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Apollo-16: Second to last

Anatoly Zak, Spaceflight Correspondent
Apr 30, 2016, 20:42 UTC

Sen—Apollo-16 became the second lunar expedition of the J-series Apollo-Saturn system, which relied on upgraded technology and beefed-up resources. Like Apollo-15 before it, the latest trip to the Moon included three spacewalks and the use of an electric lunar rover. As before, the expedition was heading to the geologically significant highland region of the Moon—this time to the vicinity of the Descartes crater. The Apollo-16 crew included a veteran of the Gemini and Apollo programs, John Young, lunar module pilot Charles Duke and command module pilot Thomas Mattingly.

A Saturn-5 rocket carrying Apollo-16 lifted off from launch pad 39A at Cape Canaveral, Florida, on April 16, 1972, at 17:54 UTC. After a four-day trouble-free journey they arrived at lunar orbit and got ready for a descent to the surface on April 20.

As had been experienced a few times before, technical glitches began plaguing the Orion lunar module: The crew struggled with a stuck communications antenna and with a pressure controller on one of the clusters of the attitude control engines.

However more serious problems developed onboard the Casper command and service module, which was supposed to remain in lunar orbit. The first attempt by Tom Mattingly to maneuver the ship after the separation with the lunar module had to be aborted when the pilot discovered that the guiding mechanism of the main engine was causing severe vibrations onboard.

Fortunately, mission control quickly isolated the problem and the lunar expedition was allowed to proceed after few hours in limbo for the crew.

Once again, the pilots had to switch to manual control during the final descent. And yet again, the landing on April 21, at 02:23 UTC, was hair-raising but successful.

The first spacewalk on the lunar surface also went smoothly. Taking lessons from the Apollo-15 mission, engineers equipped the astronauts with upgraded drilling gear, which proved to be much more efficient than on the previous mission.

The biggest problem was an accidentally cut 48-line cable critical for a suit of freshly deployed scientific instruments.

During their rover trip the astronauts picked a football-size rock, which turned out to be the largest piece of the Moon delivered by the Apollo expeditions.

At the end of the first 7-hour 11-minute sortie, the astronauts attempted a lunar version of a "grand-prix" performance, when Young was racing the rover around a moderately flat area of the lunar surface, while Duke was filming the action.

During the second spacewalk, the astronauts drove south toward the large mountain looming more than half a kilometer tall. They drove rock-strewn slopes and eventually had to park their car and climb on foot.

During their geological field trips, the astronauts tried in vain to find signs of volcanic activity, which scientists confidently predicted in the area, instead finding rocks of the intermixed igneous and impact origin. The confused geological history of the region would later become the main scientific surprise of the mission.

On the way back to the lunar module, they had to drive under a shower of lunar dust, because of a damaged fender on one of the wheels of the rover.

While the second moonwalk lasted a record-breaking 7 hours 23 minutes, the third excursion to the surface had to be cut from seven to five hours to make up time lost during the engine trouble on Casper before the descent.

In an effort to do as much as possible, Young broke another record for driving on the Moon, reaching 17 kilometers per hour. The third and final sortie ultimately lasted 5 hours 40 minutes. In total, Young and Duke logged 20 hours 14 minutes in lunar spacewalks, covered 27 kilometers and picked 95.4 kilograms of samples.

Their stay on the Moon lasted 71 hours 02 minutes.

The ascent stage of the lunar module blasted off from the lunar surface on April 24, 1972, at 01:25 UTC.

After Young and Duke reunited with Mattingly, the Casper command and service module left lunar orbit almost a day earlier than planned. On their way home on April 25, Mattingly made a 1-hour 24-minute spacewalk from the command module to the service module, retrieving film from cameras which had photographed the lunar surface while Casper was orbiting the Moon.

On April 27, 1972, at 19:45 UTC, the command module made a successful water landing in the Pacific Ocean.

Apollo-16 was the fifth successful human expedition to the Moon, but also the penultimate mission.