Apollo 11 — when tech needed innovation and a bit of piloting

By today’s standards, the landing by humans on the Moon was technologically primitive.

Keep in mind, the Apollo 11 mission happened before the Internet; in fact, the first two nodes of the ARPAnet, from which the Internet sprung, wouldn’t be connected until several months later. Apollo is credited with pushing micro-miniaturization of electronics. Without it, the Apollo Guidance Computer would not have been possible, or at least weighed many times more than it did. This machine, which aided the landing of the Eagle lunar module on the Moon, had 2048 words of memory, each word being 16 bits long. It had a clock speed at 2.048 MHz, about 1/500th to 1/1000th of current smartphones, which may have multiple processors at 1 to 2 GHz.

In the end, the computer was overloaded, and pilot Neil Armstrong took over to make a landing under manual control with read-out assistance from astrodynamicist Edwin “Buzz” Aldrin. (The computer did not die; it was over-saturated with computation tasks, but continued to function.)

The landers that preceded Apollo to the Moon did not have digital computers.  The Surveyor series of landers had servos, which fed back to various spacecraft systems, resulting in soft landings.

Apollo Guidance Computer and display/keypad

Apollo Guidance Computer and display/keypad

Engineering design was dominated by drafting boards; computer graphics was in its primitive developmental stages, and along with it, interactive CAD of mechanical parts was barely beginning. The NASA STRuctual ANalysis program (NASTRAN) was under development during this time, finally being released to NASA in 1968, after the Saturn V was designed.

On the other hand, some things haven’t changed much. There is no miniaturization of a human crew. They need a certain amount of consumables, which must be stored for the trip. Rocket engines still use chemical propulsion. LOX/RP-1 (liquid oxygen and refined kerosene), the propellant combination used by the Saturn V first stage, is still a mainstay of launch vehicle design. The efficiency of translating chemicals into F=MA (or really F=v*dm/dt) has not appreciably changed.

And yet, with all the technology constraints and unchanging laws of physics, American primitive technology and ingenuity got humans to the surface of the Moon, and brought them safely back to Earth.  … And yet, 45 years later …..

That first landing did not go completely according to plan. Armstrong had to take over, with Aldrin’s assistance. Armstrong was under pressure to pick a safe spot quickly (which the automatic systems had not done), and put the craft down. By the time it landed, the Eagle had about 15-20 seconds of fuel left. Mission Control in Houston very likely had a sinking feeling that this could end badly; hence the comment about “a bunch of guys about to turn blue. We’re breathing again. Thanks a lot.”

A re-enactment of the landing, based on radio transmissions, transcripts, and video, shows just how close they were to ending in disaster. (Kudos to Thamtech, LLC, for assembling the site together a couple of years ago.)

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.