Engineering topics

Yang, L. C.

Publications and source records attributed to Yang, L. C..

At least 37 records · Page 2

NASA NTRS1979

Underwater seismic source

Apparatus for generating a substantially oscillation-free seismic signal for use in underwater petroleum exploration, including a bag with walls that are flexible but substantially inelastic, and a pressured gas supply for rapidly expanding the bag to its fully expanded condition is described. The inelasticity of the bag permits the application of high pressure gas to rapidly expand it to full size, without requiring a venting mechanism to decrease the pressure as the bag approaches a predetermined size to avoid breaking of the bag.

Yang, L. C.↗

NASA NTRS1979

Seismic vibration source

A system for vibrating the earth in a location where seismic mapping is to take place is described. A relatively shallow hole formed in the earth, such as a hole 10 feet deep, placing a solid propellant in the hole, sealing a portion of the hole above the solid propellant with a device that can rapidly open and close to allow a repeatedly interrupted escape of gas. The propellant is ignited so that high pressure gas is created which escapes in pulses to vibrate the earth.

Dowler, W. L.↗

NASA NTRS1979

Performance characteristics and statistics of a laser initiated microdetonator

The test results of 320 units of the laser initiated microdetonator are summarized. The commercially fabricated units used a lead styphnate/lead azide/HMX (1 mg/17.5 mg/13.5 mg) explosive train design contained in a miniature aluminum can and completed with a glass-metal seal window. The test parameters were the high and low laser energy, high and low temperature, laser pulse duration, laser wavelength and nuclear radiation (5 x 10 to the 6th rads of 1 MeV gamma ray). The performance parameters were the laser energy for ignition and the actuation response time. Included also is a description of the development of a flexible, continuously advanced train of explosive devices by using the units, miniature optics and fiber optics.

Yang, L. C.↗

NASA NTRS1978

Self-sterilizing canister

Canister, originally conceived for remote sterilization of spacecraft packages, could be used terrestrially to handle samples in biologically hazardous environments. Multiwalled canister includes inner layer of pyrotechnic powder. For sterilization, electrically activated squib ignites powder, raising temperature of outer surface of canister to 230 degrees centigrade for several minutes. Thermal-buffer inner layer prevents inside temperature for exceeding 100 degrees centigrade to protect contents from damage. Samples in field hospitals and other emergency situations could also be handled by equipment.

Yang, L. C.↗

NASA NTRS1977

Compact pulsed laser having improved heat conductance

A highly efficient, compact pulsed laser having high energy to weight and volume ratios is provided. The laser utilizes a cavity reflector that operates as a heat sink and is essentially characterized by having a high heat conductivity, by being a good electrical insulator and by being substantially immune to the deleterious effects of ultra-violet radiation. Manual portability is accomplished by eliminating entirely any need for a conventional circulating fluid cooling system.

Yang, L. C.↗

NASA NTRS1976

Laser fiber optics ordnance initiation system

Recent progress on system development in the laser initiation of explosive devices is summarized. The topics included are: development of compact free-running mode and Q-switched lasers, development of low-loss fiber optic bundles and connectors, study of nuclear radiation effects on the system, characterization of laser initiation sensitivities of insensitive high explosives, and the design methods used to achieve attractive system weight and cost savings. Direction for future work is discussed.

Yang, L. C.↗

NASA NTRS1975

Inherent time delay for dielectric breakdown in shock-loaded x-cut quartz

Dielectric breakdown in shock-loaded x-cut quartz is examined under conditions of both impact loading and Q-switched laser-irradiation loading. It is observed that breakdown is characterized by an inherent time delay which depends on the magnitude of the electric field. For pulse duration less than about 30 ns, dielectric breakdown is not observed.

Graham, R. A.↗

NASA NTRS1975

Compact laser through improved heat conductance

A 16-joule-pulse laser has been developed in which a boron nitride heat-conductor enclosure is used to remove heat from the elements. Enclosure is smaller and lighter than systems in which cooling fluids are used.

Yang, L. C.↗

NASA NTRS1974

Laser system to detonate explosive devices

Detonating system is not affected by electromagnetic interference. System includes laser source, Q-switch, and optical fiber connected to explosive device. Fiber can be branched out and connected to several devices for simultaneous detonation.

Menichelli, V. J.↗

NASA NTRS1974

Laser-actuated mechanical device

Actuator is portable and can be used in high-temperature (over 500 C) environments by incorporating tungsten metal film and quartz window. Actuator can be triggered when it is not directly in laser beam path by utilizing fiber optics. It is advantageous for remotely switching ultra-high voltage systems.

Murphy, A. J.↗

NASA NTRS1974

Stress waves generated in thin metallic films by a Q-switched ruby laser

Investigation results on stress waves generated by Q-switched ruby laser irradiated thin metal films under confinement, studied over a wide range of film materials and film thicknesses, are reviewed. The results indicate that the dependence on these parameters is much weaker than is predicted by heat transfer estimations commonly used to describe the interaction of laser irradiation with unconfined bulk-solid surfaces.

Yang, L. C.↗

NASA NTRS1974

Optically detonated explosive device

A technique and apparatus for optically detonating insensitive high explosives, is disclosed. An explosive device is formed by containing high explosive material in a house having a transparent window. A thin metallic film is provided on the interior surface of the window and maintained in contact with the high explosive. A laser pulse provided by a Q-switched laser is focussed on the window to vaporize the metallic film and thereby create a shock wave which detonates the high explosive. Explosive devices may be concurrently or sequentially detonated by employing a fiber optic bundle to transmit the laser pulse to each of the several individual explosive devices.

Yang, L. C.↗

NASA NTRS1974

Optically actuated two position mechanical mover

An optically actuated mechanical mover adapted to be moved from an ambient position to an active position, is disclosed. The mechanical mover essentially comprises a piston/cylinder arrangement including a piston that is contained within an internal cylindrical chamber of a housing. The cylindrical chamber is configured to permit the piston to be moved for the length of the chamber as a work stroke. A lock pin extending through the piston, and diametrically opposed walls of the chamber housing, retain the piston in the ambient position at one end of the chamber. An actuator for producing a pressure or shock wave that drives the piston is positioned at the end of the chamber corresponding to the piston ambient position.

Yang, L. C.↗

NASA NTRS1973

A laser initiated explosive device system

A laser initiated explosive system has been developed which can simultaneously initiate multiple explosive devices. Advantages of this system over electrically initiated devices (EED's) are increased safety and reliability, simplicity of laser initiated devices, and increased weight efficiency. The system design with test data are presented and a comparison between laser initiation and electrical initiation is discussed.

Yang, L. C.↗

NASA NTRS1973

A High-efficiency, Small, Solid-state Laser for Pyrotechnic Ignition

A completely self-contained, small, neodymium laser has been designed and demonstrated for use in a pyrotechnic ignition system. A nominal 16 J of laser energy (1.06 micron wavelength, 1-ms duration) was achieved in a rectangular 10.5-X 15.1-X 25.4-cm package weighting 5.14 kg. This high energy-to-weight ratio is encouraging for laser applications in which specific energy efficiency (energy per unit weight or volume) is important. The laser design concepts are described, and some results on pyrotechnic ignition are given. Some details on a laser currently under construction, which will be 1/8 the size of the above laser, are included.

Yang, L. C.↗

NASA NTRS1972

Quartz microbalance studies of an adsorbed helium film.

The resonant frequency of a quartz crystal oscillating in the thickness-shear mode changes by virtue of the mass loading due to any type of film laid down on its surfaces. For a helium film only the normal fraction remains rigidly coupled to the substrate motion. Adsorption isotherms of He-4 measured with this technique show clear departures from conventional nonsuperfluid behavior. We attribute this effect to the onset and presence of superfluidity in the film.

Chester, M.↗

NASA NTRS1972

Initiation of insensitive explosives by laser energy

Instantaneous longitudinal detonations were observed in confined columns of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and tetryl when these materials were pulsed with light energy from a focused Q-switch ruby laser. The laser energy ranged from 0.5 to 4.2 J with a pulse width of 25 ns. Enhancement of the ignition mechanism is hypothesized when a 100-nm (1000-A) thick aluminum film is vacuum-deposited on the explosive side of the window. Upon irradiation from the laser, a shock is generated at the aluminum explosive interface. Steady state detonations can be reached in less than 0.5 microseconds with less than 10% variation in detonation velocity for PETN and RDX.

Menichelli, V. J.↗

NASA NTRS1971

Detonation of insensitive high explosives by a Q-switched ruby laser.

Immediate longitudinal detonations have been observed in confined small-diameter columns of PETN, RDX, and tetryl by using a focused Q-switched ruby laser. The energy ranged from 0.8 to 4.0 J in a pulse width of 25 nsec. A 1000-A-thick aluminum film deposited on a glass window was used to generate a shock wave at the window-explosive interface when irradiated by the laser. In some cases, steady-state detonations were reached in less than .5 microsec with less than 10% variation in the detonation velocity.

Yang, L. C.↗