This simple device is what equated to a modern scientific
pocket calculator when I first entered the aerospace defense workforce (see the
photo). This is a slide rule, the "calculator" used by engineers
and scientists for 300 years before there were any electronic calculators at
all! This very slide rule is what
I designed my first airplane with, and my
first half dozen supersonic missile propulsion systems with.
For problems you could not handle pencil-and-paper with a
slide rule, there was the mainframe
computer. These were devices that filled
a room the size of a small house,
air-conditioned to about 60-65 F,
so that the magnetic iron cores and wiring would not try to melt
down! You loaded your data and programs
into the mainframe "card batch" in trays, up to 2000 cards at a time, using paper punch card technology. Job turnaround time was measured in
hours, sometimes days.
As for modern spreadsheet technology, when I first entered the workforce, repetitive calculations were manually laid
out on a big piece of paper in a matrix format.
You ran the actual calculations yourself, using a slide rule, or a bit later, a hand-held electronic calculator. You filled in the matrix slowly, literally doing each and every calculation
yourself, and finding out "up-close-and-personal"
what could go wrong with the processing of the data. That is where today's spreadsheet
software came from!
For a given manual spreadsheet job, this experience taught you exactly how to
program the calculations into a scientific programming language (in those
days, something like an early FORTRAN or
BASIC), complete with all the processing
logic and error-trapping. That required punching the program statements
onto cards, for card-batch load and
debugging (again, job turnaround time was
hours-to-days between each run). Once
you did this, you could do similar
jobs, requiring the exact same
analysis, far more quickly. (Or you could modify your program to handle other
jobs that were similar, but slightly
different in a few details.)
Most people today do not realize this, but NASA mission control in Houston did not
have any real computer consoles until the Space Shuttle first flew! During the earlier Mercury, Gemini,
and Apollo programs, those flight
controller consoles were only keyboard-controlled communication displays, each slaved to a counterpart in a back room
outside the mission control room. There
was a team of people (both men and women!) in each back room, who answered the flight controller's question
with slide rule calculations, and typed
in the answers, so that their numbers
appeared on-screen in mission control. That,
plus analog instrument readouts converted
to digital format on-screen, is literally
all the mission flight controllers had to work with!
With the exception of a mainframe-computed figure-eight
orbit between Earth and moon, NASA literally
sent men to the moon during Apollo with slide rules (just like the one in the
photo)! And, the record-breaking X-15 rocket plane (and all
its earlier progenitors), plus the SR-71
jet aircraft, and all the early
supersonic jet fighters, were designed
with nothing but slide rules. Same for
all their rocket and gas turbine engines!
And their heat protection schemes.
My slide rule still works.
I still use it when the electronics conk out, which they inevitably do, occasionally.
The slide rule never conks out like that. It's just slower.
