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Commercial aviation relies almost entirely on subsonic fixed wing aircraft to constantly move people and goods from one place to another across the globe. While air travel is an effective means of transportation providing an unmatched combination of speed and range, future subsonic aircraft must improve substantially to meet efficiency and environmental targets. The NASA Fundamental Aeronautics Subsonic Fixed Wing (SFW) Project addresses the comprehensive challenge of enabling revolutionary energy-efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies, and the development of unconventional aircraft systems, offer the potential to achieve these improvements.

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.

A computer simulation was developed to investigate the effect of wind on test track estimation of heavy truck fuel efficiency. Monte Carlo simulations were run for various wind conditions, both with and without gusts, and for two different vehicle aerodynamic configurations. The vehicle configurations chosen for this study are representative of typical Class 8 tractor trailers and use wind tunnel measured drag polars for performance computations. The baseline (control) case is representative of a modern streamlined tractor and conventional trailer. The comparison (test) case is the baseline case with the addition of a trailer drag reduction device (trailer skirt). The integrated drag coefficient, overall required power, total fuel consumption, and average rate of fuel consumption were calculated for a heavy truck on an oval test track to show the effect of wind on test results.

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and began aerobraking at Mars in March 2006. In order to save propellant, MRO used aerobraking to modify the initial orbit at Mars. The spacecraft passed through the atmosphere briefly on each orbit; during each pass the spacecraft was slowed by atmospheric drag, thus lowering the orbit apoapsis. The largest area on the spacecraft, most affected by aeroheating, was the solar arrays. A thermal analysis of the solar arrays was conducted at NASA Langley Research Center to simulate their performance throughout the entire roughly 6-month period of aerobraking. A companion paper describes the development of this thermal model. This model has been correlated against many sets of flight data. Several maneuvers were performed during the cruise to Mars, such as thruster calibrations, which involve large abrupt changes in the spacecraft orientation relative to the sun.

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and started aerobraking at Mars in March 2006. During the spacecraft's design phase, thermal models of the solar panels and instruments were developed to determine which components would be the most limiting thermally during aerobraking. Having determined the most limiting components, (from a temperature limit standpoint), thermal limits in terms of heat rate were established. Advanced thermal modeling techniques were developed utilizing Thermal Desktop and Patran Thermal. Heat transfer coefficients were calculated using a Direct Simulation Monte Carlo technique. Analysis established that the solar panels were the most limiting components during the aerobraking phase of the mission.

Application of a formally designed experiment to wind tunnel testing of a sportscar prototype was explored at the Langley Full Scale Tunnel. A two-level fractional factorial design with center points was used to determine the effect of front ride height, rear wing angle, gurney flap height, spoiler height, and yaw angle on the front downforce, rear downforce, drag, and lift-to-drag ratio of the racecar. Regression models were created for each of the responses to provide aerodynamic prediction and optimization capabilities. Prediction models provide an “aerodynamic mapping” that can be used for effective tuning of the car at the track as well as serve as a math model for numerical lap simulations.

Commercial heavy trucks are characterized as bluffbodies and have unsteady wake flows and high base drag. Base drag has been studied for many years as a primary target for aerodynamic drag reduction. Many aftend devices have been created for active or passive reduction of base drag. Base flaps are one type of device that have shown promise for drag reduction. They consist of 3 or 4 panels joined at their edges to form an open box structure. Although base flaps have been shown to reduce drag, they have not been adopted by the trucking industry because they are inconvenient to deploy on a commercial scale. A practical refinement to base flaps is the two-panel wake board (WB). It is a commercially viable solution, with easy deployment and significant drag reduction. This paper presents experimental data for two-panel wake boards with varying width and inset on an Ahmed body at yaw angles up to 12 degrees.

The CFD tools in aerodynamic design process have been commonly used in aerospace industry in last three decades. Although there are many CFD software algorithms developed for aerodynamic applications, the nature of a complex, three-dimensional geometry in incompressible highly separated, viscous flow made computational simulation of ground vehicle aerodynamics more difficult than aerospace applications. However, recent developments in computational hardware and software industry enabled many new engineering applications on computational environment. Traditional production process has largely influenced by computational design, analysis, manufacturing and visualization. Different aspects of linking advanced computational tools and aerodynamic vehicle design challenges are discussed in the present work. Key technologies like parallel computation, turbulence modeling and CFD/wind tunnel compatibility issues are presented.

On January 14, 2004 President George W Bush outlined a new vision for NASA that has humans venturing back to the moon by 2020. With this ambitious goal, new tools and models have been developed to help define and predict the amount of space radiation astronauts will be exposed to during transit and habitation on the moon. A representative scenario is used that includes a trajectory from LEO to a Lunar Base, and simplified CAD models for the transit and habitat structures. For this study galactic cosmic rays, solar proton events, and trapped electron and proton environments are simulated using new dynamic environment models to generate energetic electron, and light and heavy ion fluences. Detailed calculations are presented to assess the human exposure for transit segments and surface stays.

Aerodynamic drag, lift, and side forces have a profound influence on fuel efficiency, vehicle speed, stability, acceleration and performance. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. The present study simulates the external flow field around a heavy truck with three prototype add-on drag reduction devices using a computational method. The model and the method are selected to be three dimensional and time-dependent. The Reynolds-averaged Navier Stokes equations are solved using a finite volume method. The Renormalization Group (RNG) k-ε model was elected for closure of the turbulent quantities. The run cases were chosen so that the influence of each drag reduction device could be established using a regression model from a Design of Experiments (DOEX) derived test matrix.

In view of manned missions targeted to the Moon, for which radiation exposure is one of the greatest challenges to be tackled, it is of fundamental importance to have available a tool, which allows determination of the particle flux and spectra at any time and at any point of the lunar surface. With this goal in mind, a new model of the Moon’s radiation environment due to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) has been developed. Primary particles reach the lunar surface, and are transported all throughout the subsurface layers, with backscattering patterns taken into account. The surface itself has been modeled as regolith and bedrock, with composition taken from the results of the instruments flown on the Apollo missions, namely on the Apollo 12 from the Oceanus Procellarum landing site. Subsurface environments like lava tubes have been considered in the analysis.

As part of NASA’s Aviation Safety and Security Program, a simulation study of a twin-jet transport aircraft crew training simulation was conducted to address fidelity for upset or loss-of-control flight conditions. Piloted simulation studies were conducted to compare the baseline crew training simulation model with an enhanced aerodynamic model that was developed for high-angle-of-attack conditions. These studies were conducted in a flaps-up configuration and covered the approach-to-stall, stall and post-stall flight regimes. Qualitative pilot comments and preliminary comparison with flight test data indicate that the enhanced model is a significant improvement over the baseline. Some of the significant unrepresentative characteristics that are predicted by the baseline crew training simulation for flight in the post-stall regime have been identified.

Recently, there has been a strong emphasis on aerodynamic and aeroacoustic wind tunnel testing of automobiles. While significant level resources have been spent on investigating aerodynamics, the methodology has not changed appreciably since the beginning of aerodynamics as a science. Over the past decade, a number of global flow diagnostic techniques have been developed that drastically increase the quality and quantity of data from wind tunnel testing. One of these technologies is the use of pressure sensitive luminescent coatings, known as pressure-sensitive paint, a method which has matured considerably since its inception and is now used extensively in aerospace applications with good results. The goal of this research is to implement this technology in the full scale testing of high performance automotive vehicles. This paper discusses the details of a preliminary test, such as technique, paint formulation, camera and lighting hardware, and data reduction and analysis.

The evolution of high power microwave (HPM) sources into practical systems requires the development of compact pulsed power that can be integrated into mobile platforms. One approach to pursuing this objective, developed by researchers at Sandia National Laboratories (Sandia) [1], is to utilize parallel-stacked Blumlein transmission lines energized with a compact Marx generator. Such a configuration would be capable of driving low impedance HPM sources with a long pulse waveform. One of the limitations of this approach is field enhancement-induced breakdown at the edges of the line. Another limitation is percolation of, and subsequent breakdown of the liquid dielectric that is used in the system. This paper describes a research program that, both computationally and experimentally, is studying electrical breakdown in such transmission line configurations for a variety of dielectric materials and substrate geometries.

The great cost of added radiation shielding is a potential limiting factor in many deep space missions. For this enabling technology, we are developing tools for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of various space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. Preliminary studies of deep space missions indicate that for long duration space missions, improved shield materials will be required. The details of this new method and its impact on space missions and other technologies will be discussed. This study will provide a vital tool for evaluating Gateway designs in their usage context. Providing protection against the hazards of space radiation is one of the challenges to the Gateway infrastructure designs.

All but a small fraction of human space radiation exposure has been in Low Earth Orbit (LEO) where significant protection from extraterrestrial ionizing radiation is provided as a result of its deflection in the Earth's magnetic field. The placement of a manned outpost at the L1 Lagrange Point could mark the first long-term venture into a “deep space” radiation environment, giving rise to the associated problems of long-term space exposure. One of the first issues to address is providing protection within an L1 station from a large solar particle event. A safe haven area could be used over the duration of the event or one may consider the sleep stations where it is already necessary to have added shielding. The surrounding bodies of other closely packed crewmembers in such a shelter are expected to provide a significant fraction of a crewmember's total shielding.

External aerodynamics remains one of the major concerns in designing a new generation road vehicle. In the present study, the external aerodynamics of an Ahmed body at a scale and Reynolds number, that are representative of a car or light truck at highway speeds, is explored. An experimental model test was compared with a computational model using various back angles. In addition, the experiment allowed lift and drag to be measured at yaw angles up to ±15 degrees. Reynolds number effect on drag and lift coefficients was studied and wind averaged drag coefficients were calculated. The numerical calculations used a Reynolds-averaged, unsteady Navier-Stokes formulation. Both experimental and computational results are presented for back angles of 0-, 12.5-, and 25-degrees, then compared with each other and the data available in the literature.

Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space missions. In the present report, we present methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of lunar and Mars missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints.

An objective considered in designing the new generation of heavy trucks is fuel efficiency. This can be significantly improved by reducing the overall drag force on the truck when it is in motion. With this impetus, the external aerodynamics of a heavy truck was simulated using computational fluid dynamics and the external flow was presented using computer visualization. Initially, a thorough validation study was conducted on the Ahmed body. Consequently, the model and the method were selected to be the time-dependent, three dimensional, Reynolds-averaged Navier Stokes equations that are solved using a finite volume method. The RNG k-ε model was elected for closure of the turbulent quantities. Finally, to help the estimation of the error due to two commonly practiced engineering simplifications, a parametric study was conducted. The external flow around the truck was computed with and without the tires (-6% drag error), then with or without ground plane motion (+9% drag error).

With the resurgence of the General Aviation industry, the incentive to develop new airplanes for the low-end market has increased. Increased production of small airplanes provides the designers and manufacturers the opportunity to incorporate advanced technologies that are not readily retrofitable to existing designs. Spin resistance is one such technology whose development was concluded by NASA during the 1980’s when the production of small airplanes had slipped into near extinction. This paper reviews the development of spin resistance technology for small airplanes with emphasis on wing design. The definition of what constitutes spin resistance and the resulting amendment of the Federal Aviation Regulations Part 23 to enable certification of spin resistant airplanes are also covered.