At 12:50 p.m. ET on July 24, 1969, the Columbia capsule splashed down 900 miles southwest of Hawaii, ending the historic Apollo 11 mission. This is how NASA got Neil Armstrong, Buzz Aldrin, and Michael Collins home.
On July 20, 1969, the U.S. won the space race. After a series of embarrassing defeats at the hands of the Soviets, the engineering marvel that was the Saturn V had captured victory through brute force, taking three Americans to lunar orbit, and successfully depositing two on the surface below. For many Americans, it was a day of celebration, but for the three men that had secured victory—Neil Armstrong, Buzz Aldrin, and Michael Collins—the challenges were far from over.
With history already made, all that was left was to make their way home. But the difficulties associated with launching a spacecraft off the lunar surface, docking with another craft in orbit, propelling the crew hundreds of thousands of miles, and surviving the blazing heat of reentry were daunting. A single failure of the launch apparatus would doom Armstrong and Aldrin to an icy grave in our night sky, and concerns that it might happen were so prevalent that President Richard Nixon had a speech prepared for the possibility.
As the countdown to the crew’s second launch of the Apollo 11 mission crept toward zero, there was no fanfare and no adoring crowds in spectator stands. There were just two men, a barely tested spacecraft held together in some places with nothing more than tape, and an astronaut carrying their ticket home some 70 miles above.
It took the accumulated efforts of thousands of people, engineering miracles, and the skill, grit, and determination of the three-man crew to get them to the moon, and it would take no less to get them back.
“In ancient days, men looked at stars and saw their heroes in the constellations,” Nixon would say if they failed. “In modern times, we do much the same, but our heroes are epic men of flesh and blood.”
Here's what it took to get three astronauts back home.
A Spacecraft Like No One Had Ever Seen
The Apollo 11 mission was a triumph for the Saturn V, which stands to this day as the most powerful rocket mankind has ever constructed, but Aldrin and Armstrong’s second launch was in a much stranger looking ship.
Today, the lander we called Eagle stands among America’s most iconic imagery, but at the time, it bore little resemblance to what most Americans thought a spaceship should look like.
To be specific, it was ugly. Its ragged edges, wrinkled metallic foil, and spider-like legs looked nothing like the streamlined spacecraft depicted in movies—and that was by design.
“We called it ‘the Bug,’” Gene Cernan, the mission commander on Apollo 17, once said. “And to me it looked like some gigantic monster that was going to hop down New York City just gobbling up society.”
While early plans for the lander may have included artist’s renderings of large windows and a rounded craft, engineers quickly dismissed those ideas. Windows were heavy, as were aesthetically pleasing contoured bodies that would hide the mechanical workings of the ship beneath. Even with the most powerful rocket in history, every ounce mattered, and as a result, some portions of the craft were famously only a few thin sheets of foil thick.
“You have to remember that the LM was carried in the Saturn’s protective shroud and only operated in the vacuum of space,” Thomas J. Kelly, Grumman’s chief engineer on the lunar module, explained. “That allowed us to design it from the inside out because we had no concerns for aerodynamics at all, which resulted in the distinctive look for the LM.”
Necessity dictated that the Lunar Module had to be both a landing platform and a launch platform, forcing an unusual design that layered the ascent stage above the descent stage on the spacecraft. The crew used the engines on the descent stage to manage their landing, then they’d leave that stage behind, firing the ascent stage’s lunar module ascent engine (LMAE) to propel them back up into orbit.
It may not have had much in common with the spaceships Americans had grown accustomed to seeing in the films of the 50s and 60s, but it was light, utilitarian, and functional.
At least, it was designed to be. The real test had yet to come.
Launching a Rocket on Another World
The ascent module may not have looked much like the massive Saturn V that delivered it, but the two had one thing in common: a failure during launch would mean certain death for its occupants.
Grumman had subcontracted the ascent module’s engine’s development to Bell, who believed in the concept of reliability through simplicity. Unlike the Saturn V, which earned its name through its use of five massive F-1 engines, the ascent module utilized a single fixed-thrust hypergolic rocket engine that traded the F-1’s kerosene and liquid oxygen fuel for a combination of Aerozine 50 and dinitrogen tetroxide.
When the two chemicals came into contact with one another, there was a spontaneous combustion reaction that would propel the ascent module off of the descent module and into lunar orbit. As a result, the ascent module’s propulsion system was the least complex of any rocket in the Apollo program.
At 1:54 p.m., the 180-pound ascent module engine fired, producing about 3,500 pounds of thrust for 435 seconds. Thanks to the moon’s reduced gravity, the 32,500 pound spacecraft was soon accelerating to a velocity of 2,000 meters per second. Quick as it was, the launch was a long and anxious journey—it would be four hours before the Eagle and its crew would meet up with the command module in orbit. For that stretch of time, Aldrin and Armstrong rode with no seating, limited control, and no guarantee that they would be able to successfully dock with the Command Module.
The Ascent Module’s Reaction Control System (RCS) fired as the Eagle elevated to about 13 miles below the Command Module’s orbit, rounding out its orbit around the moon. A number of short course corrections accomplished through the same RCS system slowly elevated the craft up to the Command Module’s altitude, and at 5:53 p.m., 128 hours and three minutes after lifting off from earth, Aldrin and Armstrong reunited with their orbiting companion Michael Collins in the Command and Service Module (CSM), or simply, Columbia.
The Lunar Lander known as Eagle had successfully carried mankind to the moon’s surface, kept them alive, and taken off once again into the darkness of space. Monumental as the achievement was, it would be impossible to bring the history-making craft home.
Four hours after Armstrong and Aldrin reached the CSM, they jettisoned their lunar lifeboat.
240,000 Miles of Icy Death
Now, with the Lunar Module gone and nothing left between the crew and their home but 240,000 miles of space, it was time to fire up Columbia’s engines.
At 12:56 a.m. on July 22, the Command Module’s Service Propulsion System (SPS) fired. A far more powerful engine than the one that had flown Aldrin and Armstrong up from the moon’s surface, the SPS consisted of a helium pressurization system, a propellant feed system, a propellant gauging and utilization system (that included sensors for display inside the cabin of the spacecraft and back at mission control), and of course, the rocket engine itself.
The system used helium as a pressurizing gas, inhibited nitrogen tetroxide for an oxidizer, and a blended hydrazine fuel made up of a mixture of around 50 percent unsymmetrical dimethyl hydrazine and 50 percent anhydrous hydrazine. The result was a more complex platform than the ascent propulsion system with quite a bit more power. The SPS could produce 21,900 pounds of thrust at intervals ranging from less than half of a second all the way up to twelve-and-a-half minutes.
A controlled two-and-a-half minute burn from the SPS, initiated from behind the moon, placed the astronauts on a trajectory for home. Mission Control held their breath, unsure if the engine had fired until Columbia emerged from behind the moon and they re-acquired the signal conveying the spacecraft’s telemetry data. It wasn’t long before they were able to confirm: Apollo 11 was coming home.
The trip would be a cramped one. Columbia was a gumdrop shaped spacecraft reminiscent of the earlier Gemini designs. At 10 feet 7 inches from the base to the apex and 12 feet 10 inches around at the base, the entire spacecraft allotted just 210 cubic feet of living space inside. With all of the instrumentation and equipment, it left less room for the astronauts than might be found in most luxury sedans, and it would have to be home for the three men for about three more days.
An Unwelcoming Earth
After traveling hundreds of thousands of miles, beating the odds, and making it back to Earth, the three-man crew of Apollo 11 were not out of the woods yet.
As they approached their reentry timetable, powerful thunderstorms were bearing down on Columbia’s intended splashdown location. With limited fuel, waiting out the storm wasn’t an option. The only choice was to use the bell shape of the spacecraft as a sort of wing, reentering the atmosphere at just such an angle as to stretch out their landing zone by a few hundred miles.
Columbia was designed specifically for such a possibility and a number of pre-selected landing zones had already been established for just such a scenario, but like most elements of the Apollo 11 mission, there remained a great deal of uncertainty as to how well the spacecraft would perform.
While the exterior of the ship was symmetrical, the interior was designed to position the majority of the weight near the crew’s feet—giving the craft a specific orientation for reentry. At supersonic speeds and the proper angle, that small lean created by the strategic weight placement resulted in some degree of lift, allowing the craft to fly, if ever so slightly, further than an uncontrolled descent would allow.
About 12 hours before the crew of Apollo 11 were to reenter earth’s atmosphere, they got the call: they were to fly with their lift vector in the up position for about 90 seconds as they reentered. According to NASA’s math, that should add about 215 miles to their anticipated flight path. It was a risky decision, but certainly a less risky one than coming down in a raging thunderstorm in the middle of the Pacific.
At 12:50 p.m. on July 24, Columbia splashed down in the Pacific Ocean just 1.94 miles from their intended landing point with the primary recovery carrier, the USS Hornet, just 15 miles out. Within an hour of hitting the water, Armstrong, Aldrin, and Collins were taken aboard the Hornet where they were placed in isolation over concerns about “moon germs.” Despite many scientists believing it to be an unnecessary precaution, the crew remained in quarantine for 21 more days after their return. The astronauts did as they were instructed, even if they didn’t see it as very logical.
"Look at it this way," Mike Collins mused years later. "Suppose there were germs on the moon. There are germs on the moon, we come back, the command module is full of lunar germs. The command module lands in the Pacific Ocean, and what do they do? Open the hatch. You got to open the hatch! All the damn germs come out!"
NASA would eventually drop the quarantine requirement for Apollos 15, 16, and 17, but for Aldrin, Armstrong, and Collins, those three weeks may have been some of the most surreal of the entire journey.
They had reached the unreachable, done what no had done before, and now, back on Earth, they were the only three human beings to have ever left this world and reached another one.
The Earth they had left behind was gone, and in its place was a new one—one that knew man could reach the stars. It was the start of a new era, and as they emerged from their 21 days of isolation, they found that the lives they led before were gone too.
They were no longer astronauts. They were heroes.
Alex Hollings is the editor of the Sandboxx blog and a former U.S. Marine that writes about defense policy and technology. He lives with his wife and daughter in Georgia.
