Special Coverage

Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water

Computer-Automated Evolution of Spacecraft X-Band Antennas

A document discusses the use of computer-aided evolution in arriving at a design for X-band communication antennas for NASA’s three Space Technology 5 (ST5) satellites, which were launched on March 22, 2006. Two evolutionary algorithms, incorporating different representations of the antenna design and different fitness functions, were used to automatically design and optimize an X-band antenna design. A set of antenna designs satisfying initial ST5 mission requirements was evolved by use these algorithms.

Posted in: Briefs, TSP, Software, CAD / CAM / CAE, CAD, CAM, and CAE, Mathematical models, Antennas, Antennas, Spacecraft

Practical Loop-Shaping Design of Feedback Control Systems

Actuator rates are incorporated into a design from the start.

An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Architecture, Electronic control systems, Sensors and actuators, Architecture, Electronic control systems, Sensors and actuators

Fully Printed High-Frequency Phased-Array Antenna on Flexible Substrate

This flexible design enables applications in high-frequency RFID sensors, smart cards, electronic paper, and flat-screen displays.

To address the issues of flexible electronics needed for surface-to-surface, surface-to-orbit, and back-to-Earth communications necessary for manned exploration of the Moon, Mars, and beyond, a room-temperature printing process has been developed to create active, phased-array antennas (PAAs) on a flexible Kapton substrate.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Antennas, Integrated circuits, Wireless communication systems, Antennas, Integrated circuits, Wireless communication systems, Additive manufacturing, Spacecraft

Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites

Better understanding of triaxial braided composites will lead to improved aerospace and automotive structures.

In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process.

Posted in: Briefs, TSP, Materials, CAD / CAM / CAE, CAD, CAM, and CAE, Failure modes and effects analysis, Composite materials, Fibers, Fans, Jet engines

Selective Functionalization of Carbon Nanotubes: Part II

Different species are deposited at different distances.

An alternative method of low-temperature plasma functionalization of carbon nanotubes provides for the simultaneous attachment of molecular groups of multiple (typically two or three) different species or different mixtures of species to carbon nanotubes at different locations within the same apparatus. This method is based on similar principles, and involves the use of mostly the same basic apparatus, as those of the methods described in “Low-Temperature Plasma Functionalization of Carbon Nanotubes” (ARC-14661-1), NASA Tech Briefs, Vol. 28, No. 5 (May 2004), page 45.

Posted in: Briefs, Materials, Joining, Gases, Materials properties, Nanomaterials

Catalyst for Carbon Monoxide Oxidation

This catalyst forms carbon dioxide in a high-powered, pulsed CO2 laser.

In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly.

Posted in: Briefs, TSP, Materials, Lasers, Lasers, Carbon monoxide, Catalysts

Titanium Hydroxide — a Volatile Species at High Temperature

Titanium hydroxide, TiO(OH)2 (g), has been identified as the primary reaction product of TiO2    (s) + H2O (g) at high temperatures (1,200–1,400 °C) through the use of the transpiration technique. This technique is a well-established method used to measure equilibrium pressures at 1 atm. Reactive O2 /H2O mixtures of gases flow over the sample, and react to form volatile Ti hydroxides. The collected reaction gas condensate is analyzed to determine the vapor and dissociation pressures. From the amount of condensate and its relation to the partial pressures of the reactive gases, the identity of the volatile hydroxide can be determined. From the relation of product pressure to temperature, thermodynamic enthalpy and entropy of formation can be calculated.

Posted in: Briefs, TSP, Materials, Water, Oxygen, Titanium, Test procedures

Hybrid Heat Exchangers

A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C–C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Heat exchangers, Heat exchangers, Composite materials, Conductivity, Heat resistant alloys

Orbital Winch for High-Strength, Space-Survivable Tethers

An Orbital Winch mechanism enables high-load, multi-line tethers to be deployed and retracted without rotating the spool on which the tether is wound. To minimize damage to the tether and the wound package during retraction or deployment under load, it can incorporate a Tension Management Module that reduces the infeed tension by a factor of 15 through the use of a powered capstan with guide rollers. This design eliminates the need for rotating high-voltage electrical connections in tether systems that use propellantless electro-dynamic propulsion. It can also eliminate the need for rotating optical connections in applications where the tether contains optical fibers.

Posted in: Briefs, Mechanical Components, Mechanics, Electronic control units, Fiber optics, Electronic control units, Fiber optics, Tools and equipment, Packaging, Fibers, Spacecraft

Steerable Hopping Six-Legged Robot

Motions of spring legs are coordinated in both launch and landing.

The figure depicts selected aspects of a six-legged robot that moves by hopping and that can be steered in the sense that it can be launched into a hop in a controllable direction. This is a prototype of hopping robots being developed for use in scientific exploration of rough terrain on remote planets that have surface gravitation less than that of Earth. Hopping robots could also be used on Earth, albeit at diminished hopping distances associated with the greater Earth gravitation.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Springs, Terrain, Robotics, Pistons

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