### Speaker: Joseph Grcar

Title: Episodic History of Calculations for Exterior Ballistics

Abstract: Exterior ballistics studies the trajectories of bullets and artillery shells, or in Leonard Euler's phrase, the path of an object thrown into the air. Military technologists predicted trajectories using Isaac Newton's model of a point-mass with aerodynamic drag from Euler in 1753 to ENIAC in 1946. For this purpose they invented various computing methods: ballistic tables, numerical integration, differential analyzers, and finally electronic computers. Indeed, the United States supported inventing computers precisely to construct artillery firing tables in the second World War. Beyond the many fascinating historical events, this long period offers a test for understanding the history of engineering technology. I propose a concept of episodic change in the history of engineering analogous to the paradigm shifts in the history of science.

Bio: Joseph Grcar conducts research on the history of computing. His 2010 article in Historia Mathematica identified Newton as the inventor of "Gaussian" elimination in Europe. Grcar was a computational scientist at national laboratories in Livermore and in Berkeley for many years, where he was one of the original developers of the Chemkin software for chemical kinetics. He specialized in calculations for reacting fluid flows, combustion, and linear algebra in which he originated the partial reorthogonalization technique for Lanczos methods. A matrix and a polynomial are named after him. Grcar received a doctorate in mathematics from the University of Illinois in 1980.

Y2E2-101