prepregged with carbonaceous organic resins and/or pitches and are laid up or molded about a mandrel, to form a carbon-fiber reinforced organic-matrix composite part shaped like a "U" channel, a "T"-bar, or a combination of the two. The molded carbon-fiber reinforced organic-matrix composite part is then pyrolized in an inert atmosphere, to convert the organic matrix materials to carbon. At this point, cylindrical piston blanks are cored from the "U"-channel, "T"-bar, or combination part. These blanks are then densified by reimpregnation with resins or pitches which are subsequently carbonized. Densification is also accomplished by direct infiltration with carbon by vapor deposition processes. Once the desired density has been achieved, the piston billets are machined to final piston dimensions; coated with oxidation sealants; and/or coated with a catalyst. When compared to conventional steel or aluminum alloy pistons, the use of carbon-carbon composite pistons reduces the overall weight of the engine; allows for operation at higher temperatures without a loss of strength; allows for quieter operation; reduces the heat loss; and reduces the level of hydrocarbon emissions.

Rivers, H. Kevin↗
NASA NTRS2000

Carbon Fiber Reinforced Carbon Composite Rotary Valve for an Internal Combustion Engine

Carbon fiber reinforced carbon composite rotary sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or wrap-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties do not present the sealing and lubrication problems that have prevented rotary sleeve and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

Northam, G.Burton↗
NASA NTRS2000

Pistons and Cylinders Made of Carbon-Carbon Composite Materials

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon-carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin↗
NASA NTRS2000

IC Engine Applications of Carbon-Carbon

Many of the properties of carbon-carbon make it an ideal material for reciprocating materials of intermittent combustion (IC) engines. Recent diesel engine tests, shown herein, indicate that the thermal and mechanical properties of carbon-carbon are adequate for piston applications, However, reducing the manufacturing costs and providing long term oxidation protection are still issues that need to be addressed.

Northam, G. Burton↗
NASA NTRS1999

Method of Fabricating Chopped-Fiber Composite Piston

A three-dimensional piston molding is fabricated from a mixture of chopped, carbon tow filaments of variable length, which are prepregged with carbonaceous organic resins and/or pitches and molded by conventional molding processes into a near net shape, to form a carbon-fiber reinforced organic-matrix composite part. Continuous reinforcement in the form of carbon-carbon composite tapes or pieces of fabric can be also laid in the mold before or during the charging of the mold with the chopped-fiber mixture, to enhance the strength in the crown and wrist-pin areas. The molded chopped-fiber reinforced organic-matrix composite parts are then pyrolized in an inert atmosphere, to convert the organic matrix materials to carbon. These pyrolized parts are then densified by reimpregnation with resins or pitches, which are subsequently carbonized. Densification is also accomplished by direct infiltration with carbon by vapor deposition processes. Once the desired density has been achieved, the piston molds are machined to final piston dimensions, and piston ring grooves are added. To prevent oxidation and/or to seal the piston surface or near surface, the chopped-fiber piston is coated with ceramic and/or metallic sealants: and/or coated with a catalyst.

Rivers, H. Kevin↗
NASA NTRS1999

Cyclic Cryogenic Thermal-Mechanical Testing of an X-33/RLV Liquid Oxygen Tank Concept

An important step in developing a cost-effective, reusable, launch vehicle is the development of durable, lightweight, insulated, cryogenic propellant tanks. Current cryogenic tanks are expendable so most of the existing technology is not directly applicable to future launch vehicles. As part of the X-33/Reusable Launch Vehicle (RLV) Program, an experimental apparatus developed at the NASA Langley Research Center for evaluating the effects of combined, cyclic, thermal and mechanical loading on cryogenic tank concepts was used to evaluate cryogenic propellant tank concepts for Lockheed-Martin Michoud Space Systems. An aluminum-lithium (Al 2195) liquid oxygen tank concept, insulated with SS-1171 and PDL-1034 cryogenic insulation, is tested under simulated mission conditions, and the results of those tests are reported. The tests consists of twenty-five simulated Launch/Abort missions and twenty-five simulated flight missions with temperatures ranging from -320 F to 350 F and a maximum mechanical load of 71,300 lb. in tension.

Rivers, H. Kevin↗
NASA NTRS1999

Carbon Fiber Reinforced Carbon Composite Valve for an Internal Combustion Engine

A carbon fiber reinforced carbon composite valve for internal combustion engines and the like formed of continuous carbon fibers throughout the valve's stem and head is disclosed. The valve includes braided carbon fiber material over axially aligned unidirectional carbon fibers forming a valve stem; the braided and unidirectional carbon fibers being broomed out at one end of the valve stem forming the shape of the valve head; the valve-shaped structure being densified and rigidized with a matrix of carbon containing discontinuous carbon fibers: and the finished valve being treated to resist oxidation. Also disclosed is a carbon matrix plug containing continuous and discontinuous carbon fibers and forming a net-shape valve head acting as a mandrel over which the unidirectional and braided carbon fibers are formed according to textile processes. Also disclosed are various preform valves and processes for making finished and preform carbon fiber reinforced carbon composite valves.

Rivers, H. Kevin↗
NASA NTRS1999

Lightweight Exhaust Manifold and Exhaust Pipe Ducting for Internal Combustion Engines

An improved exhaust system for an internal combustion gasoline-and/or diesel-fueled engine includes an engine exhaust manifold which has been fabricated from carbon- carbon composite materials in operative association with an exhaust pipe ducting which has been fabricated from carbon-carbon composite materials. When compared to conventional steel. cast iron. or ceramic-lined iron paris. the use of carbon-carbon composite exhaust-gas manifolds and exhaust pipe ducting reduces the overall weight of the engine. which allows for improved acceleration and fuel efficiency: permits operation at higher temperatures without a loss of strength: reduces the "through-the wall" heat loss, which increases engine cycle and turbocharger efficiency and ensures faster "light-off" of catalytic converters: and, with an optional thermal reactor, reduces emission of major pollutants, i.e. hydrocarbons and carbon monoxide.

Northam, G. Burton↗
NASA NTRS1999

Carbon Fiber Reinforced Carbon Composites Rotary Valves for Internal Combustion Engines

Carbon fiber reinforced carbon composite rotary, sleeve, and disc valves for internal combustion engines and the like are disclosed. The valves are formed from knitted or braided or warp-locked carbon fiber shapes. Also disclosed are valves fabricated from woven carbon fibers and from molded carbon matrix material. The valves of the present invention with their very low coefficient of thermal expansion and excellent thermal and self-lubrication properties, do not present the sealing and lubrication problems that have prevented rotary, sleeve, and disc valves from operating efficiently and reliably in the past. Also disclosed are a sealing tang to further improve sealing capabilities and anti-oxidation treatments.

Northam, G. Burton↗
NASA NTRS1999

Carbon-Carbon Piston Architectures

An improved structure for carbon-carbon composite piston architectures consists of replacing the knitted fiber, three-dimensional piston preform architecture described in U.S. Pat. No. 4.909,133 (Taylor et al.) with a two-dimensional lay-up or molding of carbon fiber fabric or tape. Initially. the carbon fabric or tape layers are prepregged with carbonaceous organic resins and/or pitches and are laid up or molded about a mandrel. to form a carbon-fiber reinforced organic-matrix composite part shaped like a "U" channel, a "T"-bar. or a combination of the two. The molded carbon-fiber reinforced organic-matrix composite part is then pyrolized in an inert atmosphere, to convert the organic matrix materials to carbon. At this point, cylindrical piston blanks are cored from the "U" channel, "T"-bar, or combination part. These blanks are then densified by reimpregnation with resins or pitches which are subsequently carbonized. Densification is also be accomplished by direct infiltration with carbon by vapor deposition processes. Once the desired density has been achieved, the piston billets are machined to final piston dimensions; coated with oxidation sealants; and/or coated with a catalyst. When compared to conventional steel or aluminum-alloy pistons, the use of carbon-carbon composite pistons reduces the overall weight of the engine; allows for operation at higher temperatures without a loss of strength; allows for quieter operation; reduces the heat loss; and reduces the level of hydrocarbon emissions.

Rivers, H. Kevin↗
NASA NTRS1999

Process for Making Carbon-Carbon Turbocharger Housing Unit for Intermittent Combustion Engines

An improved. lightweight, turbine housing unit for an intermittent combustion reciprocating internal combustion engine turbocharger is prepared from a lay-up or molding of carbon-carbon composite materials in a single-piece or two-piece process. When compared to conventional steel or cast iron, the use of carbon-carbon composite materials in a turbine housing unit reduces the overall weight of the engine and reduces the heat energy loss used in the turbo-charging process. This reduction in heat energy loss and weight reduction provides for more efficient engine operation.

Northam, G. Burton↗