Historical Context - Extraordinary Demands of War
After the United States entered World War II in 1941, the Ballistics Research Laboratory of the U.S. Army (BRL) faced a growing demand for artillery firing tables that provided trajectory information to hit intended targets. Previously, these tables were prepared by “human computers” who performed complex mathematical computations using a simple desk calculator.
Front view of 240mm howitzer just before firing into German-held territory, 1944, National Archives.
Excerpt of Ballistic Research Laboratory report describing computations necessary for canon artillery firing tables, 1967, Defense Technical Information Center.
Technological Barriers
The BRL needed a machine to compute firing tables with greater speed and accuracy. Existing computers, including the Bush differential analyzer and Mark l, were slow and inaccurate because they relied on electromechanical parts. There was no programmable computer available to handle different calculations. These technological barriers led to Project PX.
Excerpt of an ENIAC technical report describing how existing machines could only solve a limited class of problems, 1945, National Archives.
Vannevar Bush's differential analyzer, 1930, Computer History Museum.
Mark l computer at Harvard University, Harvard University.
Project PX
In 1943, the BRL commissioned a team at the University of Pennsylvania to develop a computer that could perform the diverse calculations required for firing tables. This classified program, called Project PX, led to the development of the Electronic Numerical Integrator and Computer, or ENIAC for short.
American howitzers shell German forces retreating near Carentan, France, 1944, National Archives.
1942 edition of abbreviated firing tables, American Heritage.