Apollo Guide
Apollo 15 Landing Site
The HFE involved drilling two holes into the regolith to depths of 1.6 to 2.3
meters. The second hole and measurement was to confirm the readings from the
first hole. The temperature was measured at several depths within each hole by
platinum resistance thermometers placed at several points in the lower parts of
the holes and several thermocouples placed in the upper part of the holes. The
rate at which temperature increases with depth is a measure of the heat flowing
from the Moon's interior. The drilling caused some heating within the hole,
although the effects of this heating decayed with time. Also, temperatures in
the upper part of the regolith vary as the amount of incident sunlight changes
throughout the lunar day and night. By monitoring temperatures in the drill
holes over a long period of time, these effects can be accounted for, allowing a
determination of the average heat flow rate at the landing site.
Heat flows from hot regions to cooler regions. The interior of the Moon is warm compared to the surface, therefore heat flows from the interior to the surface where it is lost into space by radiation. This heat is mainly produced by the decay of natural radioactive elements thorium, uranium, and potassium, raising the heat of the interior of the Moon. The Heat Flow experiment was designed to measure the heat loss from the interior of the Moon.
The results of the Heat Flow Experiment were used to set the limits on the amount of radioactivity - the long-term source of internal heating of the Moon - and to set limits on models of the thermal history of the Moon. The rate at which a planet loses its internal heat to space is an important control on the level of tectonism (faulting and folding of the planet's surface due to internal deformation) and volcanic activity on the planet. This loss of internal heat was measured by the Heat Flow Experiments on Apollo 15 and 17. This experiment was also attempted on Apollo 16, but failed due to a broken cable connection.
The HFE involved drilling two holes into the regolith to depths of 1.6 to 2.3 meters. The second hole and measurement was to confirm the readings from the first hole. The temperature was measured at several depths within each hole by platinum resistance thermometers placed at several points in the lower parts of the holes and several thermocouples placed in the upper part of the holes. The rate at which temperature increases with depth is a measure of the heat flowing from the Moon's interior. The drilling caused some heating within the hole, although the effects of this heating decayed with time. Also, temperatures in the upper part of the regolith vary as the amount of incident sunlight changes throughout the lunar day and night. By monitoring temperatures in the drill holes over a long period of time, these effects can be accounted for, allowing a determination of the average heat flow rate at the landing site.
The HFE found that the surface layer temperature during the night was -197ºC (76ºK) rising to a maximum of +85ºC (358ºK) during the day. The temperature at 1.5 meters under the surface was a constant -20ºC (253ºK), indicating the regolith is an excellent thermal insulator. The results of these measurements indicate a heat flow of 21 milliwatts per square meter at the Apollo 15 landing site and of 16 milliwatts per square meter at the Apollo 17 landing site. The Earth's average heat flux is 87 milliwatts per square meter. The small value of the lunar heat flow was expected, given the Moon's small size and the observation that it has been nearly dead volcanically for the last 3 billion years. Because the heat flow was measured at only two locations, it is not known how representative these values are for the Moon as a whole. However, because both measurements were obtained near boundaries between mare and highland regions, it is thought that the measured heat flows are probably 10-20% higher than the average value for the entire Moon.
The seismic information, magnetometer, and heat flow experiments contributed the principal information about the Moon’s interior. It is now believed the Moon’s crust is multi-layered and 50 kilometers thick, with a secondary boundary occurring about 20 kilometers under the surface. The upper mantle has been determined to consist of olivine or olivine-pyroxene matter, and to be quite homogeneous, extending about 500 kilometers down. Below this level the seismic data infers the interior is iron-enriched, although there is insufficient data to determine if the Moon has a molten core.
Non - Normal
Contingent EVA 2 - One Man , Two Hours
Description and Rationale
A second contingent EVA timeline is presented for a situation where only one crewman will egress .* The use of this EVA timeline , as for the other contingent timeline , will require a real time decision . All of the reasons , or even if one would be cons idered in real time , have not yet been determined . One reason might be the failure of one PLSS to check out . Another might be a LM subsystem malfunction which required continuous monitoring . Other suppos itions could require a decision to conduct a one man EVA.
As for Contingent EVA 1, it is assumed that the CDR can egress . However , if this is not possible , each crewman should be capable of accomplishing the other crewman 's tasks .
For this contingent situation the crewman on the surface should be able to accomplish most of the nominal activities within two hours . He may , however , require verbal assistance from the other crewman as well as more time to perform the tasks which he nominally does not perform.
* The Final Flight Mission Rules for Apollo 11 will govern the selection of the crewman to egress and the EVA he will accomplish.
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