Apollo 15 astronaut Jim Irwin’s EVA “Yo-Yo” used—and broken—on the lunar surface

Flown lunar surface EVA retractable tether used on the lunar surface by Apollo 15 Lunar Module Pilot Jim Irwin. The original brown strap was used to attach it to Irwin’s PLSS (life support backpack)and to carry tools during lunar surface operations. Part of the FV Space Collection.

This tether, referred to by astronauts as a ‘yo-yo,’ has become the source of some funny confusion in the conspiracy theory world, as they thought a “yo-yo” was the wire and pulley system hanging from the ceiling to fake the low-gravity lunar surface movements. Seriously — annotated video

Accompanied by a signed letter from Apollo 15 Commander Dave Scott (below) which reads, in part: “I hereby certify that the EVA Retractable Tether (‘Yo-yo’) included with this letter was used by Lunar Module Pilot (LMP) Jim Irwin during the lunar surface activities of Apollo 15…The purpose of the Yo-yo was to enable the astronaut to carry certain tools attached to his spacesuit and be readily available without having to carry them by hand. These include the scoop and tongs, both of which were used by Jim Irwin in sampling rocks and soil near Elbow crater on the Moon during EVA-1. This Yo-yo was also used for the Universal Hand Tool (UHT) to assist in ALSEP deployment (Boyd Bold release); however during the ALSEP deployment, this particular Yo-yo failed when the string connecting the clamp broke at its attach point on the clamp, and the clamp was lost on the Moon. We returned the Yo-yo to Earth; and subsequent disassembly after the mission showed that both the bowline and the figure-eight knot attaching the cord to the clamp had untied, thus allowing the cord to retract into the housing…After this post-mission analysis the Yo-yo was reassembled to its current configuration (however the original clamp was replaced in this assembly). An improved clinch knot was installed on large Yo-yos for subsequent missions.

This large yo-yo has been in my personal collection since returning to Earth.”

As noted in the Apollo 15 Mission Report (chapter 14, 5.7), both retractable tethers failed during lunar surface operations; the Commander’s tether cord broke during the first extravehicular activity, and the tool clamp came off the end of the Lunar Module Pilot’s tether. “The Lunar Module Pilot carried the optional, somewhat larger, 1-pound pull tether.”

is stamped with a part number of SEB33100291-303 and serial number SN 1025. The device measures approximately 6.25 x 2.75 x 1.5, 0.7 pounds. Attached to the end of the 35″ retractable cord is a replacement double-jawed spring-closing mechanism with an incorporated eyelet for attachment to the tether cord.