T + 45 years — the view from the pad

Sunday, July 20, marks the 45th anniversary of the Eagle landing at Tranquility Base on the Moon.

That journey started on July 16, 1969, with the launch of Apollo 11 from Launch Complex 39 (specfically Pad 39A) at Kennedy Space Center, Merritt Island, FL. The Saturn V rocket, with three stages and the Apollo spacecraft on top, stood 111 meters (363 feet) tall. The first stage tank had a diameter of 10.1 meters (33 feet).

It weighed 2950 metric tons (6.5 million lbm), and was lifted off the pad by 34 MN (meganewtons, 7.6 million lbf). The result is that it lifted off the pad relatively slowly. With a thrust-to-weight (T/W) ratio of 1.17, its acceleration off the pad was 1.66 m/s2 (5.45 ft/s2). (Recall that Earth’s surface gravity is 9.807 m/s2 (32.17 ft/s2).

As a result, compared to many other rockets, including the Space Shuttle, it feels a bit like slow motion. To that, add cameras that capture the launch at 500 frames per second (fps), and then play that back at a normal frame rate. The result is slowing down the motion by a factor of 16 to 20 (for 30 to 24 fps respectively). At this rate, you get to appreciate in detail the tremendous forces at play here.

Mark Gray, executive producer for Spacecraft Films, provided commentary for this clip of the launch at 500 fps. Posted five years ago, it gives amazing insight into the engineering that went into the pad, and the kind of forces at play when a Saturn V was ignited and lifted off.

In later decades, Pad 39A would see the launch of many Space Shuttle missions. In April 2014, the pad was leased to SpaceX, which is modifying it to support Falcon 9 v1.1 and Falcon Heavy launches.

And if you’re trying to find it, here it is.

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