Incredible flight-ready secondary landing strut for an Apollo Lunar Module (LM), measuring 50″ in length and 5″ in diameter, with outer cylinder end wrapped in heat-resistant material painted with black Pyromark coating for protection against Descent Engine heating during landing. One end of the strut features a ball-joint fitting with loose attachment made to attach to an LM primary strut; the finely machined ball end is coated with a dry lubricant that lends it a gray finish. The opposing link end of the secondary strut was designed to attach to the deployment truss of the LM landing gear. The link end and inner cylinder section is stamped thrice with part numbers: “LDW320M10578-3,” “LDW320 23553-13-4, ‘ASSY,’” and “EO C2, LDW320 23554-5-2.” The ball-joint end of outer cylinder is similarly marked: “LDW320M10574-3.” Includes the original shipping box (stamped “Flight Item”) and containment bag with Grumman Aerospace Corporation label, which reads: “Part Name: Secondary St Ay…Contract No. NAS9-1100…Mfg. Part No. LDW320-23553-13-4, Mfg. Code No. 26512, Method of Pack: A/III, Clean Level: A, Item No. CBGHC, Qty. 1ea., Date Packed: 2/71.” In fine condition. Accompanied by a diagram of an LM secondary strut as featured in the article ‘Apollo Lunar Module Landing Gear’ by William F. Rogers.
An Apollo Lunar Module featured four separate landing-gear assemblies equipped with energy absorption capabilities provided by honeycomb cartridges in the single primary and the two secondary struts. The primary strut, which is attached to the LM descent-stage outrigger assembly, consists of a lower inner cylinder that fits into an upper outer cylinder to provide compression stroking at touchdown. The secondary struts also have an inner and an outer cylinder and are capable of both tension and compression stroking. According to the Rogers article: ‘Gear stroking in all landings has been minimal. The lunar soil has absorbed an estimated 60 percent of the touchdown energy through footpad penetration and sliding, resulting in secondary-strut tension stroking of about 10 centimeters (4 inches).’ Analysis has shown that the chances of fully stroking any strut was only one in a thousand. A significant piece of Lunar Module landing gear that represents a unique and iconic aspect of the historic Apollo program.
Terms and abbreviations used in our descriptions.