BOSTON, MASS.- RR Auction's Spring Space and Aviation sale closes on April 21. This significant auction features over 700 items, ranging from the dawn of aviation to the commercial spaceflight of today.

A large quantity of flown items featured in the sale includes; a Space Shuttle computer flown for twenty missions on four Orbiters. Built by IBM, the computer is comprised of two units: the Central Processing Unit (CPU) and the Input/Output Processor (IOP). Between 1981 and 1991, these units flew on a combined twenty Space Shuttle missions aboard the Columbia, Challenger, Discovery, and Atlantis, beginning with STS-2 and ending with STS-40. They also flew together on four missions: STS-6, STS-7, STS-8, and STS-35. The decade-long use of these units, from the second Shuttle mission to the forty-first, effectively spans the entire time that this GPC configuration was standard. A major computer upgrade in 1991 consolidated the two boxes into a single unit, and the two-piece GPC was rendered obsolete. An ultra-rare Space Shuttle General Purpose Computer, the brains of, at one time, the world's most advanced spacecraft. (Estimate: $50,000+)

In addition, Charles Conrad's LM checklist clip flaked with lunar dust. The aluminum checklist clip, used inside the Lunar Module' Intrepid,' has a 1-inch square white Velcro patch on the front retaining embedded lunar soil material. It was used to secure checklists and logged over 31 hours on the moon's surface during November 19-20, 1969. Includes a handwritten letter of provenance signed by Apollo 12 Commander Charles Conrad. (Estimate: $35,000+)

Also up is a schematic of the Space Suit EMU flown on Apollo 13. Fred Haise's detailed schematic of the carried around the moon as part of the Apollo 13 Lunar Module Systems Data Book. This schematic provides intricate details of the multiple components which comprise the Apollo Extravehicular Mobility Unit, or moonwalking ability space suit. The exaggerated size of the space suit allows easier viewing of the numerous subsystems which provide oxygen, electrical power, cooling, communications, and other functions that enabled an Apollo astronaut to function in a vacuum on the lunar surface.(Estimate: $10,000+)

Among American flags are those carried by Tom Stafford and Dave Scott. Stafford's Apollo 10 flown flag is the fastest flown flag in the history of space travel, along with several of Scott's Apollo 15 Lunar Landed Flags in various formats.

Important autographs include a fully signed Apollo 11 photo of the US flag raising in the Sea of Tranquility, autographs of the Mercury 7 astronauts, and a wealth of other signed photographs.

Online bidding for the Space Exploration auction by RR Auction will conclude April 21. For more information, go to www.rrauction.com.