Mechanical & Fluid Systems

Instrumented Bolt Measures Bending Moments Within Itself

The direction as well as the magnitude of bending can be determined. The Ultrabend bolt is a specially designed bolt instrumented with strain gauges (see figure) that are connected into twin Wheatstone-bridge circuits. The geometric arrangement of the strain gauges is such that by suitable electrical switching of the Wheatstone-bridge circuits, these circuits can be made to either (1) suppress responses to bending and torsional stresses while putting out signals indicative of axial preload or (2) suppress responses to axial and torsional stresses while putting out signals indicative of the magnitude and direction of the bending moment in the bolt. Switching between these two measurement modes is accomplished by use of field-effect transistors controlled by a logic circuit.

Posted in: Mechanics, Briefs

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Launching Payloads Into Orbit at Relatively Low Cost

A report proposes the development of a system for launching payloads into orbit at about one-fifth the cost per unit payload weight of current systems. The system would be based on the formerly secret PILOT microsatellite- launching system developed in response to the Soviet launch of Sputnik-1. The PILOT system was a solid-fuel, aerodynamically spun and spin-stabilized, five-stage rocket with onboard controls including little more than an optoelectronic horizon sensor and a timer for triggering the second and fifth stages, respectively. The proposal calls for four improvements over the PILOT system to enable control of orbital parameters:

Posted in: Briefs, TSP

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Improved Quick-Release Pin Mechanism

An improved quick-release pin mechanism supplants a prior such mechanism in which the pin bears a shear load to hold two objects together. The prior mechanism, of a ball-locking design, can fail when vibrations cause balls to fall out. The load-bearing pin is an outer tube with a handle at one end (hereafter denoted the near end). Within the outer tube is a spring- loaded inner tube that includes a handle at its near end and a pivoting tab at its far end. The pin is inserted through holes in the objects to be retained and the inner tube is pushed against an offset pivot inside the outer tube to make the tab rotate outward so that it protrudes past the outer diameter of the outer tube, and the spring load maintains this configuration so that the pin cannot be withdrawn through the holes. Pushing the handles together against the spring load moves the locking tab out far enough that the tab becomes free to rotate inward. Then releasing the inner-tube handle causes the tab to be pulled into a resting position inside the outer tube. The pin can then be pulled out through the holes.

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Diaphragm Pump With Resonant Piezoelectric Drive

Resonance is used to amplify the stroke and thus the flow rate. A diaphragm pump driven by a piezoelectric actuator is undergoing development. This pump is intended to be a prototype of lightweight, highly reliable pumps for circulating cooling liquids in protective garments and high-power electronic circuits, and perhaps for some medical applications. The pump would be highly reliable because it would contain no sliding seals or bearings that could wear, the only parts subject to wear would be two check valves, and the diaphragm and other flexing parts could be designed, by use of proven methods, for extremely long life. Because the pump would be capable of a large volumetric flow rate and would have only a small dead volume, its operation would not be disrupted by ingestion of gas, and it could be started reliably under all conditions.

Posted in: Mechanics, Briefs

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Capacitors Would Help Protect Against Hypervelocity Impacts

A proposal investigates alternatives to the present “bumper” method of protecting spacecraft against impacts of meteoroids and orbital debris. The proposed method is based on a British highvoltage- capacitance technique for protecting armored vehicles against shapedcharge warheads.

Posted in: Briefs, TSP

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Reverse-Tangent Injection in a Centrifugal Compressor

The compressor flow can be stabilized against stall and surge. Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. If not suppressed, such instabilities interrupt the smooth flow of the working fluid and, in severe cases of surge, give rise to pressure and flow oscillations that can be strong enough to damage the compressor and adjacent equipment.

Posted in: Briefs, TSP

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Magnetostrictive Inertial-Reaction Linear Motors

Fine positioning could be achieved at temperatures from near absolute zero to ambient. Linear-translation motors containing inertial-reaction masses driven by magnetostrictive actuator elements are undergoing development. These motors could be used to make fine position adjustments in diverse scientific and industrial instruments that operate at temperatures ranging from near absolute zero to room temperature; for example, they could be used to drive translation stages in scanning tunneling microscopes that operate at liquid-helium temperature (4 K), or to move cryogenic-temperature optical elements that must be located at long but precise distances from each other (as in interferometers). [These motors should not be confused with proposed magnetostrictive motors that would move in "inchworm" fashion and would be used for similar purposes, described in "Magnetostrictive Actuators for Cryogenic Applications," NASA Tech Briefs, Vol. 20, No. 3 (March 1996), page 84.]

Posted in: Briefs

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