Crew and spacecraft
Apollo 15 was to be the first of three ‘J-missions’ that were to stay on the lunar surface not for two but for three days. For this purpose, it would carry a lunar module with a lift-off weight of 16.5 tons, about a thousand kilograms more than its predecessors. Next to additional stocks of food, fuel, and oxygen, its cargo was to include the firstever Moon vehicle, the ‘Lunar Roving Vehicle’, called LRV for short or simply lunar rover in NASA parlance.
The decision to develop a lightweight vehicle that could be folded up to occupy as little space as possible was not made before spring of 1969. With their mobility thus improved to a marked extent, the astronauts would be able to cover much longer distances on the lunar surface, see more, observe more, and gather a greater number of samples in a variety of places.
The expectations of the science team were great indeed. In addition, the geological training of the astronauts played a much greater part in the preparations for the J-missions. The astronauts of mission 15, 16, and 17 were – as far as possible – thoroughly trained by experienced geologists in ‚moonlike‘ terrain on Earth.
Although the chapter of the Apollo project that was about to begin was to be the most successful in scientific terms, the political acceptance of the Moon flights was changing dramatically. Only two years earlier, President Nixon had posed proudly with the crew of Apollo 11. Now, however, he made it increasingly clear to NASA that, while the first lunar landing had been an important political signal sent by the USA to the Soviet Union and the global public, Nixon himself thought that ever more subsequent missions were too expensive – particularly so as he could not turn them to political profit. Even NASA’s decision to award an order for building the rover to the Boeing Company met with violent criticism. However, the 40 million dollars spent on developing the LRV hardly carried any weight compared to the cost of the entire Apollo program, which was then officially said to amount to 23 billion dollars.
Commander of Apollo 15 was to be David Scott, who had flown on Gemini VIII together with Neil Armstrong in 1966 and on Apollo 9 in 1969. James Irwin was assigned Lunar Module Pilot, and Alfred Worden was made Command Module Pilot – for both, Apollo 15 was the first flight into space. The command module was given the name ‘Endeavor’ while the lunar module bore the name ‘Falcon’.
Apollo 15 lifted off from the Kennedy Space Center on July 26, 1971, at 9:34 local time. When the first stage separated after burn-out, the second stage ignited when the first stage was still very close to the rocket. If the fiery jet from the second stage had ignited the exhaust of the first stage, a disaster might have resulted.
However, the journey proceeded without incident, and on July 30, Apollo 15 was flying above the far side of the Moon, having entered its orbit on schedule. The landing site selected demonstrated how NASA’s self-confidence had grown, for Apollo 15 was to touch down in the midst of the Apennine mountains that rear up nearly 4000 meters, at a site close to the Hadley Rille, a lava channel 116 kilometers long, 1000 meters wide, and 400 meters deep that is situated in a plane ‘bay’ at the eastern edge of Mare Imbrium. The ‘Sea of Rains’ is the largest of the impact craters on the near side of the Moon that are visible from Earth with the naked eye and are filled with solidified lava without exception. This called for a daring approach from the east.
On July 30, Scott and Irwin undocked the lunar module from the command module. During the descent, Scott noticed that ‘Falcon’ was not exactly on course and corrected the deviation manually. A little later, the lunar module ‘scraped’ across the high mountains at the eastern edge of the Imbrium basin at the previously calculated altitude. Scott and Irwin later remembered that the view from the window had been fascinating. At 23:16:29 CET, the astronauts landed only a few hundred meters away from the target touchdown site. As both astronauts had had a very long working day, the first EVA was moved to the next (terrestrial) day.
However, before the two went to enjoy a prolonged rest, Scott described their first impressions in a spontaneous address that has remained legendary among lunar geologists to this day. For this purpose, the two put on their space suits and helmets, evacuated the air from the cabin, and opened the hatch in the top of ‘Falcon’. Scott stuck out his head, rested his arms on the outer fairing, and reported directly to the ‘back room’ in Houston, where the scientists stayed close to but separated from Mission Control. It was a perfect, detailed, 360-degree take of this exciting landing site, which Scott documented in numerous photographs.
On the Moon
On the next day, they actively explored the vicinity. On July 31 at 14:12 CET, Scott stepped onto the lunar surface, followed by Irwin a few minutes later. Unlike the preceding missions, they did not begin by installing the ‘Apollo Lunar Surface Experiment Package’ (ALSEP) but turned first to commissioning the lunar rover. No problems were encountered in getting the ‘parcel’ (which weighed 210 kilograms on Earth) ready to start, and off they went with 2.5 horsepower per wheel.
It was an unwritten ‘law’ obeyed by all mobile Apollo crews that only the commander should operate the – very basic – controls. At first, only the rear wheels could be steered but not the front wheels. While this took some getting used to, it did not hamper anything. When Scott switched on the rover on the second day, the front axis could be steered as well, which he commented by saying, “Hey, you let some of those Marshall guys come up here and fix it, didn‘t you?”, meaning one of the engineers from the NASA center where the rover had been assembled. The very first ride in the rover was an enormous step ahead. Driving slowly, Scott and Irwin covered about 1000 meters to the edge of the impressive Hadley Rille, a volcanic channel through which burning-hot liquid lava flowed into the Imbrium basin three billion years ago. Two kilometers further along, they reached the foot of Mount Hadley where they collected important rock samples at the edge of the Imbrium basin.
Back at the lunar module, the astronauts installed the ALSEP package and endeavored – in vain – to drill holes several meters deep for taking samples and conducting physical measurements. The following day was one of the most productive for lunar research. Four kilometers south of the landing site, Scott and Irwin – at last! – found a rock that consisted almost entirely of a calcium-rich aluminum silicate called plagioclase, a piece of anorthosite rock from the original crust of the Moon. In the general euphoria, the term ‘Genesis rock‘ took hold immediately. They also knocked samples off a rock that was colored green by volcanic glass. At the same time, they recorded the spectacular scenery in innumerable photographs. Scott, an engineer and pilot, proved an extremely gifted and highly motivated geologist. The third excursion, too, yielded significant observations, this time mainly concerned with the edge of the Hadley Rille. The scientists’ euphoria knew no bounds.
Before flying back to join Alfred Worden in the command module Endeavor, David Scott conducted a ‘classical’ experiment: Observed by the TV camera, he simultaneously dropped from his hands his own geologist’s hammer and a falcon feather, which naturally arrived simultaneously on the ground. He did this to demonstrate that in the vacuum of the Moon, the impact of attraction on both bodies is exactly the same (and that it is air drag that slows down the feather on Earth), a theory formulated by Galileo as early as the 17th century. Scott then parked the rover at some distance to the lunar module and aimed the TV camera at the lander to record the lift-off. Next to it, he built a small memorial containing the names of all astronauts and cosmonauts who had lost their lives since the beginning of the space age.
After two days and almost 20 hours, Scott and Irwin set out on their return flight on August 2, 1971, having spent almost 19 hours outside the lunar module gathering 76.7 kilograms of samples to take home. During that time, Alfred Worden had been photographing the lunar surface from the command module, using a special camera system mounted in the outer bay of the service module that produced images of hitherto unparalleled resolution. During the flight back to Earth, Worden went outside to recover the film cassettes. After the lunar orbit had been left behind, there was a moving exchange of messages of gratitude between the crew and the scientists that had been following Apollo 15 live from Houston. All were aware that this was the most productive mission in the Apollo program so far. The deployment of the lunar rover as a ‘mobile research platform’ marked an enormous step ahead.
On August 7, 1971, Apollo 15 returned to Earth. While the ‘Genesis rock’ was indeed old, it was not as old as had been hoped for: ‘only’ 4.1 instead of 4.4 billion years. It was to be Apollo 17 which would bring the oldest sample of the first Moon crust back to Earth. Nevertheless, the ‘Genesis rock’ was a very important find. The samples taken from the mountains at the edge of the Imbrium basin helped to determine the time of the impact even more precisely than those of Apollo 14, namely 3.82 billion years before our time. This gave geologists an ‘anchor’ for determining the age of other areas elsewhere on the Moon. The Hadley Rille, in turn, permitted a look into the depths revealing the layer structure of the lava flows that make up the mare plains of the Moon.
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.