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The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization.

Cloud properties retrieved from satellite data are used to diagnose aircraft icing threat in single layer and multilayered ice-over-liquid clouds. The algorithms are being applied in real time to the Geostationary Operational Environmental Satellite (GOES) data over the CONUS with multilayer data available over the eastern CONUS. METEOSAT data are also used to retrieve icing conditions over western Europe. The icing algorithm's methodology and validation are discussed along with future enhancements and plans. The icing risk product is available in image and digital formats on NASA Langley ‘s Cloud and Radiation Products web site, http://www-angler.larc.nasa.gov.

An experimental research effort was begun to develop a database of airplane aerodynamic characteristics with simulated ice accretion over a large range of incidence and sideslip angles. Wind-tunnel testing was performed at the NASA Langley 12-ft Low-Speed Wind Tunnel using a 3.5% scale model of the NASA Langley Generic Transport Model. Aerodynamic data were acquired from a six-component force and moment balance in static-model sweeps from α = -5 to 85 deg. and β = -45 to 45 deg. at a Reynolds number of 0.24x10⁶ and Mach number of 0.06. The 3.5% scale GTM was tested in both the clean configuration and with full-span artificial ice shapes attached to the leading edges of the wing, horizontal and vertical tail. Aerodynamic results for the clean airplane configuration compared favorably with similar experiments carried out on a 5.5% scale GTM.

Following the satellite-level thermal vacuum test for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation spacecraft, project thermal engineers determined that the radiator used to cool the Integrated Lidar Transmitter subsystem during its operation was oversized. In addition, the thermal team also determined that the operational heaters were undersized, thus creating two related problems. Without the benefit of an additional thermal vacuum test, it was necessary to develop and prove by analysis a laser temperature control scheme using the available resources within the spacecraft along with proper resizing of the radiator. A resizing methodology and new laser temperature control scheme were devised that allowed, with a minimum of 20% heater power margin, the operating laser to maintain temperature at the preferable set point. This control scheme provided a solution to a critical project problem.

A new approach for development of a 50-kW directly solar-pumped iodine laser (DSPIL) system as a space-based power station was made using a confocal unstable resonator (CUR). The CUR-based DSPIL has advantages, such as performance enhancement, reduction of total mass, and simplicity which alleviates the complexities inherent in the previous system, master oscillator/power amplifier (MOPA) configurations. In this design, a single CUR-based DSPIL with 50-kW output power was defined and compared to the MOPA-based DSPIL. Integration of multiple modules for power requirements more than 50-kW is physically and structurally a sound approach as compared to building a single large system. An integrated system of multiple modules can respond to various mission power requirements by combining and aiming the coherent beams at the user's receiver.

This study addresses the possibility of beaming laser power from synchronous lunar orbits (the L1 and L2 LaGrange points) to a manned long-range lunar rover. The rover and two versions of a satellite system (one powered by a nuclear reactor; the other by photovoltaics) are described in terms of their masses, geometry, power needs, mission and technological capabilities. Laser beam power is generated by a laser diode array in the satellite and converted to 30 kW of electrical power at the rover. Present technological capabilities, with some extrapolation to near future capabilities, are used in the descriptions. The advantages of the two satellite/rover systems over other such systems and over rovers with on-board power are discussed along with the possibility of enabling other missions.

In 1988, a 1067 m long touchdown zone on each end of the Kennedy Space Center (KSC) Shuttle Landing Facility (SLF) was modified from its original heavy-broom finish with transverse grooves configuration to a longitudinal corduroy surface texture with no transverse grooves. The intent of this modification was to reduce the spin-up wear on the Orbiter main gear tires and provide for somewhat higher crosswind capabilities at that site. The modification worked well, so it was proposed that the remainder of the runway be modified as well to permit even higher crosswind landing capability. Tests were conducted at the NASA Langley Aircraft Landing Dynamics Facility (ALDF) to evaluate the merit of such a modification. This paper discusses the results of these tests, and explains why the proposed modification did not provide the expected improvement and thus was not implemented.

Current aircraft operating problems that must be alleviated for future high-density terminal areas are safety, dependence on weather, congestion, energy conservation, noise, and atmospheric pollution. The MLS under development by FAA provides increased capabilities over the current ILS. It is, however, necessary and urgent to develop the airborne system's capability to take maximum advantage of the MLS capabilities in order to solve the terminal area problems previously mentioned. A major limiting factor in longitudinal spacing for capacity increase is the trailing vortex hazard. Promising methods for causing early dissipation of the vortices are being explored. Also, flight procedures for avoiding the hazard will be explored.

The five basic elements affecting runway traction for jet transport aircraft operation are identified and described in terms of pilot, aircraft system, atmospheric, tire, and pavement performance factors or parameters. Runway traction is so affected by the interaction of these elements that it becomes an impossible task to discuss the effects of each element individually. For this reason, this paper discusses runway traction under the general headings of dry, wet and flooded, and snow and ice conditions. Where possible, research results are summarized, and means for restoring or improving runway traction for these different conditions are discussed.

NASA antiskid braking system research programs are reviewed. These programs include experimental studies of four antiskid systems on the Langley Landing Loads Track, flight tests with a DC-9 airplane, and computer simulation studies. Results from these research efforts include identification of factors contributing to degraded antiskid performance under adverse weather conditions, tire tread temperature measurements during antiskid braking on dry runway surfaces, and an assessment of the accuracy of various brake pressure-torque computer models. This information should lead to the development of better antiskid systems in the future.

Various conditions can cause an aircraft to assume a roll or tilt angle on the runway, causing the nose tire(s) to produce significant uncommanded cornering forces if the nose gear is free to swivel. An experimental investigation was conducted using a unique towing system to measure the cornering forces generated by a tilted aircraft tire. The effects of various parameters on these cornering forces including tilt angle, trail, rake angle, tire inflation pressure, vertical load, and twin-tire configuration were evaluated. Corotating twin-tires produced the most severe cornering forces due to tilt angle. A discussion of certain design and operational considerations is included.

The condition of aircraft tires and runway surfaces can be crucial in meeting the stringent demands of aircraft ground operations, particularly under adverse weather conditions. Gaining a better understanding of the factors influencing the tire/pavement interface is the aim of several ongoing NASA Langley research programs which are described in this paper. Results from several studies conducted at the Langley Aircraft Landing Dynamics Facility, tests with instrumented ground vehicles and aircraft, and some recent aircraft accident investigations are summarized to indicate effects of different tire and runway properties. The Joint FAA/NASA Runway Friction Program is described together with some preliminary test findings. The scope of future NASA Langley research directed towards solving aircraft ground operational problems related to the tire/pavement interface is given.

One of the risks associated with wet runway aircraft operation is the ingestion of water spray produced by an aircraft's tires into its engines. This problem can be especially dangerous at or near rotation speed on the takeoff roll. An experimental investigation was conducted in the NASA Langley Research Center Hydrodynamics Research Facility to measure the flow rate and trajectory of water spray produced by an aircraft nose tire operating on a flooded runway. The effects of various parameters on the spray patterns including distance aft of nosewheel, speed, load, and water depth were evaluated. Variations in the spray pattern caused by the airflow about primary structure such as the fuselage and wing are discussed. A discussion of events in and near the tire footprint concerning spray generation is included.

One of the factors needed to describe the handling characteristics of the Space Shuttle Orbiter during the landing rollout is the response of the vehicle's tires to variations in load and yaw angle. An experimental investigation of the cornering characteristics of the Orbiter main gear tires was conducted at the NASA Langley Research Center Aircraft Landing Dynamics Facility. This investigation compliments earlier work done to define the Orbiter nose tire cornering characteristics. In the investigation, the effects of load and yaw angle were evaluated by measuring parameters such as side load and drag load, and obtaining measurements of aligning torque. Because the tire must operate on an extremely rough runway at the Shuttle Landing Facility at Kennedy Space Center (KSC), tests were also conducted to describe the wear behavior of the tire under various conditions on a simulated KSC runway surface. Mathematical models for both the cornering and the wear behavior are discussed.

While the initial development phase of Doppler Global Velocimetry (DGV) has been successfully completed, there remains a critical next phase to be conducted, namely the determination of an error budget to provide quantitative bounds for measurements obtained by this technology. This paper describes a laboratory investigation that consisted of a detailed interrogation of potential error sources to determine their contribution to the overall DGV error budget. A few sources of error were obvious; e.g., Iodine vapor absorption lines, optical systems, and camera characteristics. However, additional non-obvious sources were also discovered; e.g., laser frequency and single-frequency stability, media scattering characteristics, and interference fringes. This paper describes each identified error source, its effect on the overall error budget, and where possible, corrective procedures to reduce or eliminate its effect.

An experimental investigation of the flow over the rear end of a 0.16 scale notchback automobile configuration has been conducted in the NASA Langley Basic Aerodynamics Research Tunnel (BART). The objective of this work was to investigate the flow separation that occurs behind the backlight and obtain experimental data that can be used to understand the physics and time-averaged structure of the flow field. A three-component laser velocimeter was used to make non-intrusive, velocity measurements in the center plane and in a single cross-flow plane over the decklid. In addition to off-body measurements, flow conditions on the car surface were documented via surface flow visualization, boundary layer measurements, and surface pressures.