1,145 research outputs found
Detection of High Altitude Explosions by Observation of Air Fluorescence
Detection of high altitude explosions based on observation of fluorescence radiation of excited nitrogen molecule or nitrogen ion from ground and from satellite
The Continuing Quest for Missile Defense: When Lofty Goals Confront Reality
For almost three quarters of a century, the United States has spent billions of dollars and countless person-hours in the pursuit of a national missile defense system that would protect the country from intercontinental ballistic missiles (ICBM) carrying nuclear warheads. The system currently in place consists of 44 long-range antiballistic missiles stationed in Alaska and California to protect the United States from a possible nuclear weapon carrying ICBM attack from North Korea. After all this effort, this system is still imperfect, being successful only 10 out of 18 tests. This book will provide an historical description of past efforts in national missile defenses to understand the technical difficulties involved. It will also explain how national security concerns, the evolving international environment, and the complexities of US politics have all affected the story. The book will also describe the current systems in place to protect allies and troops in the field from the threat of shorter range missiles. Finally, the book will describe the current US vision for the future of missile defenses and provide some suggestions for alternative paths.https://cupola.gettysburg.edu/books/1142/thumbnail.jp
Detection Techniques of Microsecond Gamma-Ray Bursts using Ground-Based Telescopes
Gamma-ray observations above 200 MeV are conventionally made by
satellite-based detectors. The EGRET detector on the Compton Gamma Ray
Observatory (CGRO) has provided good sensitivity for the detection of bursts
lasting for more than 200 ms. Theoretical predictions of high-energy gamma-ray
bursts produced by quantum-mechanical decay of primordial black holes (Hawking
1971) suggest the emission of bursts on shorter time scales. The final stage of
a primordial black hole results in a burst of gamma-rays, peaking around 250
MeV and lasting for a tenth of a microsecond or longer depending on particle
physics. In this work we show that there is an observational window using
ground-based imaging Cherenkov detectors to measure gamma-ray burst emission at
energies E greater than 200 MeV. This technique, with a sensitivity for bursts
lasting nanoseconds to several microseconds, is based on the detection of
multi-photon-initiated air showers.Comment: accepted for publication in the Astrophysical Journa
Index to NASA tech briefs, 1971
The entries are listed by category, subject, author, originating source, source number/Tech Brief number, and Tech Brief number/source number. There are 528 entries
Time domain analysis of switching transient fields in high voltage substations
Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho
Index to NASA Tech Briefs, 1972
Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number
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Defense Technical Information Center thesaurus
This DTIC Thesaurus provides a basic multidisciplinary subject term vocabulary used by DTIC to index and retrieve scientific and technical information from its various data bases and to aid DTIC`s users in their information storage and retrieval operations. It includes an alphabetical posting term display, a hierarchy display, and a Keywork Out of Context (KWOC) display
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