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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.
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Compact, lightweight camera which advances film frames without use of conventional sprockets and slip clutches obtains time lapse photomicrographs of human cell growth in a zero-G environment over a period of about a month.
Mechanical device for reducing the stresses imposed on ball bearings when bearings are exposed to forces caused by vibration is described. Bearing protector is press fitted on rotor shaft and slip fitted into bearing housing. Bearing stop which contacts inner race stops shaft and bearing when moving along shaft axis and removes load from ball bearings.
Heat shrinkable Teflon tubing is cut to size, slipped onto shaft, heated to shrink tightly to shaft, or machined to final outside diameter size. Shaft bushings fabricated from shrinkable Teflon tubing provide economic close fitting sleeves that prevent galling and contamination in valves.
Method for predicting nozzle performance of microthrust rockets is discussed. Method is numerical and uses simplified computer program on IBM 360/65 computer. Analysis is based on slender channel equations with slip boundary conditions at walls. Implicit finite difference scheme is used to calculate pressure and velocity profiles along channel.
Experimental aerodynamic investigations were made in the Grumman 36-inch hypersonic wind tunnel on a .00435 scale model of the H-32 reusable space shuttle booster. The objectives of the test were to determine the static stability characteristics and control surface effectiveness at hypersonic speeds. Data were taken at M = 8.12 over a range of angles of attack between -5 and 85 deg at beta = 0 deg and over a range of side slip angles between -10 and 10 deg at alpha = 0 and 70 deg. Six component balance data and base-cavity pressure data were recorded.
The dust problem and fender design for the LRV were studied under reduced gravity with a lunar soil simulant. The test equipment, soil characteristics of the lunar soil simulant, and the test procedures are described. It is concluded: (1) The fender plus flap design is adequate. (2) Vacuum conditions tend to eliminate or reduce suspended dust clouds. (3) Reduced gravity conditions tend to increase the dust problems. (4) Slow starting speeds are necessary to minimize slip and reduce initial dust generation.
Single crystals of 2H SiC were observed to undergo phase transformations at temperatures as low as 400 C. Some 2H crystals transformed to a structure with one-dimensional disorder along the crystal c axis. Others transformed to a faulted cubic/6H structure. The transformation is time and temperature dependent and is greatly enhanced by dislocations. Observations indicate that the transformation takes place by means of a slip process perpendicular to the c axis. Cubic SiC crystals were observed to undergo a solid state transformation above 1400 C.
Experimental data are presented for the tangential and radial stresses in the disks of the 36,000 horsepower, 4000 rpm turbine for the M-1 engine oxidizer turbopump. The two-stage Curtis turbine is a special light-weight design utilizing thin conical disks with hollow sheet metal blades attached by electron-beam welding techniques. The turbine was fabricated from Inconel 718, a nickel-chromium alloy. The stresses were obtained by strain-gage measurements using a slip-ring assembly to transmit the electrical signals. Measurements were made at different rotative speeds and different thermal loads. In addition to presenting test data, the report describes test equipment, design of associated hardware, test procedures, instrumentation, and tests for the selection and calibration of strain gages.
In two phase flow systems line losses comprise frictional and momentum pressure drops. For design purposes, it would be desirable to estimate the line losses employing a one-dimensional calculation. Two methods for computing one-dimensional momentum flux at a test section discharge station are compared to the experimental value for a range of two-phase flow conditions. The one-dimensional homogeneous model appears to be more accurate generally in predicting the momentum than the variable slip model.
An experimental investigation was conducted to study the performance of an aircraft tire under cyclic braking conditions and to study the performance of a currently operational aircraft antiskid braking system. Dry, damp, and flooded runway surface conditions were used in the investigation. The results indicated that under cyclic braking conditions the braking and cornering-force friction coefficients may be influenced by fluctuations in the vertical load, flexibility in the wheel support, and the spring coupling between the wheel and the tire-pavement interface. The cornering capability was shown to be negligible at wheel slip ratios well below a locked-wheel skid under all test surface conditions. The maximum available brake-force friction coefficient was shown to be dependent upon the runway surface condition, upon velocity, and, for wet runways, upon tire differences. Moderate reductions in vertical load and brake system pressure did not significantly affect the overall wet-runway performance of the tire.
For single-phase media, the critical discharge velocity, the sonic velocity, and the pressure pulse propagation velocity can be expressed in the same form by assuming isentropic, equilibria processes. In two-phase mixtures, the same concept is not valid due to the existence of interfacial transports of momentum, heat, and mass. Thus, the three velocities should be treated differently and separately for each particular condition, taking into account the various transport processes involved under that condition. Various attempts are reviewed to predict the critical discharge rate or the propagation velocities by considering slip ratio (momentum change), evaporation (mass and heat transport), flow pattern, etc. Experimental data were compared with predictions based on various theorems. The importance is stressed of the time required to achieve equilibrium as compared with the time available during the process, for example, of passing a pressure pulse.
Surface temperature distribution measurements for turbine vanes and blades were obtained by measuring the infrared energy emitted by the airfoil. The IR distribution can be related to temperature distribution by suitable calibration methods and the data presented in the form of isotherm maps. Both IR photographic and real time electro-optical methods are being investigated. The methods can be adapted to rotating as well as stationary targets, and both methods can utilize computer processing. Pressure measurements on rotating components are made with a rotating system incorporating 10 miniature transducers. A mercury wetted slip ring assembly was used to supply excitation power and as a signal transfer device. The system was successfully tested up to speeds of 9000 rpm and is now being adapted to measure rotating blade airflow quantities in a spin rig and a research engine.
Three spacecraft configurations were designed for operation as a high powered synchronous communications satellite. Each spacecraft includes a 1 kw TWT and a 2 kw Klystron power amplifier feeding an antenna with multiple shaped beams. One of the spacecraft is designed to be boosted by a Thor-Delta launch vehicle and raised to synchronous orbit with electric propulsion. The other two are inserted into a elliptical transfer orbit with an Atlas Centaur and injected into final orbit with an apogee kick motor. Advanced technologies employed in the several configurations include tubes with multiple stage collectors radiating directly to space, multiple-contoured beam antennas, high voltage rollout solar cell arrays with integral power conditioning, electric propulsion for orbit raising and on-station attitude control and station-keeping, and liquid metal slip rings.
An investigation was made to determine the feasibility of an automatic braking system for arresting the motion of an airplane by sensing and controlling braked wheel decelerations. The system was tested on a rotating drum dynamometer by using an automotive tire, wheel, and disk-brake assembly under conditions which included two tire loadings, wet and dry surfaces, and a range of ground speeds up to 70 knots. The controlling parameters were the rates at which brake pressure was applied and released and the Command Deceleration Level which governed the wheel deceleration by controlling the brake operation. Limited tests were also made with the automatic braking system installed on a ground vehicle in an effort to provide a more realistic proof of its feasibility. The results of this investigation indicate that a braking system which utilizes wheel decelerations as the control variable to restrict tire slip is feasible and capable of adapting to rapidly changing surface conditions.
A digital tape recorder was used on the Mariner Mars 1971 spacecraft to record television and scientific data. Data were recorded at 132 kilobits/sec and were reproduced at one of five available rates (16.2, 8.1, 4.05, 2.05, or 1.0125 kilobits/sec) selected by ground command to be congruous with the spacecraft-to-earth communications link performance. The transport mechanism contained 167 m of 1.2 cm magnetic recording tape. A single motor was used to drive the peripheral drive transport. During development of the design, stick slip problems were encountered. A design life of 2400 tape passes was achieved during the mission.
The stresses in a sheet with an interference-fit bolt have been calculated for two sheet-bolt interface conditions: a frictionless interface and a fixed (no-slip) interface. The stress distributions were calculated for various combinations of sheet and bolt moduli. The results show that for repeated loading the local stress range is significantly smaller if an interference bolt is used instead of a loosely fitting one. This reduction in local stress range is more pronounced when the ratio of bolt modulus to sheet modulus is large. The analysis also indicates that currently used standard values of interference cause yielding in the sheet.
Sapphire and ruby were very difficult to press-forge because they deformed without cracking only in a limited temperature range before they melted. Spinel crystals were somewhat easier and MgO, CaO, and TiC crystals much easier to forge. The degree of recrystallization that occurred during forging (which was related to the ease and type of slip intersections) varied from essentially zero in Al2O3 to complete (i.e., random polycrystalline bodies were produced) in CaO. Forging of bi- and polycrystalline bodies produced incoherent bodies as a result of grain-boundary sliding. Strengths of the forged crystals were comparable to those of dense polycrystalline bodies of similar grain size. However, forged and recrystallized CaO crystals were ductile at lower temperatures than dense hot-pressed CaO. This behavior is attributed to reduced grain-boundary impurities and porosity. Fracture origins could be located, indicating that fracture in the CaO occurs internally as a result of surface work hardening caused by machining.-
Review of the procedures and results of a program designed to remove the threat of sources of molecular and particulate contamination of critical optical, electrical, and mechanical elements in spacecraft. The results of recent contamination-probing thermal-vacuum tests indicate that some of the materials and practices commonly used to protect critical surfaces from molecular or particulate contamination can themselves represent significant threats. These contamination sources include clean-room and clean-tent materials, gloves, tissues, and covering or packaging materials. Mass and infrared spectral analyses of these materials and the environments and instruments exposed to them show that the contaminants are mostly plasticizers, slip or antistatic agents, and binders used in the manufacture of these products. Products of particular threat include vinyl gloves, boots, clean-tent walls, and some polyethylene sheets and bags. Techniques for reducing these threats are discussed.