Crew and spacecraft
The lunar programme had been running for no more than four years when Apollo 16 became the tenth manned Apollo mission. From the time when John F. Kennedy proclaimed the goal of landing on the Moon in 1961, a wide range of ideas and plans about the future objectives of US spaceflight activities had been discussed. Originally, nine more missions had been planned to follow the one on which Neil Armstrong took his famous 'small step'. Bowing to political pressure, however, NASA decided to end the series of lunar missions after Apollo 17.
Still, the experiences of the first flights to the Moon were of inestimable value, and the progress made in astronautics and the exploration of the Solar System was enormous. However, hopes that there might soon be a permanently inhabited station on the Moon had to be abandoned. After the great success of the Apollo 15 mission, two more ‘J-missions’ involving a three-day stay on the Moon were to be flown as a crowning glory for science. For the first time, a mission was destined for the lunar highlands, a part of the near side of the Moon that is heavily cratered and thus very old. Apollo 11 and 12, as well as Apollo 15, touched down in relatively young volcanic plains. The area investigated by Apollo 14 was heavily marked by the results of the impact that formed the Imbrium basin. The Moon’s original crust! That was the target.
The landing site in the Descartes highlands was located in the so-called Cayley Plains, an area which was believed to have been the scene of a different kind of volcanism. Commander of Apollo 16 was the most experienced astronaut NASA ever had: John Young. The modest Navy officer had previously been on Gemini III and Gemini X as well as on Apollo 10, the final test run before the first lunar landing. Later, he would command the first space shuttle on its flight into orbit and bring it back to Earth safely.
His crewmates included the Command Module Pilot, Ken Mattingly, who had lost his place in the crew of Apollo 13 shortly before the launch because of a suspected rubella infection, and Charlie Duke as Lunar Module Pilot. For these two, it was their first flight into space. During the Apollo 11 mission, Duke had made a name for himself as a coolheaded ‘CapCom’, or capsule communicator: only an astronaut was permitted to communicate with Apollo astronauts by radio from Earth because of his familiarity with the special jargon. The command module was given the name ‘Casper’, the lunar module was called ‘Orion’. Like Young, Mattingly was to command a space shuttle later on.
Apollo 16 was the first and only case in the history of the Apollo programme where a launch was deferred by several weeks. This was due to several technical misgivings that do not appear very serious in retrospect. The mechanism for separating the command module from the lunar module appeared incapable of building up enough pressure for implementing the maneuver reliably. Moreover, irregularities were found in John Young‘s space suit, and finally, a few leaks had to be sealed in the Saturn V rocket.
On April 16, 1972, Apollo 16 at last lifted off smoothly at 12:54 local time. Twelve minutes later, right on schedule, the spacecraft reached its orbit around Earth. There the crew had to deal with some minor problems with the air conditioning and the attitude control system for the third stage before the spacecraft could set out on its route to the Moon, escaping the Earth’s gravity field with an initial velocity of about 40,000 kilometres per hour. As in the previous missions, the lunar module was drawn from the third rocket stage and docked on to the tip of the command module. Next, the assembly consisting of the lunar module and the command module with its service module was given spin around the longitudinal axes, another routine maneouvre, called ‘barbecue mode’. It ensures that one side of the spacecraft is not overheated by the Sun shining permanently on it but is allowed to cool off by turning to the other side that faces away from the Sun.
74 hours after launch, they reached lunar orbit. A little later, Young and Duke entered the lunar module to prepare the landing maneuver. 96 hours after lift-off they drew away from the command module ‘Casper’ in the lunar module ‘Orion’. However, a problem arose when the backup system for tilting the service module‘s main engine was tested. As in the Apollo 13 accident, it was not clear whether the engines of the lunar module could be used for returning to Earth in case the mission had to be aborted unexpectedly.
In Houston, the problem was analyzed for several hours before the go-ahead could be given for landing on the Moon. In actual fact, the mission came quite close to an abort. After a delay of six hours, the module moved safely and smoothly to the landing site which Young was able to identify clearly from as far up as four thousand meters. Manually controlled by John Young, the gentle touchdown took place on April 21, 1972, at 3:23:35 CET, only 270 meters to the north and 60 meters to the west of the site originally envisaged.
On the Moon
Because of the delays that occurred during the uncoupling maneuver, Young and Duke already had a long working day behind them. For this reason, NASA changed the programme for the first hours on the lunar surface and ordered them to take a break for sleeping. After breakfast, the astronauts began to don their space suits, which in the restricted space available was a highly laborious exercise that required mutual assistance. Moreover, some irritation was caused by leaks in the new drink bags, which Charlie Duke commented to Houston in the following words: “I wouldn‘t give you two cents for that orange juice as a hair tonic; it mats it down completely.”
A little later, both astronauts were standing on the lunar surface; aged 36 at the time, Charlie Duke was the youngest of the twelve astronauts who had been on the lunar surface. After unpacking the lunar rover, the two astronauts installed the instruments for the physical experiments which were concerned with measuring Moon quakes, the heat flow under the surface and the minute nuclear particles of the exosphere, meaning ions and atoms that are knocked out of the surface of the Moon by the solar wind, forming a kind of atmosphere which, however, is billions of times thinner than Earth’s.
Next, they used the time remaining for their first excursion to drive to a crater one kilometer west of the landing site called ‘Flag Crater’. Thanks to their intense training in the field, Young and Duke had developed a keen eye for the geological tasks with which the scientists had taught them to perform. Despite the perfection in their field work, however, they soon saw that the hopes and expectations of the lunar researchers would not be fulfilled: none of the rocks they found had the typical fine-grained texture of volcanic rock; instead, virtually all samples showed breccia features, consisting of fragments of all sizes that were fused together by the great heat caused by the impact of an enormous asteroid.
On the third day, Young and Duke took samples from a large rock they called ‘House Rock’ four and a half kilometers away from ‘Orion’ – and once again, they found no trace of volcanism. When Duke scraped some dust from under another block called ‘Shadow Rock’, he commented it by saying, “In west Texas, you get a rattlesnake; here, you get permanently shadowed soil”.
A few hours after the third excursion, the two astronauts lifted off for the command module in its orbit around the Moon. Charlie Duke left a family photograph behind on the lunar surface which today could be found exactly as it was then, although the colors would be probably have faded because UV radiation is much more intense on the Moon which, unlike Earth, is not protected from harmful energy-rich radiation by a magnetic field. John Young and Charlie Duke spent 20 hours and 14 minutes outside the lunar module. At 17.1 kilometers per hour, their speed record on the lunar surface remains unbroken to this day. Thanks to the rover they were able to gather 94.3 kilograms of Moon rock to bring back to Earth. In addition, their measurements and detailed descriptions of the environment of the landing site rounded off the success of the mission.
In scientific terms, Apollo 16 was a minor sensation. In all previous missions, the interpretations of the available images had always been close to the reality which the astronauts found on the spot – not, however, without individual surprises that were of great significance for research. Apollo 16 produced two major scientific revelations in geology: First, it became clear that the effect of the enormous impacts that hit the young crust of the Moon more than three and a half to four billion years ago was almost global – gigantic clouds of red-hot rock and dust scoured the surface of the Moon, structuring the landscape. When the proverbial clouds of dust consisting of superfine particles had settled, large swaths of the lunar surface had acquired a layer of dust that looked like volcanic deposits in satellite photographs.
With regard to the volcanism they had suspected, scientists now had to think again: their models involving, on the one hand, ‘alkaline’, low-silicon volcanism in the basins as found by Apollo 11, 12 and 15 and an ‘acid’ silicon-rich form of volcanism in the highlands were all wrong. The fact remains, however, that there are other sites not far from Apollo 16 showing direct signs of highland volcanism, leaving that part of lunar geology an unsolved mystery to this day.
Apollo 16 splashed down in the Pacific on 27 April 1972, at 20:45 CET. The Apollo programme was now close to the limits of feasibility, and its technical components had proven nearly perfect in real life.
The texts presented here were created by the DLR Institute of Planetary Research and space expert Gerhard Daum for the exhibition ‘Apollo and Beyond’ at the Technik Museum Speyer. Among other things, the history of the Apollo programme is showcased in detail using both text and images. In addition, full-scale models of the Apollo 11 Lunar Module ‘Eagle’, the Apollo 15 Lunar Roving Vehicle and an Apollo space suit for visiting the Moon’s surface, as well as a 3.4-billion-year-old rock collected from the Apollo 15 landing site can be seen in a lunar landscape.