Mechanical & Fluid Systems

Ball Bearings Equipped for In Situ Lubrication on Demand

Operational lifetimes can be prolonged. In situ systems that provide fresh lubricants to ball/race contacts on demand have been developed to prolong the operational lives of ball bearings. These systems were originally intended to be incorporated into ball bearings in mechanisms that are required to operate in outer space for years, in conditions in which lubricants tend to deteriorate and/or evaporate. These systems may also be useful for similarly prolonging bearing lifetimes on Earth.

Posted in: Briefs, Mechanical Components, Mechanics, Life cycle analysis, Lubricants, Bearings, Parts


Software for Secondary-School Learning About Robotics

The ROVer Ranch is an interactive computer program designed to help secondary-school students learn about space-program robotics and related basic scientific concepts by involving the students in simplified design and programming tasks that exercise skills in mathematics and science.

Posted in: Briefs, Mechanical Components, Mechanics, Computer simulation, Computer software and hardware, Education, Education and training, Robotics


Gifford-McMahon/Joule-Thomson Refrigerator Cools to 2.5 K

This system is relatively simple. A compact refrigerator designed specifically for cooling a microwave maser low noise amplifier is capable of removing heat at a continuous rate of 180 mW at a temperature of 2.5 K. This refrigerator is a combination of (1) a commercial Gifford-McMahon (GM) refrigerator nominally rated for cooling to 4 K and (2) a Joule-Thomson (J-T) circuit. The GM refrigerator pre-cools the J-T circuit, which provides the final stage of cooling. The refrigerator is compact and capable of operating in any orientation. Moreover, in comparison with a typical refrigerator heretofore used to cool a maser to 4.5 K, this refrigerator is simpler and can be built at less than half the cost.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Amplifiers, Radar, Product development, Cooling


Improving Control in a Joule-Thomson Refrigerator

A report discusses a modified design of a Joule-Thomson (JT) refrigerator under development to be incorporated into scientific instrumentation aboard a spacecraft.In most other JT refrigerators (including common household refrigerators), the temperature of the evaporator (the cold stage) is kept within a desired narrow range by turning a compressor on and off as needed. This mode of control is inadequate for the present refrigerator because a JT-refrigerator compressor performs poorly when the flow from its evaporator varies substantially, and this refrigerator is required to maintain adequate cooling power. The proposed design modifications include changes in the arrangement of heat exchangers, addition of a clamp that would afford a controlled heat leak from a warmer to a cooler stage to smooth out temperature fluctuations in the cooler stage, and incorporation of a proportional + integral + derivative (PID) control system that would regulate the heat leak to maintain the temperature of the evaporator within a desired narrow range while keeping the amount of liquid in the evaporator within a very narrow range in order to optimize the performance of the compressor. Novelty lies in combining the temperature- and cooling-power-regulating controls into a single control system.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Electronic control units, Heat exchangers, Performance upgrades, Cooling, Compressors, Spacecraft


High-Temperature, High-Load-Capacity Radial Magnetic Bearing

Speed and temperature limits of rolling element bearings can be exceeded. A radial heteropolar magnetic bearing capable of operating at a temperature as high as 1,000 °F (≈540 °C) has been developed. This is a prototype of bearings for use in gas turbine engines operating at temperatures and speeds much higher than can be withstood by lubricated rolling-element bearings.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Magnetic materials, Bearings, Gas turbines


Blended Buffet-Load-Alleviation System for Fighter Airplane

Reductions in buffet loads translate to longer fatigue lives. The capability of modern fighter airplanes to sustain flight at high angles of attack and/or moderate angles of sideslip often results in immersion of part of such an airplane in unsteady, separated, vortical flow emanating from its forebody or wings. The flows from these surfaces become turbulent and separated during flight under these conditions. These flows contain significant levels of energy over a frequency band coincident with that of low-order structural vibration modes of wings, fins, and control surfaces. The unsteady pressures applied to these lifting surfaces as a result of the turbulent flows are commonly denoted buffet loads, and the resulting vibrations of the affected structures are known as buffeting. Prolonged exposure to buffet loads has resulted in fatigue of structures on several airplanes. Damage to airplanes caused by buffeting has led to redesigns of airplane structures and increased support costs for the United States Air Force and Navy as well as the armed forces of other countries. Time spent inspecting, repairing, and replacing structures adversely affects availability of aircraft for missions.

Posted in: Briefs, Mechanical Components, Mechanics, Aircraft structures, Finite element analysis, Fatigue, Aerodynamics, Military aircraft, Turbulence


Split-Resonator, Integrated-Post Vibratory Microgyroscope

This design is better suited to mass production. An improved design for a capacitive sensing, rocking-mode vibratory microgyroscope is more amenable to mass production, relative to a prior design. Both the improved design and the prior design call for a central post that is part of a resonator that partly resembles a cloverleaf or a flower. The prior design is such that the post has to be fabricated as a separate piece, then bonded to the rest of the resonator in the correct position and orientation. The improved design provides for fabrication of the post as an integral part of the resonator and, in so doing, makes it possible to produce a waferful of microgyroscopes, without need to fabricate, position, and attach posts.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Sensors and actuators, Fabrication, Production, Vibration, Mountings


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