Search NASA⌕ Search

SEARCH · Search NASA

Results for “Tactics”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Contribution to solving the energy crisis - Simulating the prospects for low cost energy through silicon solar cells

PECAN (Photovoltaic Energy Conversion Analysis) is a highly interactive decision analysis and support system. It simulates the prospects for widespread use of solar cells for the generation of electrical power. PECAN consists of a set of integrated APL functions for evaluating the potential of terrestrial photovoltaics. Specifically, the system is a deterministic simulator, which translates present and future manufacturing technology into economic and financial terms, using the production unit concept. It guides solar cell development in three areas: tactical decision making, strategic planning, and the formulation of alternative options.

Kran, A.↗
NASA NTRS1979

Historical development of worldwide supersonic aircraft

Aerodynamic problems in the development of supersonic aircraft, their solutions, and innovative design features are presented. Studies of compressibility, introduction of jets, supersonic phenomena, transonic drag and lift, longitudinal and directional stability, dynamic pressure fields, and advent of the supersonic fighter are discussed. The flight research aircraft such as the Bell X-1 and the Douglas-558, the century series models, reconnaissance aircraft, the multimission tactical fighter, and the current generation fighters such as F-16 and F-18 are described. The SCAT program is considered, along with supersonic developments in Great Britain, France, and USSR. It is concluded that the sonic boom still appears to be an inherent problem of supersonic flight that particularly affects overland commercial flight, and efforts continue for increased efficiency for economic and performance gains and increased safety for military and civilian aircraft.

Spearman, M. L.↗
NASA NTRS1974

Application of IPAD to missile design

The application of an integrated program for aerospace-vehicle design (IPAD) to the design of a tactical missile is examined. The feasibility of modifying a proposed IPAD system for aircraft design work for use in missile design is evaluated. The tasks, cost, and schedule for the modification are presented. The basic engineering design process is described, explaining how missile design is achieved through iteration of six logical problem solving functions throughout the system studies, preliminary design, and detailed design phases of a new product. Existing computer codes used in various engineering disciplines are evaluated for their applicability to IPAD in missile design.

Santa, J. E.↗
NASA NTRS1980

A hill-sliding strategy for initialization of Gaussian clusters in the multidimensional space

A hill sliding technique was devised to extract Gaussian clusters from the multivariate probability density estimate of sample data for the first step of iterative unsupervised classification. Each cluster was assumed to posses a unimodal normal distribution. A clustering function proposed distinguished elements of a cluster under formation from the rest in the feature space. Initial clusters were extracted one by one according to the hill sliding tactics. A dimensionless cluster compactness parameter was proposed as a universal measure of cluster goodness and used satisfactorily in test runs with LANDSAT multispectral scanner data. The normalized divergence, defined by the cluster divergence divided by the entropy of the entire sample data, was utilized as a general separability measure between clusters. An overall clustering objective function was set forth in terms of cluster covariance matrices, from which the cluster compactness measure could be deduced. Minimal improvement of initial data partitioning was evaluated by this objective function in eliminating scattered sparse data points. The hill sliding clustering technique developed herein has the potential applicability to decomposition any multivariate mixture distribution into a number of unimodal distributions when an appropriate distribution function to the data set is employed.

Park, J. K.↗
NASA NTRS1980

Flight-measured effects of boattail angle and Mach number on the nozzle afterbody flow of a twin-jet fighter

The paper presents the flight-measured nozzle afterbody surface pressures and engine exhaust nozzle pressure-area integrated axial force coefficients on a twin-jet fighter for varying boattail angles. The objective of the tests was to contribute to a full-scale flight data base applicable to the nozzle afterbody drag of advanced tactical fighter concepts. The data were acquired during the NASA F-15 Propulsion/Airframe Interactions Flight Research Program. Nozzle boattail angles from 7.7 deg to 18.1 deg were investigated. Results are presented for cruise angle of attack at Mach numbers from 0.6 to 2.0 at altitudes from 20,000 to 45,000 feet. The data show the nozle axial force coefficients to be a strong function of nozzle boattail angle and Mach number.

Plant, T. J.↗
NASA NTRS1980

Investigation of advanced thrust vectoring exhaust systems for high speed propulsive lift

The paper presents the results of a wind tunnel investigation conducted at the NASA-Langley research center to determine thrust vectoring/induced lift characteristics of advanced exhaust nozzle concepts installed on a supersonic tactical airplane model. Specific test objectives include: (1) basic aerodynamics of a wing body configuration, (2) investigation of induced lift effects, (3) evaluation of static and forward speed performance, and (4) the effectiveness of a canard surface to trim thrust vectoring/induced lift forces and moments.

Hutchison, R. A.↗
NASA NTRS1980

Debugging embedded computer programs

Every embedded computer program must complete its debugging cycle using some system that will allow real time debugging. Many of the common items addressed during debugging are listed. Seven approaches to debugging are analyzed to evaluate how well they treat those items. Cost evaluations are also included in the comparison. The results indicate that the best collection of capabilities to cover the common items present in the debugging task occurs in the approach where a minicomputer handles the environment simulation with an emulation of some kind representing the embedded computer. This approach can be taken at a reasonable cost. The case study chosen is an embedded computer in a tactical missile. Several choices of computer for the environment simulation are discussed as well as different approaches to the embedded emulator.

Kemp, G. H.↗
NASA NTRS1980

Data base for the prediction of inlet external drag

Results are presented from a study to define and evaluate the data base for predicting an airframe/propulsion system interference effect shown to be of considerable importance, inlet external drag. The study is focused on supersonic tactical aircraft with highly integrated jet propulsion systems, although some information is included for supersonic strategic aircraft and for transport aircraft designed for high subsonic or low supersonic cruise. The data base for inlet external drag is considered to consist of the theoretical and empirical prediction methods as well as the experimental data identified in an extensive literature search. The state of the art in the subsonic and transonic speed regimes is evaluated. The experimental data base is organized and presented in a series of tables in which the test article, the quantities measured and the ranges of test conditions covered are described for each set of data; in this way, the breadth of coverage and gaps in the existing experimental data are evident. Prediction methods are categorized by method of solution, type of inlet and speed range to which they apply, major features are given, and their accuracy is assessed by means of comparison to experimental data.

Mcmillan, O. J.↗
NASA NTRS1969

Effect of wing-transition location and slotted and unslotted flaps on aerodynamic characteristics of a fighter model at high subsonic speeds

An investigation was conducted in the Langley 8 foot transonic pressure tunnel to determine the effects of wing transition location and of slotted and unslotted full span flaps on the longitudinal aerodynamic characteristics of a 1/15 scale model of a variable wing sweep tactical fighter model. Tests were at Mach numbers from 0.70 to 0.85 for a wing leading edge sweep of 26 deg.

Ayers, T. G.↗
NASA NTRS1981

Comparisons of AEROX computer program predictions of lift and induced drag with flight test data

The AEROX aerodynamic computer program which provides accurate predictions of induced drag and trim drag for the full angle of attack range and for Mach numbers from 0.4 to 3.0 is described. This capability is demonstrated comparing flight test data and AEROX predictions for 17 different tactical aircraft. Values of minimum (skin friction, pressure, and zero lift wave) drag coefficients and lift coefficient offset due to camber (when required) were input from the flight test data to produce total lift and drag curves. The comparisons of trimmed lift drag polars show excellent agreement between the AEROX predictions and the in flight measurements.

Axelson, J.↗
NASA NTRS1981

Configuration aerodynamics

Static aerodynamic research related to aircraft configurations in their cruise or combat modes is discussed. Subsonic transport aircraft, transonic tactical aircraft, and slender wing aircraft are considered. The status and plans of Langley's NTF configuration research program are reviewed. Recommendations for near term configuration research are made.

Polhamus, E. C.↗
NASA NTRS1981

F100 engine diagnostic system status to date

An engine diagnostic system, proposed for the F100 engine, was tested in five specially modified Tactical Air Command F-15 aircraft during a 16-month flight evaluation. After more than 3300 engine operating hours encompassing almost 900 flights during the flight evaluation, these aircraft provided a data base, still being analyzed, that has shown successful demonstration of the original functional characteristics. Four general design requirements, recording engine operating time/low cycle fatigue event detection, engine trim, and trend and performance data collection were demonstrated. Also, validation of maintenance actions taken and indicated needed maintenance were successfully demonstrated.

Boyless, J. A.↗
NASA NTRS1980

Thrust-vectored differential turns

Barrier surface construction in the joint space of the differential turning game for thrust-vectored vs. conventional aircraft is discussed. Differential-turn studies are based on modifications of existing computer programs including an energy-turn program, and one which generates hodograph data. Optimal turning flight in energy approximation is discussed for the conventional aircraft configurations. It is concluded that any advantages realized from thrust-vectoring are minor, unless hover is possible, where advantages would be major at low energies, and affect tactics at high energies as well.

Kelley, H. J.↗
NASA NTRS1982

Clocks for airborne systems

The potential performance of compact oscillators, needed for the development of accurate clocks for future airborne systems (such as Identification Friend or Foe schemes), is addressed. In particular, extensive testing of rubidium oscillators manufactured by Efratom is discussed. The results indicate that an accuracy of better than 10 microseconds should be achievable in tactical aircraft provided that appropriate measures are adopted to counter the many environmental factors. In a favorable environment a stability of better than 5 x 10 to the -13th power for one day is achievable with present commercial units, but improvements are required to suit operation in an aircraft. With further development of rubidium controlled clocks the ultimate limitation on time accuracy in aircraft will probably be associated with time dissemination, maintenance difficulties and doctrinal hurdles.

Houlding, N.↗
NASA NTRS1982

Flight tests for the assessment of task performance and control activity

The tests were performed with the helicopters BO 105 and UH-1D. Closely connected with tactical demands the six test pilots' task was to minimize the time and the altitude over the obstacles. The data reduction yields statistical evaluation parameters describing the control activity of the pilots and the achieved task performance. The results are shown in form of evaluation diagrams. Additionally dolphin tests with varied control strategy were performed to get more insight into the influence of control techniques. From these test results recommendations can be derived to emphasize the direct force control and to reduce the collective to pitch crosscoupling for the dolphin.

Pausder, H. J.↗
NASA NTRS1982

Impingement of an oblique shock wave on a cylinder

This paper presents a numerical simulation of impingement of an oblique shock wave on a cylinder. The study was undertaken to understand the three-dimensional shock wave and boundary-layer interactions occurring on problems such as the impingement of the bow shock wave from the Shuttle nose on an external tank, and store-carriage interference on a supersonic tactical aircraft. A thin-layer approximation of the Navier-Stokes equations is solved by a mixed explicit-implicit scheme for a supersonic Mach 4 flow with an incident shock angle of 25 deg. Both laminar and turbulent flows are investigated. Surface pressures show large extents of upstream influence, except near windward plane. Based on plots of velocity at the first mesh points above the cylinder body, a conjectured limiting-streamline pattern is constructed. Three-dimensional separation is studied, and the role of crossflow is discussed.

Hung, C. M.↗