This book contains everything you need to know about free-space laser beam propagation modeling and simulation, and the mathematics for target irradiance calculation. The author describes four different beam propagation methods (including the new, fast harmonic expansion method) and two direct target irradiance calculation methods. Kolmogorov statistics are used for turbulence simulations but you can easily use other models. The author also solves lots of examples with Mathcad and you can request the code. People often assume that, since I've written many books, I'm a rich man.  No one gets rich writing technical books.  If I had no other income except for book royalties, I'd have just enough money to purchase one cheap hamburger per day.  So, there must be other reasons for writing technical books.  I do it because I want to make a difference in this world today, and I want to leave something of myself in this world after I die. In the last 50 years Andrew (Andy) Motes has been (in roughly chronological order) a sharecropper, woodcutter, trapper, grocery-store clerk, motorcycle mechanic, electronic technician, electronic engineer, computer software developer, space systems engineer or "rocket scientist," laboratory research scientist, laser physicist, author, teacher, college professor, military officer, civil servant, defense contractor, and International Arms Dealer. He received his BS degree in Electrical Engineering from the University of Arkansas in 1978; his MS degree in Engineering from the Air Force Institute of Technology in 1979 with a specialty in air and spacecraft Navigation, Guidance, and Control theory; and his PhD in 1987 from the University of New Mexico with a specialty in laser physics and electro-optics. All his degrees were earned while serving on active duty in the US Air Force. He worked on President Reagan's SDI (Strategic Defense Initiative or "Star Wars") program, the Army's THEL (Tactical High Energy Laser) program, the Air Force's ABL (Airborne Laser) program, and NASA's Next Generation Space Relay Architecture. He has been licensed to practice engineering in multiple states including New Mexico, Colorado, and Arkansas. He has written > 20 books, nine commercial educational software packages (including the award winning and best-selling software called School-Mom), and many scientific journal and magazine articles. He taught Astronautical Engineering and control theory at the US Air Force Academy, Physics and Electronic Design at John Brown University, retired from the US Air Force Reserves in 2007 at the rank of Colonel, and retired from federal civil service in 2012.