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Apollo 11

Lunar Module Eagle

Close-up of the Lunar Module Eagle — descent and ascent stages — on the surface at Tranquility Base (AS11-40-5922, NASA).

Eagle (LM‑5) was the Apollo 11 Lunar Module — the two‑stage spacecraft that carried Armstrong and Aldrin from lunar orbit to the surface and back. Its call sign in the air-to-ground transcript is “Eagle”; after touchdown the crew adopted the surface call sign “Tranquility Base.”

The descent stage carried the descent propulsion system, landing gear, and stowed surface equipment (including the EASEP experiments and sample tools in the MESA); it served as the launch platform and was left on the Moon. The ascent stage carried the crew cabin and returned them to lunar orbit to rendezvous and dock with Columbia. During the powered descent the Lunar Surface Operations Plan called for an immediate post‑landing check of the LM’s launch capability before any surface activity. After crew transfer back to the CSM, the ascent stage was jettisoned.

The crew’s surface inspection of Eagle (debriefing §10.39) found it sound: a quad-1 jet-plume deflector looked slightly more wrinkled than quad-4, the secondary-strut insulation was thermally damaged and peeled in places (the primary struts were undamaged), and the landing-probe sensors were bent at their upper attach points. The ship’s two logged surface gremlins were benign (Mission Report §16, via the anomaly register): the mission timer stopped shortly after landing — the crew found it frozen at a meaningless 903:34:47 — from a probable cracked solder joint in its cordwood electronics, and recovered after 11 hours powered off to cool (§16.2.1); and simultaneous post-landing venting froze fuel in the descent fuel/helium heat exchanger, letting engine heat soakback drive a trapped line to an estimated 700–800 psia before the exchanger thawed half an hour later — future missions changed the venting order (§16.2.2). Lunar lift-off (debriefing Vol 2, §12) began with “an appreciable bang of the PYRO’s and a fair amount of debris… tossed out” at staging, then a smooth onset with no jolt; the ascent itself was a gentle, “wallowing,” low-frequency Dutch-roll trajectory the crew called “very pleasant” and far milder than their simulations. The abandoned descent stage still stands at Tranquility Base, sharp enough in LROC orbital imagery to cast a measurable shadow.

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