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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Main-Sequence CMEs as Magnetic Explosions: Compatibility with Observed Kinematics

We examine the kinematics of 26 CMEs of the morphological main sequence of CMEs, those having the classic three-part bubble structure of (1) a bright front eveloping (2) a dark cavity within which rides (3) a bright blob/filamentary feature. Each CME is observed in Yohkoh/SXT images to originate from near the limb (> or equal to 0.7 R(sub Sun) from disk center). The basic data (from the SOHO LASCO CME Catalog) for the kinematics of each CME are the sequence of LASCO images of the CME, the time of each image, the measured radial distance of the front edge of the CME in each image, and the measured angular extent of the CME. About half of our CMEs (12) occur with a flare, and the rest (14) occur without a flare. While the average linear-fit speed of the flare CMEs (1000 km/s) is twice that of the non-flare CMEs (510 km/s), the flare CMEs and the non-flare CMEs are similar in that some have nearly flat velocity-height (radial extent) profiles (little acceleration), some have noticeably falling velocity profiles (noticeable deceleration), and the rest have velocity profiles that rise considerably through the outer corona (blatant acceleration). This suggests that in addition to sharing similar morphology, main-sequence CMEs all have basically the same driving mechanism. The observed radial progression of each of our 26 CMEs is fit by a simple model magnetic plasmoid that is in pressure balance with the radial magnetic field in the outer corona and that propels itself outward by magnetic expansion, doing no net work on its surroundings. On average over the 26 CMEs, this model fits the observations as well as the assumption of constant acceleration. This is compatible with main-sequence CMEs being magnetically driven, basically magnetic explosions, with the velocity profile in the outer corona being largely dictated by the initial Alfien speed in the CME (when the front is at approx. 3 (sub Sun), analogous to the mass of a main-sequence star dictating the luminosity.

Moore, Ron↗
NASA NTRS2006

Unsteady Analysis of Turbine Main Flow Coupled with Secondary Air Flow

Two numerical approaches are used to model the interaction between the turbine main gas flow and the wheelspace cavity seal flow. The 3-D, unsteady Reynolds-averaged Navier-Stokes equations are solved with a CFD code based on a structured grid to study the interaction between the turbine main gas flow and the wheelspace cavity seal flow. A CFD code based on an unstructured grid is used to solve detailed flow feature in the cavity seal which has a complex geometry. The numerical results confirm various observations from earlier experimental studies under similar flow conditions. When the flow rate through the rim cavity seal is increased, the ingestion of the main turbine flow into the rim seal area decreases drastically. However, a small amount of main gas flow is ingested to the rim seal area even with very high level of seal flow rate. This is due to the complex nature of 3-D, unsteady flow interaction near the hub of the turbine stage.

Hah, Chunill↗
NASA NTRS2010

Space Shuttle Main Engine Liquid Air Insulation Redesign Lessons Learned

The Space Shuttle Main Engine Liquid Air Insulation redesign was required to prevent the reoccurance of the STS-111 High Pressure Speed Sensor In-Flight Anomaly. The STS-111 In-Flight Anomaly Failure Investigation Team's initial redesign of the High Pressure Fuel Turbopump Pump End Ball Bearing Liquid Air Insulation failed the certification test by producing Liquid Air. The certification test failure indicated not only the High Pressure Fuel Turbopump Liquid Air Insulation, but all other Space Shuttle Main Engine Liquid Air Insulation. This paper will document the original Space Shuttle Main Engine Liquid Air STS-111 In-Flight Anomaly investigation, the heritage Space Shuttle Main Engine Insulation certification testing faults, the techniques and instrumentation used to accurately test the Liquid Air Insulation systems on the Stennis Space Center SSME test stand, the analysis techniques used to identify the Liquid Air Insulation problem areas and the analytical verification of the redesign before entering certification testing, Trade study down selected to three potential design solutions, the results of the development testing which down selected the final Liquid Air Redesign are also documented within this paper.

Darrell Gaddy↗
NASA NTRS2010

Cassini Main Engine Assembly Cover Flight Management and Performance

The Cassini spacecraft has performed its four year Prime Mission at Saturn and is currently in orbit at Saturn performing a two year extended mission. 12Its main engine nozzles are susceptible to impact damage from micrometeoroids and on-orbit dust. The spacecraft has an articulating device known as the Main Engine Assembly (MEA) cover which can close and shield the main engines from these threats. The cover opens to allow for main engine burns that are necessary to maintain the trajectory. Periodically updated analyses of potential on-orbit dust hazard threats have resulted in the need to continue to use the MEA cover beyond its intended use and beyond its design life. This paper provides a detailed Systems-level overview of the flight management of the MEA cover device and its flight performance to date.

Somawardhana, Ruwan P.↗
NASA NTRS1976

Parametric study of the noise produced by the interaction of the main rotor wake with the tail rotor

A model was designed, fabricated and wind tunnel tested to identify some of the parameters which were pertinent to the noise produced by the interaction of the main rotor wake with the tail rotor. The model provided for variations in many geometric and operating parameters. The initial set of tests indicated that the noise produced by the tail rotor was, in general, sensitive to the location of the vortex interaction on the tail rotor disk, direction of rotation, lateral rotor fin spacing, tip speed and the operating mode of the tail rotor; and generally insensitive to main rotor thrust coefficient, longitudinal spacing and tail rotor to main rotor rotational speed ratios. Refinements in the analyses to adequately predict the noise phenomenon have been outlined to complement further experimental investigations.

Balcerak, J. C.↗
NASA NTRS1977

Update on development of the Space Shuttle main engine /as of 5 May 1977/

The development and testing of the Space Shuttle main engine are described. The preburners, main injector, main combustion chamber, and 35:1 expansion ratio test nozzle were successfully run at full power level (109 percent of rated power level). Integral combustion stability aids damped induced instability oscillations within 6 milliseconds. Three significant turbomachinery problems were identified and solved during the past year. These problems involved high-pressure fuel turbopump subsynchronous whirl, severe overheating of the turbine bearing and components and, in the high-pressure oxidizer turbopump, burning that first occurred in the drain cavity downstream of the primary oxidizer seal.

Johnson, J. R.↗
NASA NTRS1977

The main peculiarities of the processes of the deformation and destruction of lunar soil

The main results of study of the physical and mechanical properties of lunar soil, obtained by laboratory study of samples returned from the moon by Luna 16 and Luna 20, as well as by operation of the self-propelled Lunokhod 1 and Lunokhod 2 on the surface of the moon, are analyzed in the report. All studies were carried out by single methods and by means of unified instruments, allowing a confident comparison of the results obtained. The investigations conducted allowed the following values of the main physical-mechanical properties of lunar soil to be determined: in the natural condition the solid density corresponds to the porosity of 0.8; the modal value of the carrying capacity is 0.4 kg/square cm; adhesion is 0.04 to 0.06 kg/square cm; and the internal angle of friction is 20 to 25 degree. The main mechanisms of deformation and destruction of the soil are analyzed in the report, and the relationships between the mechanical properties and physical parameters of the soil are presented.

Leonovich, A. K.↗
NASA NTRS1979

Analytical investigation of the landing dynamics of a large airplane with a load-control system in the main landing gear

The results of an evaluation of an active load-control landing gear computer program (ACOLAG) for predicting the landing dynamics of airplanes with passive and active main gears are presented. ACOLAG was used in an analytical investigation of the landing dynamics of a large airplane with both passive and active main gears. It was concluded that the program is valid for predicting the landing dynamics of airplanes with both passive and active main gears. It was shown that the active gear reduces airframe-gear forces and airplane motions following initial impact, and has the potential for significant reductions in structural fatigue damage relative to that which occurs with the passive gear.

Mcgehee, J. R.↗
NASA NTRS1981

Acoustic performance evaluation of an advanced UH-1 helicopter main rotor system

An experimental investigation of the high-speed impulsive noise characteristics of an advanced main rotor system for the UH-1 helicopter has been conducted. Models of both the advanced main rotor system and the UH-1 main rotor system were tested at one-quarter scale in the Langley 4- by 7-meter (V/STOL) Tunnel using the General Rotor Model System (GRMS). Tests were conducted over a range of simulated flight and descent velocities. The tunnel was operated in the open-throat configuration with acoustic treatment to improve the acoustic characteristics of the test chamber. In-plane acoustic measurements of the high-speed impulsive noise demonstrated a 7 to 8 dB reduction in noise generation is available by using the advanced rotor system on the UH-1 helicopter.

Hoad, D. R.↗
NASA NTRS1981

Discovery of three X-ray luminous pre-main-sequence stars

Three X-ray sources found serendipitously in Einstein images of the Taurus-Auriga cloud complex were observed at the McGraw-Hill Observatory and are found to be associated with stars of approximately 12 mag with weak H-alpha emission. The stars lie on the edges of dark clouds and are spectroscopically similar to the least active emission-line pre-main-sequence stars. Although they lie well above the ZAMS in the H-R diagram, they do not exhibit ultraviolet excess, strong optical variability, or evidence for mass outflow/inflow characteristics of the more active T Tauri stars. Their only unusual property is high X-ray luminosity (approximately 10 to the 30th ergs/s). It is suggested that the X-ray emission from pre-main-sequence stars is not closely linked to the conditions giving rise to their unusual spectroscopic properties. The emission may instead represent an enhanced form of the coronal activity producing X-rays observed in late-type main-sequence stars.

Feigelson, E. D.↗
NASA NTRS1983

A photoelectric lightcurve survey of small main belt asteroids

A survey to obtain photoelectric lightcurves of small main-belt asteroids was conducted from November 1981 to April 1982 using the 0.91- and 2.1-m telescopes at the University of Texas McDonald Observatory. A total of 18 main-belt asteroids having estimated dimaters under 30 km were observed with over half of these being smaller than 15 km. Rotational periods were determined or estimated from multiple nights of observation for nearly all of these yielding a sample of 17 small main-belt asteroids which is believed to be free of observational selection effects. All but two of these objects were investigated for very short periods in the range of 1 min to 2 hr using power spectrum analysis of a continuous set of integrations. No evidence for such short periods was seen in this sample. Rotationally averaged B(1,0) magnitudes were determined for most of the surveyed asteroids, allowing diameter estimates to be made. Imposing the suspected selection effects of photogaphic photometry on the results of this survey gives excellent agreement with the results from that technique. This shows that the inability of photographic photometry to obtain results for many asteroids is indeed due to the rotational parameter of those asteroids.

Binzel, R. P.↗
NASA NTRS1984

136-foot main parachute for recovery of Space Shuttle Solid Rocket Boosters

A 136-ft-D(0) main parachute system has been developed to replace the present 115-ft-D(0) main parachutes currently flown on the Space Shuttle Solid Rocket Boosters (SRB's) for the purpose of reducing the velocity at water impact. This cluster of three larger main parachutes will decelerate the 170,000-pound SRB to a terminal nominal impact velocity of 75 feet per second (ft/s) as compared to the present velocity of 88 ft/s. The paper discusses the design, development, and manufacturing of this 136-ft parachute.

Rodier, R. W.↗
NASA NTRS1984

The lower main sequence and the nature of secondary stars in ultracompact binaries

The possible nature of the secondary stars in ultracompact binary stellar systems (with orbital periods of less than about 1 hr) are systematically investigated. Using a simplified stellar evolution code, which assumes isentropic stellar models, nearly 3000 separate models for hydrogen-burning main-sequence stars with masses less than 0.3 solar mass are generated. The effects of the (homogeneous) chemical composition on the properties of such stars and in, particular, on the minimum main-sequence mass are explored in detail. It is found that this minimum mass is a sensitive function of the hydrogen content and can be as small as 0.035 solar mass. The properties of fully degenerate low-mass stars, as well as low-mass stars that are not in thermal equilibrium are also studied. In particular, it is shown that the thermal time scale of such nonequilibrium stars may exceed 10 billion yr. The results also confirm the existence of a second branch of the main sequence and shed new light on the thermal instability of this branch. The available observational information on the three known ultracompact binary systems (4U 1626-67, G61-29, 4U 1916-05) is summarized, and the results of the stellar model calculations are combined with the empirical results to place constraints on the properties of the secondary stars.

Rappaport, S.↗
NASA NTRS1985

Experimental study of main rotor tip geometry and tail rotor interactions in hover. Volume 2: Run log and tabulated data

A model scale hover test was conducted in the Sikorsky Aircraft Model Rotor hover Facility to identify and quantify the impact of the tail rotor on the demonstrated advantages of advanced geometry tip configurations. The existence of mutual interference between hovering main rotor and a tail rotor was acknowledged in the test. The test was conducted using the Basic Model Test Rig and two scaled main rotor systems, one representing a 1/5.727 scale UH-60A BLACK HAWK and the others a 1/4.71 scale S-76. Eight alternate rotor tip configurations were tested, 3 on the BLACK HAWK rotor and 6 on the S-76 rotor. Four of these tips were then selected for testing in close proximity to an operating tail rotor (operating in both tractor and pusher modes) to determine if the performance advantages that could be obtained from the use of advanced geometry tips in a main rotor only environment would still exist in the more complex flow field involving a tail rotor. This volume contains the test run log and tabulated data.

Balch, D. T.↗
NASA NTRS1984

Space Shuttle Main Engine overhaul program

The Space Shuttle Main Engine first flight set from the Orbiter Columbia was returned to Rockwell International/Rocketdyne Division in Canoga Park, California for overhaul after five successful development flights. The three main engines have been completely disassembled and the hardware assessed for space flight effects. Schedules to overhaul subsequent flight engines have been established based on operational requirements of the Space Transportation System. To support these requirements, a dedicated Space Shuttle Main Engine Overhaul Center is being built at the Canoga Park Rocketdyne Facility incorporating the latest in manufacturing, inspection, and data processing equipment.

Stohler, S.↗
NASA NTRS1985

Space Shuttle main engine product improvement

The current design of the Space Shuttle Main Engine has passed 11 certification cycles, amassed approximately a quarter million seconds of engine test time in 1200 tests and successfully launched the Space Shuttle 17 times of 51 engine launches through May 1985. Building on this extensive background, two development programs are underway at Rocketdyne to improve the flow of hot gas through the powerhead and evaluate the changes to increase the performance margins in the engine. These two programs, called Phase II+ and Technology Test Bed Precursor program are described. Phase II+ develops a two-tube hot-gas manifold that improves the component environment. The Precursor program will evaluate a larger throat main combustion chamber, conduct combustion stability testing of a baffleless main injector, fabricate an experimental weld-free heat exchanger tube, fabricate and test a high pressure oxidizer turbopump with an improved inlet, and develop and test methods for reducing temperature transients at start and shutdown.

Lucci, A. D.↗
NASA NTRS1985

Main propulsion system design recommendations for an advanced Orbit Transfer Vehicle

Various main propulsion system configurations of an advanced OTV are evaluated with respect to the probability of nonindependent failures, i.e., engine failures that disable the entire main propulsion system. Analysis of the life-cycle cost (LCC) indicates that LCC is sensitive to the main propulsion system reliability, vehicle dry weight, and propellant cost; it is relatively insensitive to the number of missions/overhaul, failures per mission, and EVA and IVA cost. In conclusion, two or three engines are recommended in view of their highest reliability, minimum life-cycle cost, and fail operational/fail safe capability.

Redd, L.↗
NASA NTRS1985

Aerodynamic evaluation of the redesigned Space Shuttle Main Engine hot-gas manifold

The current Space Shuttle Main Engine hot-gas manifold configuration contains three transfer ducts connecting the fuel bowl and the main injector torus. For the current study, a new hot-gas manifold was designed to improve on a previously tested two-duct concept. This was accomplished by eliminating separated flow regions, reducing local velocities, and providing as uniform a flowfield as possible. The two-duct hot-gas manifold tested in this study showed significant improvement over the existing three-duct design. The circumferential pressure gradient was reduced by 67 percent. The system total pressure loss from the discharge of the 180-degree turn to the transfer duct exit was 60 percent less than with the three duct hot gas manifold. Although only limited fluctuating pressure data were taken in the main injector, indications are that the environment there has been improved.

Vogt, S. T.↗