🚀 OTD 55 years ago, Apollo 15 launched to the moon, carrying the first EV to drive the lunar surface.
And here’s the Apollo 15 Flight Director / Attitude Indicator (FDAI or “8 Ball” 🎱) that was used to fly to the moon and back, the newest addition to the space collection.at work.
A photo in comments below shows this very unit on the Command Module instrument deck post flight, directly above the Apollo Guidance Computer’s DSKY interface and facing the Commander’s seat.
The FDAI was the primary visual reference for spacecraft orientation in three-dimensional space. Inside, it is a magnificent electromechanical clockwork, with motors inside the sphere that rotates on three orthogonal axes… while remaining attached to the instrument with electrical connections. (see comments below for interior shots)
This instrument showed the spacecraft’s attitude (or orientation) by rotating a ball. Pitch and yaw were read directly from the rotating sphere; roll was indicated by a circumferential pointer (white triangle at 4 o’clock). It also acted as a "flight director", using three yellow needles to indicate how the astronauts should maneuver the spacecraft by showing the deviation from target. Three more rate meters along the outer edges showed how fast the spacecraft was rotating about each axis.
Originally conceived as multiple separate instruments, astronauts, many of them test pilots, advocated for a unified display modeled after an aircraft’s artificial horizon, resulting in this elegant and highly intuitive navigational device.
Manufactured by Honeywell, the side label reads: "Indicator Attitude Flight Director, NAA/S & ID Control No. ME432-0168-0502, Mfr Serial No. 10028AAN1054, Mfr Part No. JG26469, Contract No. M7J7XAH-4700055, Mfr Date 31 Jan 1969." The instrument retains its two original umbilical cables and bears multiple inspection stamps, including "NAM 289," matching the stamp on the accompanying North American Rockwell "Temporary Parts Removal Tag." Four threaded studs on the back of the unit mounted a coldplate from the spacecraft Environmental Control System, circulating coolant to regulate the temperature of the unit while in use.
After its Apollo 15 service, this FDAI was formally repurposed from Apollo to support Skylab missions, then transferred to the Space Shuttle program in 1975 for simulation studies at Rockwell International. The internals were last tested in 1982, and it was retired from service in 1998. Apollo 15 Commander David Scott reviewed the transfer documents, curious as to how it was separated from his spacecraft.
• The first LM Pilot explains gimbal lock with the aid of one of my other FDAIs: here
• My LM version of the FDAI… built by a different company! blog here
• CuriousMarc and crew got one working again! See the 🎱 rolling: video (I have lent them my LM FDAI for comparison). And Master Ken did a wonderful blog post showing the inner workings.
• FDAI Interior photos by Space1
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And my prior FB post has writeups on six other Apollo 15 artifacts, including the communication headset and paper map used on the very first lunar rover drive across the surface of the moon.
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