Mechanical & Fluid Systems

Automated System for Fluid and Electrical Connections

The Smart Umbilical Mating System (SUMS) is an automated, three-degreeof- freedom, scalable system for quickly mating, demating, and/or remating ganged umbilicals. SUMS connects electrical and fluid paths between spacecraft and ground support equipment whether liftoff or side mount for NON T-0 umbilicals. SUMS prevents electrical arcing and leakage of fluids by providing for automated alignment of mating connectors and verification of mating. SUMS could readily be adapted to such other applications as servicing of aircraft, orbiting spacecraft, or ground vehicles. Major elements of SUMS include mating cones equipped with force sensors with integral latches; computer control; robotic vision with tracking aided by laser beams; actuation by a compliant pneumatic motor; and a secondary mate plate, which holds the ground-side fluid electrical connectors in proper alignment, is pneumatically actuated to complete mating once the cones have been latched, and is the only part of the system that one must change to adapt SUMS to different applications. A commercial version plumbed with electrical power, communications, fuel, lubricants, and coolant fluids could be installed at a central location for servicing land vehicles. SUMS could be utilized between moving vehicles. Automated functions could include electronic identification of vehicles to prevent errors; recording of data about the vehicle; its consumption of fluids; sampling for wear analysis; maintenance scheduling; distance traveled; and topping off or changing of all fluids in the correct amounts.

Posted in: Machinery & Automation, Briefs, TSP

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Sonic-Boom Tests of Model of a Supersonic Business Jet Plane

A report discusses wind-tunnel tests of a scale model of a con- ceptual two-engine jet airplane designed to carry 10 passengers, have a range of 4,000 miles (≈6,400 km), cruise at a mach number of 2.0, and generate a low sonic boom [char- acterized by a shock overpressure of ≤ 0.5 lb/ft2 (≤24 Pa)]. The model could optionally include either of two differently sized nacelle submodels representing alternative engine designs. In each test, the pressure was measured at intervals along a horizontal line at a specified height below the model. One conclusion drawn from predicted and measured pressure values is that it is more difficult to tailor the geometry of this airplane for low sonic boom than it is to do so for a larger supersonic airplane capable of carrying 300 passengers and for which the allowable shock overpressure is 1.0 lb/ft2 (48 Pa). It was found that decreasing the allowable overpressure intensifies the conflicts between the design choices for reducing sonic boom and those for increasing aerodynamic efficiency. It was also found that due to the nacelles’ aft location, their contribution to the shock overpressures could be expected to be small enough to be unnoticeable by an observer on the ground.

Posted in: Mechanics, Briefs, TSP

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Optimization of Synthetic Jet Actuators

A report presents a study oriented toward optimization of synthetic jet actuators. [A syn- thetic jet actuator is a fluidic control device that partly resembles a loudspeaker. It typically comprises a piezo- electric actuator/ diaphragm situated in a cavity, facing an orifice or nozzle at the opposite end of the cavity.] The instant report describes an experimental synthetic jet actuator equipped for tuning through variation of some of its cavity dimensions and its excitation frequency and for selection of either (1) clamping of the edge of the diaphragm between flat surfaces or (2) pinning of the edge of the diaphragm between steel O rings. The report goes on to discuss the effects of the cavity and nozzle geometry, diaphragm design, excitation frequency, and other design features on the vibrational resonance of the diaphragm, the acoustic resonance of the cavity, the coupling (or lack thereof) of these resonances, and the overall performance as characterized by the displacement at the center of the diaphragm or the speed of the jet at a specified distance from the orifice. Conclusions reached in this study are that (1) the pinning configuration results in better performance than does the clamping configuration and (2) the maximum performance is achieved by matching the resonant frequencies of the diaphragm and the cavity.

Posted in: Mechanics, Briefs, TSP

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Hexfoil Rotary Flexures

These devices would afford high accuracy of centration. Hexfoil rotary flexures have been proposed as pivots suitable for use in precise optical instruments. In the application that inspired the hexfoil concept, there is a requirement for a limited-rotation mirror gimbal that would maintain, with unprecedented accuracy, coincidence among the axes of rotation and a fiducial mark on the mirror, over the entire range of rotation. Theoretically, a hexfoil rotary flexure could satisfy this requirement.

Posted in: Mechanics, Briefs, TSP

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Improvements in the Use of Water Washes in Testing for NVR

Effectiveness of washing and sensitivity of detection are increased. Some improvements have been made to enhance the role of water as a test solvent for determining the amount of hydrocarbon nonvolatile residue (NVR) present on an item of hardware that is required to be totally or nearly devoid of such residue. Water is now used as an NVR-testing solvent because (1) even highmolecular- weight hydrocarbon greases are at least slightly soluble in water, (2) water is safer and less expensive than are chlorofluorocarbon solvents [in particular, 1,1,2- trichloro-1,2,2-trifluoroethane (also known as CFC-113), which was used previously in testing for hydrocarbon NVR], and (3) CFC solvents are expensive and are now recognized as environmentally harmful.

Posted in: Mechanics, Briefs, TSP

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Flight Research on Supersonic Laminar Flow

Flow over a suitably designed airfoil can remain largely laminar, even at supersonic speed. Some airfoil designs have been shown by theory and small-scale tests to be capable of passively maintaining laminar flow at super -sonic speeds. More recently, flight tests have proven that these designs can maintain large runs of laminar flow at higher Reynolds numbers in harsh flight environments. The flight tests were conducted for the purposes of observing laminar flow at speeds up to mach 2.0 and determining the conditions under which laminar flow breaks down.

Posted in: Mechanics, Briefs

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Improved Flange Design for Cryogenic Vacuum O-Ring Seals

Spring-loaded joints could be made less bulky. A compact spring-loading design has been proposed to increase the reliability of seals in the joints of vacuum cryogenic systems. Heretofore, such joints have been, variously, compact or reliable, but not both, for the following reasons: In all such joints, sealing is effected by compression of soft metal (typically, indium or alloys of indium) O rings between flanges. Over time, the soft O-ring metal flows, with consequent reduction of preload, sometimes leading to loss of seal. To ensure reliable seals, it is necessary to spring-load the flanges to maintain compression of the O rings. However, spring-loaded joints of traditional design are not compact.

Posted in: Mechanics, Briefs, TSP

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