Chapter 3 of 10

Sixty Seconds of Fuel and a Field of Boulders

Manual fly-over of West Crater and touchdown at Tranquility Base (GET 102:45:40)

Told in Eagle’s imagined voice · the events are real · source

AS11-44-6642 (21 July 1969) --- The Apollo 11 Lunar Module ascent stage, with astronauts Neil A.
EagleFour hundred feet up, my autopilot was steering us straight into a crater the size of a football stadium, rimmed with car-sized boulders.
NASA/JSC
01It was West Crater. Landing on those jagged rocks would snap my legs or pierce my fuel tanks. With fuel burning away fast, Neil flipped my control switch to semi-manual mode.
Neil skimmed me horizontally like a helicopter while Buzz stared at my instruments, calling out our speed and height.
02"Forty feet, down two and a half... picking up some dust!" My rocket plume blasted millions of years of loose gray soil across the ground as Houston called the sixty-second fuel warning, then thirty seconds.
One month after its first image of the Apollo 11 landing site was acquired, NASA Lunar Reconnaissance Orbiter passed over the site again providing a new view of the historic site.
EagleFive feet below my saucer-shaped footpads, three thin metal feelers reached out for the Moon.
NASA/GSFC/Arizona State University
03 The instant one of my 67-inch wire probes brushed the soil, it closed a switch that lit a glowing blue 'LUNAR CONTACT' lamp on the dashboard. "Contact light!" Buzz called out.
My engine cut off, I dropped the last three feet into the dust with twenty-five seconds of fuel left, and my four legs locked into history.
04Inside my legs, aluminum honeycomb cartridges crushed slightly to absorb the impact. "Houston, Tranquility Base here. The Eagle has landed." My lower body had found its permanent home.

The big idea

Hanging 67-inch wire probes beneath the footpads warned the crew the exact millisecond they touched the ground, letting them shut the engine off safely before kicking up dangerous pressure underneath.

Think about it

Why did Eagle use long wire probes hanging below its footpads instead of waiting for the heavy legs themselves to hit the ground?

In this chapter: Throttleable Descent Propulsion System, 67-inch lunar contact probes, and honeycomb crush struts

Sources: Main record

Machine illustration: AI-made. Photos: NASA Image and Video Library, credited on each picture.

Chapter 3 of 10

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