Powered Descent Initiation (PDI) is a term used during the Apollo program Moon landing missions to describe the maneuver of the Apollo Lunar Module as it descended from lunar orbit to a rocket-powered landing. [1]

"Eagle was GO to ignite its descent engine, and Armstrong and Aldrin locked their eyes to the glowing numbers displayed before them. They were almost at an invisible junction of height, speed, range, and time when everything would join together for commitment. When the instruments told them that they were 192 miles from their projected landing site, and were precisely 50,174 radar~measured feet above the long shadows of the moon, they would unleash decelerating thrust and begin slowing their speed for the touchdown.....this was it. PDI. Powered Descent Initiate."[2]

References

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  1. ^ A Running Start - Apollo 17 up to Powered Descent Initiation
  2. ^ Moon Shot The Inside Story of America's Race to the Moon, Alan Shepard/Deke Slayton Page 17 First Edition

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Apollo Lunar Module

except powered descent initiation through takeoff. The LM descended to 47,400 feet (9.0 mi; 14.4 km) above the lunar surface, then jettisoned the descent stage

Tranquility Base

gravitational field, resulted in navigation errors which pushed the powered descent initiation point about 3 miles (4.8 km), and thus the computer-targeted landing

Apollo 17

Eric M.; Glover, Ken (eds.). "A Running Start – Apollo 17 up to Powered Descent Initiation". Apollo 17 Lunar Surface Journal. NASA. Archived from the original

PDI

indicator, for aircraft bombing Power Distance Index, a measure of social power acceptance Powered Descent Initiation, of Apollo moon landing This disambiguation

Harrison Schmitt

Archive. Retrieved June 7, 2024. "A Running Start – Apollo 17 up to Powered Descent Initiation". Apollo Lunar Surface Journal. Archived from the original on

Apollo 15

scientific work. Aboard Falcon, Scott and Irwin prepared for powered descent initiation (PDI), the burn that was to place them on the lunar surface, and

Gene Cernan

Retrieved April 19, 2015. "A Running Start - Apollo 17 up to Powered Descent Initiation". Apollo 17 Lunar Surface Journal. NASA. June 10, 2014. Archived

Orbital maneuver

Insertion, injection and sometimes initiation are used to describe entry into a descent orbit, e.g. the Powered Descent Initiation maneuver used for Apollo lunar