APL Colloquium

April 26, 2019

Colloquium Topic: Measurements and Analysis of Ship-Induced Optical Turbulence on an Arleigh Burke Class Destroyer

Heat convection from a ship deck and air flow around the superstructure can produce optical turbulence above and around the ship, affecting high energy laser (HEL) beam propagation. Optical turbulence causes random variations in the index of refraction along the beam path, which can lead to beam degradation and wander. Increased turbulence near the laser source enhances the integrated effect over the beam path, potentially resulting in significantly less power delivered to the target. To study this effect, in June 2018 we installed sonic anemometers and other measuring equipment on the USS Spruance (DDG 111). Measurements were taken over several days both in port and underway, in a variety of weather and operating conditions, to quantify the level of ship-induced optical turbulence at multiple locations above the ship’s forward deck. The data was analyzed to look for correlations between turbulence levels and other measured quantities such as wind speed and the difference between the air and deck temperature. Wave propagation models were used to predict the effect of the measured turbulence values on HEL beam propagation. We will present results from these studies and discuss our current plans for follow-on experiments.

Colloquium Speaker: Joseph Blau

Dr. Joseph Blau was born in Santa Barbara, CA in 1962. He graduated from Yorktown High School in Yorktown Heights, NY in 1980, and was awarded a National Merit Scholarship. He studied Computer Science at UCLA, then transferred to UC Santa Barbara in 1982, where he earned a Bachelor of Science in Physics in 1987. He earned a Master of Science in Physics from UC San Diego in 1989, and a Ph.D. in Physics from the Naval Postgraduate School in 2002. Dr. Blau has worked at NPS since 1989; he is currently appointed as a Research Associate Professor of Physics.

Over the past 30 years, Dr. Blau has designed and studied high energy lasers for military applications. His research has guided the development and understanding of many operational lasers around the world, and he has also done extensive work on the integration of laser weapons into Naval platforms to defend against various threats. His most recent work has been on atmospheric propagation of laser beams, including an underway experiment last year onboard the USS Spruance. Dr. Blau has published more than 50 scientific papers and given more than 200 conference presentations, and he has advised more than 100 NPS students on their thesis research, including RDML Douglas Small and RDML Daryl Caudle. Dr. Blau is the co-recipient of the 2015 Directed Energy Award from the Association of Old Crows.

Dr. Blau is presenting on behalf of LT Jacob Busby, recipient of an APL Naval Postgraduate School Applied Physics Award.