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app-d.html
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<!DOCTYPE HTML>
<HTML>
<head>
<title>Chariots for Apollo, Appendix D</title>
<meta http-equiv=Content-Type content="text/html; charset=UTF-8">
</head>
<BODY BGCOLOR="#FFFFFF">
<h1>Appendix D<br>Apollo 11 Experiments</h1>
<p>
<h3>Early Apollo Scientific Experiments Package (EASEP)</h3>
<p>
The <i>Apollo 11</i> scientific experiments for deployment on the lunar
surface near the touchdown point of the lunar module were stowed in the
lander's scientific equipment bay at the left rear quadrant of the
descent stage looking forward.<p>
The early Apollo scientific experiments package was carried only on this
flight; subsequent Apollo lunar landing missions carried the more
comprehensive Apollo lunar surface experiments package.<p>
EASEP consisted of two basic experiments: a passive seismic experiments
package (PSEP) and a laser ranging retroreflector (LRRR). Both
experiments were independent, self-contained packages that weighed a
total of 77 kilograms and occupied 0.34 cubic meters of space.<p>
PSEP used three long-period seismometers and one short-period vertical
seismometer for measuring meteoroid impacts and moonquakes. Data
gathered would be useful in determining the interior structure of the
moon; for example, does the moon have a core and mantle like the earth?
The seismic experiment package had four basic subsystems: a structure
thermal subsystem for shock, vibration, and thermal protection; an
electrical power subsystem generating 34 to 36 watts by solar panel
array; a data subsystem to receive and decode Manned Space Flight
Network uplink commands and downlink experiment data and to handle power
switching tasks; and a passive seismic experiment subsystem to measure
lunar seismic activity and to detect inertial mass displacement.<p>
The LRRR experiment was a retroreflector array, made from cubes of fused
silica, with a folding support structure for aiming and aligning the
array toward the earth. Laser ranging beams from the earth were
reflected back to their point of origin for precise measurement of
earth-moon distances, motion of the moon's center of mass, lunar radius,
and earth geophysical information.<p>
Earth stations that beamed lasers to the LRRR included the McDonald
Observatory, Fort Davis, Texas; Lick Observatory, Mount Hamilton,
California; and the Catalina Station of the University of Arizona.
Scientists in other countries also bounced laser beams off the LRRR.<p>
Principal investigators for these experiments were Dr. Carroll C. Alley,
University of Maryland (LRRR), and Dr. Gary V. Latham, Lamont Geological
Observatory (PSEP).<p>
<p>
<h3>Apollo Lunar Radioisotopic Heater (ALRH) </h3>
<p>
An isotopic heater system, built into the passive seismometer package
that the Apollo 11 crew left on the moon, protected the seismic recorder
during frigid lunar nights.<p>
The heater, developed by the Atomic Energy Commission, was the first
major use of nuclear energy in a manned space flight mission. Each of
the two heaters was fueled with 34 grams of plutonium 238. Heat was
given off as the well-shielded radioactive material decayed. During the
lunar day, the seismic devices sent back to the earth data on lunar
seismic activity, or moonquakes. During the 340-hour lunar night, when
temperatures dropped as low as -173 degrees C, the 15-watt heaters kept
the seismometer at a minimum of -54 degrees C. Exposure to lower
temperatures would have damaged the instrument.<p>
The heaters were 7.6 centimeters in diameter, 7.6 centimeters long, and
weighed 57 grams each, including multiple layers of shielding and
protective materials. The complete seismometer package weighed 45
kilograms. Both heaters were mounted in the seismic package before
launch. During the lunar surface walk, the lunar module pilot
transported the package a short distance away and set up the equipment.
There was no handling risk to the crew. The plutonium fuel was encased
in various materials chosen for radiation shielding and for heat and
shock resistance. These materials included a tantalum-tungsten alloy, a
platinum-rhodium alloy, titanium, fibrous carbon, and graphite, with an
outer layer of stainless steel.<p>
Extensive safety analyses and tests were performed by Sandia
Laboratories at Albuquerque, New Mexico, to determine the effects of an
abort or any conceivable accident in connection with the moon flight.
The safety report by the Interagency Safety Evaluation Panel, made up of
representatives of NASA, the AEC, and the Department of Defense,
concluded that the heater presented no undue safety problem to the
general population under any accident condition deemed possible for the
Apollo mission.
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