EP-95 ON THE MOON WITH APOLLO 16
 
 

[1] Introduction

 

The Apollo 16 mission to the Moon's surface is expected to be launched from (:ape Kennedy on 16 April 1972 and to land a few days later in the highlands region of the Moon, near the crater Descartes. A sketch of the front side of the Moon is shown in figure 1 and the location of the landing site is shown in relation to other sites. This landing site is extremely important from the viewpoint of lunar science. It will give the astronauts their first chance to collect rocks in the lunar highlands, believed by some scientists to be the oldest region on the Moon, and also to study and collect new volcanic rocks on the Moon. These rocks along with those already collected may provide the key with which to understand the early history of the Moon. They may also provide some new facts on the history of our solar system and of the Earth.

The actual surface on which the Lunar Module or LM* will land is everywhere pock-marked by craters of various sizes. The smallest craters known are less than 1/1000 inch across; the largest exceed 50 miles. Some craters are very old (several billion years) but most were produced during the past few million years when objects from space struck the Moon. At velocities of 8 to 20 miles per second, these objects possess very high energy even more than an equivalent mass of TNT! Such objects are still hitting the Moon. And the Earth, also. You can look into the sky at night and see "shooting stars," evidence that such impacts are still taking place on the Moon. Our atmosphere protects us. (These objects burn in the atmosphere because of the high temperatures caused by friction.) But what about the astronauts on the Moon where there's no protective atmosphere? Although the craters are still being produced, there is no danger to the astronauts because collisions with the Moon are very infrequent. For example, an object larger than 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 the result of running water. 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 16 over those of earlier missions. Total duration of the mission has increased 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; it is now planned to be 73 hours. The amount of time spent by the astronauts on the lunar surface outside the LM, which has become known as Extravehicular Activity or EVA, has more than doubled to a planned 21 hours. The EVA time will be spent in three periods of 7 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 1,200 pounds. And finally, the astronauts will have with them for the second 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.

A summary of major events for the entire Apollo 16 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. The uv photography will be.....

 


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FIGURE 1.- Front side of the Moon.

FIGURE 1.- Front side of the Moon. This side always face the Earth. Shown here are locations of the previous Apollo landings (circles) and of the impacts on the Moon of spent S-IVB stages (diamonds) and LM ascent stages (squares). The numbers in the symbols are the mission numbers. The sound waves created in the Moon by the impacts travel through the Moon; they are used to study the interior of the Moon. NASA PHOTO S-72-16338.

 

[3] ....continued during the journey to the Moon and pictures will be obtained at various distances from the Earth. Studies of these uv photos will help us interpret similar data for other planets. We currently have such photos of Mars and Venus. It is likely that most of the exploration of other planets during the next century will be done remotely by highly sophisticated robot space probes, carrying with them advanced computers that will be able to solve complicated problems. These will be necessary because of the great distances involved. Do you realize that the time needed for light to travel to Jupiter and back to Earth is about 1 1/2 hours? This is the time needed to send and receive radio messages. A message to Pluto and back would take about 12 hours.

During the journey to the Moon and before the landing? one of the spent stages of the rockets that were used to lift 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, 14 and 15 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 its 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....

 


FIGURE 2.-Orbit and ground track of Apollo 16.

FIGURE 2.-Orbit and ground track of Apollo 16. Because the Moon rotates, the ground track is different for each revolution of the CSM.

 

...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, illustrated in figure 3. The LM 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 communications 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.

When the astronauts leave the LM, a process appropriately termed egress and shown in figure 4, they must wear a suit that protects them from the Moon's high vacuum. This suit is illustrated in figure 5. 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.

 


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FIGURE 3.-The Lunar Module (LM).

FIGURE 3.-The Lunar Module (LM). The shaded portion, the descent stage, remains on the Moon when the astronauts have in the ascent stage to rendezvous with the CM and return to Earth. Scientific equipment is stored in the Mesa.

 


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FIGURE 5.-Astronaut suit and equipment.

FIGURE 5.-Astronaut suit and equipment. The suit prevents exposure of the astronaut to the Moon's vacuum. It incorporates many improvements over the suits used on early Apollo flights. Sketched also are several items of equipment.

 

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.

The rest of this guidebook is a discussion of the astronauts' equipment and of their activities on the lunar surface and in orbit.

 


FIGURE 4.-Egress. Apollo 11 astronaut Aldrin is shown egressing from the LM. Note the ladder that leads down one leg from the platform.

FIGURE 4.-Egress. Apollo 11 astronaut Aldrin is shown egressing from the LM. Note the ladder that leads down one leg from the platform. NASA PHOTO S-71-31090.


*Abbreviations and acronyms are very useful in situations where time is limited, such as a mission to the Moon's surface. Common ones are noted in this book where first used. An extensive list is given at the end of the text.


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