The Movie ‘Hidden Figures’ – Perspective from a Mortar Infantryman

Published February 11, 2017

The Oscar-nominated film “Hidden Figures” tells the stories of three African-American women employed as “computers” at NASA in the early 1960s. These women — Katherine Johnson, Dorothy Vaughan and Mary Jackson — did much of the number-crunching of the early space program.

Back in the day, I was an infantry mortar platoon leader. My unit featured three 81 mm guns and their fire crews, a fire direction center, and three forward observers. Mortars fire their rounds at a high angle. This enables the mortars to fire from a protected position and even to attack targets in protected positions. But, without a direct line of sight to the target, the fire direction center needs to be in communication with a forward observer.

With the location of the target, a computer at the fire direction center could calculate the correct angle and direction of the mortar tube and charge for the round. With a round “near” the target, the forward oberserver can call in adjustments.

My buddy Tom Sturrock, who brought the story of computers at NASA to my attention, was an artilleryman in Viet Nam. He was stationed at one of the interlocking fire bases that General Westmoreland strung through the length of South Viet Nam, like a backbone. The artillery, nickname “King of Battle,” thus supported the infantry, “Queen of Battle,” throughout the country.

Tom was, among other things, a computer at his firebase. His calculations had to be much more precise than my computer’s calculations. This was because the maximum effective range of the 105 mm howitzer was 7 miles (11,000 meters), as compared to the maximum effective range of the 81 mm mortar of 2 miles (6,000 meters). The range and precision are much greater for the howitzer because it fires its round through a rifled gun (which imparts a spin, for stability in flight) with much greater velocity. In contrast, the mortar essentially lobs the round downfield (the inside of the mortar tube is in fact slightly rifled, but so little that the mortar round is typically given fins to help with stability). 

By World War II, the maximum effective range of ship-mounted guns was reaching to and even beyond the horizon. From ancient days, the curvature of the earth was easy enough to determine from the heights of the point of observation and the tallest part of a ship when it was first observed, and the distance from one to another.

Because of the curvature of the earth, the observation post of the fire control system would be placed on the tallest part of the ship. With range and direction to the target, the computer would determine the direction and elevation of the guns, and the charge for the rounds.

In the case of the Japanese battleship Yamato, its massive 18 inch guns could fire 25 miles, which is beyond the horizon. So, an observer would be sent aloft, in a balloon, to determine direction and distance to the target. Supposedly, the Yamato would destroy its target from beyond the horizon, before it could even be observed, no less brought into range of the guns of its target. (Things didn’t work out well for the “invincible” Yamato and its sister battleship. They seldom do.)

The next step in ballistics involves the ballistic missile, from short-range to intercontinental ballistic missile. Ballistic missiles are so called because they are only guided or controlled for a relatively small distance. Mostly, if not entirely, their flight path is determined by their initial trajectory.

From time to time, the U.S. tests its ICBMs. This means firing one from the continental United States westward over the Pacific Ocean, to a target in, for example, the Marshall Island more than 4,000 miles away. While questions have been raised as to whether atmospheric or magnetic influences over the North Pole would have effect an ICBM sent over the North Pole, as opposed to one sent over the Pacific Ocean, I hope we never find out.

We now come to ballistics and the Voyager I and Voyager II missions.Voyager I took off in 1977 to explore Jupiter, Saturn, Saturn’s moon Titon, and then deep space. Voyager II took off at about the same time, to explore Jupiter, Saturn, Uranus, Neptune and then deep space.

While the Voyager capsules were equipped with tiny rockets in order make small corrections, mostly their flights were ballistic (or uncontrolled).

What is really neat about these missions is their “cushion shots.” Like in a game of billiards, the capsules “bounce off” their intermediate targets’ gravity fields and continue their flights.

According to NASA, Voyager I passed from the Solar System into deep space in 2013. At the time, until its fuel is completely depleted, it is reporting back on space conditions determined more by the Milky Way galaxy and less by the Solar System.

The invention of the abacus, the place-holder number system, the slide rule, mechanical computers (calculating machines), and vacuum-tube digital computers, the replacement of vacuum tubes by circuit boards, and now the development of artificial intelligence, may seem at each point to diminish the role of the human person in computing.

Looking back, we can appreciate the roles played by those who, at the cutting edge of the technology of their day, acted as computers even if, looking forward, it is not clear what role there will remain for us.