Effects due to proximity-induced electric dipole moments on Br + H2 collisions in an intense laser field
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Zimmerman, I. H.↗
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A numerical study of the effects of wind tunnel wall proximity on an airfoil model
A procedure was developed for modeling wind tunnel flows using computational fluid dynamics. Using this method, a numerical study was undertaken to explore the effects of solid wind tunnel wall proximity and Reynolds number on a two-dimensional airfoil model at low speed. Wind tunnel walls are located at varying wind tunnel height to airfoil chord ratios and the results are compared with freestream flow in the absence of wind tunnel walls. Discrepancies between the constrained and unconstrained flows can be attributed to the presence of the walls. Results are for a Mach Number of 0.25 at angles of attack through stall. A typical wind tunnel Reynolds number of 1,200,000 and full-scale flight Reynolds number of 6,000,000 were investigated. At this low Mach number, wind tunnel wall corrections to Mach number and angle of attack are supported. Reynolds number effects are seen to be a consideration in wind tunnel testing and wall interference correction methods. An unstructured grid Navier-Stokes code is used with a Baldwin-Lomax turbulence model. The numerical method is described since unstructured flow solvers present several difficulties and fundamental differences from structured grid codes, especially in the area of turbulence modeling and grid generation.
Potsdam, Mark↗
Overview of Experimental Investigations for Ares I Launch Vehicle Development
Another concern for the vehicle during its design trajectory was the separation of the first stage solid rocket booster from the upper stage component after it had depleted its solid fuel propellant. There has been some concern about the interstage of the first stage from clearing the nozzle of the J2-X engine. A detailed separation aerodynamic wind tunnel investigation was conducted in the AEDC VKF Tunnel A to help to investigate the interaction aerodynamic effects5. A comparison of the separation plane details between the Ares I architecture and the Ares I-X demonstration flight architecture is shown in figure 12. The Ares I design requires a more complex separation sequence and requires better control in order to avoid contact with the nozzle of the upper stage engine. The interstage, which houses the J2-X engine for the Ares I vehicle, must be able to separate cleanly to avoid contact of the J2-X engine. There is only about approximately 18 inches of buffer inside the interstage on each size of the nozzle so this is a challenging controlled separation event. This complex experimental investigation required two separate Ares I models (upper stage and first stage with interstage attached) with independent strain gauge balances installed in each model. It also required the Captive Trajectory System (CTS) that was needed to precisely locate the components in space relative to each other to fill out the planned test matrix. The model setup in the AEDC VKF Tunnel A is shown in figure 13. The CTS remotely positioned the first stage at the required x, y, and z positions and was able to provide interactions within 0.2" of the upper stage. A sample of the axial force on the first stage booster is shown in figure 14. These results, as a function of separation distance between the two stages, are compared to pre-test CFD results. Since this is a very challenging, highly unsteady flow field for CFD to correctly model, the experimental results have been utilized by GN&C discipline to more accurately represent the interaction aerodynamics. In addition to the integrated forces and moments obtained from the test, flow visualization data was obtained from this test in the form of Schlieren photographs, as shown in figure 15, which show the shock structure and interaction effects after the two stages separate during flight. This separation test was crucial in the successful flight test of the Ares I-X vehicle and provided the GN&C discipline with the unpowered proximity aerodynamic effect for a separation of the Ares I vehicle.
Tomek, William G.↗
Aerodynamic results of a separation effects test on a 0.01-scale model (52-OTS) of integrated SSV in the AEDC/VKF 40-by-40 inch supersonic wind tunnel A, volume 1
Experimental aerodynamic investigations were conducted, during the period July 18-19, 1974, in the AEDC/VKF Tunnel A facility on a 0.01-scale model (52-OTS) of the integrated space shuttle vehicle, including only one SRB. The purpose of the investigation was to obtain data for close-in proximity (SRB to orbiter/tank) effects with the orbiter/tank combination at relatively high alpha and beta attitudes, and with the SRB separation motors off. The AEDC Captive Trajectory System (CTS), which supported the SRB, was used in conjunction with the tunnel primary sector (supporting the orbiter/tank) to obtain grid type separation effects data. The one symmetrical SRB model was used interchangeably to obtain both right-hand and left-hand SRB data. Free-stream data were also obtained for the orbiter/tank and for the SRB. This data was used to provide baselines for proximity effects. The entire investigation was conducted at a free-stream Mach number of 4.5 with unit Reynolds number ranging from 4.0 to 6.5 million per foot.
Campbell, J. H., II↗
The Transition Phase in the Take-Off of an Airplane, Special Report
An investigation was undertaken to determine the character and importance of the transition phase between the ground run and steady climb in the takeoff of an airplane and the effects of various factors on this phase and on the airborne part of the takeoff as a whole. The information was obtained from a series of step-by-step integrations, which defined the motion of the airplane during the transition and which were based on data derived from actual takeoff tests of a Verville AT airplane. Both normal and zoom takeoffs under several loading and takeoff speed conditions were considered. The effects of a moderate wind with a corresponding wind gradient and the effect of proximity of the ground were also investigated. The results show that, for normal takeoffs, the best transition was realized at the lowest possible takeoff speed. Moreover, this speed gave the shortest overall takeoff distance for normal takeoffs. Zoom takeoffs required a shorter overall takeoff run than normal takeoffs, particularly with a heavy landing, if the obstacle to be cleared was sufficiently high (greater than 50 feet); no advantage was indicated to the airplane with a light loading if the height to be cleared was less. The error resulting from the neglect of the transition in the calculation of the airborne distance of takeoff was found to vary from 4% with the heaviest loading considered to -4% with the lightest loading for normal takeoffs over a 100-ft obstacle; the percentage error was twice as great for a 50-foot obstacle. For zoom takeoffs the error attained much greater values. The average wind gradient corresponding to a 5-mile-per-hour surface wind reduced the airborne distance required to clear a 50-foot obstacle by about 9% with the lightest loading and 16% with the heaviest loading; for both cases. The overall reduction due to this wind was approximately twice that resulting from the wind gradient alone. A simple expression for the reduction of observed takeoff performance to no-wind conditions is presented. Ground effect is shown to reduce the airborne distance to attain a height of 50 foot by 10% with the lightest loading and 16% with the heaviest loading; for a 100-foot obstacle the percentage reduction was about 1/2 as great.
Wetmore, J. W.↗
Effect of hand-based sensors on manipulator control performance
Manipulator task categories and motion phases require various hand-based information systems to meet the control performance requirements. The effect of proximity, tactile and force/torque sensors on the performance of remote manipulator control is discussed. An overview is presented on various experimental hand-based information systems which provide the manipulator controller some non-visual 'awareness' of the task environment. The rest of the paper describes and evaluates various control experiments performed at JPL using hand-mounted proximity sensors to guide and control hand motion near solid objects.
Bejczy, A. K.↗
The Transition Phase in the Take-Off of an Airplane
Report presents the results of an investigation to determine the character and importance of the transition phase between the ground run and steady climb in the take-off of an airplane and the effects of various factors on this phase and on the air-borne part of the take-off as a whole. The information was obtained from a series of step-by-step integrations, which defined the motion of the airplane during the transition and which were based on data derived from actual take-off tests of a Verville AT airplane. Both normal and zoom take-offs under several loading and take-off speed conditions were considered. The effects of a moderate wind with a corresponding wind gradient and the effect of proximity of the ground were also investigated.
Wetmore, J W↗
Shuttle primary reaction control system engine exhaust plume contamination effects
Space Shuttle proximity operations constitute an important part of the SSF induced external environment. The impingement of primary reaction control system (PRCS) engine plumes on SSF functional surfaces during docking or berthing and separation leads to concerns about molecular contamination and high speed particle impact. The Shuttle Plume Impingement flight Experiment (SPIE) was designed to provide a direct measure of both the molecular contamination and particle impact rates produced by Shuttle PRCS engines in the LEO environment. The measured permanent deposition produced by PRCS engine firings was less than that assumed in current SSF programatic assessments. Only two to three possible high velocity particle impact pits were observed on the RMS end effector hardware.
Koontz, Steve↗
Effects of thrust reversing in ground proximity
The changes in stability and control characteristics encountered by a thrust reversing aircraft during its final approach, landing, and ground roll are described. These changes include a strong pitch-up accompanied by the loss of horizontal tail and aileron control effectiveness. The magnitude of reverser induced changes in ground effect are much larger than corresponding changes in free air. Some unexpected unsteady motions exhibited in wind tunnel by an aircraft model with reversers operating in ground proximity are also described. The cause of this oscillatory behavior was determined to be an unsteady interaction between the wall jets formed by impingement of reverser jets on the ground and the on-coming free stream. Time histories of rolling moments measured by the wind tunnel balance or support system were removed and frequencies were scaled by Strouhal number to full scale. Corrected time series were used to simulate the motion of a fighter aircraft with thrust reversers in ground effect. The simulation predicted large roll angles and nose down attitude at touchdown. Some phenomena of jet attachment to solid surfaces are discussed and areas for future research are recommended.
Joshi, P. B.↗
The effect of short term exposures to 100 percent oxygen on the fine structure of proximal convoluted tubules
Short term pure oxygen exposure effects on rats proximal convoluted tubular cell structure
Hess, R. T.↗
Effect of dietary antioxidant level and oxygen exposure on the fine structure of the proximal convoluted tubules
Dietary antioxidant vitamin level effects on fine structure of proximal convoluted tubules in rats, studying changes due to oxygen toxicity
Hess, R. T.↗
Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground
A wind-tunnel investigation has been conducted to determine the effect of ground proximity on the aerodynamic characteristics of thick highly cambered rectangular wings with aspect ratios of 1. 2, 4, and 6. The results showed that, for these aspect ratios, as the ground war, approached all wings experienced increases in lift-curve slope and reductions in induced drag which resulted in increases in lift-drag ratio. Although an increase in lift-curve slope was obtained for all aspect ratios as the ground was approached, the lift coefficient at an angle of attack of 0 deg for any given aspect ratio remained nearly constant. The experimental results were in general agreement with Wieselsberger's ground-effect theory (NACA Technical Memorandum 77). As the wings approached the ground, there was an increase in static longitudinal stability at positive angles of attack. When operating in ground effect, all the wings had stability of height at positive angles of attack and instability of height at negative angles of attack. Wing-tip fairings on the wings with aspect ratios of 1 and 2 produced small increases in lift-drag ratio in ground effect. End plates extending only below the chord plane on the wing with an aspect ratio of 1 provided increases in lift coefficient and in lift-drag ratio in ground effect.
Fink, Marvin P.↗
Recommendations for ground effects research for V/STOL and STOL aircraft and associated equipment for large scale testing
The current understanding of the effects of ground proximity on V/STOL and STOL aircraft is reviewd. Areas covered include (1) single jet suckdown in hover, (2) fountain effects on multijet configurations, (3) STOL ground effects including the effect of the ground vortex flow field, (4) downwash at the tail, and (5) hot gas ingestion in both hover and STOL operation. The equipment needed for large scale testing to extend the state of the art is reviewed and developments in three areas are recommended as follows: (1) improve methods for simulating the engine exhaust and inlet flows; (2) develop a model support system that can simulate realistic rates of climb and descent as well as steady height operation; and (3) develop a blowing BLC ground board as an alternative to a moving belt ground board to properly simulate the flow on the ground.
Kuhn, Richard E.↗
AERODYNAMIC OBSERVATIONS FROM FLIGHT TESTS OF TWO VTOL AIRCRAFT
Effect of ground proximity, wing-stall phenomena, pitching moments, and power requirements on vtol aircraft
GROUND EFFECT↗
Investigation of Interference of a Deflected Jet with Free Stream and Ground on Aerodynamic Characteristics of a Semispan Delta-Wing VTOL Model
An investigation of the mutual interference effects of the ground, wing, deflected jet stream, and free stream of a semispan delta-wing VTOL model at zero and low forward speeds has been conducted in the 17-foot test section of the Langley 300-MPH 7-by 10-foot tunnel. The model consisted of two interchangeable semispan clipped delta wings, a simplified fuselage, and a high-pressure jet for simulation of a jet exhaust. Attached to the wing behind the jet were various sets of vanes for deflecting the jet stream to different turning angles. The effect of ground proximity gave the normally expected losses in lift at zero and very low forward speeds (up to about 60 or 80 knots for the assumed wing loading of 100 lb/sq ft); at higher forward speeds ground effects were favorable. At low forward speeds, out of ground effect, the model encountered large losses in lift and large nose-up pitching moments with the model at low angles of attack and the jet deflected 90 deg or 75 deg (the angles required for VTOL performance and very low forward speeds). Rotating the model to higher angles of attack and deflecting the jet back to lower angles eliminated these losses in lift. Moving the jet rearward with respect to the wing reduced the losses in lift and the nose-up moments at all speeds within the range of this investigation.
Spreemann, Kenneth P.↗
The ground effects of a powered-lift STOL aircraft during landing approach
The effects of ground proximity on a powered lift STOL aircraft are presented. The data are from NASA's Quiet Short Haul Research Aircraft (QSRA) flown at landing approach airspeeds of less than 60 knots with an 80 lb/sq ft wing loading. These results show that the ground effect change in lift is positive and does significantly reduce the touchdown sink rate. These results are compared to those of the YC-14 and YC-15. The change in drag and pitching moment caused by ground effects is also presented.
Stevens, Victor C.↗
Optical devices for proximity operations study and test report
Operational and physical requirements were investigated for a low-light-level viewing device to be used as a window-mounted optical sight for crew use in the pointing, navigating, stationkeeping, and docking of space vehicles to support space station operations and the assembly of large structures in space. A suitable prototype, obtained from a commercial vendor, was subjected to limited tests to determine the potential effectiveness of a proximity optical device in spacecraft operations. The constructional features of the device are discussed as well as concepts for its use. Tests results show that a proximity optical device is capable of performing low-light-level viewing services and will enhance manned spacecraft operations.
Smith, R. A.↗
Ground effect aerodynamics
The results of experimental and analytical studies on an isolated lifting rotor in ground effect at low advance ratios are discussed. The experiments show that the favorable effect of ground proximity in hover disappears rapidly with small increases in advance ratio. Two flow regimes occur, a recirculation of the rotor wake is present at the low end of the advance ratio range investigated and a ground vortex is formed as advance ratio increases, causing irregular changes in the hub moments with advance ratio. Experimental results also show that translational acceleration has a significant effect on the ground effect of a lifting rotor. Hot wire measurements of the flow field under the ratio in ground effect are also presented. The experimental data are analyzed to determine effective values of the inflow in ground effect.
Curtiss, H. C., Jr.↗