Results for “AFTS” — Page 65

NASA NTRS1989

Numerical simulation of flow through a two-strut scramjet inlet

A three-dimensional, Reynolds-averaged Navier-Stokes code has been used to numerically analyze flow through a two-strut, supersonic combustion ramjet (scramjet) inlet configuration. It solves the governing equations in full conservation form using either a fully explicit or explicit-implicit method. An algebraic, two-layer eddy-viscosity model is used for turbulent flow calculations. The analysis allows inclusion of end effects that are caused by the aft placement of the cowl on the underside of the inlet. A special grid has been developed to accommodate the struts embedded in the inlet flowfield. Detailed numerical results are presented here for the two-strut configuration, and a comparison is made with the available experimental results.

Kumar, Ajay↗

NASA NTRS1989

Innovative pylon concepts for engine-airframe integration for transonic transports

Pylon cross-sectional geometries that are believed to reduce pylon/wing installation drag are analyzed. The basic design philosophy is to alleviate flow acceleration near the pylon/wing junction by aerodynamic means. This involves reshaping the pylon, particularly on the inboard side. In some instances this is achieved by moving the pylon trailing edge closure aft of the wing trailing edge. A three-dimensional Euler code was used for the analysis. Promising pylon shapes are identified for further investigation.

Naik, Dinesh A.↗

NASA NTRS1989

Average-passage simulation of counter-rotating propfan propulsion systems as applied to cruise missiles

Counter-rotating propfan (CRP) propulsion technologies are currently being evaluated as cruise missile propulsion systems. The aerodynamic integration concerns associated with this application are being addressed through the computational modeling of the missile body-propfan flowfield interactions. The work described in this paper consists of a detailed analysis of the aerodynamic interactions between the control surfaces and the propfan blades through the solution of the average-passage equation system. Two baseline configurations were studied, the control fins mounted forward of the counter-rotating propeller and the control fins mounted aft of the counter-rotating propeller. In both cases, control fin-propfan separation distance and control fin deflection angle were varied.

Mulac, Richard A.↗

NASA NTRS1989

A direct-inverse transonic wing-design method in curvilinear coordinates including viscous-interaction

Progress in the direct-inverse wing design method in curvilinear coordinates has been made. A spanwise oscillation problem and proposed remedies are discussed. Test cases are presented which reveal the approximate limits on the wing's aspect ratio and leading edge wing sweep angle for a successful design, and which show the significance of spanwise grid skewness, grid refinement, viscous interaction, the initial airfoil section and Mach number-pressure distribution compatibility on the final design. Furthermore, preliminary results are shown which indicate that it is feasible to successfully design a region of the wing which begins aft of the leading edge and terminates prior to the trailing edge.

Ratcliff, Robert R.↗

NASA NTRS1989

Analysis of vibrations of the National Transonic Facility model support system using a 3-D aeroelastic code

Vibrations of the National Transonic Facility model support system were analyzed using Computational Aeroelasticity Program-Transonic Small Disturbance, a three-dimensional transonic small disturbance code designed for aeroelastic analysis of complete aircraft. The model support system was represented as a tunnel-spanning flexible wing whose structural properties were obtained from measured responses. Aeroelastic transients were calculated and analyzed to obtain modal stability characteristics. The results show that there is tendency to exhibit a hump mode instability in one of the modes, and that there are other weakly damped or unstable modes. Most of the motion is in the aft section of the model support system. The close proximity of the solid wind-tunnel diffuser side walls to the model support system is shown to have adverse effects on its aeroelastic stability characteristics. When the effects of the wind-tunnel walls are modeled, the analyses indicate the presence of wind-tunnel resonance modes which are not present when free-air boundary conditions are used.

Whitlow, Woodrow, Jr.↗

NASA NTRS1989

Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack

The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take/off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller mode to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.

Hughes, Christopher E.↗

NASA NTRS1989

COLD-SAT orbital experiment configured for Atlas launch

The design and requirements for the proposed cryogenic on-orbit liquid depot storage, acquisition, and transfer (COLD-SAT) satellite experiment, which is to be launched by Atlas I, are examined. The COLD-SAT experiments are categorized as class I and II; class I involves technology related to space transportation missions and class II represents alternative fluid management operations and data. The hardware for the COLD-SAT experiments consists of three hydrogen tanks contained in the experimental module; the experimental module is connected to a three-axis-controlled spacecraft bus, and thrusters are positioned on the forward and aft ends of the spacecraft and on the cylindrical portion of the experimental module. The components and systems of the experiment module and the types of experiments that can be conducted in each tank are described. Diagrams of the spacecraft configuration are provided.

Shuster, J. R.↗

NASA NTRS1990

Stowable Mechanical Sound Suppressor

Stowable sound suppressor conceived for high-speed commercial transport (HSCT) engines. Suppressor is located just aft of variable nozzle of engine. During takeoff, when suppression of noise required, multisegmented system of separators rotates out of center plug across nozzle stream. Actuation accomplished by single ball-screw drive and links, similar to spokes in umbrella. With iris nozzle translated forward, circumferential row of tubes exposed. Pattern of tubes and separators form suppressor configuration. Flow stream through slots and tubes sized to takeoff area. Useful on any turbo-jet engine in which active suppression of sound required.

Thompson, Edward R.↗

NASA NTRS1989

Aircraft modal supression system: Existing design approach and its shortcomings

The bending of flexible body aircraft may degrade the ride coMfort of passengers. This is especially noticeable towards the aft end of the aircraft (due to the relatively large tail surfaces) which may easily be excited when flying through turbulence. In addition, some aircraft may experience a front body bending mode which can be annoying to the cabin crew and first class passengers. Normally, this dominant body bending mode falls between 1 to 5 Hz. This range is easily perceived by the human body. Also, in some situations, the rigid body control law may be out of phase with the mode and aggravate the vibration. Hence, an active modal suppression system is desirable for improving the ride quality of the airplane. The size of the mathematical model, which has both the airplane rigid body and flexible characteristics, could easily exceed 100 states. The computational burden and fidelity of this large structural model is addressed.

Ho, J. K.↗

NASA NTRS1986

Independent Orbiter Assessment (IOA): Analysis of the rudder/speed brake subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbiter Rudder/Speedbrake Actuation Mechanism is documented. The function of the Rudder/Speedbrake (RSB) is to provide directional control and to provide a means of energy control during entry. The system consists of two panels on a vertical hinge mounted on the aft part of the vertical stabilizer. These two panels move together to form a rudder but split apart to make a speedbrake. The Rudder/Speedbrake Actuation Mechanism consists of the following elements: (1) Power Drive Unit (PDU) which is composed of hydraulic valve module and a hydraulic motor-powered gearbox which contains differentials and mixer gears to provide PDU torque output; (2) four geared rotary actuators which apply the PDU generated torque to the rudder/speedbrake panels; and (3) ten torque shafts which join the PDU to the rotary actuators and interconnect the four rotary actuators. Each level of hardware was evaluated and analyzed for possible failures and causes. Criticality was assigned based upon the severity of the effect for each failure mode. Critical RSB failures which result in potential loss of vehicle control were mainly due to loss of hydraulic fluid, fluid contaminators, and mechanical failures in gears and shafts.

Wilson, R. E.↗

NASA NTRS1986

Independent Orbiter Assessment (IOA): Analysis of the body flap subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items (PCIs). To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbiter Body Flap (BF) subsystem hardware are documented. The BF is a large aerosurface located at the trailing edge of the lower aft fuselage of the Orbiter. The proper function of the BF is essential during the dynamic flight phases of ascent and entry. During the ascent phase of flight, the BF trails in a fixed position. For entry, the BF provides elevon load relief, trim control, and acts as a heat shield for the main engines. Specifically, the BF hardware comprises the following components: Power Drive Unit (PDU), rotary actuators, and torque tubes. The IOA analysis process utilized available BF hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Of the 35 failure modes analyzed, 19 were determined to be PCIs.

Wilson, R. E.↗

NASA NTRS1986

Independent Orbiter Assessment (IOA): Analysis of the auxiliary power unit

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Auxiliary Power Unit (APU). The APUs are required to provide power to the Orbiter hydraulics systems during ascent and entry flight phases for aerosurface actuation, main engine gimballing, landing gear extension, and other vital functions. For analysis purposes, the APU system was broken down into ten functional subsystems. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. A preponderance of 1/1 criticality items were related to failures that allowed the hydrazine fuel to escape into the Orbiter aft compartment, creating a severe fire hazard, and failures that caused loss of the gas generator injector cooling system.

Barnes, J. E.↗

NASA NTRS1987

Independent Orbiter Assessment (IOA): Analysis of the electrical power distribution and control subsystem, volume 1

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Electrical Power Distribution and Control (EPD and C) hardware. The EPD and C hardware performs the functions of distributing, sensing, and controlling 28 volt DC power and of inverting, distributing, sensing, and controlling 117 volt 400 Hz AC power to all Orbiter subsystems from the three fuel cells in the Electrical Power Generation (EPG) subsystem. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Of the 1671 failure modes analyzed, 9 single failures were determined to result in loss of crew or vehicle. Three single failures unique to intact abort were determined to result in possible loss of the crew or vehicle. A possible loss of mission could result if any of 136 single failures occurred. Six of the criticality 1/1 failures are in two rotary and two pushbutton switches that control External Tank and Solid Rocket Booster separation. The other 6 criticality 1/1 failures are fuses, one each per Aft Power Control Assembly (APCA) 4, 5, and 6 and one each per Forward Power Control Assembly (FPCA) 1, 2, and 3, that supply power to certain Main Propulsion System (MPS) valves and Forward Reaction Control System (RCS) circuits.

Schmeckpeper, K. R.↗

NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 1

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware, and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. The IOA product for the RCS analysis consisted of 208 hardware and 2064 EPD and C failure mode worksheets that resulted in 141 hardware and 449 EPD and C potential critical items (PCIs) being identified. A comparison was made of the IOA product to the NASA FMEA/CIL baseline. After comparison and discussions with the NASA subsystem manager, 96 hardware issues, 83 of which concern CIL items or PCIs, and 280 EPD and C issues, 158 of which concern CIL items or PCIs, and 280 EPD and C issues, 158 of which concern CIL items or PCIs, remain unresolved. Volume 1 contains the subsystem description, assessment results, and some of the IOA worksheets.

Prust, Chet D.↗

NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 2

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 2 continues the presentation of IOA worksheets.

Prust, Chet D.↗

NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 3

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 3 continues the presentation of IOA worksheets.

Prust, Chet D.↗

NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 4

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 4 continues the presentation of IOA worksheets and contains the potential critical items list.

Prust, Chet D.↗

NASA NTRS1988

Independent Orbiter Assessment (IOA): Assessment of the reaction control system, volume 5

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the aft and forward Reaction Control System (RCS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter RCS hardware and EPD and C systems. Volume 5 contains detailed analysis and superseded analysis worksheets and the NASA FMEA to IOA worksheet cross reference and recommendations.

Prust, Chet D.↗