Apollo 12: The electrifying return to the Moon

On November 14, 1969, the second manned mission to land on the Moon lifted off from Cape Kennedy, Florida. Four months after the historic Apollo 11 landing, it was the first true manned exploration mission to the lunar surface and one that opened the way to even more ambitious landings over the next three years.

Why return to the Moon?

This is a question that many people were asking even back in 1969. Though the historic importance of the first lunar landings is well understood today, and in the wake of Apollo 11 many top NASA brass were already lobbying for Moon colonies to be established and even the staging of the first manned missions to Mars, but there were also objections to continuing the Apollo program.

Some argued that Apollo 11 had been a great victory in the Cold War and there was no need to build on it with more landings. Others saw it as a great adventure story that had already been told, so what was the point of just playing out the same plot over and over. Meanwhile, some resented the costs of Apollo, which was the equivalent of that of a small war – especially when the US was already engaged in a very unpopular hot war in Indochina.

But there were other arguments for the landings. Essentially, Apollo had already been completed by 1964. Most of the money had already been spent, most of the work had been done, there was a fleet of Saturn V rockets ready to go, and improved versions of the Command Service Module (CSM) and the Lunar Module (LM) were already on order and being built.

In addition, the Moon is much bigger than many people realize. It has a surface area larger than that of Africa and, while lifeless, it can tell us much about the origins of our Earth and the solar system. It was also argued that there could be mineral deposits and unique resources that could spur on whole new industries if properly exploited.

But the most immediate argument was that Apollo 11 had accomplished little more than demonstrating that it was possible to land safely on the Moon and return. For all their heroism, Neil Armstrong and Buzz Aldrin spent less time on the Moon than some people do waiting in an airport for a connecting flight. That, plus their limited equipment and the emphasis on caution meant they could do little more than raise the flag, take a few pictures, collect a few samples, and set up a simple instrument package.

Beginning the exploration

Apollo 12 would be different. Because Apollo 11 had been successful, 12's original mission as a backup landing was canceled and now it could pursue much more ambitious goals. Namely, to become the first real manned exploration mission to the Moon. For this, the astronauts would test a much more accurate landing technique, go farther from base, collect more geological samples, make a stereo and multi-spectral surface photographic survey, and set up a more sophisticated nuclear-powered Apollo Lunar Surface Experiments Package (ALSEP).

They would even carry out the first space salvage mission, involving the astronauts visiting the unmanned Surveyor 3 lander from which they would retrieve parts for analysis. Meanwhile, the Command Module Pilot would be photographing candidate landing sites from lunar orbit.

More importantly, the objectives of the Apollo 12 landing would open the way to exploring rugged and even mountainous regions of the Moon in the higher latitudes far from the equator and at different times of the lunar day. In other words, if Apollo 11 was the pathfinder, Apollo 12 was about getting down to work.

The cast and crew

Apollo 12 consisted of two spacecraft resting atop the skyscraper-sized Saturn V launcher at the Kennedy Space Center Launch Complex 39, Pad A, in Florida. Visible as the nose of the giant rocket was the CSM, radio call sign Yankee Clipper. Stowed inside the S-IVB third stage was the LM, call sign Intrepid.

The all-US Navy crew was led by the Mission Commander, Commander Charles "Pete" Conrad Jr., who was making his third trip into space after flying on Gemini 5 in 1965 and Gemini 11 in 1966. His Command Module Pilot was Commander Richard Francis "Dick" Gordon Jr., who also flew on Gemini 11, and his Lunar Module Pilot, Commander Alan LaVern Bean. Bean was a replacement for the original pilot, Clifton C. Williams Jr., who was killed in a T-38 jet crash near Tallahassee, Florida, in October 1967.

This was a more lighthearted crew than Apollo 11, who seemed very aware of their place in history and US foreign policy. In contrast, the men of Apollo 12 looked on their mission almost like a road trip and were given to joking and mild pranking – an attitude encouraged by the antics of their all-US Air Force back up crew, who even went so far as to make a spoof documentary of the mission that gently ribbed their Navy colleagues.

Lightning strikes twice

November 14, 1969, wasn't the best day for a space launch. A cold front was descending with a north wind, bringing in overcast skies and rain as the barometer plummeted. As the Apollo 12 slowly rose from the pad at 16:22 GMT, it was the first Saturn V launch to take place during a rainstorm.

This would have been just another bit of space trivia if it weren't for the fact that at 36.5 seconds into the flight the rocket was struck by lightning and the massive electric arc shot down from the rocket through its ionized exhaust plume.

While the Saturn V itself was unaffected, the CSM was in real trouble and the mission faced an abort decision. The safety circuits in the Service Module shutdown the three fuel cells that powered the spacecraft. Leaving the CSM on batteries only. Voltage dropped, instruments were knocked out, telemetry to Mission Control was interrupted and every warning light on the control panel lit up.

Then, at 52 seconds, a second lightning strike hit, knocking out the "8-ball" attitude indicator on the main control panel.

This would have been the end of the mission if it hadn't been for Electrical, Environmental and Consumables Manager John Aaron, who recalled a similar telemetry failure during a ground test. He told the flight director, "Flight, EECOM. Try SCE to Aux."

The Flight Director Gerald Griffin, CAPCOM Gerald Carr, and Mission Commander Conrad didn't understand immediately what Aaron meant, but Lunar Module Pilot Bean did. Essentially, it was like the modern all-purpose tech fix of turning it off and on again, and it worked as the fuel cells came back online.

As Apollo 12 reached orbit attached to the S-IVB third stage, Mission Control and the crew were faced with the fastest checkout ever as they made a detailed examination of the S-IVB, the CSM, and the LM to make sure it was safe to continue the mission. In the end, the GO command was given and the S-IVB restarted, sending Conrad, Gordon, and Bean on their way to the Moon. A little over three days later, on November 18 at 3:47 GMT, they went into lunar orbit.

Moon landing 2.0

The next day, November 19, the Intrepid lander undocked from Yankee Clipper and started its descent to the lunar surface. The landing site was in Oceanus Procellarum (Ocean of Storms) at latitude 3.01239°S and longitude 23.42157°W. The site was chosen to build on the success of Apollo 11 by landing at a very specific site.

To do this, Apollo 12 tested a new method for making precision landings. When Apollo 11 set down, it could only land somewhere within a wide elliptical area. Apollo 12 would try to land within a few hundred yards of a given location.

The problem that NASA encountered in lunar landings is that the Moon has a very uneven gravitational field due to uneven, sub-surface masses called mascons, which tug at the descending spacecraft. What the mission planners did was turn the mascons into an asset rather than a liability by taking a page from the sailor's handbook.

If a sailboat is crossing a stretch of open water from, for example, Calais to Dover, it can't just aim at Dover and set off. Try that, and the vessel will make landfall miles off course. This is because the water in between has many shifting currents. So, to get to Dover, the skipper has to get out the charts and tide tables, calculate how the currents will push the boat off course, and then aim, not at Dover, but at some point off to one side. Now, instead of pushing the boat off course, the currents actually guide it to the desired destination.

In the case of Apollo 12, NASA planners used what they'd learned about mascons from previous missions, calculated how they would push the LM off course, then aimed at a point that would let the craft land with great precision, which Conrad and Bean did on November 19, 1969, at 06:54 GMT.

Extravehicular activity take 1

Three hours after landing, Conrad and Bean prepared to leave the LM and at 11:32 GMT stepped out of the lander. As Conrad descended the ladder, he opened the modularized equipment stowage assembly and activated the television camera stowed inside to transmit images of him setting foot on the Moon at 11:44 GMT. Because Conrad was shorter than Neil Armstrong, his first words on the Moon were, "Whoopie! Man, that may have been a small one for Neil, but that's a long one for me."

After Bean followed to the surface at 12:13 GMT, the two astronauts got to work. The S-band erectable antenna for high-bandwidth contact with Earth and solar wind composition experiment were deployed, and the US flag was raised.

Then the mission had its first real setback. Where Apollo 11 had a monochrome camera. Apollo 12 brought along a more advanced, high-resolution color television camera. However, it had a very short career. When Bean repositioned the camera from the LM to the surface, he accidentally pointed it at the Sun and burned out the Secondary Electron Conduction (SEC) tube, putting paid to the camera and ending video transmission from the surface.

Annoying as this was, there was still much to do during the first EVA. There was the Apollo Lunar Surface Experiments Package (ALSEP) to deploy and its nuclear fuel to be loaded into the package's radio-thermal generator. The ALSEP was set up about 700 ft (213 m) from the LM then turned on. Sixty-nine minutes after the powering up, Mission Control started receiving data.

The ALSEP consisted of several experiments, including the Passive Seismometer Experiment, which was so sensitive that it recorded the footsteps and other activities by the astronauts on the surface or inside the LM; the Magnetometer Experiment for measuring the Moon's magnetic field; a Solar Wind Spectrometer; a Suprathermal ion detector experiment; and the Cold Cathode Gage to study the Moon's near-non-existent atmosphere.

In addition, the astronauts collected 36.82 lb (17.61 kg) of geological samples before ending the EVA after three hours and 59 minutes.

Extravehicular Activity take 2

On November 20, after a seven-hour rest period, Conrad and Bean resealed their spacesuits and stepped back onto the surface of the Moon. Aside from collecting another 38.8 lb of samples, retrieving the solar wind composition foil for analysis back on Earth, and conducting an extensive photographic survey, including the use of stereoscopic cameras, Conrad and Bean conducted a real first.

To learn more about how the lunar environment affects materials, and as a way to show the American taxpayers what their money was buying, Apollo 12 was tasked with being the first and only time to date that astronauts have visited a lander on another world.

As they collected rock and soil samples, they walked to the site where Surveyor 3 had been sitting inert since its batteries had failed two years before. They photographed the lander, removed a cable, a painted tube, and unpainted tube, the robotic arm's scoop, and the television camera. These were all carefully bagged for return to Earth.

Their mission almost completed, Conrad and Bean tried to brush the lunar dust, which was much worse than at the Apollo 11 site, off their spacesuits before finally reentering the LM for the last time at 07:44 GMT after three hours and 49 minutes. In all, they had been outside the craft for seven hours and 45 minutes, collected 75.73 lb of samples and gone as far as 1,350 ft (411 m) from the LM when they visited Surveyor 3.

Goodbye Lunar Module

After 31 hours and 31 minutes on the Moon, Intrepid's Ascent Stage fired its engine on November 20 at 14:25 GMT. It rendezvoused with Yankee Clipper at 17:58 GMT. About two and a half hours later, after Conrad and Bean had returned to the CSM and stowed their samples, the Ascent Stage was jettisoned. But that was not the end of its job.

After jettisoning, the Ascent Stage was maneuvered under remote control to make a planned impact on the Moon. After firing its engine for 82 seconds, it hit the surface about 45 miles east-southeast of the Apollo 12 landing site. The impact was picked up by the ALSEP seismograph as the Moon rang like a bell for an hour. This not only returned valuable information about the Moon's interior but also allowed scientists to calibrate the instrument package left behind.

Return to Earth

After returning to Yankee Clipper, the crew remained in lunar orbit for an extra day, taking more pictures to scout out future landing sites. Then, on November 21 at 20:49 GMT, after 88 hours and 58 minutes during which it had completed 45 orbits, the CSM fired its engine to send Apollo 12 back to Earth.

On November 24, Yankee Clipper reentered the Earth's atmosphere. Unbeknownst to the crew, Mission Control was sweating because it was suspected that the lightning strikes after launch may have damaged the explosive bolts that were to deploy the parachutes. Since there was nothing that could be done, it was decided not to worry the astronauts.

It was a difficult reentry as the spacecraft experienced massive g forces, but the parachutes worked properly. The Command Module landed in rough seas in the South Pacific Ocean about 575 miles east of American Samoa. The impact was hard enough to jar loose the heat shield and an unstowed 16 mm camera jumped from its mount to deliver Bean a glancing blow in the forehead, giving him a mild concussion and a cut that required six stitches.

The crew was picked by US navy divers an hour after splashdown and flown by helicopter to the carrier USS Hornet. Leaving the aircraft in gas masks in case they were carrying any lunar microbes, they were immediately placed in the mobile quarantine facility to await being flown to the lunar Receiving Laboratory in Houston, Texas.

After 10 days, four hours, 36 minutes, and 24 seconds, Apollo 12 was home.

Read more on the historic Apollo Moon Missions.