In high school I toured Oakland Center, the regional air-traffic control center for much of the U.S. west coast. The controller with whom I sat had the big circular display we've all seen, and I noticed one contact labeled "NASA 714" moving away from the coast to the southwest, and I asked what it was.

It was the Gerard P. Kuiper Airborne Observatory¹, a converted C-141 transport with a telescope inside, en route to Hawaii on a mission. (Nice!)

"714" is also the badge number of Detective Joe Friday from the "Dragnet" TV series², and is a telephone area code serving part of Southern California³.

The "cylinder" part came when I was casting about for an HN handle, and it sounded good in combination with 714.

1: https://en.m.wikipedia.org/wiki/Kuiper_Airborne_Observator 2: https://www.perfessorbill.com/misc/badge714.htm 3: https://en.m.wikipedia.org/wiki/Area_codes_714_and_657