Rocket-propelled Vehicle Research Articles

Research on guidance information extraction technology of strap-down seeker based on adaptive cubature Kalman filter

In comparison to the traditional platform seeker, strap-down seeker, which is firmly connected with rocket-propelled vehicle, has a lot of strength in a smaller size, a simpler structure, and a lower cost. However, because it is fixed on the rocket-propelled vehicle, inertial line-of-sight(LOS) angular velocity demanded by guidance system could not be directly obtained during the rocket-propelled vehicle flight. In this paper, according to the coordinate transformation relationship, the inertial LOS angular velocity decoupling model is established. Aiming at measurement error characteristics of a seeker, a guidance information extraction algorithm which is on basis of the adaptive cubature Kalman filter is studied, and the digital simulation experiment is carried out in combination with the engineering practice. The simulation data demonstrate that the suggested algorithm has a significant effect on improving the filtering estimation stability and accuracy of guidance information extraction and guaranteeing the accuracy of rocket-propelled vehicle hits.

Trajectory Optimization of Long-Range Guided Rocket-Propelled Vehicle Based on Pseudo-spectral Sequential Convex Programming

Aiming at the trajectory optimization problem of long-range guided rocket-propelled vehicles with multiple constraints, an improved pseudo-spectral sequence convex programming, which takes into account the efficiency and accuracy of optimization, is proposed. First, taking the change rate of the angle of attack and the bank angle as the control variables, the vehicle’s dynamic equation is discretized by using the flipped Radau pseudo-spectral method, and the trajectory optimization problem including start, end, and path constraints is transformed into a convex optimization problem by using the continuous linearization method, and then the solution is obtained by using the original dual interior point method. To make the optimized trajectory near the no-fly zone or the severe weather area more accurate, the concept of the predicted separation point is introduced to subdivide the trajectory. The simulation results show that the improved pseudo-spectral sequence convex programming has high discretization accuracy and fast solution speed, and can be applied to the online use of long-range guided rocket-propelled vehicles.

A Mars hopping vehicle propelled by a radioisotope thermal rocket: thermofluid design and materials selection

Rocket-propelled vehicles capable of travelling a kilometre or more in a ballistic ‘hop’ with propellants acquired from the Martian atmosphere offer the potential for increased mobility and planetary science return compared with conventional rovers. In concept, a radioisotope heat source heats a core or ‘thermal capacitor’, which in turn heats propellant exhausted through a rocket nozzle to provide thrust. A systematic study of the thermodynamics, heat transfer and selection of core materials for a Mars hopper was undertaken. The aim was to advance the motor design and assess technical risks and feasibility. Analytical and numerical motor models were developed; the former to generate thermodynamic performance limits, an ideal hop distance and plot a materials selection chart using simple explicit relations. The numerical model assessed the effect of core configuration and geometry. A hop coefficientChopis shown to characterize the effect of core geometry independently of core material and temperature. The target hop distance of 1 km is shown to be robust. A moderate advantage to pebble-bed cores over a core consisting of straight channels was suggested. High-performance engineering ceramics such as boron carbide offer the longest hop providing the core temperature can be increased significantly above 1200 K.

Analytic performance considerations for lifting ascent trajectories of winged launch vehicles

The so-called rocket equation, which was first derived by Konstantin Tsiolkovsky, allows to determine the velocity increase of a rocket-propelled vehicle as a function of propellant consumption and the effective velocity of the exhaust gases. It is, however, strictly valid only for a constant effective exhaust velocity and in the absence of external forces, such as atmospheric drag or gravity. Empirical corrections and analytic approximations have been developed to account for deviations from these conditions for ballistic launch vehicles. The rocket equation is, however, inadequate for performance calculations of winged launch vehicles with aerodynamic ascent and especially air breathing propulsion, which may experience significant aerodynamic forces and large variations in the effective exhaust velocity. In order to enable fast, yet accurate performance assessments for such vehicles, a class of analytic solutions for the equation of motion along the trajectory of launch vehicles with lifting ascent has been derived.

Optimal flight paths for winged, supersonic flight vehicles — extension to the case where thrust can be vectored

The theory of optimal flight paths goes back to 1951, when Tsien and Evans found the optimal thrust program for a vertically ascending sounding rocket. Hibbs, in 1952, solved the problem of the optimal burning program for horizontal flight of a winged, rocket propelled vehicle. Miele has carried out much work in this field, mostly using*the assumption of constant thrust, and working without the aid of a digital computer, (which is necessary to achieve results). Reference 3 gives a summary of early work in this field.Recently, the problem of optimal climb paths of a ballistic rocket, away from the vertical, has been shown in Ref. 4 to have a simple analytic solution. The problem of a winged supersonic rocket missile, assuming the thrust acts along flight path, has been solved in Ref. 5.

Optimal flight paths for a winged supersonic rocket vehicle

In 1951, Tsien and Evans successfully solved the problem of finding the optimum flight path for a vertically ascending sounding rocket (Ref. 1). Hibbs, in 1952, solved the problem of finding the optimum burning program for horizontal flight of a winged, rocket-propelled vehicle (Ref. 2). Since then work on optimal flight paths within the atmosphere has stagnated, most work being done for constant thrust, programmed in angle, in vacuo.The present work extends Tsien and Evans', and Hibbs' work, to flight paths off the vertical. Although the simpler paths produced analytical solutions in the time domain, the present solution is not analytic and is carried out numerically using distance or path length as the independent variable.

Reduced-gravity simulators for studies of man's mobility in space and on the moon.

A brief review of some reduced-gravity simulators recently developed at NASA's Langley Research Center to study specific problems relating to man's mobility in various space missions is presented in this paper along with a discussion of the manner in which these devices can be applied to other mobility problems. The devices covered in this review are the lunar walking simulator, the rotating space station simulator, and the lunar landing research facility being utilized by the Spacecraft Research Branch of LRC. These facilities are applicable to a rather broad field of space activities including such aspects as man walking on the lunar surface in a pressurized space suit, flying over the lunar surface with a backpack propulsion unit or a small rocket-propelled vehicle, driving a surface roving vehicle, and orbital assembly of spacecraft components. These facilities can also be applied to studies of space missions on other planets, moons, and asteroids.

Interstellar Vehicle propelled by Terrestrial Laser Beam

IN a recent article Marx1 examined the possibility that interstellar travel may be accomplished in the lifetime of an astronaut. He pointed out that the attainment of relativistic velocities by a rocket-propelled vehicle is hampered by the low efficiency, which is a result of the energy acquired by the ejected mass. Marx suggested that if an interstellar vehicle were driven by the pressure exerted on it by a light beam transmitted from the Earth, then, because the recoil momentum and energy would now be acquired by an extremely massive body—the Earth—the energy wasted would be negligible.

ELECTRICAL PROPULSION CAPABILITIES FOR LUNAR EXPLORATION

The logical result of a successful Apollo program can be expected to be a large scale operation involving manned lunar exploration and colonization. The potential role of electrical propulsion in such an operation is examined. Primary emphasis is placed on the identification of mission capabilities for providing logistic support. Electrical engine and nuclear-mechanical power conversion system experience is projected to the 1 to 10 Mw range and used to identify expected system characteristics. Both thermal arc and ion engines are considered. A basic mission profile is defined, and typical trajectory characteristics are discussed. The low thrust characteristic velocity requirement for the basic mission is identified and used to generate parametric mission performance characteristics for one-way, round-trip, and multitrip missions. These data indicate the interrelations between gross weight, power rating, specific impulse, and total propulsion time and their effect on payload capabilities. The resulting data then are compared with the capabilities of comparable chemical and nuclear rocket-propelled vehicles. (auth)

Gravitational Stress in Aerospace Medicine

Heretofore, information on the physiological effects of gravitational stress has been difficult to embrace because it has been scattered among government technical reports and in a wide variety of journals. With the advent of rocketpropelled vehicles of unlimited speed and the recent entrance of man into space, there came an urgent need to compile and review the literature. This task was given to 2 members of Wright Field Aero Medical Laboratory, which organization sponsored this volume, one of a series on aviation medicine and space biology from the Guggenheim Center for Aviation, Health, and Safety at the Harvard School of Public Health. The editors, Drs. Otto H. Gauer and George D. Zuidema, enlisted some 12 other enthusiastic contributors from the same and several other laboratories. In the foreword, Col. John Paul Stapp, a pioneer in this field of research, considers it most appropriate for this monograph to come from 2

Scientific Research with Rockets and Satellites

The great progress which has been made in the development of rocket motors of very high power and of methods of automatic guidance and control of rocket-propelled vehicles has been amply demonstrated by the launching, first of artificial satellites and then of deep space probes, capable of hitting the moon or passing beyond it to become artificial planets. The glare of publicity, however, does not fall to anything like the same extent on the scientific research which may be, and is being, carried out with the use of space vehicles. We begin by considering some of the branches of physical science which can benefit greatly from the availability of facilities for carrying out observations in space.

The Effect of Vehicle Structure on Propulsion System Dynamics and Stability

In this paper, the relationship between the propulsion system and the vehicle structure is investigated. It appears that the structural behavior cannot be neglected when the propulsion sys tem is designed. This is so because the dynamic behavior and stability of l iquid propellant systems can be shown to be dependent on the structural characteristics of the vehicle i t is m o u n t e d in . A general analysis of the interaction between the propulsion sys tem and the vehicle structure is presented and also applied to a monopropel lant rocket-propelled vehicle. The rocket propulsion system and the vehicle structure are analyzed by servomechanism techniques . The complete vehicle sys tem is represented by a block diagram and appropriate transfer funct ions are est imated for the various portions of the sys tem. The complete sys tem is equivalent to a mult i loop servomechanism. The Satche diagram which is analogous to a Nyquist diagram is then used to evaluate the over-all stability. The results of the stability analysis are presented in terms of the natural frequency of the vehicle structure, the combust ion lag, and the distribut ion of mass between various portions of the vehicle.

Influence of Earth's Gravitation on the Requirements of the Vertical Trajectory Rocket with Special Reference to Escape

The problem of reaching extreme altitudes is basically one of overcoming the earth's gravitation. Therefore, when the earth's gravitation is analyzed with respect to its influence on a rocketpropelled vehicle in a vertical trajectory, a theoretical analysis of the problem of reaching extreme altitudes is readily obtained. Since such an analysis is not new, the first portion of the paper is a review of the fundamental dynamic considerations of the problem. The review includes showing how the effect of earth's gravity on the requirement of the long-range rockets can be evaluated by the concept of a gravitational velocity, or a minimum velocity that must be attained by the rocket to achieve its objective. An ideal rocket for minimum expenditure of energy would leave the earth with a speed equal to the gravitational velocity and coast to its objective. The paper considers the principal differences between the ideal and actual long-range rockets, inasmuch as it accounts for the additional energy required of the actual rocket due to the time for acceleration of such a rocket to a gravitational velocity of escape. It also accounts for the variation of earth's gravitational attraction upon the rocket overpowered as well as coasting flight. As a result of these considerations a table of correction factors is given which can be used with the ideal rocket equations to give approximate actual rocket results.