THE APOLLO 15 LMP'S LUNAR SURFACE "YO-YO."
Flown on Apollo 15, an EVA Retractable Tether ("Yo-yo"), the main unit approximately 4 x 3 x 1 inches, the clamp 2 x 1½ x 1½ inches. The clamp attached to the unit by a slender, 35-inch retractable brown cord. 1-inch brown nylon webbing strap for attaching the unit to the right strap of the PLSS. The main unit with part number "SEB33100291-303" and serial number "1025." The clamp with part number "SEB33100292-303" and serial number "1030," and wording "Assy. not for flight."
USED DURING LUNAR SURFACE EVAS BY JIM IRWIN, LUNAR MODULE PILOT. As DAVE SCOTT explains in his SIGNED provenance letter, "The EVA Retractable Tether ('Yo-yo') is a small, pull-cord attachment clamp used for general purpose item retention during lunar surface operations. The unit is strapped to the astronaut's suit and readily available for use ... The tether cord of the Yo-yo assembly is kept under constant tension by the retractor mechanism and fastened securely to the tether clamp ... The tether clamp is a double jawed, spring closure mechanism with an incorporated eyelet for attachment to the tether cord....
"The purpose of the Yo-yo was to enable the astronaut to carry certain tools attached to his spacesuit and readily available without having to carry them by hand. These include the scoop and the 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)." The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11. Parts of the ALSEP were spring-loaded and would deploy automatically after removing several "Boyd Bolts" with the screwdriver-like UHT.
Scott continues, "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." 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. At 122:21:18 during the mission, Commander Scott exclaimed "My yo-yo doesn't cut it out here. Huh. My yo-yo's broken. There went my yo-yo."
An elaborate item of lunar surface equipment, with unusual history.