Tech Briefs

Solving Complex Engineering Challenges of Large Composite Aerostructures

Large-scale composite parts present unique design and manufacturing challenges in aerospace.

Composites are becoming the material of choice for the manufacture of large, complex aerostructures. The aft section of the jumbo Airbus A380 and the wings of the military transport Airbus A400, for example, are all made of carbon-fiber composites. Boeing, for the first time, is building an all-composite airframe and wings for its groundbreaking 787 airliner. Because of these and other recent manufacturing achievements, there is little doubt that composite materials will be used extensively in many future aircraft programs — from wide-body jets and commercial airliners to regional, business, and “very light” airplanes.

Posted in: Briefs, Manufacturing & Prototyping, Aircraft structures, Composite materials, Business and general aviation aircraft, Commercial aircraft, Military aircraft

Repairing Fractured Bones by Use of Bioabsorbable Composites

Less surgery would be necessary, and full strength would be restored sooner.

A proposed method of surgical repair of fractured bones would incorporate recent and future advances in the art of composite materials. The composite materials used in this method would be biocompatible and at least partly bioabsorbable: that is, during the healing process following surgery, they would be wholly or at least partly absorbed into the bones and other tissues in which they were implanted. Relative to the traditional method, the proposed method would involve less surgery, pose less of a risk of infection, provide for better transfer of loads across fracture sites, and thereby promote better healing while reducing the need for immobilization by casts and other external devices. One requirement that both the traditional and proposed methods must satisfy is to fix the multiple segments of a broken bone in the correct relative positions. Mechanical fixing techniques used in the traditional method include the use of plates spanning the fracture site and secured to the bone by screws, serving of wire along the bone across the fracture site, insertion of metallic intramedullary rods through the hollow portion of the fractured bone, and/or inserting transverse rods through the bone, muscle, and skin to stabilize the fractured members. After the bone heals, a second surgical operation is needed to remove the mechanical fixture(s). In the proposed method, there would be no need for a second surgical operation.

Posted in: Briefs, TSP, Bio-Medical, Medical, Surgical procedures, Biomaterials, Composite materials

An Alternative for Emergency Preemption of Traffic Lights

This system resolves potential conflicts among emergency vehicles.

An electronic communication and control system has been developed as a prototype of advanced means of automatically modifying the switching of traffic lights to give priority to emergency vehicles. This system could be used alternatively or in addition to other emergency traffic-light-preemption systems, including a variety of systems now in use as well as two proposed systems described in “Systems Would Preempt Traffic Lights for Emergency Vehicles” (NPO-30573), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 36. Unlike those prior systems that depend on detection of sounds and/or lights emitted by emergency vehicles, this system is not subject to severe range limitations. This system can be retrofitted into any pre-existing traffic-light control system, without need to modify that system other than to make a minimal number of wire connections between the two systems.

Posted in: Briefs, TSP, Electronics & Computers, Wireless communication systems, Performance upgrades, Traffic management, Rescue and emergency vehicles and equipment

Vehicle Transponder for Preemption of Traffic Lights

This unit provides timely information on statuses of vehicles and intersections.

The purpose of this article is to describe, in more detail, the transponder installed in each vehicle that participates in the emergency traffic-light-preemption system described in the immediately preceding article.

Posted in: Briefs, TSP, Electronics & Computers, Traffic management, Rescue and emergency vehicles and equipment

Intersection Monitor for Traffic-Light-Preemption System

This unit provides real-time phase data essential for effective preemption.

The figure shows an intersection monitor that is a key subsystem of an emergency traffic-light-preemption system that could be any of the systems described in the three immediately preceding articles and in “Systems Would Preempt Traffic Lights for Emergency Vehicles” (), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 36. This unit is so named because it is installed at an intersection, where it monitors the phases (in the sense of timing) of the traffic lights. The mode of operation of this monitor is independent of the type of traffic-light-controller hardware or software in use at the intersection. Moreover, the design of the monitor is such that (1) the monitor does not, by itself, affect the operation of the traffic-light controller and (2) in the event of a failure of the monitor, the traffic-light controller continues to function normally (albeit without preemption).

Posted in: Briefs, TSP, Electronics & Computers, Sensors and actuators, Product development, Traffic management

Automated Announcements of Approaching Emergency Vehicles

Pedestrians would be given advance warning.

Street intersections that are equipped with traffic lights would also be equipped with means for generating audible announcements of approaching emergency vehicles, according to a proposal. The means to generate the announcements would be implemented in the intersection-based subsystems of emergency traffic-light-preemption systems like those described in the two immediately preceding articles and in “Systems Would Preempt Traffic Lights for Emergency Vehicles” (NPO-30573), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 36.

Posted in: Briefs, TSP, Electronics & Computers, Exterior lighting, Product development, Traffic management, Rescue and emergency vehicles and equipment

Digital Front End for Wide-Band VLBI Science Receiver

An upgrade to the very long baseline interferometry (VLBI) science receiver (VSR) — a radio receiver used in NASA’s Deep Space Network (DSN) — is currently being implemented. The current VSR samples standard DSN intermediate frequency (IF) signals at 256 MHz and after digital down-conversion records data from up to four 16-MHz baseband channels. Currently, IF signals are limited to the 265-to-375-MHz range, and recording rates are limited to less than 80 Mbps. The new digital front end, denoted the Wideband VSR, provides improvements to enable the receiver to process wider bandwidth signals and accommodate more data channels for recording. The Wideband VSR utilizes state-of-the-art commercial analog-to-digital converter and field-programmable gate array (FPGA) integrated circuits, and fiber-optic connections in a custom architecture. It accepts IF signals from 100 to 600 MHz, sampling the signal at 1.28 GHz. The sample data are sent to a digital processing module, using a fiber-optic link for isolation. The digital processing module includes boards designed around an Advanced Telecom Computing Architecture (ATCA) industry-standard backplane. Digital signal processing implemented in FPGAs down-convert the data signals in up to 16 baseband channels with programmable bandwidths from 1 kHz to 16 MHz. Baseband samples are transmitted to a computer via multiple Ethernet connections allowing recording to disk at rates of up to 1 Gbps.

Posted in: Briefs, TSP, Electronics & Computers, Antennas, Architecture, Fiber optics

Full-Duplex Digital Communication on a Single Laser Beam

The laser beam would be transmitted with one modulation and retroreflected with another modulation.

A proposed free-space optical communication system would operate in a full-duplex mode, using a single constant-power laser beam for transmission and reception of binary signals at both ends of the free-space optical path. The system was conceived for two-way data communication between a ground station and a spacecraft in a low orbit around the Earth. It has been estimated that in this application, a data rate of 10 kb/s could be achieved at a ground-station- to-spacecraft distance of 320 km, using a laser power of only 100 mW. The basic system concept is also applicable to terrestrial free-space optical communications.

Posted in: Briefs, Electronics & Computers, Lasers, Wireless communication systems, Spacecraft

Pointing Reference Scheme for Free-Space Optical Communications Systems

A technique is proposed for referencing infrared transmit lasers with silicon detectors.

A scheme is proposed for referencing the propagation direction of the transmit laser signal in pointing a free-space optical communications terminal. This recently developed scheme enables the use of low cost, commercial silicon-based sensors for tracking the direction of the transmit laser, regardless of the transmit wavelength. Compared with previous methods, the scheme offers some advantages of less mechanical and optical complexity and avoids expensive and exotic sensor technologies.

Posted in: Briefs, TSP, Electronics & Computers, Lasers, Satellite communications, Sensors and actuators, Silicon alloys

Microwave Oscillators Based on Nonlinear WGM Resonators

Optical signals are phase-modulated with spectrally pure microwave signals.

Optical oscillators that exploit resonantly enhanced four-wave mixing in nonlinear whispering- gallery- mode (WGM) resonators are under investigation for potential utility as low-power, ultra-miniature sources of stable, spectrally pure microwave signals. There are numerous potential uses for such oscillators in radar systems, communication systems, and scientific instrumentation.

Posted in: Briefs, TSP, Electronics & Computers, Antennas, Oscilloscopes, Radar, Telecommunications, Test equipment and instrumentation

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