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Showing papers in "Journal of Spacecraft and Rockets in 1973"


Journal ArticleDOI
TL;DR: In this article, an axial coordinate with origin at beginning of precombustionshock pressure rise was established for the pre-combustion-hock pre-expansion phase, where the initial boundary-layer momentum thickness was calculated based on initial boundary layer momentum thickness.
Abstract: T e = area = diameter of duct = fuel-air equivalence ratio = Mach number = pressure = Reynolds number based on initial boundary-layer momentum thickness s — axial coordinate with origin at beginning of precombustionshock pressure rise; s = s/(s0 + sd); st = s0 + sd Sdt SQ = displacements of interaction region downstream and upstream of fuel injector, respectively = temperature = value of exponent in pressure-area relationship 7]c = combustion efficiency 0 = boundary-layer momentum thickness Subscripts a = combustor entrance / = final pressure s — condition following shock f0 > tf — total, plenum condition of air and fuel, respectively w =• condition at wall

153 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented calculations of the blade cavitation compliance obtained from free streamline cascade theory and demonstrated the various influences of angle of attack, blade angle, blade thickness and cavitation number.
Abstract: The serious POGO instability experienced by many liquid propellant rockets results from a closed loop interaction between the first longitudinal structural mode of vibration and the dynamics of the propulsion system. One of the most important features in the latter is the cavitation compliance of the turbopumps. This report presents calculations of the blade cavitation compliance obtained from free streamline cascade theory and demonstrates the various influences of angle of attack, blade angle, blade thickness and cavitation number. Discrepancies between calculated and experimentally derived values are discussed.

63 citations


Journal ArticleDOI
TL;DR: In this article, the axisymmetric analog is applied to solutions of boundary-layer equations to calculate laminar, transitional, and turbulent heating rates on arbitrary blunt-nosed three-dimensional bodies at angle of attack in hypersonic flow.
Abstract: A method is developed which calculates laminar, transitional, and turbulent heating rates on arbitrary blunt-nosed three-dimensional bodies at angle of attack in hypersonic flow. The geometry of the body may be specified analytically, or generated from a doubly cubic spline fit to coordinate points. Inviscid surface streamlines are calculated from Euler's equation using a prescribed pressure distribution. Laminar and turbulent heating rates are determined along a streamline by applying the axisymmetric analog to solutions of the axisymmetric boundary-layer equations. The location of the transition region may be specified optionally by geometric location, momentum thickness Reynolds number, or integrated unit Reynolds number along a streamline. Transitional heating rates are then calculated as a weighted average of the local laminar and turbulent values. Either ideal gas or equilibrium air properties may be used. Results are presented for blunted circular cones, and a typical delta-wing space shuttle orbiter at angle of attack. In comparison with experimental data, the present method was found to yield accurate laminar heating rates and reasonably accurate transitional and turbulent heating rates. The computer program developed to calculate the results presented herein requires only a few seconds of computing time per streamline on the CDC 6600 computer.

63 citations


Journal ArticleDOI
TL;DR: The optimal control for an evasive target in a particular pursuit-evasion conflict has been determined and the solution to an associated minimax type problem is indicated, viz., the choice of gain for the pursuer so as to minimize the (maximum) miss of the optimal evader.
Abstract: The optimal control for an evasive target in a particular pursuit-evasion conflict has been determined. The pursuit vehicle has a fixed gain proportional navigation guidance system in which a pure time delay is present. The mathematical model assumes two-dimensional linearized dynamics. It is found that for fixed control energy, the evasive control depends strongly upon the gain and time delay of the pursuit system. Even in the worst case, however, the evader can significantly increase the miss distance that results from no evasive action. In addition, the results indicate the solution to an associated minimax type problem, viz., the choice of gain for the pursuer so as to minimize the (maximum) miss of the optimal evader. The results indicate that for all cases the optimal gain is approximately equal to the fuel optimal gain against a nonmaneuvering adversary and lower than the value obtained by a no-delay differential game analysis.

50 citations


Journal ArticleDOI
TL;DR: In this paper, the flowfield and base pressure characteristics of an internal-externalexpansion, truncated plug nozzle are described over the pressure ratio range from "open" wake to "closed" wake conditions.
Abstract: The flowfield and base pressure characteristics of an internal-external-expansion, truncated plug nozzle are described over the pressure ratio range from "open" wake to "closed" wake conditions. The effect of plug length on these characteristics, including the process of wake "closure" is also presented. An existing method for calculating the flowfield and base pressure, for closed wake operation, is modified to include the internal shock wave generated near the shroud exit. The supersonic portion of the flow is calculated using rotational axisymmetric method of characteristics. The technique of Hartree is employed so that the downstream characteristic point locations can be chosen to fit the developing flowfield. An overexpansion technique is used to detect the internal shock wave in the vicinity of the shroud exit so that its effect on the plug base pressure could be determined. Good agreement between the analytical results and experimental data is obtained for closed wake operations.

47 citations



Journal ArticleDOI
TL;DR: In this article, a study of the over-all operating characteristics of a parallel rail solid fuel-pulsed micro-thruster is presented, where the effect of several electrical circuit parameters (capacitance, inductance, resistance) on performance (impulse bit, specific impulse, efficiency) is investigated.
Abstract: A study of the over-all operating characteristics of a parallel rail solid fuel-pulsed microthruster is presented. Specifically, the effect of several electrical circuit parameters (capacitance, inductance, resistance) on performance (impulse bit, specific impulse, efficiency) has been investigated. The experimental results, combined with a simple model for the mass ablation and the acceleration mechanisms, provide useful correlations between thruster geometrical and electrical circuit parameters and its performance. These results should be useful in improving the performance and optimizing the design of a thruster for a given mission.

39 citations


Journal ArticleDOI
TL;DR: In this paper, a new design approach is presented to provide a conservative estimate of the buckling strength of laminated anisotropic circular cylinders under axial compression, based on the special theory for uniform axisymmetric shape imperfections which is valid for imperfections of the order of the shell wall thickness.
Abstract: A new design approach is presented to provide a conservative estimate of the buckling strength of laminated anisotropic circular cylinders under axial compression. The analysis is based on Koiter's "special theory" for uniform axisymmetric shape imperfections which is valid for imperfections of the order of the shell wall thickness. Fourteen three-ply, glass-epoxy cylinders containing random imperfections of small mean square amplitude were characterized in terms of an equivalent axial imperfection component. Good agreement was found between theory and experiment for the range of imperfection amplitudes encountered.

38 citations


Journal ArticleDOI
TL;DR: In this article, a 10% scale-model disk-gap-band-type parachute assemblies trailing in the Viking forebody wake were conducted over the range of Mach 0.2 to 2.6.
Abstract: Several experimental investigations to obtain the drag performance of 10% scale-model disk-gap-band-type parachute assemblies trailing in the Viking forebody wake were conducted over the range of Mach 0.2 to 2.6. The wind-tunnel tests varied both the canopy trailing distance and ratio of suspension line length to canopy diameter. The data obtained permitted optimization of both parameters. Parachute drag performance in the forebody wake is markedly degraded transonically beginning at Mach 0.6, reaching a minimum value at Mach 1.0, then approaches the subsonic value for the selected configuration as Mach number is increased to 1.4. Further increase in Mach number causes the drag coefficient to again decline. A 20% increase in parachute-alone transonic drag coefficient was obtained by increasing suspension-line length ratio from 1.16 to 1.73.

32 citations


Journal ArticleDOI
TL;DR: In this article, the attitude control of a spinning satellite using solar radiation pressure is studied for the general case of attutide motion in an arbitrary orbit, and the response data, presented as functions of the system parameters, show the controller's effectivenss in damping the most severe disturbances in a fraction of an orbit.
Abstract: Nutation damping and attitude control of a spinning satellite using solar radiation pressure is studied for the general case of attutide motion in an arbitrary orbit. The nonlinear, nonautonomous, coupled equations of motion involving large numbers of parameters are only amenable to a numerical approach. The response data, presented as functions of the system parameters, show the controller's effectivenss in damping the most severe disturbances in a fraction of an orbit. The controller provides versatility to the satellite, enabling it to change its preferred orientation in orbit and, hence, undertake diverse missions. An illustrative example using mass properties representative of INTELSATIV and the Canadian communications satellite (Anik-1) demonstrates the feasibility of the concept. The semipassive character promises an increased lifetime with an effective reduction in cost.

32 citations


Journal ArticleDOI
TL;DR: In this article, the occurrence of asymmetric wake configurations, and associated side forces and yawing moments, during high-incidnce flight of slender, axisymmetric missile configurations was investigated, and the root causes of wake asymmetries and means of inhibiting their occurrence were explored.
Abstract: This paper deals with the occurrence of asymmetric wake configurations, and associated side forces and yawing moments, during high-incidnce flight of slender, axisymmetric missile configurations The relevant phenomena are characterized experimentally, and the root causes of wake asymmetries and means of inhibiting their occurrence are explored It is concluded that certain flowfield disturbance devices may be effective in significantly reducing the maximum values of yawing moments induced by asymmetric disposition of wake vortices

Journal ArticleDOI
TL;DR: In this paper, the concepts for total power systems in greater detail, on breadboard implementation and testing of critical subsystems associated with the total system approach, and on studies to increase the understanding of solar array/ space plasma interactions so that the selection of array materials and physical designs can be based on a knowledge of the requirements and penalties involved.
Abstract: REVIOUS high-voltage solar array (HVSA) studies conducted1"7 under the sponsorship of NASA-LeRC have all come to similar conclusions with regard to the relative power system performance gains possible with the HVSA, the generalized techniques for implementation, the specific problem areas associated with device requirements, and the analytic evaluation of HVSA operation in the space environment. This paper considers forms most practical for ion propulsion and high-power communication satellite applications. Attention is focused on defining the concepts for total power systems in greater detail, on breadboard implementation and testing of critical subsystems associated with the total system approach, and on studies to increase the understanding of solar array/ space plasma interactions so that the selection of array materials and physical designs can be based on a knowledge of the requirements and penalties involved.

Journal ArticleDOI
TL;DR: An array of more than three instruments with noncolinear input axes is assumed, with the true value of the vector being measured completely unknown, and an estimation algorithm is described which minimizes the maximum possible error magnitude for the given set of instrument outputs.
Abstract: Minimax algorithms for failure detection and identification for redundant noncolinear arrays of single-degree-of-freedom gyros and accelerometers are described. These algorithms are optimum in the sense that detection occurs as soon as it is no longer possible to account for the instrument outputs as the outputs of good instruments operating within their noise tolerances, and identification occurs as soon as it is true that only a particular instrument failure could account for the actual instrument outputs within the noise tolerance of good instruments. An estimation algorithm is described which minimizes the maximum possible estimation error magnitude for the given set of instrument outputs. Monte Carlo simulation results are presented for the application of the algorithms to an inertial reference unit consisting of six gyros and six accelerometers in two alternate configurations.

Journal ArticleDOI
TL;DR: The Balloon Launched Decelerator Test (BLDT) series conducted at White Sands Missile Range (WSMR) during July and August of 1972 flight qualified the NASA Viking '75 decelerator system at conditions bracketing those expected for Mars.
Abstract: The Balloon Launched Decelerator Test (BLDT) series conducted at White Sands Missile Range (WSMR) during July and August of 1972 flight qualified the NASA Viking '75 decelerator system at conditions bracketing those expected for Mars. This paper discusses the decelerator system design requiremnts, compares the test results with prior work, and discusses significant considerations leading to successful qualification in earth's atmosphere. The Viking decelerator system consists of a single-stage mortar-deployed 53-foot nominal diameter disk-gap-band parachute. Full-scale parachutes were deployed behind a full-scale simulated Viking vehicle at Mach numbers from 0.47 to 2.18 and dynamic pressures from 6.9 to 14.6 psf. Analyses show that the system is qualified with sufficient margin to perform successfully for the Viking mission.

Journal ArticleDOI
TL;DR: In this paper, the authors developed guidance laws for tactical missiles which take into account the following important dynamic and random effects: random target motion, homing sensor measurement noise, bounded control level, bounded acceleration level, and missile autopilot dynamics.
Abstract: : Guidance laws are developed for tactical missiles which take into account the following important dynamic and random effects: random target motion, homing sensor measurement noise, bounded control level, bounded acceleration level, and missile autopilot dynamics. Several different guidance laws are derived using optimal stochastic control theory and evaluated by computer simulation. An important conclusion of this work is that when intercept accuracy is appreciably limited by missile maneuvering capability, a control policy obtained by taking control saturation into account can yeild significantly better performance than control policies derived assuming that control levels are unconstrained.

Journal ArticleDOI
TL;DR: In this paper, the inertial orientation of the OSO-7 spacecraft from the times at which known stars or planets transit planes fixed in the spacecraft is calculated using the star scanner.
Abstract: Calculation of the inertial orientation of the OSO-7 spacecraft from the times at which known stars or planets transit planes fixed in the spacecraft. Both the reference planes and the timing information are provided by the star scanner instrument aboard the spacecraft, while the star identification and the statistical estimation of a set of parameters describing the spacecraft attitude are accomplished in a ground station computer facility. A recursive least-squares determination is made of a vector of first-order differential corrections to the attitude state vector. Preliminary analysis indicates the system accuracy to be 3 arc min in each attitude Euler angle.

Journal ArticleDOI
TL;DR: Several closely-spaced dished accelerator grid systems have been fabricated and tested on a 30 cm-diam Hg bombardment thruster and they appear to be a solution to the stringent requirements imposed by the near-term, high-thrust, low-specific impulse electric propulsion missions as discussed by the authors.
Abstract: Several closely-spaced dished accelerator grid systems have been fabricated and tested on a 30-cm-diam Hg bombardment thruster and they appear to be a solution to the stringent requirements imposed by the near-term, high-thrust, low-specific impulse electric propulsion missions. The grids were simultaneously hydroformed and then simultaneously stress relieved. The ion extraction capability and discharge chamber performance were studied as the total accelerating voltage, the ratio of net-to-total voltage, grid spacing, and dish direction were varied.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the problems associated with restarting hybrid rocket motors (i.e., motors wherein a liquid or gaseous oxidizer is injected into the port of a solid fuel grain with subsequent mixing and combustion of the oxidizer and fuel) following a brief period of extinguishment.
Abstract: Experimental investigation of the problems associated with restarting hybrid rocket motors (i.e., motors wherein a liquid or gaseous oxidizer is injected into the port of a solid fuel grain with subsequent mixing and combustion of the oxidizer and fuel) following a brief period of extinguishment. The results include the finding that the ignition delay on restart is decreased because less energy is absorbed by the fuel before the surface reaches the ignition point.

Journal ArticleDOI
TL;DR: In this paper, a numerical integration method for the reduction of yawonde data from instrumented projectiles in free flight has been developed Yawsonde data represent two-dimensional information (solar aspect angle and spin) while the actual motion is three-dimensional (pitch, yaw, and spin).
Abstract: : A numerical integration method for the reduction of yawsonde data from instrumented projectiles in free flight has been developed Yawsonde data represent two-dimensional information (solar aspect angle and spin) while the actual motion is three-dimensional (pitch, yaw, and spin) The method obtains a best fit of the aerodynamic coefficients in the equations of motion using numerical integration The coefficients are iteratively adjusted Linear aerodynamic coefficients have been derived from the flight of an M549, 155mm rocket assisted projectile

Journal ArticleDOI
TL;DR: In this article, an analytical and experimental study of boundary layer flow over an aerodynamic surface rejecting heat to a cool environment was conducted following reentry of a Space Shuttle vehicle, showing that a surface to freestream temperature ratio greater than unity tended to destabilize the boundary layer, hastening transition and separation.
Abstract: Results of an analytical and experimental study of boundary layer flow over an aerodynamic surface rejecting heat to a cool environment. This occurs following reentry of a Space Shuttle vehicle. Analytical studies revealed that a surface to freestream temperature ratio, greater than unity tended to destabilize the boundary layer, hastening transition and separation. Therefore, heat transfer accentuated the effect of an adverse pressure gradient. Wind tunnel tests of a 0012-64 NACA airfoil showed that the stall angle was significantly reduced while drag tended to increase for freestream temperature ratios up to 2.2.

Journal ArticleDOI
TL;DR: Comments are given on the combined use of Monte Carlo and sensitivity analysis as an efficient and accurate way of improving thermal analysis.
Abstract: Alternatives to "worst-case" thermal analysis are discussed, and a Monte Carlo method is developed for treating the uncertainties inherent in property data for such analysis. Comparison is made with another treatment of such problems using sensitivity analysis. Comments are given on the combined use of Monte Carlo and sensitivity analysis as an efficient and accurate way of improving thermal analysis. Comparison of various analytical treatments is given by means of an example problem.

Journal ArticleDOI
TL;DR: In this paper, Lumped-parameter thermal network modeling techniques are derived for spacecraft thermal environment analysis and the application of these techniques to thermal/vacuum testing is described, and a major computer program required by these techniques is outlined.
Abstract: Definitions are given for spacecraft-surface thermal environment characteristics. Lumped-parameter thermal network modeling techniques are derived for spacecraft thermal environment analysis. The application of these techniques to thermal/vacuum testing is described. A major computer program required by these techniques is outlined. It is noted that this approach has been used to determine thermal environments for the Skylab ATM.

Journal ArticleDOI
TL;DR: In this article, the Boltzmann equation was used to determine the ion temperature and total charge in the exhaust of a He-Ne laser-powered FPGA and the percentage ionization can be found, and estimates made of the gas dynamic portion of the thrust.
Abstract: : Spatial and temporal measurements of the electron density were made using a He-Ne laser. The multiple pass Mach-Zehnder interferometer detects densities above ten to the fifteenth power particles/cubic centimerers. Using these data and free streaming solutions to the Boltzmann equation, which model the expansion of the exhaust, we determine the ion temperature and total charge in the exhaust. The percentage ionization can than be found, and estimates made of the gas dynamic portion of the thrust.

Journal ArticleDOI
TL;DR: In this article, three potentially dangerous flow separation phenomena involving the delta wing have been identified, each of which could seriously compromise the flight dynamics, i.e., leeside shock-induced separation, sudden leading-edge stall, and subsonic leading edge vortex and vortex burst.
Abstract: The unsteady aerodynamics of a candidate delta-wing shuttle orbiter have been investigated. Three potentially dangerous flow separation phenomena involving the delta wing have been identified, each of which could seriously compromise the flight dynamics. They are 1) leeside shock-induced separation, 2) sudden leading-edge stall, and 3) the subsonic leading-edge vortex and vortex burst. Each of these unsteady flow phenomena can be triggered by control surface deflection. Furthermore, wing stall and control-induced separation effects interact with the relatively large fuselage, increasing the coupling between lateral and directional stability characteristics. Trajectory shaping may be the most powerful means of dealing with these flow separation effects. The re-entry trajectory can be tailored to avoid or quickly traverse the unstable flow regions. However, it is prudent to use available means to control the duration and extent of separated flow when traversing the critical flow region. The unstable flow boundaries may be altered by modification of the wing planform, airfoil section, control deflections, etc.


Journal ArticleDOI
TL;DR: In this article, a transient internal ballistics model was developed incorporating nonsteady continuity and energy equations for the chamber, non-steady energy equation for the propellant condensed phase, and a modified Zeldovich heat feedback function.
Abstract: Solid rocket performance during rapid pressure excursions differs greatly from predictions based on steady-state burning rate data. Rapid pressurization (150-250 kpsi/sec) following a sudden throat area decrease in a low L* combustor produces pressure overshoots of 10% and indicated burning rate overshoots in excess of 50%. A transient internal ballistics model was developed incorporating nonsteady continuity and energy equations for the chamber, nonsteady energy equation for the propellant condensed phase, and a modified Zeldovich heat feedback function for the propellant (which for the conditions considered is known to burn with a thin quasi-steady reaction zone). Sensitivity analyses using the model indicate that accurate surface temperature and temperature sensitivity data are needed. With reasonable estimates of surface reaction zone temperature and measurements of temperature sensitivity of burning rate, good agreement between the measured and the calculated p vs t was found for a nonmetallized composite propeliant in a low L* combustor. High pressure exponent, high temperature sensitivity of burning rate, high dAJdt, low burning rate, and low L* prominently increase the dynamic effects.

Journal ArticleDOI
TL;DR: In this paper, a semianalytical method capable of analyzing both lunar and Earth orbiters is presented, which is focused on predicting the evolution of the orbit as affected by third body perturbations together with those of the rotating primary.
Abstract: A semianalytical method capable of analyzing both lunar and Earth orbiters is presented. Primary attention is focused on predicting the evolution of the orbit as affected by third body perturbations together with those of the rotating primary. The singly averaged (literal) equations of motion are expanded by machine to high order in the parallax factor and the mean motion ratio. The equations are numerically integrated to yield the orbital evolution for a wide range of initial conditions. In addition, a purely analytical method is introduced to yield the orbital lifetimes for a special class of orbits. this assumption is clearly violated in the case of the Earth-moon system. Thus in carrying out the expansion, a time rate of change for all terms containing the third body position must be included. This yields a further expansion of the disturbing function in terms of the mean motion ratio ri \ the ratio of the mean motion of the disturbing body to that of the satellite. To carry out the expansions in terms of the parallax factor and the mean motion ratio and then to average the equations of motion over one orbit requires an excessive amount of algebra for the higher order terms. To aid in the algebraic computations, a general algebraic manipulation routine was developed and was used to compute the average (literal) equations of motion to eighth order in the parallax factor and to second order in the mean motion ratio with corresponding cross terms up to and including fifth order in parallax. In addition to the third body effects, the gravity harmonics of the rotating primary must be considered. For the moon, these equations may be averaged over the orbital period since the moon rotates slowly. However, for the more rapidly rotating Earth, this analysis is invalid as the orbital mean motion may be nearly commensurate with the rotation of the primary. To avoid this problem, the equations of motion are numerically averaged from one-half orbit behind to one- half orbit ahead of the present position of the satellite. These averaged rates are then used in the total variations of the ele- ments. At present a full 7x7 and 4x4 field is used for the Earth and moon, respectively. When the tesseral harmonics are not required, only terms containing 72, /22, /3 and /4 are used and the variational equations are calculated explicitly.

Journal ArticleDOI
TL;DR: In this paper, a fluidic sounding rocket motor ignition system using a two component aerodynamic resonance heating device called the pneumatic match has been presented, where temperatures in excess of 600 C were generated in closed resonance tubes which were excited by a free air jet from a simple convergent nozzle.
Abstract: Fluidic sounding rocket motor ignition has been found to be feasible using a system without stored energy and with the complete absence of electrical energy and wiring. The fluidic ignitor is based on a two component aerodynamic resonance heating device called the pneumatic match. Temperatures in excess of 600 C were generated in closed resonance tubes which were excited by a free air jet from a simple convergent nozzle. Using nitrocellulose interface material, ignition of boron potassium nitrate was accomplished with air supply pressures as low as 45 psi. This paper describes an analytical and experimental program which established a fluidic rocket motor ignition system concept incorporating a pneumatic match with a simple hand pump as the only energy source.

Journal ArticleDOI
TL;DR: In this article, the attitude stability criteria and nutation decay times for a dual-spin satellite with a large flexible solar array were analyzed and both rotor and platform damping were included.
Abstract: Attitude stability criteria and nutation decay times for a dual-spin satellite with a large flexible solar array are found. Both rotor and platform damping are included. A continuum mechanics analysis of the solar array develops practical information regarding array natural modes, and these represent additional degrees of freedom. With proper mass balancing, the equations for spin variables can be decoupled from those for transverse variables. Assuming the solar array to be rigid, the ratio of rotor inertia to the geometric mean of the vehicle transverse inertias must be greater than unity for stability unless there is energy dissipation in the despun section. This is a significant extension of the "major axis rule.' Upper and lower stability boundaries exist for the nutation damper damping constant and the damper performance is best at high nutation frequencies. Introducing array flexibility leads to modifications of the stability boundaries when the nutation frequency becomes close to an array natural frequency.

Journal ArticleDOI
TL;DR: In this paper, an empirical method is developed for predicting the modal damping of a combined parallel-stage shuttle model by means of damping measurements performed on the individual substructures.
Abstract: An empirical method is developed for predicting the modal damping of a combined parallel-stage shuttle model by means of damping measurements performed on the individual substructures. Correlations are first determined for each component in terms of damping energy as a function of peak kinetic energy and modal amplitude. The results are then used to predict component damping energies corresponding to the respective kinetic energies and amplitudes that occur for the new modes of the combined system. Modal characteristics for the system, other than damping, are obtained by a real eigenvalue solution of dynamic equations developed by Hurty's procedure of substructures. System equations, which include component modal damping, are also solved by a complex eigenvalue approach for comparison with results of the empirical method.