Forty-five years ago today, Neil Armstrong locked his heels under the Apollo 11 commander's seat. He and Buzz Aldrin and Mike Collins were flying to the moon.
The 36-story-tall Saturn V, the largest machine ever, clawed its way out of Earth's gravity well at 9:32 a.m. ET with 7.5 million pounds of thrust. It roared with all the primeval thunders of history, pounding and hammering into launch-pad steel and concrete.
Birds flew for safety. Wildlife ran for shelter. The mighty rocket’s shock waves slammed into millions of chests, shaking bones, fluttering skin and clothes. The unbelievable crowd could only lean into the pounding energy of the Saturn V. The ground trembled. Coins in pockets rattled. The unrelenting thunder shattered ear drums. Armstrong heard and felt it all, even through his helmet and earphones. He shouted through the ear-splitting roar, telling capsule communicator Bruce McCandless, "Roger, clock. We got a roll program."
Mission Control heard the report, saw the clock running and Apollo 11 rolling onto its proper heading, but none of them could feel the ponderous, slow-motion, rough and rocky ride that Neil was feeling. The ruckus and noise were overwhelming, but with only a passing minute-plus, the numbing sound was beginning to fade. Neil could now hear new noises: the slamming and banging and sloshing of millions of gallons of fuel. "Roll's complete and pitch is programming," he reported. "One Bravo."
NBC News' Jay Barbree, author of 'Neil Armstrong: A Life of Flight,' provides a day-by-day account of Apollo 11.
Neil, Mike, and Buzz were on their desired flight path. One Bravo was now their abort mode. They were high enough and moving fast enough to leave most of the noise behind, and Neil felt he could now hear Mission Control despite the herky-jerky thunderous ride.
All of the Saturn V's stages seemed to be vibrating simultaneously as they flew through feathery white ice-crystal clouds — growing in weight. Their G load was building, and they were slamming into the area of maximum aerodynamic pressure that would do its best to rip and tear the Saturn V/Apollo 11 stack apart.
But Max-Q's uncomfortable shaking lasted only a moment. Meanwhile, back at Cape Canaveral, the record-setting crowd could see a fiery river trailing the Apollo 11 train. They watched it pass the large flag standing before them, with a ghostly ring of contrail dancing around the joints of the Saturn V's stages.
The astronauts reached an altitude of 12 miles, moving 2,800 miles per hour, and suddenly the engine skirt was gone. A new sound was slamming through the crew cabin.
"Houston, be advised the visual is 'go' today,” Neil reported, seeing beyond their spacecraft for the first time as he and Mike and Buzz enjoyed the ride. Saturn V's upper stages had turned into gentle giants. They flew beyond the last particles of atmosphere, and their ride became quiet and serene, as smooth as glass.
Just a short distance away, Neil saw tongues of flame lash briefly. Solid rockets on the Saturn V's discarded first stage were igniting to push it away from Apollo 11. No one wanted a “highway in the sky” collision at this point.
Apollo 11 was now 190 miles downrange, 72 miles high, moving at 7,400 miles per hour. Neil told McCandless, "You sure sound clear down there, Bruce. Sounds like you're sitting in your living room."
Bruce came back. "You all are coming through beautifully, too."
The second stage continued to burn, and the Apollo 11 train climbed faster and faster and sped into Earth orbit.
This was the beginning of their planned holding path around Earth, and Neil knew its purpose was twofold. First, it gave the launch team a longer window for liftoff. Second, it gave Mission Control and the crew two and a half hours orbiting Earth to make sure the astronauts and the machine were ready to function far, far away.
Once all were satisfied Mission Control called. "Apollo 11, this is Houston, you are 'go' for TLI."
Neil Armstrong held up a gloved fist. "We thank you."
TLI — Trans Lunar Insertion — was the flight maneuver needed for Apollo 11's crew to reach the lunar surface.
"Apollo 11, this is Houston, stand by!"
"Roger," Neil acknowledged, and the astronauts braced themselves.
"Ignition," Neil told Mission Control. "We’re on our way."
- Part 1: How Neil Armstrong Got Ready for the Moon
- Read an Excerpt from 'Neil Armstrong: A Life of Flight'
- Neil Armstrong Book Gets Inside a Moonwalker's Mind
This is Part 2 of an eight-part series retracing the Apollo 11 mission to the moon, day by day. The account is based on material from Jay Barbree's newly published book, "Neil Armstrong: A Life of Flight." Check back with NBCNews.com on Thursday for the story of Apollo 11's outbound journey.
Barbree will discuss the Apollo legacy on "Virtually Speaking Science," an hourlong talk show that airs on Blog Talk Radio and in the Exploratorium's Second Life virtual auditorium. The show airs July 21 at 8 p.m. ET.