Rural Americans, circa 1935. (They didn’t pay someone to rip their jeans!
BRLESC I (Ballistic Research Laboratories Electronic Scientific Computer¹) (1962)
Army Research Laboratory mathematician/programmer Norma Stec and her assistant Lou Moeller are monitoring a satellite tracking calculation on the console of a massive high-speed 68-bit digital computer, a $3 million machine built by the US Army's Ballistic Research Laboratory at Aberdeen Proving Ground with assistance from the National Bureau of Standards and designed to take over the computational workload of EDVAC² and ORDVAC³, which themselves were successors of ENIAC⁴. The 35 kW machine was capable of five million (bitwise) operations per second. Fixed-point additions taking 5 µs, floating-point additions took 5 to 10 µs, multiplication took 25 µs, and division took 65 µs. The applications of BRLESC included exterior ballistics⁵ and problems such as high altitude, solar and lunar trajectories, computation for the preparation of firing tables and guidance control data for Ordnance weapons, including free flight and guided missiles as well as ballistic measurement problems, including photogrammetric, ionospheric, and damping of satellite spin calculations, reduction of satellite Doppler tracking data, and computation of satellite orbital elements⁶. The arithmetic unit alone contained 1,727 vacuum tubes of 4 types, 853 transistors of 3 types, 46,500 diodes of 2 types, and 1,600 pulse transformers. Logical events are controlled by a five-phase megacycle clock, permitting decisions at the rate of 5 MHz. The storage system of the machine consists of a high-speed magnetic ferrite core memory of 4,096 words. Each word is 72 bits long, which is equivalent computationally to approximately 19 decimal digits, since 4 parity bits and 4 sign bits are not included in the operands. The complete read-write cycle time of this memory is 1.5 µs.
The applications of BRLESC were as follows:
1. Exterior ballistics problems such as high altitude, solar and lunar trajectories, computation for the preparation of firing tables and guidance control data for Ordnance weapons, including free flight and guided missiles.
2. Interior ballistic problems, including projectile, propellant, and launcher behaviour, e.g., physical characteristics of solid propellants, equilibrium composition, and thermodynamic properties of rocket propellants, computation of detonation waves for reflected shock waves, vibration of gun barrels and the flow of fluids in porous media.
3. Terminal ballistic problems, including nuclear, fragmentation, and penetration effects in such areas as explosion kinetics, shaped charge behaviour, ignition, and heat transfer.
4. Ballistic measurement problems, including photogrammetric, ionospheric, and damping of satellite spin calculations, reduction of satellite doppler tracking data, and computation of satellite orbital elements.
5. Weapon systems evaluation problems, including antiaircraft and antimissile evaluation, war game problems, linear programming for solution of Army logistical problems, probabilities of mine detonations, and lethal area and kill probabilities of mine detonations, and lethal area and kill probability studies of missiles.