On the Moon with Apollo 15.
A Guidebook to Hadley Rille and the Apennine Mountains.
The Apollo 15 mission to the Moon’s surface is expected to be launched from Cape Kennedy on 26 July 1971 and to land a few days later near a very large and majestic mountain range, the Apennine Mountains. A sketch of the front side of the landing site is shown in relation to other sites. This landing site is extremely attractive from the viewpoint of lunar science. It will give the astronauts their first chance to collect rocks from lunar mountains and to study at firsthand a feature, termed rille, which resembles in many ways the channels cut on Earth by meandering streams. The origin of rilles is proabably not the same as that of the familiar terrestrial stream-cut channels because no water is present now on the Moon’s surface and probably never existed there. The origin of rilles is a puzzle.
Near the landing site are Hadley Mountain, which rises about 14,000 feet above the surrounding lowlands and Mount Hadley Delta, which rises about 11,000 feet. The actual surface on which the Lunar Module or LM* will land is everywhere pocked-marked by craters of various sizes. The smallest craters known are less than 1/1000 inch across; the largest exceed 50 miles. The craters were produced during the past few million years when objects from space struck the moon. The craters are still being produced but there is no danger to the astronaut because collisions with the Moon are very infrequent. For example, an object larger than a birdseed would strike the landing site only once every few years. But because erosion is so slow on the Moon, the craters produced millions of years ago are still preserved and appear as seen in photographs throughout this guidebook. The mechanisms of erosion, the process by which rocks and soil are removed from a particular spot, are very different on the Earth, and the Moon. Most terrestrial erosion is accomplished by running water and is relatively rapid. Most lunar erosion is the result of impacting objects and the resulting craters destroy previously existing ones.
Since the first manned lunar landing, Apollo 11, in July 1969, significant improvements in both equipment and procedures have increased dramatically the capabilities of Apollo 15 over those of previous missions. Total duration of the mission has increased from 9 days to a planned time of about 12 1/2 days and a maximum of 16 days. Actual time for the LM to remain on the lunar surface has doubled, from 33.5 hours previously to a planned 67.3 hours. The amount of time spent in three periods of 7, 7, and 6 hours’ duration. The weight of the scientific equipment that will be used in lunar orbit has increased from 250 pounds to 1,050 pounds. The weight of the scientific equipment to be landed on the lunar surface has increased from 510 pounds to about 1200 pounds. And finally, the astronauts will have with them for the first time a small, four-wheeled vehicle for travel over the Moon’s surface. It is termed Rover and can carry two astronauts, equipment, and rocks. Unlike the Russian vehicle Lunokhod that was recently landed and is still operating, it cannot be operated remotely from Earth.
A summary of major events for the entire Apollo 15 mission is shown in Table 1. Scientific activities while the spacecraft is in orbit around the Earth, consist mainly in photographing the Earth with film that is sensitive to ultraviolet (uv) radiation for the purpose of examining various terrestrial, cloud, and water features. By using uv, we hope to “see” these features more clearly than we could see them with visible visible light. From space, the atmosphere gets in the way of seeing. The situation is somewhat akin to that of using sunglasses to reduce glare, so the wearer can see better. The uv photography will be continued during the journey to the Moon and pictures will be obtained at various distances from the Earth. During this journey and before the landing on the Moon, one of the spent stages of the rockets that were used to loft the spacecraft from the Earth, and designated S-IVB, will be crashed into the Moon. The Sound waves generated by the S-IVB impact travel through the Moon and will be detected by sensitive receivers (seismometers) now operating at the Apollo 12 and 14 sites. (This experiment is discussed more fully later in this guidebook.)
Shortly after placing their spacecraft in orbit about the Moon, the astronauts separate it into two parts. One part, the combined Command and Service Modules (CSM), remains in lunar orbit while the other part, the Lunar Module (LM), descends to the surface.
One astronaut remains in the CSM and performs many scientific experiments. These orbital experiments will obtain data over a large part of both front and back sides of the Moon because the path of the point directly beneath the spacecraft, termed ground track, is different for each revolution of the spacecraft. See figure 2. Notice that the orbit of the CSM is not parallel to the equator. If the Moon did not rotate about its axis, the ground track would change very little on each successive revolution of the CSM. However, the Moon does rotate slowly about it axis. It completes one full revolution every 28 earth-days and therefore the ground track is different for each CSM revolution.
Several of these orbital experiments will measure the approximate chemical composition of the Moon’s surface materials. Others are intended to measure the variations of gravity and of the magnetic field around the Moon. A laser altimeter will be used to obtain precise elevations of features that lie on the Moon’s surface beneath the orbiting CSM. An extensive set of photographs will be obtained. The pilot will observe and photograph many features on the Moon never before available to astronauts.
The other two astronauts descend to the surface of the Moon in the LM. The rest of this guidebook is a discussion of their equipment and of their activities.
The LM, illustrated in figure 3, lands two astronauts on the Moon’s surface. It has two parts, a descent stage and an ascent stage. THe descent stage contains a rocket engine, fuel necessary to land both stages, a four-wheeled battery-powered vehicle to be used on the Moon, water and oxygen, and scientific equipment to be left on the Moon when the astronauts return to Earth. The other part, the ascent stage, contains the following items: (1) equipment for communication with the Earth and with the CSM, (2) navigational equipment, (3) a computer, (4) food, oxygen, and other life-support supplies, and (5) another rocket engine and fuel needed to leave the Moon and rendezvous with the CSM. All three astronauts return to Earth in the Command Module.
Soon after the LM lands on the Moon, about 11/2 hours, the astronauts will spend a half hour describing and photographing the surrounding area. The commander will open the upper hatch and stand with his head and shoulders outside the LM. During this Standup Extravehicular Activity (SEVA), the LM cabin will be open to the lunar atmosphere and will therefore be under vacuum conditions. Both astronauts must wear their space suits. Because the commander’s head will be above the LM, he will have excellent visibility of the landing site. If the LM lands within 100 yards, the length of a football field, of the planned spot, then the commander will see the panoramic sketched in figure 4. He will shoot photographs, which will include panoramas, with both 500 mm and 60 mm lens. His verbal descriptions during the the SEVA will help Mission Control to accurately pinpoint the actual landing site. Of equal importance is the fact that the descriptions will assist in the continuing evaluation of the surface science plans. It is likely that the astronauts will draw attention during the SEVA to some surface features, previously overlooked, that we will wish to exxamine sometime during the three EVA’s.
When the astronauts leave the LM, a process appropriately termed egress and shown in figure 5, they must wear a suit that protects them from the Moon’s high vacuum . This suit is illustrated in figure 6, Although it was designed to allow freedom of movement, it still restricts considerably the motion of the astronauts. An example may be useful. Think how difficult it is to run, chop wood, or work outdoors on an extremely cold day in winter when you wear many layers of clothes. The astronauts’ suits are even more restrictive. The Portable Life Support System (PLSS) contains the oxygen needed by the astronaut and radios for communication. It also maintains the temperature inside the suit at a comfortable level for the astronaut.
Landing Site Description
The Apollo 15 landing area, termed Hadley-Apennine is situated in the north central part of the Moon (latitude 26* 04′ 54″ N. longitude 03* 39′ 30″ E) at the western foot of the majestic Apennine Mountains, and by the side of Hadley Rille. See figure 1. The Apennines rise 12,000 to 15,000 feet above the lunar surface and ring the southeastern edge of Mare Imbrium (Sea of Rains). For comparison with Earth features, the steep western edge of the Apennine Mountains is higher than either the eastern face of the Sierra Nevadas in the western U.S. or the edge of the Himalayan Mountains that rises several thousand feet above the plains of India. The actual landing point was selected so the astronauts could study the sinuous Hadley Rille, the Apennine Mountain and several other geological features. A beautiful perspective view of the loval landing site, as seen from an angle of about 30 degrees, is shown in the precision that is available from modern-day digital computers and the insights that can come only from an artist. Thus the features are very accurately drawn but they are displayed in a way that the human eye will see them,
In the rest of this section, I will discuss the several geologic features present at the landing site: The APennine Mountains, Hadley Rille, the Cluster of craters at the foot of Hadley Mountain, and the North Complex. ALl of them are clearly visible in figure 7.