Mechanical & Fluid Systems

Brush-Wheel Samplers for Planetary Exploration

A report proposes brush-wheel mechanisms for acquiring samples of soils from remote planets. In simplest terms, such a mechanism would contain brush wheels that would be counter-rotated at relatively high speed. The mechanism would be lowered to the ground from a spacecraft or other exploratory vehicle. Upon contact with the ground, the counterrotating brush wheels would kick soil up into a collection chamber. Thus, in form and function, the mechanism would partly resemble traditional street and carpet sweepers. The main advantage of using of brush wheels (in contradistinction to cutting wheels or other, more complex mechanisms) is that upon encountering soil harder than expected, the brushes could simply deflect and the motor(s) could continue to turn. That is, sufficiently flexible brushes would afford resistance to jamming and to overloading of the motors used to rotate the brushes, and so the motors could be made correspondingly lighter and less power hungry. Of course, one could select the brush stiffnesses and motor torques and speeds for greatest effectiveness in sampling soil of a specific anticipated degree of hardness.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Wheels, Soils, Test equipment and instrumentation, Spacecraft

Lightweight Energy Absorbers for Blast Containers

Aluminum foam liners tested for possible replacement of solid lead liners.

Kinetic-energy- absorbing liners made of aluminum foam have been developed to replace solid lead liners in blast containers on the aft skirt of the solid rocket booster of the space shuttle. The blast containers are used to safely trap the debris from small explosions that are initiated at liftoff to sever frangible nuts on hold-down studs that secure the spacecraft to a mobile launch platform until liftoff.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Containers, Aluminum, Foams, Insulation, Booster rocket engines, Entry, descent, and landing

Small, Untethered, Mobile Robots for Inspecting Gas Pipes

These robots would be powered by gas flows.

Small, untethered mobile robots denoted gas-pipe explorers (GPEXs) have been proposed for inspecting the interiors of pipes used in the local distribution natural gas. The United States has network of gas- distribution pipes with a total length of approximately 109 m. These pipes are often made of iron and steel and some are more than 100 years old. As this network ages, there is a need to locate weaknesses that necessitate repair and/or preventive maintenance. The most common weaknesses are leaks and reductions in thickness, which are caused mostly by chemical reactions between the iron in the pipes and various substances in soil and groundwater.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Natural gas, Robotics, Corrosion, Hoses, Inspections

Noncircular Cross Sections Could Enhance Mixing in Sprays

Preliminary results suggest that elliptical cross sections may be best.

A computational study has shown that by injecting drops in jets of gas having square, elliptical, triangular, or other noncircular injection cross sections, it should be possible to increase (relative to comparable situations having circular cross section) the entrainment and dispersion of liquid drops. This finding has practical significance for a variety of applications in which it is desirable to increase dispersion of drops. For example, in chemical-process sprays, increased dispersion leads to increases in chemical-reaction rates; in diesel engines, increasing the dispersion of drops of sprayed fuel reduces the production of soot; and in household and paint sprays, increasing the dispersion of drops makes it possible to cover larger surfaces.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Computational fluid dynamics, Performance upgrades, Spraying

Probe Without Moving Parts Measures Flow Angle

Flow angle is computed from forces measured by use of strain gauges.

The measurement of local flow angle is critical in many fluid-dynamic applications, including the aerodynamic flight testing of new aircraft and flight systems. Flight researchers at NASA Dryden Flight Research Center have recently developed, flight-tested, and patented the force-based flow-angle probe (FLAP), a novel, force-based instrument for the measurement of local flow direction. Containing no moving parts, the FLAP may provide greater simplicity, improved accuracy, and increased measurement access, relative to conventional moving-vane-type flow-angle probes.

Posted in: Briefs, Mechanical Components, Mechanics, Computational fluid dynamics, Measurements, Sensors and actuators, Sensors and actuators, Product development, Aerodynamics

Bio-Inspired Engineering of Exploration Systems

Exploration systems with capabilities imbibed from nature enable new operations that were otherwise very difficult or impossible to accomplish.

The multidisciplinary concept of "bioinspired engineering of exploration systems" (BEES) is described, which is a guiding principle of the continuing effort to develop biomorphic explorers as reported in a number of articles in the past issues of NASA Tech Briefs. The intent of BEES is to distill from the principles found in successful nature-tested mechanisms of specific "crucial functions" that are hard to accomplish by conventional methods but that are accomplished rather deftly in nature by biological organisms. The intent is not just to mimic operational mechanisms found in a specific biological organism but to imbibe the salient principles from a variety of diverse bio-organisms for the desired "crucial function." Thereby, we can build explorer systems that have specific capabilities endowed beyond nature, as they will possess a combination of the best nature-tested mechanisms for that particular function. The approach consists of selecting a crucial function, for example, flight or some selected aspects of flight, and develop an explorer that combines the principles of those specific attributes as seen in diverse flying species into one artificial entity. This will allow going beyond biology and achieving unprecedented capability and adaptability needed in encountering and exploring what is as yet unknown. A classification of biomorphic flyers into two main classes of surface and aerial explorers is illustrated in the figure, with examples of a variety of biological organisms that provide the inspiration in each respective subclass.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Design processes, Architecture, Architecture, Kinematics, Systems engineering, Robotics

Piezoelectrically Actuated Shutter for High Vacuum

This vacuum-compatible shutter generates an acceptably small magnetic field.

A piezoelectrically actuated shutter is undergoing development for use in experiments on laser cooling of atoms. The shutter is required to be compatible with ultrahigh vacuum [pressure of 10-9 torr (≈1.3 X 10-7 Pa) or less] and to be capable of performing reliably in the vacuum for at least one year. In operation, the shutter would enable the collection and launch of successive samples of cold atoms and would enable the interrogation of the immediately preceding sample while preventing disturbance of the atoms of that sample by light from the collection region.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Lasers, Lasers, Cooling, Valves

Flight Tests of a Ministick Controller in an F/A-18 Airplane

Pilots' opinions were generally favorable.

In March of 1999, five pilots performed flight tests to evaluate the handling qualities of an F/A-18 research airplane equipped with a small-displacement center stick (ministick) controller that had been developed for the JAS 39 Gripen airplane (a fighter/attack/ reconnaissance airplane used by the Swedish air force). For these tests, the ministick was installed in the aft cockpit (see figure) and production support flight control computers (PSFCCs) were used as interfaces between the controller hardware and the standard F/A-18 flight-control laws.

Posted in: Briefs, Mechanical Components, Mechanics, Architecture, Flight control systems, Architecture, Flight control systems, Human machine interface (HMI), Flight tests, Fixed-wing aircraft

Mirrors Containing Biomimetic Shape-Control Actuators

Local bending would be controlled to obtain desired surface figures.

Curved mirrors of a proposed type would comprise lightweight sheets or films containing integral, biologically inspired actuators for controlling their surface figures. These mirrors could be useful in such applications as collection of solar energy, focusing of radio beams, and (provided sufficient precision could be achieved) imaging. These mirrors were originally intended for use in outer space, but it should also be possible to develop terrestrial versions.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mirrors, Sensors and actuators, Sensors and actuators, Biomechanics

Folded Resonant Horns for Power Ultrasonic Applications

Ultrasonic actuators can be made shorter.

Folded horns have been conceived as alternatives to straight horns used as resonators and strain amplifiers in power ultrasonic systems. Such systems are used for cleaning, welding, soldering, cutting, and drilling in a variety of industries. In addition, several previous NASA Tech Briefs articles have described instrumented drilling, coring, and burrowing machines that utilize combinations of sonic and ultrasonic vibrational actuation. The main advantage of a folded horn, relative to a straight horn of the same resonance frequency, is that the folded horn can be made shorter (that is, its greatest linear dimension measured from the outside can be made smaller). Alternatively, for a given length, the resonance frequency can be reduced. Hence, the folded-horn concept affords an additional degree of design freedom for reducing the length of an ultrasonic power system that includes a horn.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Downsizing, Amplifiers, Amplifiers, Tools and equipment, Product development, Drilling, Industrial vehicles and equipment

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