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Filler developed for gaps between insulating tiles on Space Shuttle finds application in industries that use tiles for thermal or environmental protection. Filler consists of tight-fitting ceramic tubes and fibrous alumina. Combination resists high wind loads while providing requisite heat protection. Quartz-thread stitching holds envelope together.
Procedure for improving tile resistance to impact damage described in new report on tile densification. Developed for Space Shuttle reusable surface insulations, procedure has potential application when space restrictions necessitate thin layers of insulation with low thermal conductivity. Examples are advanced heat engines, such as adiabatic diesel and automotive gas turbine, as well as fast-heating high-temperature ovens.
The use of an engineering data management system to facilitate the extensive stress analyses of the space shuttle orbiter thermal protection system is demonstrated. The methods used to gather, organize, and store the data; to query data interactively; to generate graphic displays of the data; and to access, transform, and prepare the data for input to a stress analysis program are described. Information related to many separate tiles can be accessed individually from the data base which has a natural organization from an engineering viewpoint. The flexible user features of the system facilitate changes in data content and organization which occur during the development and refinement of the tile analysis procedure. Additionally, the query language supports retrieval of data to satisfy a variety of user-specified conditions.
Data are presented from Space Shuttle flight measurements of the temperature distribution within the gaps of the reusable surface insulation tiles. This is the first of a series of flight measurements in which the gap width and tile surface edge radius will be systematically varied. The data show several interesting features including the time and effect of boundary-layer transition. The local heating rates into the gap surfaces are calculated from the measured temperature distribution down the gap at two locations.
Durable shell-tile thermal-protection system consists of interlocking upper and lower hard caps, incorporating appropriate stiffeners and enclosing lightweight fibrous insulation. New shell tile more durable than reusable surface insulation (RSI) currently used on Space Shuttle orbiter.
Waterproofing agent, vaporized in bubbler transported by gas flowing in system and deposits in pores of tiles. Vapor carried through hole of approximately 1/16 inch (1.6.mm) diameter made in tile coating. Technique used to waterproof buildups (concrete and brick) and possibly fabrics.
Acid etching, densification, and silica cement ensure strong bond. Key step in preparation for bonding to glazed tile is etching quartz fabric and tile with acid. This increases adhesion of silica cement used to form bond. Procedures use high-temperature materials exclusively and therefore suitable for securing flexible seals and heat barriers around doors and viewing ports in furnaces and kilns.
Presented are several methods to study a system of tiles bonded elastically to a finite flexible plate responding to an impulse. First, a one-dimensional (1-D) approximation to the system is constructed using Timoshenko beam theory and transfer matrices. This simulates a strip one tile wide. Modal analysis determines the transient response to an impulse of short duration. Also presented are parametric studies of the effect of bond stiffness and the effect of stiffening from inplane stresses produced by large out-of-plane deflections. A two-dimensional (2-D) model is constructed from the eigenfunctions of the 1-D model in a Galerkin method using pairwise products of the 1-D modes as trial functions. Comparison of the two models establishes a factor applied to peak impulse pressure for results to agree.
Stress distributed so high load borne. Fastener bonded in densified hole or captured in plug of similar refractory material, which in turn bonded in hole in parent tile. Plug or bonding distributes mechanical load from fastener to broad region surrounding fastener, reducing local stress concentration and likelihood of breakage. Bonded-plug method has been successful in attaching mechanical fasteners to porous silica refractory tiles used on outer surface of Space Shuttle orbiter.
The coupled response to a large impulse on tiles bonded to a finite plate is studied. The analysis includes geometric nonlinearity born from boundary restraint in the plane, which stiffens the plate transversely. It also includes material nonlinearities born from plasticity of the plate's material and from properties of a polymer bond including memory and dissipation. The equations of motion are solved by the Galerkin method using linearized eigenfunctions of the system as trial functions. A strip of plate which is one tile wide is modeled.
Irregular surfaces mapped and digitized for numerical-control machinery. Fast, accurate laser scanning system measures size and shape of cavity without making any physical contact with cavity and walls. Measurements processed into control signals for numerically controlled machining of tile or block to fit cavity. System generates map of grid points representing cavity and portion of outer surface surrounding cavity. Map data used to control milling machine, which cuts tile or block to fit in cavity.
Simple tool cuts hemispherical recesses in soft ceramic tiles. Designed to expose wires of thermocouples embedded in tiles without damaging leads. Creates neat, precise holes around wires. End mill includes axial hole to accommodate thermocouple wires embedded in material to be cut. Wires pass into hole without being bent or broken. Dimensions in inches. Used in place of such tools as dental picks, tweezers, spatulas, and putty knives.
To determine shuttle orbiter wing loads during ascent, wing load instrumentation was added to Columbia (OV-102). This instrumentation included strain gages and pressure orifices on the wing. The loads derived from wing pressure measurements taken during STS 61-C did not agree with those derived from strain gage measurements or with the loads predicted from the aerodynamic database. Anomalies in the surface immediately surrounding the pressure orifices in the thermal protection system (TPS) tiles were one possible cause of errors in the loads derived from wing pressure measurements. These surface anomalies were caused by a ceramic filler material which was installed around the pressure tubing. The filler material allowed slight movement of the TPS tile and pressure tube as the airframe flexed and bent under aerodynamic loads during ascent and descent. Postflight inspection revealed that this filler material had protruded from or receeded beneath the surface, causing the orifice to lose its flushness. Flight tests were conducted at NASA Ames Research Center Dryden Flight Research Facility to determine the effects of any anomaly in surface flushness of the orifice installation on the measured pressures at Mach numbers between 0.6 and 1.4. An F-104 aircraft with a flight test fixture mounted beneath the fuselage was used for these flights. Surface flushness anomalies typical of those on the orbiter after flight (STA 61-C) were tested. Also, cases with excessive protrusion and recession of the filler material were tested. This report shows that the anomalies in STS 61-C orifice installations adversely affected the pressure measurements. But the magnitude of the affect was not great enough to account for the discrepancies with the strain gage measurements and the aerodynamic predictions.
Complex refractive index and dielectric permittivity studies of presently used Space Shuttle tile materials at millimeter wavelengths reveal these tiles to exhibit similar absorption characteristics to those of fused silica materials. This absorption is mainly related to the water content in the specimen. A strong birefringence is observed at least in one of these fibrous refractory composite materials.
Eddy-current probe nondestructively and indirectly indicates whether screed present under ceramic tile on aluminum substrate. Transducer coil excites eddy currents in aluminum substrate material. Response appears on oscilloscope or meter. Changes in response indicate spatially abrupt changes in substrate. Intended for use on insulating tiles on Space Shuttle, potential terrestrial applications in nondestructive testing.
The application of a high-resolution time-domain reflectometer (TDR) to the detection of faulty bonds in space shuttle tile structures is discussed. Experimental measurements on bonded and debonded tiles are included to demonstrate the technique. Computer simulations were used to verify the experimental results. A criterion for bond verification is proposed.
Combination of template and routing tool cuts ceramic tiles to final dimensions. Template guides router along precisely defined planes to accurately and uniformly shave chamfers on edge of tiles. Legs of template temporarily bonded to workpiece by double-backed adhesive tape. Adaptable to in-situ final machining of other nominally flat, narrow surfaces.
This report summarizes work that has been performed to date on the strength of a cryotank insulation system using Rohacell foam and TUFI-coated AETB-12 ceramic tiles directly bonded to a simulated graphite-epoxy tank wall. Testing utilized a custom specimen design which consists of a long tensile specimen with eccentric loading to induce curvature similar to the curvature expected due to 'pillowing' of the tank when pressurized. A finite element model was constructed to predict the specific element strains in the test article, and to assist with design of the test specimen to meet the specific goals of curvature and laminate strain. The results indicate that the heat treated 3.25-pcf density Rohacell foam does not provide sufficient strength for the induced stresses due to curvature and stress concentration at the RTV bondline to the TUFI tile. The test was repeated using higher density non-heat treated Rohacell foam (6.9 pcf) without foam failure. The finite element model was shown to predict specimen behavior, and validation of the model was successful. It is pertinent to mention that the analyses described herein accurately predicted the failure of the heat treated foams and based on this analysis method it is expected that the untreated 3.25 pcf Rohacell foam will be successful.