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Apollo 11 Plus 45: How Neil Armstrong Saved the Day on the Moon

Image: Eagle in lunar orbit

Apollo 11's Eagle lunar module begins its descent to the moon on July 20, 1969, in a photo taken from the Columbia command module just after separation.NASA

Thirteen hundred feet above the moon's surface, Neil Armstrong and Buzz Aldrin began their final descent in the Eagle lunar module. It was 4:15 p.m. Eastern time, 45 years ago today.

Transparent flames gushed downward as the Eagle slowed. Neil had flown his mission right along the edge of the razor. He and Buzz functioned as one. Now they were doing more than just falling moonward. They were so close Neil had to fly the lunar lander. He punched "Proceed" into his keyboard. The computer would handle the immediate descent tasks. Buzz would back up both man and electronic brain, so Neil could adapt to flying in a vacuum.

A momentary smile crossed Neil's face. It was time to see if all the training he went through to reach the moon was worth it. Neil was betting it was. He was hopeful it had given him the skills to get the job done.

NBC News' Jay Barbree, author of 'Neil Armstrong: A Life of Flight,' provides a day-by-day account of Apollo 11.

Neil looked through his triangular window and studied the desolate, crater-pocked surface before him. He had made many simulated runs, pored over dozens of photographs taken by Apollo 10 marking the way, landmark by landmark, down to the Sea of Tranquility. He knew their intended landing site as well as he knew familiar airfields back home, and he immediately saw they weren't where they were supposed to be. Damn!

Eagle had overshot by four miles. A slight navigational error and a faster-than-intended descent speed accounted for their lunar module missing its planned touchdown spot. Neil studied the rugged surface rising toward him, and Buzz noted a crater wider than a football field. Eagle was running out of fuel and heading straight for a gaping lunar pit filled with boulders larger than Purdue jitneys.

Scientifically, it would be great to land next to and explore a crater gouged into lunar soil, but Neil quickly ascertained that the slope around it was too steep. If Eagle landed on a tilt, they could never launch back into orbit.

With not a second to waste, Neil realized he was on his own. This was where experience and training came into play, and he looked beyond the crater. He gripped Eagle’s maneuvering handle and translator with a touch honed by years of flying the smallest and the largest, the slowest and the fastest. Neil knew the "thin edge" well — hell, he'd written the manual, and he had to fly as he'd never flown before.

A look back at the Apollo 11 mission

Knowledge, experience, touch — the skill of flying the Gemini 8 capsule to an emergency landing from orbit, bringing in the X-15 rocket plane from its Pasadena flyover, ejecting from his crippled jet fighter over Korea, ejecting from a lunar landing trainer seconds before crashing — all of it, everything came down to this moment.

Neil’s fingers alternately tightened and eased on the maneuvering handle and translator as they sailed downward at 20 feet per second. He nudged the power, slowing to nine feet per second. He attuned his senses to the rocking motions and the skids. Sixteen small attitude thruster rockets kept Eagle aligned throughout its descent. A level touchdown was their ticket to safety, survival, and the return home.

Mission Control listened. They were mesmerized. They were in awe of the voices closing in on the lunar surface. Neil flew. Buzz watched the landing radar, called out the numbers that represented split-second judgment and flying skills.

Buzz was no novice. Jet-speed combat in his F-86 with Chinese fighters over the ugly mountains of Korea had brought him to this point. He had no questions about the pilot next to him. He knew how Neil thought things through thoroughly and then did what he thought was right, and he usually arrived at the correct decision. Of all the pilots he had met and flown with, Buzz knew, without question, none came close to Neil Armstrong. He was simply the best pilot Buzz had ever seen.

"700 feet, 21 down, 33 degrees," Buzz chanted.

"600 feet, down 19.

"540 feet, down at — 30.

"At 400 feet, down at 9."

"Eagle, looking great," astronaut Charlie Duke, the landing’s CapCom, chimed in from Mission Control. "You’re go."

Despite the confidence in the astronauts' voices, there was still a problem: No place to land. Rocks, more boulders, surface debris strewn everywhere.

Neil fired the Eagle's left bank of maneuvering thrusters. The larger rockets scooted the lunar module across rubble billions of years old. Beyond the eons of lunar debris, a smooth, flat area.

"On one minute, a half down," Buzz told him.

"70," Neil answered.

"Watch your shadow out there.

"50, down at two and a half, 19 forward.

"Altitude velocity light. ...

"Eleven forward. Coming down nicely," Buzz told him.

Mission Control was dead silent. What the hell could they tell Neil Armstrong?

"200 feet, four and a half down.

"Five and a half down.

"120 feet, three and a half down, nine forward, 5 percent.

"OK, 75 feet. There’s looking good," Buzz told him as he stared at the obvious place Neil had chosen to land.

"60 seconds," Charlie Duke reminded them.

Eagle had 60 seconds of fuel left in its tanks, and no wanted to think about it. If the descent engine gulped its last fuel before the Eagle touched down, they would crash, falling to the surface without power.

What those in Mission Control did not know was that Neil wasn't all that concerned about fuel. He felt that once he was under 50 feet it didn't really matter. If the engine did quit, from that height at one-sixth the gravity, they would settle safely onto lunar dust.

Image: Descent

A series of video images shows the view out the window as the Eagle lunar module descended toward the moon's surface on July 20, 1969.NASA

Neil calmly aimed for his new landing spot. He kept one thought uppermost in his mind: Fly. Eagle swayed gently from side to side as the thrusters responded.

"Light's on," Buzz told Neil as he watched an amber light blink the low-fuel signal, and then he intoned the numbers like a priest, steady and clear, "30 feet, faint shadow."

"Forward drift?" Neil asked his co-pilot, wanting to be sure he was moving toward known surface.

"Yes. OK," Buzz said.

"Contact light."

Eagle's probe had touched lunar soil.

"OK, engine stop.

"ACA out of detent."

"Out of detent," Neil confirmed. The engine throttle was out of notch and firmly in idle position.

"We copy you down, Eagle," Charlie Duke told them, and then he waited.

Three seconds for the voices to rush back and forth, Earth to the moon, and moon back to Earth.

Neil, being Neil, had to be certain. He studied the lights on the landing panel to be sure of what they’d just accomplished.

Four lights gleamed brightly. Four marvelous lights, welcoming them to another world where no human had ever been. Four lights banished all doubt. Four round landing pads at the end of Eagle’s legs rested, level, in lunar dust.

Neil’s voice was calm, confident, most of all clear: "Houston, Tranquility Base here. The Eagle has landed."

It was 4:17:42 p.m. Eastern time, 45 years ago today.

Image: Shadow of LM

The shadow of Apollo 11's Eagle lunar module looms on the surface of the moon in a picture taken out the window after the landing on July 20, 1969.NASA

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IN-DEPTH

This is Part 6 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 New York Times best seller, "Neil Armstrong: A Life of Flight." Check back with NBCNews.com later Sunday for the story of the first moonwalk.

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 Monday at 8 p.m. ET.