Did Apollo 11 Command Module Pilot Michael Collins ask for a fourth gimbal for Christmas, while looking for the lunar ascent module? If so, is a recording of this available for posterity? Or a transcript?
Video cued at 02:24
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A transcript exists in the Apollo 11 Lunar Surface Journal, Postlanding Activities, with extensive annotations. The exchange begins at Mission Elapsed Time 104:59:27. Owen Garriott has just taken over as CapCom:
104:59:27 Garriott: Columbia, Houston. Over.
104:59:34 Collins: Columbia. Go.
104:59:35 Garriott: Columbia, Houston. We noticed you are maneuvering very close to gimbal lock. I suggest you move back away. Over.
104:59:43 Collins: Yeah. I am going around it, doing a CMC Auto maneuver to the Pad values of roll 270, pitch 101, yaw 45.
104:59:52 Garriott: Roger, Columbia. (Long Pause)
105:00:30 Collins: (Faint, joking) How about sending me a fourth gimbal for Christmas.
[Armstrong - "This is Mike at his best. We had a four-gimbal platform on Gemini."]
followed by several paragraphs explaining in depth what gimbal lock is and why it would risk losing the inertial platform (IMU) orientation and necessitate a lengthy reinitialisation.
This discussion also links to an ALSJ background page about Gimbal Angles, Gimbal Lock, and a Fourth Gimbal for Christmas where the above transcript excerpt reappears. A fourth gimbal for Apollo had been considered by MIT in 1963
The difficulties near gimbal lock can be avoided by the addition of a fourth gimbal to the IMU. (...)
at the expense of extra mechanical and computational and operational complexity.
