Mechanical & Fluid Systems

Afterbody Cushions for Instrumented Penetrator Projectiles

Pneumatic cushions have been proposed for protecting the afterbodies of two-body instrumented soil-penetrator projectiles. These cushions would be, essentially, doughnut-shaped miniature versions of automotive airbags, designed for rapid inflation upon impact.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Soils, Pneumatic systems, Protective structures, Test equipment and instrumentation, Mining vehicles and equipment, Spacecraft
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Ultrasonic Measurement of Bending of Bolts

Work performed at Johnson Space Center has brought about a major improvement in the means for measuring the bending that occurs whenever stress is applied to a bolted joint. This major improvement is a measurement method based on ultrasonics. The strain gauges used heretofore in the space program in efforts to measure bending loads or deformations in bolted joints have proven inadequate, in that it has been difficult to perform accurate measurements by use of them. The art of ultrasonics offers an alternative and superior means of performing such measurements; as such, it can be expected to contribute to cost savings and increased safety, not only in the space program but also in military and commercial applications — wherever there are stressed bolted joints that could pose bending hazards. The ability to measure stresses in joints accurately can be expected to contribute to understanding the mechanisms that produce stress failures in critical joints and thereby contribute to the success of efforts to design safeguards that will lower risks to both vehicles and personnel.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Failure analysis, Fatigue, Fasteners, Test procedures
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Using Electromagnetic Drag on Tethers To De-Orbit Spacecraft

Two papers propose the use of electrically conductive tethers to remove spent or dysfunctional spacecraft from orbit around the Earth in order to reduce the hazard of orbital debris. In comparison with onboard rockets, these tethers would be more cost-effective, more reliable, and less massive. Once deployed, a tether would not require an onboard power supply. Both ends of the tether would be equipped with electrodes to make electrical contact with the ionosphere and thereby complete an electrical circuit. The orbital motion of the tether across the Earth's magnetic field would induce an electrical current in the tether. The consequent electrical heating of the tether would gradually dissipate the orbital kinetic energy of the spacecraft. It has been estimated that a typical spacecraft could be removed from orbit in weeks or months in this way, whereas the satellite might otherwise remain in orbit for years or even centuries.

Posted in: Briefs, Mechanical Components, Mechanics, Electrical systems, Electrical systems, Conductivity, Entry, descent, and landing, Satellites
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Spherical-Coordinates Encoder Module

The spherical-coordinates encoder module (SCEM) is a relatively simple and inexpensive electromechanical apparatus for quickly and easily measuring three-dimensional offsets between objects at distances of the order of a few feet ( ≈1 m). The SCEM was developed specifically for measuring offsets between spacecraft payload trunnions and trunnion supports during ground-based payload-transfer operations; it could also be readily used, for example, to measure offsets to guide the maneuvering of large objects during the assembly of heavy machinery or structures. The SCEM eliminates the need for time-consuming, tedious, error-prone measurements by use of such tools as scales, tapes, and protractors, followed by equally tedious and error-prone manual calculations, manual recording of data, and verbal communication of data.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Measurements, Microelectricmechanical device, Microelectromechanical devices, Microelectricmechanical device, Microelectromechanical devices, Assembling, Automation, Materials handling
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Bushing-Mounted Drag Chain

The figure illustrates a chair-base mechanism with a bushing-mounted drag chain. The bushing-mount design provides for one end of the drag chain to be free to pivot; this provision makes it possible to wrap the drag chain to a radius smaller than that achievable in mechanisms previously designed for the same purpose. The utility of mechanisms like this one lies in applications in which rotation of machinery involves significant turning radii, so that bending of cables that run through drag chains involve relatively tight arcs.

Posted in: Briefs, Mechanical Components, Mechanics, Robotics, Bearings, Mountings, Industrial vehicles and equipment
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Inflatable Wing Leading Edges for High Lift and Deicing

Computational simulations and wind-tunnel tests have demonstrated the feasibility of using inflatable boots on the leading edges of airplane wings, both as devices to increase lift and as pneumatic deicing actuators. Assuming success in further research and development, the first applications would likely occur as retrofits to single- and twin-engine airplanes in general aviation (GA). Later, corporate and commuter turboprop airplanes would be included. The eventual incorporation of these boots into new GA airplane designs would be even more desirable because the boots could be integrated with overall wing structures to provide laminar flow in cruise.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Wings, Computer simulation, Aircraft deicing, Elastomers, Wind tunnel tests, Aerodynamics
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Nonintrusive Flow-Measurement System

A nonintrusive flow-measurement system based on ultrasonics has been developed to replace a system based on turbine flowmeters. A turbine flowmeter must be mounted in line with a pipe; this raises the possibility of leakage at the flowmeter/pipe joints, and the flowmeter unavoidably perturbs the flow. Moreover, a turbine flowmeter is vulnerable to mechanical malfunction and can be vulnerable to corrosion or clogging, depending on the nature of the fluid. In contrast, the ultrasonic flow-measurement system does not contain any rotating or sliding mechanisms that could fail, and does not involve any penetration of the pipe, so that the flow is not perturbed and there is no risk of leakage, clogging, or corrosion.

Posted in: Briefs, Mechanical Components, Mechanics, Computational fluid dynamics, Measurements, Product development, Acoustics, Acoustics, Reliability, Reliability
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A 3D Navier-Stokes CFD Code for Analysis of Turbomachinery

The ADPAC software is a computational fluid dynamics (CFD) code for analysis of flows in turbomachines. The outstanding feature of ADPAC is the ability to solve the Navier-Stokes equations for complex three-dimensional (3D) flow fields that include multiple flow paths, and the modeling of which typically involves multiple computational grid blocks. In addition, ADPAC can handle coupled calculations in which some portions of models are rotating and some are not, as in the case of the rotating blades and stationary vanes of a turbomachine. ADPAC was developed especially for use in analyzing the performances of short-duct, ultrahigh-bypass-ratio turbofan engines, both as uninstalled and as installed; however, ADPAC is applicable to a very broad range of other turbomachines and of other flow systems.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Analysis methodologies, Computational fluid dynamics
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Hybrisol Rocket Engines

"Hybrisol" denotes a proposed rocket engine that would contain hybrid and solid-propellant parts within a single combustion chamber. ["Hybrid" as used here denotes a type of rocket engine in which a solid fuel is burned by use of a liquid or gaseous oxidizer and the flow of the oxidizer can be throttled to control the engine. Unlike conventional solid rocket propellants, a solid fuel for a hybrid rocket engine can be made relatively inert in the absence of the oxidizer and therefore presents little hazard of explosion or inadvertent ignition.] Inside a hybrisol rocket engine, there would be two concentric tubular energy-storage layers: an outer layer of conventional solid rocket propellant and an inner layer of solid hybrid fuel (see figure).

Posted in: Briefs, Mechanical Components, Mechanics, Solid propellants, Product development, Hybrid engines, Rocket engines
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Making Liquid Air in Small, Economical Quantities

A mixing apparatus combines liquid oxygen and liquid nitrogen to make liquid air in small, convenient quantities. Heretofore, equipment used to make liquid air by mixing was incapable of making batches smaller than 600 gallons (2,300 L). The present mixing apparatus produces liquid air on demand in batches as small as 100 liters; a batch of this size is suitable for filling self-contained breathing apparatuses like those worn by firefighters and others working in hostile environments.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Chemicals, Oxygen, Hazards and emergency management, Hazards and emergency operations
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