The time-optimal control of a system of rigid bodies connected in series by single-degree-of-freedom joints is studied. The dynamical equations of the system are highly nonlinear and a closed-form representation of the minimum-time feedback control is not possible. However, a suboptimal feedback control which provides a close approximation to the optimal control is developed. The suboptimal control is expressed in terms of switching curves for each of the system controls. These curves are obtained from the linearized equations of motion for the system. Approximations are made for the effects of gravity loads and angular velocity terms in the nonlinear equations of motion. Digital simulation is used to obtain a comparison of response of the optimal and suboptimal controls. The speed of response of the suboptimal control is found to compare quite favorably with the response speed of the optimal control. The analysis is applied to the control of three joints of a mechanical manipulator. Modifications of the suboptimal control for use in a sampled-data system are shown to result in good performance of a hydraulic manipulator under computer control. (Author).

These results are intended to provide quantitative flight-test information which may be useful to designers in attempting to provide for adequate low-speed control and which may be correlated with analytical analyses as presented in the third and finai report in this series (Technical Note 3677).

This report summarizes the activities and progress of Department of Agriculture entomologists working in 13 countries during the period 1951-1957. It describes the nature of the cooperative effort between the Department of Agriculture and the International Cooperation Administration, and the coordination of project activities within the host countries. Tables are presented containing data to emphasize the important material and financial participation in this program by friendly cooperative countries, and the fact that their contributions far surpass those of the United States.

The Oscar-shortlisted documentary Command and Control, directed by Robert Kenner, finds its origins in Eric Schlosser's book and continues to explore the little-known history of the management and safety concerns of America's nuclear aresenal. “A devastatingly lucid and detailed new history of nuclear weapons in the U.S. Fascinating.” —Lev Grossman, TIME Magazine “Perilous and gripping . . . Schlosser skillfully weaves together an engrossing account of both the science and the politics of nuclear weapons safety.” —San Francisco Chronicle A myth-shattering exposé of America’s nuclear weapons Famed investigative journalist Eric Schlosser digs deep to uncover secrets about the management of America’s nuclear arsenal. A groundbreaking account of accidents, near misses, extraordinary heroism, and technological breakthroughs, Command and Control explores the dilemma that has existed since the dawn of the nuclear age: How do you deploy weapons of mass destruction without being destroyed by them? That question has never been resolved—and Schlosser reveals how the combination of human fallibility and technological complexity still poses a grave risk to mankind. While the harms of global warming increasingly dominate the news, the equally dangerous yet more immediate threat of nuclear weapons has been largely forgotten. Written with the vibrancy of a first-rate thriller, Command and Control interweaves the minute-by-minute story of an accident at a nuclear missile silo in rural Arkansas with a historical narrative that spans more than fifty years. It depicts the urgent effort by American scientists, policy makers, and military officers to ensure that nuclear weapons can’t be stolen, sabotaged, used without permission, or detonated inadvertently. Schlosser also looks at the Cold War from a new perspective, offering history from the ground up, telling the stories of bomber pilots, missile commanders, maintenance crews, and other ordinary servicemen who risked their lives to avert a nuclear holocaust. At the heart of the book lies the struggle, amid the rolling hills and small farms of Damascus, Arkansas, to prevent the explosion of a ballistic missile carrying the most powerful nuclear warhead ever built by the United States. Drawing on recently declassified documents and interviews with people who designed and routinely handled nuclear weapons, Command and Control takes readers into a terrifying but fascinating world that, until now, has been largely hidden from view. Through the details of a single accident, Schlosser illustrates how an unlikely event can become unavoidable, how small risks can have terrible consequences, and how the most brilliant minds in the nation can only provide us with an illusion of control. Audacious, gripping, and unforgettable, Command and Control is a tour de force of investigative journalism, an eye-opening look at the dangers of America’s nuclear age.

Flight tests were made with a typical light airplane to investigate possibilities for obtaining reliable control at low flight speeds. It was found that satisfactory lateral control occurred consistently, even under conditions simulating extremely gusty air, at angles of attack approximately 2 degrees below that for the maximum lift coefficient (or the stall of the wing as a whole). This 2 degree margine was substantially the same both with full power and with the engine throttled and throughout the range of center-of-gravity locations tested. Supplementary tests were then made on the control at high angles of attack under actual gusty air conditions, on the possibility of entering spins, and on the amount of elevator control required for normal three-point landings. It was found that with the original plain untwisted wing obtaining the constant 2 degree margin below the stall required widely different elevator deflections for the range of power and center-of-gravity locations tested. Also, none of these settings ws high enough to produce a three-point landing.