Before they set off into space, experienced zero gravity, or walked on the moon, astronauts like Neil Armstrong (AAE’55, HDR E’70) and Eugene Cernan (ECE’56, HDR E’70) were Purdue students using slide rules for their engineering, mathematics, and statistics courses.

The Barron Hilton Flight and Space Exploration Archives, part of the Karnes Archives and Special Collections Research Center, is home to personal slide rules from seven Purdue astronaut alumni: Armstrong, Cernan, Janice Voss (AAE’75), Jerry Ross (ME’70, MS ME’72, HDR’00), Roy Bridges (MS AAE’66, HDR AAE’01), Richard Covey (MS AAE’69), and Guy Gardner (MS AAE’70). From 2004 to 2009, many of these calculation instruments were part of a larger slide rule display in the A.A. Potter Engineering Center.

Used for multiplying, dividing, and finding roots and logarithms, slide rules became largely obsolete when electronic calculators were introduced in the 1970s. But in 1987, James Alleman, a former professor of civil engineering at Purdue, began collecting alumni slide rules (ranging in size from a few inches to seven feet) to celebrate the centennial of civil engineering at the University. Around 200 alumni donated their computational devices, some of which were made in the 19th century, to the collection. 

“There was a point in time when the slide rule was king,” Alleman said when the exhibit was unveiled in 2004. “During a period of about 400 years, anything anybody built that was of any magnitude would have required a slide rule.”

When the wall display was taken down, the astronauts’ slide rules were hand-wrapped in tissue paper and transferred to a temperature- and humidity-controlled vault. The slide rules, along with carrying cases, name tags, and accompanying photos, are stored in acid-free folders in an acid-free box. Copies of letters responding to Alleman’s solicitations for slide rules are also stored in the same manner.

Although extra security measures are taken — only one folder can be viewed at a time — to ensure the slide rules are not misplaced, the archives and special collections staff encourage students, employees, and the public to visit the collection, hold a piece of history, and even snap some photos.

What are your favorite hidden gems on campus? Let us know in the comments.