A Comparison of Minimum Time Profiles for the F-104 Using Balakrishnan's Epsilon Technique and the Energy Method
Minimum time profiles for F-104 aircraft by Balakrishnan epsilon technique, comparing solutions with energy method
Iliff, K. W.↗
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Three-dimensional, minimum fuel turns for a supersonic aircraft
Three dimensional minimum fuel turns for supersoni aircraft by energy state approximation
Bryson, A. E., Jr.↗
Minimum-mass design of a plate-like structure for specified fundamental frequency
Minimum mass design of two dimensional plate-like structure with free vibration fundamental frequency or aeroelastic constraints, using optimal theory for extremum
Armand, J.-L.↗
Minimum impulse tests of 0.45-N liquid hydrazine catalytic thrusters
An exploratory test series was conducted on three types of 0.45-N (0.1 lbf) liquid hydrazine thrusters to ascertain the minimum impulse bit capability for this class of engine. The test series is described and the results are presented. The testing was performed at 21 and 145 C (70 and 300 F) while maintaining nominal 0.45 N (0.1 lbf) upstream conditions. Valve on-times as low as 0.008 sec were applied. Impulse bits were observed for thruster temperatures of 21 and 145 C (70 and 300 F), respectively.
Moynihan, P. I.↗
Minimum weight passive insulation requirements for hypersonic cruise vehicles.
Analytical solutions are derived for two representative cases of the transient heat conduction equation to determine the minimum weight requirements for passive insulation systems of hypersonic cruise vehicles. The cases discussed are the wet wall case with the interior wall temperature held to that of the boiling point of the fuel throughout the flight, and the dry wall case where the heat transferred through the insulation is absorbed by the interior structure whose temperature is allowed to rise.
Ardema, M. D.↗
Perturbation guidance for minimum time flight paths of spacecraft.
The problem of transferring a rocket vehicle from a given circular orbit to a larger coplanar circular orbit in minimum time, using a constant low-thrust rocket engine, is considered. Parameters are chosen to correspond to a transfer from the earth's orbit in heliocentric space to the orbit of Mars. A path satisfying the first order necessary conditions of variational calculus is shown to be locally minimizing by application of a set of second order conditions. A physical explanation is offered to justify the retrothrust period occurring during the flight. A neighboring optimum feedback control law, based on estimated time-to-go, is applied to this problem. State variable and terminal constraint feedback gains are calculated while one of the second order conditions, involving the backward integration of a matrix Riccati equation, is being tested.
Wood, L. J.↗
Numerical method for design of minimum-drag supersonic wing camber with constraints on pitching moment and surface deformation
A numerical method, based on linearized theory, for designing minimum-drag supersonic wing camber surfaces of arbitrary planform for a given lift, with options for constraining the pitching moment and/or the surface deformation at the trailing edge of the root chord and for selecting any desired combination of eight specified wing-loading distributions to be employed in the optimization procedure is presented. Two examples are given to illustrate applications of the method. The results indicate that relatively small drag penalties are incurred in designing wings to be self-trimming and to have a reasonable camber surface.
Sorrells, R. B.↗
Development of welded metal bellows having minimum effective diameter change
A program of analysis, design, and fabrication was conducted to develop welded metal bellows having a minimum change in effective diameter for cryogenic turbomachinery face seal applications. Linear analysis of the principle types of bellows provided identification of concepts capable of meeting basic operation requirements. For the 6-inch (.152 m) mean diameter, 1.5-inch free length bellows studied, nonlinear analysis showed that opposed and nested toroidal bellows plates stiffened by means of alternating stiffener rings were capable of maintaining constant effective diameter within 0.3% and 0.1% respectively under the operating conditions of interest. Changes in effective diameter were due principally to bellows axial deflection with pressure differential having a lesser influence. Fabrication problems associated with joining the thin bellows plates to the relatively heavy stiffener rings were encountered and precluded assembly and testing of a bellows core. Fabrication problems are summarized and recommended fabrication methods for future effort are presented.
Henschel, J. K.↗
Approximations in the minimum time-to-climb problem
The minimum time-to-climb problem is formulated as a third order system and three approximate solutions based on reduced order systems are presented. The first of these is the often used energy state, the second is the less frequently used two state and the third is a slightly altered form of the second, herein called the modified two state. These three approximations are discussed and compared both qualitatively and, by using a numerical example, quantitatively. The numerical example is also solved by the steepest descent method to provide a basis for comparison. It is concluded that the modified two state approximation is significantly better than the other two. This approximation is used to assess the sensitivity of climb performance to various vehicle parameters and it is found that, as expected, thrust and weight influence the time-to-climb most strongly.
Ardema, M. D.↗
An efficiency study on obtaining the minimum weight of a thermal protection system
Three minimizing techniques are evaluated to determine the most efficient method for minimizing the weight of a thermal protection system and for reducing computer usage time. The methods used (numerical optimization and nonlinear least squares) for solving the minimum-weight problem involving more than one material and more than one constraint are discussed. In addition, the one material and one constraint problem is discussed.
Williams, S. D.↗
Longitudinal aerodynamic performance of a series of power-law and minimum wave drag bodies at Mach 6 and several Reynolds numbers
Experimental data have been obtained for two series of bodies at Mach 6 and Reynolds numbers, based on model length, from 1.4 million to 9.5 million. One series consisted of axisymmetric power-law bodies geometrically constrained for constant length and base diameter with values of the exponent n of 0.25, 0.5, 0.6, 0.667, 0.75, and 1.0. The other series consisted of positively and negatively cambered bodies of polygonal cross section, each having a constant longitudinal area distribution conforming to that required for minimizing zero-lift wave drag at hypersonic speeds under the geometric constraints of given length and volume. At the highest Reynolds number, the power-law body for minimum drag is blunter (exponent n lower) than predicted by inviscid theory (n approximately 0.6 instead of n = 0.667); however, the peak value of lift-drag ratio occurs at n = 0.667. Viscous effects were present on the bodies of polygonal cross section but were less pronounced than those on the power-law bodies. The trapezoidal bodies with maximum width at the bottom were found to have the highest maximum lift-drag ratio and the lowest mimimum drag.
Ashby, G. C., Jr.↗
Simulator study of minimum acceptable level of longitudinal stability for a representative STOL configuration during landing approach
A fixed-base simulator study was conducted to determine the minimum acceptable level of longitudinal stability for a representative turbofan STOL (short take-off and landing) transport airplane during the landing approach. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom, and the aerodynamic inputs were based on measured wind-tunnel data. The primary piloting task was an instrument approach to a breakout at a 60-m (200-ft) ceiling.
Grantham, W. D.↗
Implementation of digital filters for minimum quantization errors
In this paper a technique is developed for choosing programing forms and bit configurations for digital filters that minimize the quantization errors. The technique applies to digital filters operating in fixed-point arithmetic in either open-loop or closed-loop systems, and is implemented by a digital computer program that is based on a digital simulation of the system. As an output the program gives the programing form required for minimum quantization errors, the total bit configuration required in the filter, and the location of the binary decimal point at each quantizer within the filter.
Phillips, C. L.↗
Simulation study of intracity helicopter operations under instrument conditions to category 1 minimums
A fixed-base simulator study was conducted to define pilot workload and task performance associated with instrument flight operations for an intracity helicopter passenger service. Displays considered necessary to provide a minimal capability under Instrument Flight Rules conditions were used to fly a representative commercial helicopter route structure in the New York area, with each terminal assumed to be equipped with a precision approach guidance system. A cross section of pilots participated as test subjects, and despite the high workload level, the results indicated that for the assumptions employed, minimums of 61 m (200 ft) ceiling and 805 m (0.5 mile) visibility were feasible.
Callan, W. M.↗
A unique concept for automatically controlling the braking action of wheeled vehicles during minimum distance stops
Test results of a unique automatic brake control system are outlined and a comparison is made of its mode of operation to that of an existing skid control system. The purpose of the test system is to provide automatic control of braking action such that hydraulic brake pressure is maintained at a near constant, optimum value during minimum distance stops.
Barthlome, D. E.↗
Preliminary study of the minimum temperatures for valid testing in a cryogenic wind tunnel
The minimum operating temperature which avoids real-gas effects, such as condensation, was determined for M sub infinity = 0.85 flow over a 0.137-meter NACA 0012-64 airfoil mounted in the Langley 1/3-meter transonic cryogenic tunnel. For temperatures within 5 K of reservoir saturation and total pressures from 1.2 to 4.5 atmospheres, the pressure distributions over the airfoil are not altered by real-gas effects. This ability to test at total temperatures below those which avoid saturation over the airfoil allows an increase in Reynolds number capability of at least 17 percent for a constant tunnel total pressure. Similarly, 17 percent less total pressure is required to obtain a given Reynolds number.
Hall, R. M.↗
Scanning NASTRAN output data for maximum and minimum values
A computer program called NASCAN (NASTRAN scan) is described. NASCAN enables users to scan lengthy NASTRAN output files for maximum and minimum values in easy user oriented categories. Areas of high stress or deflections in any of the NASTRAN rigid formats are quickly detected and listed out for project documentations. The NASTRAN model is then revised if necessary by updating an input file tape which is processed through the NASTRAN program.
Walker, D. C.↗
Development of minimum correction wind tunnels
Flow distortions due to wind tunnel wall interference may be accounted for if the model to tunnel ratio is small, but the theory becomes less reliable as the model becomes larger. This paper presents theoretical analysis and experimental evidence which supports a new concept of wind tunnel. The method employs active control of flow through the walls so that the model is in approximately free air conditions during the test. Practical considerations in the design of such a tunnel are presented. Results indicate that a minimum correction wind tunnel may be achieved with active walls of relatively low porosity.
Bernstein, S.↗