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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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Chemical analysis of blistered cones for performance evaluation of Thermo-lag material for entry heat protection of manned spacecraft
Environmental, solid-state thermal, and mechanical properties of Thermo-Lag material for entry thermal protection of advanced manned spacecraft
Performance evaluation of Thermo-lag material for advanced manned spacecraft reentry heat protection
Periodic solutions of differential equations with time lag containing small parameter
Shear lag effect on stress distribution in stiffened shells, and stress analysis of cone frustums and segments
Numerical method for determining transient blade motions of rotor with flapping and lead-lag degrees of freedom
Terminal guidance problem involving optimal control for deviations in systems with transport lag
Periodic solutions for functional differential equations with time lag, developing bifurcation theory representing delay equation extension
Magnetron ionization gauge in helium for low pressure measurement, discussing striking characteristics and time lags
Feedback controller for linear stationary differential systems with time lag and fixed unknown parameters, noting closed loop transfer function role
Time lag system performance index bounds determination and optimal feedback controller design based on min-max criteria
Lagrange multiplier in Banach space for settling optimal control in time lag system
Bicarbonate requirement for elimination of lag period of chemoautrophically grown Hydrogenomonas eutropha
An analysis has been performed for oscillatory burning of solid propellants including gas phase time lag. The gaseous flame is assumed to be premixed and laminar with a one-step overall chemical reaction. The propellant is assumed to decompose according to the Arrenhius Law, with no condensed phase reaction. With this model, strong gas phase resonance has been found in certain cases at the characteristic gas-phase frequencies, but the peaking of the acoustic admittance is in the direction favoring the damping of pressure waves. At still higher frequencies, moderate wave-amplifying ability was found. The limit of low frequency response obtained previously by Denison and Baum was recovered, and the limitations of the quasi-steady theory were investigated.
The nonlinear flap-lag coupled oscillation of torsionally rigid rotor blades in forward flight is examined using a set of consistently derived equations by the asymptotic expansion procedure of multiple time scales. The regions of stability and limit cycle oscillation are presented. The roles of parametric excitation, nonlinear oscillation, and forced excitation played in the response of the blade are determined.
Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid, in addition to bringing about a reduction in the rate of undesired heat transfer to higher temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat conduction errors and of time lag in response.
A solution is presented to an optimization problem for time lag systems by the classical method of Lagrange multipliers in a Banach space. Following terminology and assumption definitions, the regularity and controllability of the Lagrange multipliers problem is discussed, and a set of necessary conditions for an optimal control is derived. In conclusion, the solution existence, uniqueness, and sufficiency are established.
The aeroelastic instability of the coupled nonlinear flap-lag motion of a torsionally rigid helicopter blade is treated by using the perturbation method in multiple time scales. The nonlinearities present in the equations are those arising from the inclusion of moderately large deflections in the inertia and aerodynamic loading terms. The stability boundaries, amplitudes of nonlinear response, and conditions for existence of limit cycles are obtained analytically. Thus the different roles played by the forcing, parametric excitation, and nonlinear coupling in affecting the solution can be easily identified. Numerical results illustrating the behavior of the blade are presented.