Mechanical & Fluid Systems

Spacecraft Nuclear Reactor Would Be Fueled in Orbit

Two reports summarize progress thus far in the continuing development of a spacecraft nuclear reactor, some or all of the fuel rods of which would not be loaded until the spacecraft was in orbit. (Keeping the fuel rods out of the reactor core before and during launch is intended to minimize the risk of release of radioactive material in the event of a launch accident.) The report describes the design and operation of the fueling mechanism, and problems in the design and fabrication of the core. The fuel rods include uranium oxide in rhenium sleeves. The core includes niobium star-cross-section inserts and molybdenum tubes, into which the fuel rods are to be inserted.

Posted in: Mechanics, Briefs

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Designs for Safer Launching of Spacecraft Fission System

A report proposes the development of two different mechanisms that would prevent inadvertent startup of reactors in nuclear-fission-based propulsion and power systems in future spacecraft. The purpose of this development is to contribute to safety by ensuring that radioactivity is kept to normal negligible levels before and during launch and in the event of a launch accident. Once the spacecraft was safely in outer space, a motor would actuate a linear screw that would move the fuel section of the rods into the core, enabling the reactor.

Posted in: Mechanics, Briefs

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Saturation Technique for Rapid Binary Image Processing

This technique is fundamentally different from truncation of least-significant bits. An improved technique of limited-precision arithmetic has been devised for use in convolutional filtering of image data prior to conversion of the data to binary form. Both limited-precision arithmetic and conversion to binary form reduce the volume of data, thereby contributing to processing speed and reducing the sizes of circuits needed to perform, and store the results of, intermediate stages of processing. Applications in which these techniques are or could be helpful include robotic vision, recognizing and tracking moving targets, stabilizing images in hand-held video cameras, and general enhancement of images.

Posted in: Mechanics, Briefs, TSP

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Breathing-Air and Cooling Apparatus for Protective Suit

Applications can include diving, space, and firefighting suits. The figure schematically illustrates a portable life-support apparatus for any of a variety of protective suits to be worn in hostile environments. A prototype of the apparatus has been fitted to space suits for use underwater. Astronauts wear these suits during training dives in a tank of warm water, using the neutral buoyancy available in the underwater environment to simulate aspects of the zero gravitation of outer space. The apparatus provides breathing air and adjustable cooling in the suit, while maintaining overall neutral buoyancy. The apparatus is readily adaptable to such related applications as conventional diving and space suits, firefighting suits, and protective garments to be worn in hot, toxic, and/or radioactive environments.

Posted in: Mechanics, Briefs, TSP

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Thermoelectric Contact Cooler/Freezer

This cooler is efficient and quiet. A thermoelectric contact cooler/ freezer is designed to utilize thermal conduction to rapidly freeze blood and urine samples in test tubes and syringes. This apparatus is dependable, wastes little energy, contains no moving parts other than a fan, can operate in a wide temperature range and in any orientation (including in zero gravity), is quiet, and emits no chlorofluorocarbons or other greenhouse gases. It is a vast improvement over currently available convection-type cooler/freezers.

Posted in: Mechanics, Briefs, TSP

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Theory of Formation-Flying Control for Multiple Spacecraft

A report presents the mathematical basis of a method of controlling multiple spacecraft flying in formation, subject to control constraints. The spacecraft are assumed to be equipped with relative-position-sensing, relative-velocity-sensing, and communication infrastructure, and with maneuvering actuators. The method involves a leader-following control scheme. A graph is used to represent the hierarchy of, and the data dependencies among, the leading and following spacecraft. Graph-theoretic concepts are shown to play a vital role in determining the basic properties of the leader-following control architecture; hence, changes in the hierarchy (represented by changes in the graph) translate directly to the required changes in control.

Posted in: Mechanics, Briefs, TSP

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Onboard Estimation of Times of Periapsis During Aerobraking

A report proposes a technique for onboard updating of the orbital period of an aerobraking spacecraft in order to estimate the time of the next periapsis. The time of periapsis is nearly centered in the middle of the drag pass, and provides a convenient reference time for events in the sequence that controls the activities taking place onboard the spacecraft. Heretofore, updates of periapsis times have been computed on Earth on the basis of radio tracking data, then uplinked to the spacecraft. Onboard updating could increase operational efficiency and reduce costs by reducing the amount of ground and tracking support needed.

Posted in: Mechanics, Briefs, TSP

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