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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.

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At least 109 records · Page 6
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NASA NTRS1986

Wright Brothers Lectureship in Aeronautics: Experience with HiMAT remotely piloted research vehicle - An alternate flight test approach

The highly maneuverable aircraft technology (HiMAT) program explored the various and complex interactions of advanced technologies, such as aeroelastic tailoring, close-coupled canard, and relaxed static stability. A 0.44-subscale remotely piloted research vehicle (RPRV) of a hypothetical fighter airplane was designed and flight-tested to determine the effects of these interactions and to define the design techniques appropriate for advanced fighter technologies. Flexibility and high maneuverability were provided by flight control laws implemented in ground-based computers and telemetered to the vehicle control system during flight tests. The high quality of the flight-measured data and their close correlation with the analytical design modeling proved that the RPRV is a viable and cost-effective tool for developing aerodynamic, structure, and control law requirements for highly maneuverable fighter airplanes of the future.

Deets, D. A.↗
NASA NTRS1987

Effective collision strengths for electron impact excitations in S II

Electron impact collision strengths for forbidden, semiforbidden, and allowed transitions in S II calculated using the R-matrix method are presented. Configuration interaction wave functions are used to represent the six target states included in the calculation. At low impact energies the collision strengths are dominated by resonances for several transitions. The contribution from higher partial waves is obtained in the close-coupling approximation with exchange terms omitted. Results are presented for the effective collision strengths over a wide temperature range (5000-150,000 K) of astrophysical interest. The present results for the 4S(0) yields 2P(0) transition are 20-30 percent lower than previous calculations, while for the 4S(0) yields 2D(0) transition they are in good agreement. The results are approximately 30 percent higher than those of Ho and Henry (1983) for the 4S(0) yields 2P(0) transition at 80,000 K, and the difference between the two results increases with decreasing temperatures (under 80,000 K).

Tayal, S. S.↗
NASA NTRS1987

Electron-impact excitation cross sections for the b 3Sigma(+)nu state of H2

Differential and integral cross sections for electron-impact excitation of the b 3Sigma(+)nu state of H2 have been determined in the 20-100-eV impact energy region. The calibration of the cross sections was achieved through the H2 elastic scattering cross sections, which in turn were normalized to absolute He elastic scattering cross sections. Comparison is made with available experimental data and with theoretical results applying Born-Ochkur-Rudge, distorted-wave, and close-coupling approximations.

Khakoo, M. A.↗
NASA NTRS1987

Measurement of electron-impact excitation in boronlike carbon

The cross section for the electron-impact excitation of C(+) (2s2 2p 2P0)-(2s2p2 2D) is measured in a colliding-beams apparatus for several collision energies near the threshold for the process. A cross section of (1.1 + or - 0.3) x 10 to the -16th sq cm at threshold is found. Reasonable agreement is found with close-coupling calculations.

Lafyatis, G. P.↗
NASA NTRS1986

Flight testing the X-29

A testing status report is presented for the X-29 forward-swept-wing experimental aircraft, which integrates such advanced technologies as an aeroelastically tailored composite wing, a thin supercritical airfoil, three-surface pitch control, discrete variable camber, full-authority close-coupled canards, static instability, and digital fly-by-wire flight controls. X-29 flight test results to date raise several issues pertinent to the design of future combat aircraft flight control systems; for example, they bring into question the current MIL-8785C requirements on control system time delays.

Smith, Rogers E.↗
NASA NTRS1985

Parametric study of supersonic STOVL flight characteristics

A number of different control devices and techniques are evaluated to determine their suitability for increasing the short takeoff performance of a supersonic short-takeoff/vertical landing (STOVL) aircraft. Analysis was based on a rigid-body mathematical model of the General Dynamics E-7, a single engine configuration that utilizes ejectors and thrust deflection for propulsive lift. Alternatives investigated include increased static pitch, the addition of a close-coupled canard, use of boundary layer control to increase the takeoff lift coefficient, and the addition of a vectorable aft fan air nozzle. Other performance studies included the impact of individual E-7 features, the sensitivity to ejector performance, the effect of removing the afterburners, and a determination of optional takeoff and landing transition methods. The results pertain to both the E-7 and other configurations. Several alternatives were not as well suited to the E-7 characteristics as they would be to an alternative configuration, and vice versa. A large amount of supporting data for each analysis is included.

Rapp, David C.↗
NASA NTRS1986

PAN AIR analysis of the NASA/MCAIR 279-3: An advanced supersonic V/STOL fighter/attack aircraft

PAN AIR is a computer program for predicting subsonic or supersonic linear potential flow about arbitrary configurations. The program was applied to a highly complex single-engine-cruise V/STOL fighter/attack aircraft. Complexities include a close-coupled canard/wing, large inlets, and four exhaust nozzles mounted directly under the wing and against the fuselage. Modeling uncertainties involving canard wake location and flow-through approximation through the inlet and the exhaust nozzles were investigated. The recently added streamline capability of the program was utilized to evaluate visually the predicted flow over the model. PAN AIR results for Mach numbers of 0.6, 0.9, and angles of attack of 0, 5, and 10 deg. were compared with data obtained in the Ames 11- by 11-Foot Transonic Wind tunnel, at a Reynolds number of 3.69 x 10 to the 6th power based on c bar.

Madson, Michael D.↗
NASA NTRS1987

Preliminary flight assessment of the X-29A advanced technology demonstrator

Several new technologies integrated on the X-29A advanced technology demonstrator are being evaluated for the next generation of fighter aircraft. Some of the most noteworthy ones are the forward-swept wing, digital fly-by-wire flight control system, close-coupled wing-canard configuration, aeroelastically tailored composite wing skins, three-surface pitch control configuration, and a highly unstable airframe. The expansion of the aircraft 1-g and maneuver flight envelopes was recently completed over a two-year period in 84 flights. Overall flight results confirmed the viability of the aircraft design, and good agreement with preflight predictions was obtained. The individual technologies' operational workability and performance were confirmed. This paper deals with the flight test results and the preliminary evaluation of the X-29A design and technologies. A summary of the primary technical findings in structural static loads, structural dynamic characteristics, flight control system characteristics, aerodynamic stability and control, and aerodynamic performance is presented.

Hicks, John W.↗
NASA NTRS1988

25-LBF GO2/GH2 space station thruster

Multiple 25-lbf oxygen/gaseous hydrogen thruster assemblies for the Space Station propulsion application were designed and fabricated by Rocketdyne and endurance tested at the NASA/Marshall Space Flight Center. The thrusters incorporate a regeneratively cooled thrust chamber with a nozzle area ratio of 30, a 12-element coaxial injector, an ignition system, and close-coupled propellant valves. The various thruster configurations comprised of mating different injectors and thrust chambers. Over 2 million lbf-sec of impulse was demonstrated at mixture ratios from 3 to 8.4 at vacuum conditions. A thruster was subjected to over 10,000 pulses during which minimum impulse bits of less than 0.5 lb/sec were repeatedly and reliably demonstrated. A total operating time of 25.6 hr was accumulated on the thruster assemblies with one 6.1-hr. continuous firing duration. The thrusters operated between a thrust range of 11.2 and 36.6 lbf. The test results indicate that all major technology issues for long-life gaseous oxygen/gaseous hydrogen thrusters for the Space Station application have been resolved.

Finden, L. E.↗
NASA NTRS1988

Performance of a small centrifugal pump in He I and He II

The performance characteristics of a small centrifugal pump in He I and He II are determined over the temperature range of 1.6 to 4.2 K. The single-stage pump is powered by a close-coupled cryogenic induction motor. In the absence of cavitation, pump performance (head and capacity) was found to be identical for He I and He II. Developed heads up to 16 m and capacities of up to 900 liters/hr are obtained at 7000 rpm. A three-blade screw inducer was shown to require much less suction head than a six-blade propeller inducer.

Ludtke, P. R.↗
NASA NTRS1988

Electron-impact excitation of atomic oxygen

A close-coupling approximation is employed to theoretically investigate the excitation of the 3s3S0 and 3p3P states of atomic oxygen for electron impact energies ranging from 13.87-100 eV. The target states included in the expansion of the total wave function are modeled by accurate configuration-interaction wave functions. The results are consistent with recent experimental findings for the dipole-allowed 3P-3s3S0 transition.

Tayal, S. S.↗
NASA NTRS1989

Oscillator strengths and electron collisional excitation cross sections for atomic oxygen

The electron-impact excitations of 12 states of O I are analyzed using a close-coupling approximation. The absorption oscillator strengths for dipole-allowed transitions among the states are calculated. Cross sections for excitation of the states by electron impact in the energy region 13.87 to 100 eV are compared with the data of Smith (1976) and Doering and Gulcicek. It is observed that there is a correlation between the data at energies 13.87, 20, and 30 eV for the (3)P-3p(5)P transition and at energies 13.87 and 16.5 eV for the (3)P-3s(5)S(0) transitions; however, for the dipole-allowed (3)P-3d(3)D(0) and (3)P-3s(prime)(3)D(0) transitions there are discrepancies in magnitude.

Tayal, S. S.↗
NASA NTRS1988

Cavitation characteristics of a small centrifugal pump in He I and He II

The cavitation characteristics of a small preinduced centrifugal pump operating in He I and He II over the temperature range 1.8-4.2 K are presented. The pump and close-coupled induction motor operate immersed in liquid helium. A six-blade propeller inducer and a three-blade screw inducer were both tested. With this pump configuration using either inducer, there is a tremendous difference between the cavitation characteristics of He I and He II. The net positive suction head requirements for this pump with the screw inducer could not be determined for He I, but it is less than -100 mm and, depending on flow rate, ranges between 35 and 165 mm for He II.

Ludtke, P. R.↗
NASA NTRS1989

Atomic data for opacity calculations. X - Oscillator strengths and photoionisation cross sections for O III

Energy levels and electric dipole radiative transitions were determined for O III. The wavefunctions for the bound and continuum states were derived by solving coupled integrodifferential equations in the close-coupling approximation with the aid of two methods, the R-matrix and linear algebraic methods. Configuration interaction wavefunctions are presented for eight states of the O IV target with configurations of 2s(x)sp(y) (x + y = 3). Oscillator strengths are calculated for the transitions between, and photoionization cross sections from, bound states of O III with configurations of 2s(x)2p(y)nl (for n of not greater than 10 and l of not greater than 3).

Luo, D.↗
NASA NTRS1989

An in-flight investigation of ground effect on a forward-swept wing airplane

A limited flight experiment was conducted to document the ground-effect characteristics of the X-29A research airplane. This vehicle has an aerodynamic platform which includes a forward-swept wing and close-coupled, variable incidence canard. The flight-test program obtained results for errors in the airdata measurement and for incremental normal force and pitching moment caused by ground effect. Correlations with wind-tunnel and computational analyses were made. The results are discussed with respect to the dynamic nature of the flight measurements, similar data from other configurations, and pilot comments. The ground-effect results are necessary to obtain an accurate interpretation of the vehicle's landing characteristics. The flight data can also be used in the development of many modern aircraft systems such as autoland and piloted simulations.

Curry, Robert E.↗
NASA NTRS1990

Positron-alkali atom scattering

Positron-alkali atom scattering was recently investigated both theoretically and experimentally in the energy range from a few eV up to 100 eV. On the theoretical side calculations of the integrated elastic and excitation cross sections as well as total cross sections for Li, Na and K were based upon either the close-coupling method or the modified Glauber approximation. These theoretical results are in good agreement with experimental measurements of the total cross section for both Na and K. Resonance structures were also found in the L = 0, 1 and 2 partial waves for positron scattering from the alkalis. The structure of these resonances appears to be quite complex and, as expected, they occur in conjunction with the atomic excitation thresholds. Currently both theoretical and experimental work is in progress on positron-Rb scattering in the same energy range.

Mceachran, R. P.↗
NASA NTRS1990

Search for resonances in positron-atom systems

No one likes to see a scattering cross section curve that is too smooth; it is much more interesting to find bumps and wiggles and most interesting if it is possible to understand their cause. Several types of resonances were clearly established in positron-containing systems: those lying just below a degenerate threshold (like 2s-2p in hydrogenic atoms or ions) and those representing Coulomb bound states in a rearranged channel (like Ps + H reversing positron +H(-)). Recently, two new sorts of resonances have been reported for which the resonant mechanism is not clear. The first is a very low lying resonance in the e-Ps system (obtained by an adiabatic expansion method), and the second is a similarly low lying two channel resonance in the positron -H system (obtained by a close-coupling technique.) These developments encouraged the examination of such systems using the standard methods of stabilization and complex rotation. Most of the results are negative; the low lying resonances in either system are verified. Some indication of new resonances in the e(+)-He(+) system is found; this may be caused by the attraction between Ps in the n=2 state and the He(++) nucleus.

Bhatia, A. K.↗
NASA NTRS1989

A numerically exact full wave packet approach to molecule-surface scattering

A numerically exact spectral method for solving the time-dependent Schroedinger equation in spherical coordinates is described. The angular dependence of the wave function is represented on a two-dimensional grid of evenly spaced points. The fast Fourier transform algorithm is used to transform between the angle space representation of the wave function and its conjugate representation in momentum space. The time propagation of the wave function is evaluated using an expansion of the time evolution operator as a series of Chebyshev polynomials. Calculations performed for a model system representing H2 scattering from a rectangular corrugated surface yield transition probabilities that are in excellent agreement with those obtained using the close-coupling wave packet (CCWP) method. However, the new method is found to require substantially more computation time than the CCWP method because of the large number of grid points needed to represent the angular dependence of the wave function and the variation in the number of terms required in the Chebyshev representation of the time evolution operator.

Mowrey, R. C.↗