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<span class="style6">ESMD Course Material : Fundamentals of Lunar and
Systems Engineering for Senior Project Teams, with Application to a
Lunar Excavator</span><br />
<br />
Contact: David Beale, dbeale@eng.auburn.edu</div>
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<p>
<img alt="A lunar excavator's mission is to dig lunar soil." border="0" height="366" src="image002.jpg" v:shapes="Picture_x0020_1" width="474" /></p>
<p>Figure 1 A lunar excavator's mission is to dig lunar
soil</p>
<h1>Chapter X: A Roadmap to Design an Excavator Based on Systems
Engineering</h1>
<p class="style26">The objective of this chapter is to present
condensed and hyperlinked course material that chronologically
steps through the systems engineering design process to design
an excavator. Following a link will lead to a more
detailed explanation and/or additional materials.</p>
<w:sdt sdtdocpart="t" docparttype="Table of Contents" docpartunique="t" id="209345390">
<h4>Contents<w:sdtpr></w:sdtpr></h4>
<ol>
<li><a href="ChapterX.htm#SystemsEngineeringMethod">The Systems Engineering
Method</a><ol>
<li><a href="ChapterX.htm#ClassroomDiscussion">Classroom Discussion – How
to Design an Excavator</a></li>
</ol>
</li>
<li><a href="ChapterX.htm#MissionObjective">The Mission Objective</a></li>
<li><a href="ChapterX.htm#BackgroundInformation">Background Information
and Science</a><ol>
<li><a href="ChapterX.htm#BackgroundInfoChapter1">Background Information
from Chapter 1 </a></li>
<li><a href="ChapterX.htm#LunarPhysics">Lunar Physics – Background
Information from Chapter 5 </a>
</li>
<li><a href="ChapterX.htm#ThermalAnalysisandControl">Thermal Analysis and
Control</a></li>
</ol>
</li>
<li><a href="ChapterX.htm#EnvisionDisciplines">Envision the Disciplines
and Teams </a>
<ol>
<li><a href="ChapterX.htm#management_structure">Management Structure
</a></li>
<li><a href="ChapterX.htm#Communications">Communications</a><o:p></o:p></li>
</ol>
</li>
<li><a href="ChapterX.htm#PhasesofLifeCycle">The Phases of the Life
Cycle</a><o:p></o:p><ol>
<li><a href="ChapterX.htm#The_Vee_Chart">The Vee Chart</a><o:p></o:p></li>
<li>
<a href="ChapterX.htm#The_11_Systems_Engineering_Functions_and_the_SE_Functions_Triangle">The 11 Systems Engineering
Functions and the SE Functions Triangle</a><o:p></o:p></li>
</ol>
</li>
<li><a href="ChapterX.htm#Appendix">Appendix</a><o:p></o:p></li>
</ol>
</w:sdt>
<form>
<h2>
<a name="SystemsEngineeringMethod">The Systems Engineering
Metho<span class="style20">d </span></a></h2>
<p>(The Systems Engineering Method is fully explained in
<a href="Chapter2.htm#Top">Chapter 2</a>. ) </p>
<h3>First a bit of systems terminology about
<a href="Chapter2.htm#PhysicalElementsandSystemHierarchy">
elements and hierarchy</a> ……</h3>
<p>Our goal is to create a product. The "system" and
the "product" are the same thing.</p>
<p>
<o:p><em>Elements</em> of a system are not just hardware but can also include </o:p>
<font FACE="MinionPro-Regular" SIZE="3">software, and can even
include people, facilities, policies, documents and databases.</font></p>
<p>A s<span class="style13">ystem</span> can be broadly defined as an
integrated set of elements that accomplish a defined
objective.</p>
<p class="style12">A s<b><span class="style14">ubsystem</span> </b>is a system in its own right,
except it normally will not provide a useful function on its
own, it must be integrated with other subsystems (or
systems) to make a system. </p>
<p class="style31"><span class="style13">Components</span> are
elements that make up a subsystem or system. </p>
<p class="style32"><span class="style13">Parts</span> are elements on the lowest level of the
hierarchy, and are often COTS
(Commercial-off-the-Shelf). For example a resistor, link,
bolt, etc. are parts. Software could also be a "part".</p>
<p class="style12"><em>Example of a system and its subsystems,
components and parts</em>: A <span class="style14">dish antenna system</span> on earth that receives
a radio signal from a satellite, and that will automatically
point the dish toward the satellite moving across the horizon.<o:p> </o:p>
A combination of elements consisting of a motor, position and velocity sensors, controller,
software and wires to automatically position the dish toward a
satellite is the <span class="style14">motor control subsystem</span> in the
dish antenna
system. The <span class="style14">motor is a component</span> in the motor control
subsystem. The dish antenna system includes the following
subsystems: 1) the motor control
subsystem, 2) the <span class="style14">dish is a part</span>
and along with the electronics make up the
communication subsystem, 3) the structures subsystem, and 4) the
electrical power subsystem.<o:p></o:p></p>
<h3>The Engineering Design Process (EDP)</h3>
<p><o:p> </o:p>Imagine you were asked to design a <u>part</u>, <u>component</u> or <u>subsystem</u>,
for example a can opener, a mousetrap, a bicycle, an
automotive suspension, etc.</p>
<p>Question: What process would you follow?</p>
<p>Answer: <b>
<a href="Chapter2.htm#HowtoDesignSubsystemComponent">The
Engineering Design Process (EDP)</a></b> which contains the following steps in Figure 2:</p>
<ol start="1" type="1">
<li>Project Definition – meet with stakeholders, define
the mission objective(s), understand the problem.</li>
<li>Requirements Definition and Engineering
Specifications – carefully and thoughtfully develop
requirements that will guide the design creation to
follow. Clearly document the requirements and
receive stakeholder approval before proceeding. </li>
<li>Conceptual Design – generate ideas, compare using
trade studies, models, proof-of-concept prototypes, down
select to focus on a meritorious concept in the next
step.</li>
<li>Product Design, Fabrication and Test – complete all
detailed drawings, make or purchase parts and
components, assemble and measure
performance. If performance requirements are met, begin
manufacturing.</li>
</ol>
<table cellspacing="3" class="style10" style="width: 78%">
<tr class="style2">
<td class="style11">Project Definition</td>
<td class="style11">Requirements Definition</td>
<td class="style11">Conceptual Design</td>
<td class="style11">Product Design</td>
<td class="style11">Manufacturing</td>
</tr>
</table>
<p class="style5">Figure 2 Steps of the
Engineering Design Process</p>
<p>Now consider designing a <u>system</u> with
many <u>subsystems</u>, which are made up of components
and parts. It may require<span lang="EN-GB"> software
and mechanical, electrical and electronic hardware. <o:p></o:p></span></p>
<ul type="disc">
<li>System examples: The Space Transport System
(STS) in Figures 3, the Mars rover and satellites.
Not so complex systems are a camera, a programmable microwave,
a refrigerator. The chart of Figure 4 shows the "tiers"
of a "product hierarchy" for the orbiter portion of the
STS. The STS contains the Orbiter, the
External Tank and the 2 Solid Rocket Boosters as tier 1
(sub)systems<strong>. </strong> Tier 2 is shown
for the Orbiter only, and tier 3 for the Avionics
(sub)system only. Other (sub)systems at tier 2 might include
the orbiter power system, robotic arm,
communications, payload, landing gear, engines, piping,
etc. It is permissible to call a "subsystem"
a "system", as is done in Figure 4. Whether a
subsystem is called a system or a subsystem is a choice
made by a manager. </li>
</ul>
<p><o:p> </o:p><img align="left" alt="Buzz Lightyear standing in front of a space shuttle on the launch pad" height="129" hspace="12" src="SiteImageFiles/Introduction/image007.jpg" v:shapes="Picture_x0020_20" width="172" /></p>
<p><o:p> </o:p></p>
<p><o:p> </o:p></p>
<p><o:p> Figure 3: STS and Buzz Lightyear
(www.nasa.gov)</o:p></p>
<p><o:p> </o:p></p>
<p>
<img border="0" height="246" src="SiteImageFiles/Introduction/image009.gif" v:shapes="_x0000_i1036" width="576" /></p>
<p>Figure 4. STS and some of its (sub)systems in a product
hierarchy</p>
<p><o:p> </o:p><img border="0" height="51" src="SiteImageFiles/Introduction/image011.jpg" v:shapes="_x0000_i1035" width="601" /></p>
<p>Figure 5. Common Satellite Subsystems</p>
<p class="style18">Although quite different products, there
are <span class="style14">common types of subsystems</span>
in satellites, rockets and rovers. These common
types of subsystems include in Figure 5:</p>
<ul class="style19">
<li>
<p class="style17">C&DH = Command and Data Handling,</p>
</li>
<li>
<p class="style17">EPS=Electrical Power System,</p>
</li>
<li>
<p class="style17">ADC=Attitude Determination and Control,</p>
</li>
<li>
<p class="style17">Structures=Structures and Mechanisms,</p>
</li>
<li>
<p class="style17">COMM=Communications,</p>
</li>
<li>
<p class="style17">Thermal=Thermal Control,</p>
</li>
<li>
<p class="style17">Ground Station,</p>
</li>
<li>
<p class="style17">And Payload.</p>
</li>
</ul>
<p><o:p> </o:p><span lang="EN-GB">Should we call the COMM a
subsystem or system? </span>Again,
<span lang="EN-GB">either terminology is OK! But to
eliminate confusion </span>the convention hereafter will be<span lang="EN-GB"> to call the final product the
"system", and every other system below the top tier </span>
a "<span lang="EN-GB">subsystem</span>"<span lang="EN-GB">.<o:p></o:p></span></p>
<h3><a name="_Toc209794300"></a>
<a name="ClassroomDiscussion">Classroom Discussions – How
to Design an Excavator</a><o:p></o:p></h3>
<p>First you receive a <u><a href="Chapter2.htm#MissionObjectivesandConstraints">mission objective</a></u> from
your NASA sponsor. A possible mission objective for the "teleoperated
lunar excavator" is:</p>
<p><em>Create a lunar excavator prototype for studies on the
earth that will connect to a standard NASA mobility platform
plate (where there is 19" from ground to bottom of
excavator-rover interfacing plate, see Appendix), which
dumps the soil into an attached bin. The excavator weighs
less than 100 kg (not including the bin and mobility
platform). Target less than 150 W power and capable of
digging 250 kg/hour of regolith, and can be controlled from
an out-of-sight ground station.</em><o:p></o:p></p>
<p><o:p> </o:p><b>Classroom Discussion #1:</b> <b>What
subsystems might be needed for a teleoperated lunar
excavator? </b></p>
<p class="style12"><b>Note that:<o:p></o:p></b></p>
<ul class="style19">
<li>
<p class="style12">In order to create a system to meet the mission
objective, design teams would eventually be formed, one team
for each expected subsystem.<o:p></o:p></p>
</li>
<li>
<p class="style12">Specialty design teams will be
applying the EDP to design their own subsystem.</p>
</li>
<li>
<p class="style12">The teams will also be applying
"<a href="Chapter2.htm#ConcurrentEngineering">Concurrent
Engineering</a>",
where multiple subsystems are being designed simultaneously
by different teams, with strong collaboration across
boundaries of subsystems and disciplines. "The objective of concurrent
engineering is to reduce the produce development cycle
time through a better integration of activities and
processes" - NASA Systems Engineering Handbook SP-601S.
</p>
</li>
</ul>
<p><o:p></o:p>
<b>Classroom Discussion #2: List all the tasks you think
should be performed to make sure that separately designed
subsystems, when integrated together, will create a system
able to perform the mission?<o:p></o:p></b><o:p></o:p></p>
<p class="style12"><b>
<o:p> </o:p></b>The instructor should allocate enough
time for the class to discuss, and the professor lists the
answers on the board. Alternatively, the class may be
broken up into teams of 5 students that work together for 15
minutes, and then each team lists their answers on the
board. After this exercise, students will hopefully have a
good feel for what "Systems Engineering" is, without it
having been defined
yet! </p>
<p class="style12">A partial answer is hidden in text
format. To reveal it, press: <input type="button" onclick= "alert('Possible answers are: \n \n 1. Subsystem teams need to have requirements to guide the design (that are driven by mission and system needs.) \n 2. Subsystem teams need to know and define how different subsystems interface. \n 3. A subsystem should be able to operate as required by the system and mission requirements. \n 4. The team should verify that the built subsystem will operate as required. \n 5. The entire system should be tested to verify that it satisfies system and mission requirements. \n 6. Keep the subsystem and entire system within resource budgets, i.e. mass, power, link, etc. \n 7. Assess risk – what are the chances of failure of the subsystem and the failure modes, and manage the risk. \n 8. Document and store and provide access to critical documents, have a process to manage documents. \n 9. Have periodic reviews with stakeholders and all participants. \n 10. Conduct trade studies to compare subsystem design concepts. \n 11. Apply concurrent engineering practice, with strong collaboration across the boundaries of systems and disciplines. \n 12. Have a leader called a systems engineer who guides the process. \n 13. The system engineer should develop a plan for the systems engineering process (a Systems Engineering Management Plan). \n 14. Practice concurrent engineering, i.e.design teams work in parallel, integrated fashion thru communication and cooperation. \n 15. Select a project manager (for decision making, project planning) and systems engineer (to guide the systems engineering process). \n 16. Apply functional decomposition (determine “function before form”). \n 17. Break the project into phases, with review meetings between the phases. \n 18. ')"
value="Possible Answers" style="width: 115px; height: 23px"></form>
<h3>So Now What is Systems Engineering (SE)?</h3>
<p><u>Systems Engineering</u> (SE) is the
engineering process to create a system. It is a structured
process based on concurrent engineering and that
incorporates the Engineering Design Process. </p>
<p class="style17">One definition of SE is as
follows (NASA Systems Engineering Handbook SP-601S):</p>
<p class="style17">"Systems Engineering (SE) is a disciplined approach for
the definition, implementation, integration and operations
of a system (product or service) with the emphasis on the
satisfaction of stakeholder functional, physical and
operational performance requirements in the intended use
environments over its planned life cycle within cost and
schedule constraints. Systems Engineering includes the
engineering activities and technical management activities
related to the above definition considering the interface
relationships across all elements of the system, other
systems or as a part of a larger system."<o:p></o:p></p>
<p><o:p> </o:p>This and other
<a href="Chapter2.htm#WhatisSystemsEngineering">definitions
of systems engineering</a> are presented in Chapter 2.</p>
<p>The <a href="Chapter2.htm#The_Vee_Chart_Process_Model_of_the_Life_Cycle">Vee
Chart</a> (Figure 9) was created to guide
and simplify the application of the SE process through a
series of Phases. Within each phase of the Vee
chart, you will sequentially consider application of the 11
Systems Engineering Functions (Figure 10). </p>
<h2><a name="MissionObjective">The
Mission Objective</a><o:p></o:p></h2>
<p>NASA is represented by Robert Mueller as the customer or stakeholder in the project, whose expectations will
lead to statement of a mission objective. The team should
make sure that the mission objective is clearly stated, it
could also include functional, physical and operational
performance requirements for the environment and life (in
the strictest sense, requirements are not usually a part of
the mission objective as presented in Chapter 2, but we bend
the rules a bit here). </p>
<p class="style17"><o:p> Here are some examples of
mission objectives:</o:p></p>
<p class="style12"><o:p> </o:p><u>The Electro-Mechanical Excavator Prototype:<o:p></o:p></u></p>
<p class="style12">Create a lunar excavator prototype for
studies on the earth that will interface to a NASA mobility
platform (19" from ground to bottom of plate), dumps the
soil into an attached bin, weighing less than 100 kg, not
including the bin and mobility platform. Target less than
150 W power and capable of digging 250 kg/hour of regolith.<o:p></o:p></p>
<p class="style12"><o:p> </o:p><u>The Autonomous Excavator Prototype:<o:p></o:p></u></p>
<p class="style12">Create a lunar excavator prototype for studies on the
earth that will interface to a NASA mobility
platform (19" from ground to bottom of plate), dumps the
soil into an attached bin, weighing less than 100 kg, not
including the bin and mobility platform. Target less than
150 W power and capable of digging 250 kg/hour of regolith,
and functions autonomously.<o:p></o:p></p>
<p class="style12"><u>The Wireless Excavator Prototype:<o:p></o:p></u></p>
<p class="style12">Create a lunar excavator prototype for
studies on the earth that will interface to a NASA mobility
platform (19" from ground to bottom of plate), dumps the
soil into an attached bin, weighing less than 100 kg, not
including the bin and mobility platform. Target less than
150 W power and capable of digging 250 kg/hour of regolith,
and can be controlled from an out-of-sight ground station.<o:p></o:p></p>
<p>On the moon the excavator will be digging lunar soil
called "regolith". The regolith will be needed for a lunar
base - for making oxygen, for base construction, etc. The
"mobility platform" is a wheeled or tracked vehicle with a
motor that will move and locate the excavator. The
completed student excavator is attached to a NASA mobility
platform via an interfacing plate (see Appendix). You can
see a prototype mobility platform at <a href="http://www.nasa.gov/mission_pages/constellation/main/lunar_truck.html">http://www.nasa.gov/mission_pages/constellation/main/lunar_truck.html</a> .
Other mission objectives may require you to build your own vehicle to
drive the excavator.</p>
<p><o:p> </o:p>Implicit in the creation of a "lunar excavator prototype"
that will be tested on the earth is that the team has enough
forethought to realize that the design, and specifically
materials and components, must reflect the special concerns
and limitations that the lunar environment imposes. For
instance, a gasoline powered engine in a prototype may not be
a good choice since this type of actuator requires air for
combustion and hence cannot be used on
the moon. Chapter 5 <a href="Chapter5.htm#TheLunarEnvironment">Chapter5.htm#TheLunarEnvironment</a> was
written to provide the designer with the necessary
background on the lunar environment. Also, a chapter
entitled Component Design and Selection <a href="Chapter6.htm#ComponentDesignandSelection">Chapter6.htm#ComponentandMaterialSelection</a> provides
useful information for helping you select components that
have been designed for the space environment. Just as the
Cube Satellite program (<a href="http://cubesat.org/">http://cubesat.org/</a>)
allows student teams to build satellites that will operate
in space, in the foreseeable future student teams may be
making excavators that they will design, build and operate
from a campus ground station controlling an excavator on the
moon.<o:p></o:p></p>
<p><o:p> </o:p>So, in the future, student teams could build the <u>Lunar-Ready
Excavator</u> with the following mission objective:</p>
<p class="style12">Create a lunar excavator that dumps the
soil into an attached bin, weighs less than 100 kg, uses
less than 150 W power, is capable of digging 250 kg/hr of
regolith, fits within a cargo space of 1 m<sup>3</sup>, with
operational lifetime of 5 years, and can be controlled from
a ground station, run either autonomously or from ground
station commands.<o:p></o:p></p>
<p>Be prepared to perform test your prototype. If necessary
you can create your own soil bin using sand or other
commercially-available material available at a garden
center, or consider going to a beach if one is nearby. Dry
concrete mix is more representative of the soil properties
of regolith than sand and may be the most representative
choice of any easily acquired material. In the future expect that locations, such as NASA
centers, will have bins loaded with regolith simulant such
as JSC-1a for testing. </p>
<h2><a name="_Toc209794302"></a>
<a name="BackgroundInformation">
Background Information and Science</a><o:p></o:p></h2>
<p>Before going onto the next phase of the design you will
need to learn about the moon. Students
and practicing engineers will find a hostile environment
that requires careful material selection, analysis and
design so that equipment will be able to operate
successfully. </p>
<h3><a name="_Toc209794303"></a>
<a name="BackgroundInfoChapter1">Background Information from
Chapter 1 </a></h3>
<h3 class="style9"><a href="Chapter1.htm#Introduction">
Chapter1.htm#Introduction</a><o:p></o:p></h3>
<p>· The moon is quite different than the earth as a
future sight for habitation. Check out the
<a href="Chapter1.htm#ComparisonoftheEarthandMoon">comparison of
the earth and moon</a>.</p>
<p>· What is an excavator? An
<a href="Chapter1.htm#Excavators">excavator for the
earth</a> will look much different than for the moon. As
you learn more about the needs of a lunar excavator and the
lunar environment, you may not feel these excavator designs
are the best choice for lunar regolith excavation.</p>
<p>· The history of the lunar missions can be seen
at <a href="http://www.lpi.usra.edu/lunar/missions/">http://www.lpi.usra.edu/lunar/missions/</a>. This
is a really neat site. Click on any of the vehicles
(orbiters or landers) to learn more about that
mission. Look at the LCROSS and LRO missions scheduled for
late in 2008, which are intended to look for water in the
lunar craters. When NASA next sends humans to the moon, it
will be flying the Ares launch vehicle (the rocket) attached
to the Crew Exploration Vehicle (CEV) named Orion. </p>
<p>· The
<a href="Chapter1.htm#LRV2">lunar rover</a> or
"moon buggy" operated
on the surface of the moon which astronauts drove almost 7
km from the lander. A lot can be learned from successful
space systems of the past and applied to future designs. <a href="Chapter6.htm#Chapter6">Chapter
6</a> goes into the <a href="Chapter6.htm#TheLunarRovers">
details of the design of the lunar rover</a> .</p>
<p>· Much of the future lunar base will be
constructed by robots like "<a href="Chapter1.htm#robotsandvehicles">robonaut</a>"
and "<a href="Chapter1.htm#Centaur">centaur</a>". The
future rover may look like the "<a href="Chapter1.htm#chariot2">chariot</a>"</p>
<p>· A
<a href="Chapter1.htm#LunarBaseEagle">lunar base architecture</a> (base layout) at the
lunar equator is shown in Chapter 1. Location
1 is a pit where regolith has been excavated, and brought by
a hauler (2) to a processing plant (3) where oxygen is
extracted from the regolith. Other parts of the base
include a nuclear reactor (4), habitat and airlocks (5),
radio tower (6), dish antenna (7), radiators (8) and (9),
fuel cells (10) and Ga-As photovoltaic solar cell arrays
(11).</p>
<p>· A
<a href="Chapter1.htm#lunarbaseburke">base at a pole</a>
can take advantage of continuous light on the top of
mountains for continuous solar power, and cold craters which
may contain hydrogen as possibly water ice. </p>
<p>· To further that direction the NASA’s
Exploration Systems Mission Directorate (ESMD) <a href="http://www.nasa.gov/directorates/esmd/home/index.html">http://www.nasa.gov/directorates/esmd/home/index.html</a> is
dedicated to creating a "constellation of new capabilities,
supporting technologies and foundational research that
enables sustained and affordable human and robotic
exploration". </p>
<p>· <b><span lang="EN">ITAR is the
International Traffic in Arms Regulations</span></b><span lang="EN"> (<b>ITAR</b>). It
is a law and punishable with fines and imprisonment if
violated. Its purpose is to control the export and import of
defense-related articles and services, which often includes
work on NASA projects. Designs, test data, software codes,
etc. should not be shared with non-US citizens. Or, if you
have access to such data you are not allowed to share it
with non-US citizens. </span></p>
<h3><a name="LunarPhysics">Lunar Physics – Background
Information from Chapter 5 </a></h3>
<p><a href="Chapter5.htm#GravityandLunarVacuum">Lunar Gravity and Lunar Vacuum</a><o:p></o:p></p>
<p>Gravitation acceleration on the moon’s surface is 1.622
m/sec<sup>2</sup>, or about 1/6 that of
earth. Without an atmosphere the surface of
the moon has almost no pressure that an atmosphere would
create, and is classified as a "hard vacuum". </p>
<p><i class="style8">
<a href="Chapter5.htm#LunarDayandNight">Lunar Day and Night</a> </p>
<p>The lunar day and night each last about 14 earth days, except
for the poles. For ½ the year at the poles, the sun
is barely above the horizon. For the other half, the sun is
barely below the horizon.</p>
<p>
<img border="0" height="315" src="SiteImageFiles/Introduction/image015.jpg" v:shapes="Picture_x0020_5" width="575" /></p>
<p>Figure 6 Because of the moon’s small spin angle
variation, the sun’s elevation varies between +/- 1°32’
above and below the horizon near the lunar poles. High
mountains on the shadow side in the figure can be
perpetually sunlit, and craters on the sun side in the
figure can be
perpetually dark.</p>
<p><i class="style8"><a href="Chapter5.htm#Radiatation">Radiation </a></p>
<p>Radiation striking the moon includes
<span class="style14">electromagnetic wave radiation</span> that is
classified and characterized by a wave and its frequency,
and includes visible light. A second form of
radiation is <span class="style14">energized particulate radiation.</span>
Radiation not only affects temperature. The more
energetic radiation of either form can ionize material, degrading
performance and reducing useful life. Humans,
organic materials (including plastics and composites) and
electronic equipment are particularly susceptible and will
need to be protected. The sources of the
radiation include Solar Wind, Solar Cosmic Rays from Solar
Particle Events (SPE), and Galactic Cosmic Rays (GCR). </p>
<p><i class="style8">
<a href="Chapter5.htm#SurfaceTemperature">Surface Temperature</a></p>
<table border="0" cellpadding="0" cellspacing="0" width="512">
<tr>
<td nowrap valign="bottom" width="64">
<p>
</p>
</td>
<td nowrap valign="bottom" width="64">
<p>
</p>
</td>
<td colspan="3" nowrap valign="bottom" width="192">
<p align="center">
Daytime High</p>
</td>
<td colspan="3" nowrap valign="bottom" width="192">
<p align="center">
Nighttime Low</p>
</td>
</tr>
<tr>
<td nowrap valign="bottom">
<p>
</p>
</td>
<td nowrap valign="bottom">
<p>
</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°C</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°K</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°F</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°C</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°K</p>
</td>
<td nowrap valign="bottom">
<p align="center">
°F</p>
</td>
</tr>
<tr>
<td colspan="2" nowrap valign="bottom">
<p>
Mean Surface</p>
</td>
<td nowrap valign="bottom">
<p align="right">
107</p>
</td>
<td nowrap valign="bottom">
<p align="right">
380</p>
</td>
<td nowrap valign="bottom">
<p align="right">
225</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-153</p>
</td>
<td nowrap valign="bottom">
<p align="right">
120</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-243</p>
</td>
</tr>
<tr>
<td colspan="2" nowrap valign="bottom">
<p>
Equator <span class="style7">(0° Latitude)</span></p>
</td>
<td nowrap valign="bottom">
<p align="right">
122</p>
</td>
<td nowrap valign="bottom">
<p align="right">
395</p>
</td>
<td nowrap valign="bottom">
<p align="right">
252</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-158</p>
</td>
<td nowrap valign="bottom">
<p align="right">
115</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-252</p>
</td>
</tr>
<tr>
<td colspan="2" nowrap valign="bottom">
<p>
Mid-Latitudes</p>
</td>
<td nowrap valign="bottom">
<p align="right">
77</p>
</td>
<td nowrap valign="bottom">
<p align="right">
350</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
171</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-143</p>
</td>
<td nowrap valign="bottom" class="style3">
130</td>
<td nowrap valign="bottom">
<p class="style3">
-225</p>
</td>
</tr>
<tr>
<td colspan="2" nowrap valign="bottom">
<p>
Poles</p>
</td>
<td nowrap valign="bottom">
<p align="right">
-43</p>
</td>
<td nowrap valign="bottom" class="style3">
230</td>
<td nowrap valign="bottom">
<p align="right">
-45</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-63</p>
</td>
<td nowrap valign="bottom">
<p align="right">
210</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-81</p>
</td>
</tr>
<tr>
<td colspan="2" nowrap valign="bottom">
<p>
Dark Polar Crater</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-233</p>
</td>
<td nowrap valign="bottom">
<p align="right">
40</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-387</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-233</p>
</td>
<td nowrap valign="bottom">
<p align="right">
40</p>
</td>
<td nowrap valign="bottom">
<p class="style3">
-387</p>
</td>
</tr>
</table>
<p><o:p> </o:p>The above table is the
temperature of the surface of the regolith. Notice
the highest high temperature (at the equator) and the
lowest low (in a dark polar crater). During the day
the temperature of exposed equipment could be quite
different from the surface temperature. An
excavator's temperature on the shaded side will be
significantly lower than on the sunny
side. Design issues include thermal stresses and thermal
distortions, brittle failure, and the possibility of
temperatures outside the useful range for electronics and batteries.
The chapter on <a href="Chapter7.htm#Chapter7">
thermal control</a> was written to help deal with
temperature issues. </p>
<p><o:p> </o:p><i class="style8"><a href="Chapter5.htm#Micrometeoroids">Micrometeoroids</a></p>
<p>Micrometeoroids are meteoroids (naturally occurring solid
bodies traveling through space) that are less than 1mm
diameter, and based on their average density their mass will
be less than .01 g. The hit the moon at high
velocity and could damage equipment if large enough.</p>
<p><o:p> </o:p><i class="style8"><a href="Chapter5.htm#Regolith">Regolith</a></p>
<p>Neil Armstrong, as he stepped onto the moon,
stated:</p>
<p><em>"the surface is fine and powdery. I can pick it up
loosely with my toes. It does adhere in fine layers like
powdered charcoal to the sole and sides of my boots. I only
go in a small fraction of an inch. Maybe an eighth of an
inch, but I can see the footprints on my boots and the
treads in the sandy particles"</em><o:p></o:p></p>
</i><i>
<ul class="style19">
<li>Lunar
regolith</i><i class="style8"> refers to all the fragmented rock material that
covers the moon. <em>Lunar soil</em> is technically regolith
excluding rocks larger than 1 cm in size. <em>Lunar dust</em> is
technically defined as having particle sizes less the 20 μm
with a bulk density of 1.5 g/cm<sup>3</sup>.</li>
<li>The thickness of regolith layer is estimated to
be <span lang="EN">4-5
meters thick in mare regions (lunar planes) and 10-15 m in
older highland regions (plains of higher elevation than the