Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “protective structures”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Glenn Refractory Adhesive for Bonding and Exterior Repair (GRABER) Developed for Repairing Shuttle Damage

Advanced in-space repair technologies for reinforced carbon/carbon composite (RCC) thermal protection system (TPS) structures are critically needed for the space shuttle Return To Flight (RTF) efforts. These technologies are also critical for the repair and refurbishment of thermal protection system structures of future Crew Exploration Vehicles of space exploration programs. The Glenn Refractory Adhesive for Bonding and Exterior Repair (GRABER) material developed at the NASA Glenn Research Center has demonstrated capabilities for repair of small cracks and damage in RCC leading-edge material. The concept consists of preparing an adhesive paste of desired ceramic in a polymer/phenolic resin matrix with appropriate additives, such as surfactants, and then applying the paste into the damaged or cracked area of the RCC composite components with caulking guns. The adhesive paste cures at 100 to 120 C and transforms into a high-temperature ceramic during simulated vehicle reentry testing conditions.

Singh, Mrityunjay↗
NASA NTRS1974

Thermal-Structural Evaluation of TD Ni-20Cr Thermal Protection System Panels

The results of a thermal-structural test program to verify the performance of a metallic/radiative Thermal Protection System (TPS) under reentry conditions are presented. This TPS panel is suitable for multiple reentry, high L/D space vehicles, such as the NASA space shuttle, having surface temperatures up to 1200 C (2200 F). The TPS panel tested consists of a corrugation-stiffened, beaded-skin TD Ni-20Cr metallic heat shield backed by a flexible fibrous quartz and radiative shield insulative system. Test conditions simulated the critical heating and aerodynamic pressure environments expected during 100 repeated missions of a reentry vehicle. Temperatures were measured during each reentry cycle; heat-shield flatness surveys to measure permanent set of the metallic components were made every 10 cycles. The TPS panel, in spite of localized surface failures, performed its designated function.

Eidinoff, H. L.↗
NASA NTRS2004

Supersonic Rocket Thruster Flow Predicted by Numerical Simulation

Despite efforts in the search for alternative means of energy, combustion still remains the key source. Most propulsion systems primarily use combustion for their needed thrust. Associated with these propulsion systems are the high-velocity hot exhaust gases produced as the byproducts of combustion. These exhaust products often apply uneven high temperature and pressure over the surfaces of the appended structures exposed to them. If the applied pressure and temperature exceed the design criteria of the surfaces of these structures, they will not be able to protect the underlying structures, resulting in the failure of the vehicle mission. An understanding of the flow field associated with hot exhaust jets and the interactions of these jets with the structures in their path is critical not only from the design point of view but for the validation of the materials and manufacturing processes involved in constructing the materials from which the structures in the path of these jets are made. The hot exhaust gases often flow at supersonic speeds, and as a result, various incident and reflected shock features are present. These shock structures induce abrupt changes in the pressure and temperature distribution that need to be considered. In addition, the jet flow creates a gaseous plume that can easily be traced from large distances. To study the flow field associated with the supersonic gases induced by a rocket engine, its interaction with the surrounding surfaces, and its effects on the strength and durability of the materials exposed to it, NASA Glenn Research Center s Combustion Branch teamed with the Ceramics Branch to provide testing and analytical support. The experimental work included the full range of heat flux environments that the rocket engine can produce over a flat specimen. Chamber pressures were varied from 130 to 500 psia and oxidizer-to-fuel ratios (o/f) were varied from 1.3 to 7.5.

Davoudzadeh, Farhad↗
NASA NTRS1979

Research in structures and materials for future space transportation systems - An overview

The paper provides a review of some of the advances of the past decade in structures and materials that have application to future space transportation systems. The paper concentrates on metallic thermal protection systems and structures which could provide the structural efficiency, reliability, and durability dictated by future space utilization requirements. The need for completely reusable, on-board cryogenic fuel tanks is cited as the most challenging technical opportunity and potential thermostructural concepts for tanks are identified. Other critical areas needing technology advances are discussed. Finally, the unique research opportunities offered by the Shuttle Orbiter experiments program for testing structures and thermal protection systems are explored.

Kelly, H. N.↗
NASA NTRS1993

Plasma arc welding repair of space flight hardware

A technique to weld repair the main combustion chamber of Space Shuttle Main Engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloy-Z, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloy-Z while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

Hoffman, David S.↗
NASA NTRS1993

Plasma arc welding repair of space flight hardware

Repair and refurbishment of flight and test hardware can extend the useful life of very expensive components. A technique to weld repair the main combustion chamber of space shuttle main engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloyZ, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloyZ while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

Hoffman, David S.↗
NASA NTRS1970

Secondary structures and mechanisms - Design trouble area for the space shuttle

The design of secondary structures and mechanisms for a reusable space shuttle can produce problems as serious as those involved in designing the primary structure and thermal protection system. Several events involving failure of secondary structures during the X-15 flight program have been selected to illustrate potential problem areas. Similar problems may be expected on future reusable vehicles until additional research provides adequate design information in these areas.

Eldon E. Kordes↗
NASA NTRS1988

Mast material test program (MAMATEP)

The MAMATEP program, which is aimed at verifying the need for and evaluating the performance of various protection techniques for the solar array assembly mast of the Space Station photovoltaic power module, is discussed. Coated and uncoated mast material samples have been environmentally tested and evaluated, before and after testing, in terms of mass and bending modulus. The protective coatings include CV-1144 silicone, a Ni/Al/InSn eutectic, and an open-weave Al braid. Long-term plasma asher results from unprotected samples indicate that, even though fiberglass-epoxy samples degrade, a protection technique may not be necessary to ensure structural integrity. A protection technique, however, may be desirable to limit or contain the amount of debris generated by the degradation of the fiberglass-epoxy.

Ciancone, Michael L.↗
NASA NTRS2004

Damage Detection in Rotorcraft Composite Structures Using Thermography and Laser-Based Ultrasound

New rotorcraft structural composite designs incorporate lower structural weight, reduced manufacturing complexity, and improved threat protection. These new structural concepts require nondestructive evaluation inspection technologies that can potentially be field-portable and able to inspect complex geometries for damage or structural defects. Two candidate technologies were considered: Thermography and Laser-Based Ultrasound (Laser UT). Thermography and Laser UT have the advantage of being non-contact inspection methods, with Thermography being a full-field imaging method and Laser UT a point scanning technique. These techniques were used to inspect composite samples that contained both embedded flaws and impact damage of various size and shape. Results showed that the inspection techniques were able to detect both embedded and impact damage with varying degrees of success.

Anastasi, Robert F.↗
NASA NTRS1972

Thermal elastoplastic structural analysis of non-metallic thermal protection systems

An incremental theory and numerical procedure to analyze a three-dimensional thermoelastoplastic structure subjected to high temperature, surface heat flux, and volume heat supply as well as mechanical loadings are presented. Heat conduction equations and equilibrium equations are derived by assuming a specific form of incremental free energy, entropy, stresses and heat flux together with the first and second laws of thermodynamics, von Mises yield criteria and Prandtl-Reuss flow rule. The finite element discretization using the linear isotropic three-dimensional element for the space domain and a difference operator corresponding to a linear variation of temperature within a small time increment for the time domain lead to systematic solutions of temperature distribution and displacement and stress fields. Various boundary conditions such as insulated surfaces and convection through uninsulated surface can be easily treated. To demonstrate effectiveness of the present formulation a number of example problems are presented.

Chung, T. J.↗
NASA NTRS1995

Effect of Cyclic Aeroconvective Heating on Flexible Thermal Insulations

This paper describes the effect of cyclic aeroconvective heating on the thermal performance of ceramic flexible insulations considered for potential use as thermal protection systems or thermal insulations for future hypersonic vehicles such as the Reusable Launch Vehicles (RLV's) and other applications where structures require thermal protection from severe heating. The thermal response of these materials after exposure to cyclic aeroconvective heating from a plasma arc is described. The thermal insulations evaluated were Composite Flexible Blanket Insulations composed of an outer layer of aluminoborosilicate fabric and alumina insulation. The insulations were evaluated with and without a high emissivity coating. These insulations were exposed to the plasma arc stream for nine minutes reaching surface temperatures of 1150 C and a heat flux of 10.5 W/sq cm. Insulations were exposed three, six, or nine times in order to demonstrate reusability and to determine the effect oi coatings on the surface durability of these insulations. Test results demonstrated the capability of these insulations to protect either composite or metallic structures from high heating environments. It is shown that high emittance coatings reduce backface temperatures. The durability of these insulations when impacted at low velocities was also demonstrated. The interaction of the coatings with the ceramic fibers was characterized. An analytical thermal model was utilized to correlate experimental thermal test results with calculated values.

Kourtides, Demetrius A.↗
NASA NTRS1973

Structural interaction with transportation and handling systems

Problems involved in the handling and transportation of finished space vehicles from the factory to the launch site are presented, in addition to recommendations for properly accounting for in space vehicle structural design, adverse interactions during transportation. Emphasis is given to the protection of vehicle structures against those environments and loads encountered during transportation (including temporary storage) which would exceed the levels that the vehicle can safely withstand. Current practices for verifying vehicle safety are appraised, and some of the capabilities and limitations of transportation and handling systems are summarized.

Source record↗
NASA NTRS1983

Design for temperature and thermal buckling constraints employing a noneigenvalue formulation

A numerical procedure for simultaneous consideration of structural/thermal interactions during aircraft design is presented, with an emphasis on reentry vehicles such as the Orbiter. It has been shown that sequential design is inappropriate for reentry vehicles, due to the degradation of the material properties at elevated reentry temperatures. Attention is focused on thermal buckling, using an analytical technique that involves requiring that the stability matrix be positive definite, with the diagonal terms on the Gauss-Doolittle factor of the matrix also constrained to be positive. A finite element method is employed to calculate the derivative of the diagonal matrix, with optimization achieved by minimization of the mass of the structure and thermal protection system. Sample calculations are presented in terms of the aluminum structure and insulation for a section of the Orbiter wing bay.

Haftka, R. T.↗
NASA NTRS1985

New Life for Miss Liberty

Corrosion protection for the Statue of Liberty's interior structure is provided by a coating called IC 531, manufactured by Inorganic Coatings, Inc. The coating was developed by Goddard to protect structures at KSC. Inorganic Coatings has an exclusive to this high ratio potassium silicate formula. The coating is water based, nontoxic, nonflammable, and bonds to steel in 30 minutes. Tests on a variety of coated structures have been very positive.

Source record↗