SEARCH · Search NASA
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.
Manually actuated mechanical device easily raises or lowers two-section overhead garage door. Rolamite principle is used to provide controlled but varying rate of ascent or descent. Device is applicable where vertical shielding or baffling needs to be raised or lowered.
Submillipound mercury electron bombardment ion thrustor efficiency, noting cathode pole piece, baffle position and geometry influence on ion chamber performance
Closed cycle refrigeration loop in which trays holding molecular sorbent are made to serve as cooling baffles improves the performance of high vacuum systems. High performance is obtained with almost no decrease in pumping speed.
Light baffle with oblate hemispheroid surface and shading flange
Submerged fuel tank baffles to prevent sloshing in liquid propellant rocket flight
Submillipound mercury electron bombardment ion thrustor efficiency, noting cathode pole piece, baffle position and geometry influence on ion chamber performance
Development of multi-layered baffle as enclosure to protect personnel from effects of explosion during production of ammunition is discussed. Advantages of new system over previous systems are described. Illustration of typical panel structure is provided.
The conditioner design concept selected for evaluation consists of an integral reactor and baffle-type heat exchanger. Heat exchange is accomplished by flowing reactor hot gases past a series of slotted and formed plates, through which the conditioned propellant flows. Heat transfer analysis has resulted in the selection of a reactor hot gas nominal mixture ratio of 1.0, giving a combustion temperature of 1560 F with a hydrogen inlet temperature of 275 R. Worst case conditions result in a combustion gas temperature of 2060 F, satisfying the condition of no damage to the conditioner in case of failure to flow cold fluid. In addition, evaluation of hot gas flow requirements and conditioner weight has resulted in the selection of a reactor hot gas exhaust temperature of 750 R.
The activities leading to a tentative concept selection for a pressure-fed engine and propulsion support are outlined. Multiple engine concepts were evaluted through parallel engine major component and system analyses. Booster vehicle coordination, tradeoffs, and technology/development aspects are included. The concept selected for further evaluation has a regeneratively cooled combustion chamber and nozzle in conjuction with an impinging element injector. The propellants chosen are LOX/RP-1, and combustion stabilizing baffles are used to assure dynamic combustion stability.
The nuclear heating of the propellant in all of the four baseline RNS configurations studied was much lower than that of the nuclear flight module configuration with the 5000-MW NERVA analyzed previously. Although the nuclear heating has been reduced, the effect of nuclear heating on the propellant as well as the effect of nuclear heating on internal structures such as antivortex baffles, screens, and sump components cannot be neglected. In addition, it was found that the present analytical precedures were not able to predict boundary layer initiation and breakoff points with the accuracy necessary to predict propellant thermodynamic nonequilibrium (stratification) and/or mixing.
The radiation resistance corresponding to the natural modes of a finite rectangular panel is theoretically determined from the total energy radiated to the farfield. The panel is assumed to be simply supported in an infinite baffle. Asymptotic solutions for the low-frequency region are derived, and curves covering the entire frequency range for various mode shapes and aspect ratios are obtained through numerical integration. When the ratio of the acoustic wavenumber to the panel wavenumber is a constant much less than unity, the radiation resistance for all modes is a minimum if the intranodal area (the area between adjacent node lines) is square, and increases with the aspect ratio of the intranodal area.
An experimental study performed on a 20 cm electron bombardment thruster shows substantial improvements in throttled performance can be achieved if cathode discharge region diameter and length, cathode flow rate and baffle aperture area are reduced simultaneously. This improvement is related to a thruster operating mode in which arc current does not vary significantly with arc voltage. In this mode it is possible to operate the thruster at a high arc voltage and a correspondingly high primary electron energy without the penalty of a prohibitively high arc power. Langmuir probe data indicate the arc current is limited by the cathode region plasma potential and electron density which are both nearly invariant with arc voltage.
Description of a model for radon diffusion through the lunar regolith in which the atom migrates by random walk. The regolith is represented by a system of randomly oriented baffles in which the mean distance which the atom travels between two collisions takes on the role of a mean free path. The effective mean time between two collisions depends on two entities: the actual mean time-of-flight and the mean sticking time on grain surfaces for one collision. The latter depends strongly on the temperature and the heat of adsorption of radon on regolith materials. Both the mean free path as well as the heat of adsorption are either poorly known or unknown for the lunar regolith; hence these quantities are treated as free parameters. Because of the greatly different mean lifetimes against radioactive decay of Rn219, Rn220, and Rn222, the regolith acts as a powerful 'filter' for these species. Rn222 escape is significant (32%) even for a mean free path of 1 micron, a heat of adsorption of 7.0 kcal/mole and a regolith depth of 4 m. Calculations of radon escape from a 4 m thick regolith, using mean free paths of 1, 10, and 80 microns and heats of adsorption of 4.0, 5.2, and 7.0 kcal/mole show that the Rn222/Rn220 escape ratio can be as small as 7.7 and as large as, or larger than 47. The small value of 7.7 is of particular interest, because it is nearly equal to the escape ratio inferred by Turkevich et al. (1970) from their Surveyor 5 results.
A rocket-borne photometer containing two tilting-filter channels for the measurement of the forbidden OI 6300-A and 5577-A emission lines in the day airglow is described. The results of one flight substantiate the employment of tilting filters to determine accurate corrections for background continuum and provide reliable height profiles of emission intensity down to approximately 90 km. Discussions on the calibration of the instrument and its baffling against sunlight are also presented.
A 2000-hour durability test of a modified Hughes SIT-5 (Structurally Integrated Thruster, 5 cm) was conducted at the Lewis Research Center. The thruster operated with a translating screen thrust vector grid locked in position for 10 deg beam deflection. The test was essentially continuous except for seven stoppages of beam current. The neutralizer keeper voltage and thruster floating potential increased slightly with time. Performance profiles and maps of thruster characteristics were obtained at 453 and 2023 hours into the test. Overall efficiency was nearly constant at 31 - 32 percent, and operating characteristics were similar at both points in the test. A post-shutdown inspection showed negligible erosion damage to the accelerator and cathode baffle. Some erosion was found in the aperture of the neutralizer cathode.
The use of dished high perveance grids on a 15 cm modified SERT 2 thruster is shown to facilitate throttled operation over a beam current range from 60 to 600 mA. Effects of increasing the radial component of the magnetic field in the main discharge chamber and decreasing the dimensions of the cathode discharge region are examined and found to degrade performance to the extent that primary electrons are forced in toward the center-line of the thruster. Studies of the baffle aperture region of two thrusters indicate that the electric potential gradient vector is perpendicular to the local magnetic field lines when the thruster is operating properly. The correlation between the shape of the ion beam current density and that of the ion density at the screen grid within the thruster is shown to be 94%. Additional experimental studies on maximum propellant utilization, plasma ion production cost, neutral density in the cathode discharge region, double ion production in hollow cathode thrusters and thermal flow meter performance are discussed.
A supply air hood is described that provides a curtain of clean air just outside of the hood surface for protection of the operator. The design consists of an overhead plenum which extends out from the hood with tapered sides extending from the plenum to the bench, a slotted baffle plate and two perforated plates with offset holes, dust filters, and a special deflector plate. The latter introduces less than 4 cubic feet flow per minute through the special perforated area so that a sweeping effort is almost always maintained at bench level. Performance tests indicate that even under adverse exhaust conditions some of the supply air may be lost to the room, but none of the air within the hood that represents contaminated flow is entrained or displayed so that it enters the work area. This hood operates with an efficiency of about 90% exhaust for supplied air.
An investigation was performed of the conditions in which fires can result and be controlled within the bearing sump simulating that of a gas turbine engine; Esso 4040 Turbo Oil, Mobil Jet 2, and Monsanto MCS-2931 lubricants were used. Control variables include the oil inlet temperature, bearing temperature, oil inlet and scavenge rates, hot air inlet temperature and flow rate, and internal sump baffling. In addition to attempting spontaneous combustion, an electric spark and a rub (friction) mechanism were employed to ignite fires. Spontaneous combustion was not obtained; however, fires were readily ignited with the electric spark while using each of the three test lubricants. Fires were also ignited using the rub mechanism with the only test lubricant evaluated, Esso 4040. Major parameters controlling ignitions were: Sump configuration; Bearing and oil temperatures, hot air temperature and flow and bearing speed. Rubbing between stationary parts and rotating parts (eg. labyrinth seal and mating rub strip) is a very potent fire source suggesting that observed accidental fires in gas turbine sumps may well arise from this cause.