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Simplified expressions describing the transfer from a satellite orbit to the point of atmospheric entry are derived. The expressions are limited to altitude changes that are small compared with the earth's radius, and velocity changes that are small compared with satellite velocity. They are further restricted to motion about a spherical, nonrotating earth. The transfer trajectory resulting from the application of thrust in any direction at any point in an elliptic orbit is considered. Expressions for errors in distance (miss distance) and entry angle due to an initial misalinement and magnitude error of the deflecting thrust are presented. The guidance and accuracy requirements to establish a circular orbit, and orbit corrections are also discussed.
Simplified expressions describing the transfer from a satellite orbit to the point of atmospheric entry are derived. The expressions are limited to altitude changes that are small compared with the earth's radius, and velocity changes that are small compared with satellite velocity. They are further restricted to motion about a spherical, nonrotating earth. The transfer trajectory resulting from the application of thrust in any direction at any point in an elliptic orbit is considered. Expressions for errors in distance (miss distance) and entry angle due to an initial misalinement and magnitude error of the deflecting thrust are presented. The guidance and accuracy requirements to establish a circular orbit, and orbit corrections are also discussed.
Existing expressions are used to obtain the minimum propellant fraction required for return from a circular orbit as a function of vacuum trajectory range. The solutions for the parameters of the vacuum trajectory are matched to those of the atmospheric trajectory to obtain a complete return from orbit to earth. The results are restricted by the assumptions of (1) impulsive velocity change, (2) nearly circular transfer trajectory, (3) spherical earth, atmosphere, and gravitational field, (4) exponential atmospheric density variation with attitude and (5) a nonrotating atmosphere. Calculations are made to determine the effects of longitudinal and lateral range on required propellant fraction and reentry loading for a nonrotating earth and for several orbital altitudes. The single- and two-impulse method of return is made and the results indicate a "trade off" between propellant fraction required and landing-position accuracy. An example of a return mission from a polar orbit is discussed where the initial deorbit point is the intersection of the North Pole horizon with the satellite orbit. Some effects of a rotating earth are also considered. It is found that, for each target-orbital-plane longitudinal difference, there exists a target latitude for which the required propellant fraction is a minimum.
Advances in Space Science and Technology, Volume 4 provides information pertinent to the fundamental aspects of basic and applied astronautics. This book deals with one of the more practical aspects of artificial satellites, measurement of the Doppler effect. Organized into six chapters, this volume begins with an overview of the Doppler effect of Earth-circling satellites. This text then explores the possibility of the existence of intelligent beings other than man. Other chapters consider the historical development of multistage rockets and space carrier vehicles and explain the concepts and approaches to manned orbital flight. This book discusses as well the problems of bringing spacecraft safely through planetary atmospheres and onto the surface. The final chapter deals with radioactive elements as energy sources for spacecraft propulsion in orbital transfer and for travel between the worlds of the Solar System. This book is a valuable resource for biologists, astronomers, chemists, geologists, and geochemists.
During the last decade, a rapid growth of knowledge in the field of re-entry and planetary entry has resulted in many significant advances useful to the student, engineer and scientist. The purpose of offering this course is to make available to them these recent significant advances in physics and technology. Accordingly, this course is organized into five parts: Part 1, Entry Dynamics, Thermodynamics, Physics and Radiation; Part 2, Entry Abla tion and Heat Transfer; Part 3, Entry Experimentation; Part 4, Entry Concepts and Technology; and Part 5, Advanced Entry Programs. It is written in such a way so that it may easily be adopted by other universities as a textbook for a two semesters senior or graduate course on the sub ject. In addition to the undersigned who served as the course instructor and wrote Chapters, 1, 2, 3 and 4, guest lecturers included: Prof. FRANKLIN K. MOORE who wrote Chapter 5 "Entry Radiative Transfer," Prof. SHIH-I PAI who wrote Chapter 6 "Entry Radiation-Magnetogasdy namics," Dr. CARL GAZLEY, J r. who wrote Chapter 7 "Entry Deaccelera [ion and Mass Change of an Ablating Body," Dr. SINCLAIRE M. SCALA who wrote Chapter 8 "Entry Heat Transfer and Material Response," Mr.