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A flight test investigation was conducted to evaluate an infrared (IR) imaging technique to visualize off-surface flow phenomena. A single-engine, general-aviation airplane was equipped with an IR imaging system that viewed the region around the left wingtip. Vortical flow at the wingtip was seeded with sulfur hexafluoride, a gas with strong infrared absorbing and emitting characteristics. Different terrain and sky backgrounds were evaluated for their effect on IR images of vortical flow. The best IR images were obtained with a clear sky background. The results of the investigation indicate that IR flow visualization compliments existing smoke generator methods for off-surface flow visualization.

Emerging advanced controls technology will allow future generation fighter aircraft to aggressively maneuver at high angles-of-attack. Currently there is a need to develop flight-validated design methodologies and guidelines to effectively integrate this technology into future aircraft. As part of the NASA High-Alpha Technology Program (HATP), advanced controls technology is being developed in ground-based research and demonstrated using the High-Alpha Research Vehicle (HARV) as a flying testbed. Efforts are in progress to develop flight validated control law design methodologies and design guidelines which could be used to effectively exploit the capabilities provided by advanced controls at high angles of attack. This paper outlines this research effort and summarizes the design process and preliminary methodologies and guidelines developed to date.

The effectiveness of a proposed concept for shielding a manned Mars vehicle using a confined magnetic field configuration is evaluated by computing estimated crew radiation exposures resulting from galactic cosmic rays and a large solar flare event. In the study the incident radiation spectra are transported through the spacecraft structure/magnetic shield using the deterministic space radiation transport computer codes developed at Langley Research Center. The calculated exposures unequivocally demonstrate that magnetic shielding could provide an effective barrier against solar flare protons but is virtually transparent to the more energetic galactic cosmic rays. It is then demonstrated that through proper selection of materials and shield configuration, adequate and reliable bulk material shielding can be provided for the same total mass as needed to generate and support the more risky magnetic field configuration.

This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design was developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile.

Message exchange for air traffic control (ATC) purposes via data link offers the potential benefits of increasing the airspace system safety and efficiency. This is accomplished by reducing communication errors and relieving the overloaded ATC radio frequencies, which hamper efficient message exchanges during peak traffic periods in many busy terminal areas. However, the many uses and advantages of data link create additional questions concerning the interface among the human-users and the cockpit and ground systems. A flight test was conducted in the NASA Langley B-737 airplane to contrast flight operations using current voice communications with the use of data link for transmitting both strategic and tactical ATC clearances during a typical commercial airline flight from takeoff to landing. Commercial airplane pilots were used as test subjects.

Preliminary results from testing of 26 X 6.6 radial-belted and bias-ply aircraft tires at NASA Langley's Aircraft Landing Dynamics Facility (ALDF) are reviewed. These tire tests are part of a larger, on going joint NASA/FAA/Industry Surface Traction and Radial Tire (START) Program involving three different tire sizes. The 26 X 6.6 tire size evaluation includes cornering performance tests throughout the aircraft ground operational speed range for both dry and wet runway surfaces. Static test results to define 26 X 6.6 tire vertical stiffness properties are also presented and discussed.

Nonparallel and nonlinear stability of a three-dimensional boundary layer, subject to crossflow instability, is investigated using parabolized stability equations (PSE). Both traveling and stationary disturbances are considered and nonparallel effect on crossflow instability is found to be destabilizing. Our linear PSE results for stationary disturbances agree well with the results from direct solution of Navier-Stokes equations obtained by Spalart (1989). Nonlinear calculations have been carried out for stationary vortices and the computed wall vorticity pattern results in streamwise streaks which resemble remarkably well with the surface oil-flow visualizations in swept-wing experiments. Other features of the stationary vortex development (half-mushroom structure, inflected velocity profiles, vortex doubling, etc.) are also captured in our nonlinear calculations. Nonlinear interaction of the stationary and traveling waves is also studied.

Linear stability of the three-dimensional compressible attachment-line boundary-layer flow on a 60° -sweep infinite-span cylinder in a Mach 3.5 free-stream is investigated by the two-dimensional (2D) eigenvalue approach. Results of this study indicate that the supersonic attachment-line boundary layer is subjected to the oblique Tollmien-Schlichting instability, and the nonparallel effect is highly destabilizing. The critical Reynolds number based upon momentum thickness is found to be about 125, in contrast with the value of 235 for incompressible flow. The frequencies of unstable travelling modes are on the order of 100KHz for the free-stream Reynolds numbers considered in the study.

A future requirements and advanced market evaluation study indicates derivatives of current wide-body aircraft, using 1980 advanced technology, would be economically attractive through 2008, but new dedicated airfreighters incorporating 1990 technology, would offer little or no economic incentive. They would be economically attractive for all payload sizes, however, if RD and T costs could be shared in a joint civil/military arrangement. For the 1994-2008 cargo market, option studies indicate Mach 0.7 propfans would be economically attractive in trip cost, aircraft price and airline ROI. Spanloaders would have an even lower price and higher ROI but would have a relatively high trip cost because of aerodynamic inefficiencies. Dedicated airfreighters using propfans at Mach 0.8 cruise, laminar flow control, or cryofuels, would not provide any great economic benefits.

A description is given of a computer program developed at the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) for the assessment of manned space station environmental control and life support systems (ECLSS) technology. The program methodology along with the data base and mission model variables are given for 17 candidate technologies that show potential for supplying metabolic oxygen and water on manned space missions. The data base includes metabolic design loads associated with crew activity, engineering design parameters for each technology option, and cost data required for candidate life cycle cost comparisons. The method for ranking the candidate options in order to provide recommendations for space station application or subsequent development is presented.

This paper represents a first step in developing the criteria for pilot interaction with advanced controls and displays in a single pilot IFR (SPIFR) environment. The research program presented herein is comprised of an analytical phase and an experimental phase. The analytical phase consisted of a review of fundamental considerations for pilot workload taking into account existing data, and using that data to develop a SPIFR pilot workload model. The rationale behind developing such a model was based on the concept that it is necessary to identify and quantify the most important components of pilot workload to guide the experimental phase of the research which consisted of an abbreviated flight test program. The purpose of the flight tests was to evaluate the workload associated with certain combinations of controls and displays in a flight environment. This was accomplished as a first step in building a data base for single pilot IFR controls and displays.

Seventeen Environmental Control and Life Support System technology options to provide metabolic oxygen and water to sustain a multiperson crew on Space Station missions have been evaluated. The options included state-of-the-art technologies as well as advanced technologies that offer the potential for improvements in Environmental Control and Life Support Systems performance. The methodology for candidate technology recommendations was based upon specific assessment criteria as functions of prelaunch development activities and postlaunch operational considerations. The electrochemical depolarized cell option for carbon dioxide concentration, the sabatier option for carbon dioxide reduction, the static feed water electrolysis option for metabolic oxygen recovery, and vapor compression distillation and multifiltration options for waste water recovery were recommended.

Discontinuous wing leading-edge droop designs have been evaluated as a means of modifying wing autorotative characteristics and thus improving airplane spin resistance. Addition of a discontinuous outboard wing leading-edge droop to three typical light airplanes having NACA 6-series wing sections produced significant improvements in stall characteristics and spin resistance. Wind tunnel tests of two wings having advanced natural laminar flow airfoil sections indicated that a discontinuous leading-edge droop can delay the onset of autorotation at high angles of attack without adversely affecting the development of laminar flow at cruise angles of attack.

A two-component LV system was used to make detailed measurements of the flowfield around both a single-rotation and a counter-rotation propeller/nacelle. The conditions measured for the single-rotation tractor configuration include two different blade angles and two propeller advance ratios, and for the counter-rotation propeller configuration include both pusher and tractor mounts. The measurements show the increasing slipstream velocities and contraction with increasing blade angle and with decreasing advance ratio. Data for the counter-rotation system show that the aft propeller turns the flow in the opposite direction from the front propeller. Additionally, the LV system was used as a diagnostic tool to provide data to explain the large side force measured on the propeller/nacelle at angle-of-attack.

An investigation was conducted in the Langley 14- By 22-Foot Subsonic Tunnel to determine the low-speed aerodynamic characteristics of a powered generic NASP-like configuration in ground effect. The model was a simplified configuration consisting of a triangular wedge forebody, a rectangular mid-section which housed the propulsion simulation system, and a rectangular wedge aftbody. Additional model components included a delta wing, exhaust flow deflectors, and aftbody fences. Six-component force and moment data were obtained over an angle of attack range from −4° to 18° while model height above the tunnel floor was varied from 1/4 inch to 6 feet. Variations in freestream dynamic pressure, from 10 psf to 80 psf, and engine ejector pressure yielded a range of thrust coefficients from 0 to 0.8. Flow visualization was obtained by injecting water into the engine simulator inlets and using a laser light sheet to illuminate the resulting exhaust flow.

Wind tunnel investigations were conducted as part of an effort to develop a stability and control database for an aerospace plane concept across a broad range of Mach numbers. The generic conical design used in these studies represents one of a number of concepts being studied for this class of vehicle. The baseline configuration incorporated a 5° cone forebody, a 75.96° delta wing, a 16°leading-edge sweep deployable canard and a centerline vertical tail. Tests were conducted in the following NASA-Langley facilities spanning a Mach range of 0.1 to 6:30- by 60-Foot Tunnel,14- by 22-Foot Subsonic Tunnel, Low Turbulence Pressure Tunnel, National Transonic Facility, Unitary Plan Wind Tunnel, and the 20 Inch Mach 6 Tunnel. Data were collected for a number of model geometry variations and test conditions in each facility. This paper highlights some of the key results of these investigations pertinent to stability considerations about all three axes.

The design and analysis of the National Aerospace Plane (NASP) depends heavily on developing critical technology areas through the Technology Maturation Program (TMP). The TMP is being completed almost entirely in government laboratories with technology dissemination to all prime NASP contractors immediately upon completion of any portion of the technology development. These critical technology areas span the entire engineering design of the vehicle; included are structures, materials, propulsion systems, propellants, propulsion/airframe integration, controls, subsystems, and aerodynamics areas. There is currently a heavy dependence on Computational Fluid Dynamics (CFD) for verification of many of the classical engineering tools. Quite often the design of an aircraft uses wind tunnel tests for much of this verification, but for NASP, this task is almost impossible from a practical standpoint.

Tests of the Space Shuttle Orbiter nose-gear tire have been completed at NASA Langley's Aircraft Landing Dynamics Facility. The purpose of these tests was to determine the cornering and wear characteristics of the Space Shuttle Orbiter nose-gear tire under realistic operating conditions. The tire was tested on a simulated Kennedy Space Center runway surface at speeds from 100 to 180 kts. The results of these tests defined the cornering characteristics which included side forces and associated side force friction coefficient over a range of yaw angles from 0° to 12°. Wear characteristics were defined by tire tread and cord wear over a yaw angle range of 0° to 4° under dry and wet runway conditions. Wear characteristics were also defined for a 15 kt crosswind landing with two blown right main-gear tires and nose-gear steering engaged.

Supersonic wind tunnels with much lower stream disturbance levels than in conventional tunnels are required to advance transition research. The ultimate objectives of this research are to provide reliable predictions of transition from laminar to turbulent flow on supersonic flight vehicles and to develop techniques for the control and reduction of viscous drag and heat transfer. The experimental and theoretical methods used at NASA Langley to develop a low-disturbance pilot tunnel are described. Typical transition data obtained in this tunnel are compared with flight and previous wind-tunnel data and with predictions from linear stability theory,

Computational experiments have been performed for a few configurations in order to investigate the effects of external flow disturbances on the extent of laminar flow and wake drag. Theoretical results have been compared with experimental data for the AEDC cone, for Mach numbers from subsonic to supersonic, and for both free flight and wind tunnel environments. The comparisons have been found to be very satisfactory, thus establishing the utility of the present method for the design and development of “laminar flow” configurations and for the assessment of wind tunnel data. In addition, the present paper presents results of calculations concerning the effects of unit Reynolds numbers on transition. This phenomenon has been observed by a few experimental investigators but has been analyzed in detail for the first time in the present paper with the aid of the theoretical predictions.