Terry A. Willemin, P.E.

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Presents a SunCam continuing education series on the topic of:

External Ballistics, GD&T

Contact author at:
willemta@vt.edu
Blacksburg, VA

Mr. Willemin holds a master’s degree in Aerospace Engineering with a focus on compressible flow measurement from Virginia Tech. He is a summa cum laude graduate of Lamar University with a Bachelor of Science degree in Mechanical Engineering. As an undergraduate student he flew several magnetic particle distribution experiments in a mixed ballistic/microgravity environment in NASA’s Reduced Gravity Student Flight Opportunities Program (part of their Microgravity University). Also, as an undergraduate student he was granted a Ronald E. McNair (former astronaut who died in the Space Shuttle Challenger explosion) scholarship which led to his attending graduate school. Mr. Willemin was granted a US Airforce based fellowship at Virginia Tech to study scramjet inlet starting of Busemann type inlets for hypersonic vehicles. After working as an engineer for over 12 years, split between slip ring design and some wind tunnel research, he decided to take the fundamentals of Engineering exam and subsequently the Professional Engineering exam. He has 16-plus years of experience in engineering research and design and currently works as a staff engineer and manager of designer/drafters. On the side, has also taught several GD&T (geometric dimensioning and tolerancing) courses over the past six years. He currently spends an inordinate amount of time in general ballistics research. His spare time is either spent with his wife and the two youngest of his five children who still live at home or in rebuilding demilitarized firearms.

Course Title Rating Hours Price

402-External Ballistics Primer for Engineers - Part I: Aerodynamics & Projectile Motion

(4.7) 9 Reviews

3 $67.50

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Course Objectives: This course was written to introduce engineers of any discipline to the basics of external ballistics. The engineer will gain a general understanding of many of the factors, effects and forces which affect the flight path of a projectile in unpowered flight.

Course Description:

The intriguing subject of this primer explores the characteristics of the unpowered portion of flight of a projectile on a ballistic trajectory, or external ballistics. It was created for the broad range of engineers who have an interest in learning the basics of external ballistics. In order to accurately describe the factors, which affect the trajectory of an object on a ballistic flight path and the path itself, an engineer will rely on rigorous calculations, computer simulations and experimental data. For the purposes of this primer, gun related pun intended, we only resort to a conceptual understanding of the mechanics, augmented by the use of simplified equations including mentions of some of the governing equations with focuses on some specialized cases. The focus areas are kept concise so that tangential topics such as orbital mechanics are generally not treated. The course has been broken into two parts. Part I targets the aerodynamic characteristics of general projectiles in flight and relevant factors which affect its flight path. In Part II we dive into the use of associated measurement hardware an engineer or ballistician might use to characterize flight paths and conclude with a spotlight on the physics of the ballistic pendulum.

411-External Ballistics Primer for Engineers - Part II: Test Equipment

(4.8) 4 Reviews

4 $90.00

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Course Description:

In part one of this external ballistics course several factors were introduced which affect the flight of a ballistic projectile. Some basic equations were presented that are useful to a great many engineers outside of ballistics for making approximations with a fair bit of accuracy. Several flow regimes that a ballistic projectile may pass through were also treated, though there were cases that were omitted for either lack of space or complexity. Fast forward to part deux. Projectiles launched from earth generally move through air for most or all of their flight, which means understanding the properties of that air is very important. Besides air there are other flightpath modifiers including Coriolis’ effects, so many times it is important to know the direction the projectile is headed in and its speed. The list of measurement equipment used in relation to external ballistics research is extensive, however there are tools which may be more noteworthy or common than others. The balance of this part of the full course delivers descriptions and general information of some of the equipment used to measure atmospheric air pressure, humidity, windspeed, wind direction, projectile speed and direction. There are also a few characteristic comparisons in table form appended to a handful of the sections.

The tools that follow are used throughout much of engineering and research rather than being confined to external ballistics, so it is likely you have used at least some of them in relation to your own work.