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In this paper we demonstrate that the introduction of Millers Living Systems Theory
categories:
Provides an alternate way to decompose system requirements based on living systemsfunctions, and
Provides a new way to use UML based functional decomposition to model biological
functions.
Living System Theory (LST) oriented functional decompositions are applied in this paper
to a number of space environmental control and life support systems (ECLSS), namely:
In the transportation habitat, or Transhab context,
In a Martian surface habitat, or Surfacehab context,
In an extra-vehicular mobility unit, or EMU spacewalking context, and
In a surface mobility unit or SMU Martian surface exploration suit context.
The Application of Hatley-Pirbhai (HP) Diagrams to LST Categories are also reviewed inthis paper as a way to sort LST categories as input, processing, and output activities for
both Mass-Energy (ME) categories and Information Processing (IP) categories.
Finally, a subset of Millers five flows are examined for their utility in this paper,
including mission directed personnel and information flows in the mission context, as
well as Mass-Energy flows in local contexts, i.e. in the Transhab and Surfacehabcontexts.
1.1 The 20 Categories of Living Systems Theory (LST)
Table 1.1-1 presents the LST categories as they are currently understood. [1,4] Miller had
initially conceived of and introduced a formal symbology set [2] that included a different
symbol for each functional category, so that schematics of living systems might becreated, but such schematics were too obscure to ever find widespread use. Therefore we
introduce a set of 3 letter abbreviations, or trigraphs [3], also shown in table 1.1-1, which
will be used throughout the remainder of this paper to represent these categories in blockdiagrams, schematics, and flowcharts. They are designated with capital letters in square
brackets, as in the example [PRD].
LST functional categories are of these three types: categories that process matter andenergy, categories that process information, and categories that process both matter-
energy and information. One may readily observe the utility of such categories to the
human space flight, as they are useful for mapping the flows of matter, energy, and
information into and out of human living quarters. To some extent we see all of theseprocesses in play with any human occupied systems, but they are especially appropriate
for highly isolated and well defined systems such as a space station or space explorationvehicle. Why use LST categories at all? Utility is derived because a staffed facility is a
living thing, an extended version of a life form, and in that very real sense there is value
in this form of biologically oriented functional analysis, as we will see in the remainderof this paper.
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Table 1.1-1, Living System Theory (LST) Categories [1,4]
1.2 Mass-Energy Handling Categories
In his work Applications of Living Systems Theory to Life in Space [2] James Miller
discussed applying the five flows, or transmissions, in living systems to spaceflight.Those five flows are matter, energy, information, people, and money and are depicted in
the example of the ISS as shown in figure 1.2-1. From an engineering point of view, we
will largely ignore two of these flows: people flow, which is of more interest to
operational planners, and capital flow, or what Miller simply calls money flow. Whilethis is of enormous interest from a financial planning point of view to NASA, sovereign
treasuries, and private funding organizations such as the Mars Initiative, it is beyond the
scope of the present paper.
The flows remaining for detailed engineering study are matter flows, energy flows, and
information flows. Let us first examine matter flows. Matter will enter human occupiedliving spaces via the category of ingestion [ING]. Ingestion may occur in a number of
different ways: from an exterior point of view new assemblies that arrive on orbit are
attached or aggregated via either robotic control [MOT], or via human intervention[PRD] using spacewalks [MOT] to connect new elements to the exterior support structure
[SUP]. The second type of ingestion occurs via an airlock, in the case where matter is
Icon Trigraph Category Name Icon Trigraph Category Name
MATTER-ENERGY LST CATEGORIES
ING Ingestor STR ME Storage
DST Distributor EXT Extruder
CNV Convertor MOT Motor
PRD Producer SUP Supporter
INFO-PROCESSING LST CATEGORIES
INT Input Transducer MEM Memory
ITL Internal Transducer ASC Associator
DCD Decoder DEC Decider
TIM Timer ECD Encoder
NET Network OUT Output Transducer
BOTH M-E AND INFO LST CATEGORIES
BND Boundary REP Reproducer
Icon Trigraph Category Name Icon Trigraph Category Name
MATTER-ENERGY LST CATEGORIES
ING Ingestor STR ME Storage
DST Distributor EXT Extruder
CNV Convertor MOT Motor
PRD Producer SUP Supporter
INFO-PROCESSING LST CATEGORIES
INT Input Transducer MEM Memory
ITL Internal Transducer ASC Associator
DCD Decoder DEC Decider
TIM Timer ECD Encoder
NET Network OUT Output Transducer
BOTH M-E AND INFO LST CATEGORIES
BND Boundary REP Reproducer
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intended to be deployed and distributed [DST] within habitation interior spaces.
Personnel ingress from an EVA would proceed through such an airlock.
Figure 1.2-1, The Application of LST to the ISS [2]
Matter may also be expelled, or in the parlance of LST, extruded [EXT]. Extrusions may
be of any phase of matter, and might range in size from returned experimental apparatusthat is sent out on otherwise empty return trips of supply vessels, to the gaseous release of
waste products from air treatment processes. EVA egress would also fit the [EXT]
category of functionality.
Energy flow may be treated similarly. In this case energy is ingested for instance in the
solar panels, is converted [CNV] to electricity, and is then distributed [DST] to energy
consumers throughout the living quarters in question. Waste heat not converted to useful
work is collected via circulating coolant and is expelled through radiative panels thattransfer energy via thermal photon radiation directly into space as an extrusion [EXT].
Energy may also be stored, [STR] chemically in batteries or in the form of propellant, ormechanically in momentum wheels, and may be applied for motor related activities
[MOT], for instance in attitude control and station keeping.
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1.3 Information Processing Categories
Let us now turn to an analysis of information flow, which is treated by the second group
of LST categories, information categories, of which the author suggests also
simultaneously represents a categorization of communication functions. After all, howdoes information get in and out of an information enclave [BND] other than
communication? Communication represents the onboard and offboard flow ofinformation. Therefore we understand the information categories to include
telecommunications as well, where receivers are understood to represent special cases of
input transducers [INT], and transmitters are understood to represent special cases ofoutput transducers [OUT]. Within the enclave [BND], the onboard information flows
over a network [NET], regulated by a clock or timer [TIM]. Internal housekeeping data
may be added into the data stream via internal transducers [ITL], and for instance analog
data may be ingested into digital via decoders [DCD] or created from digital via encoders[ECD]. Association [ASC] may be preprogrammed in advance via software code, or may
be determined in realtime via a human presence [DEC].
It is worth pausing at this point to recognize the special role the human has in the activity
of human spaceflight. The human is an extension of a productive presence [PRD] in the
domain of matter and energy, and represents a local deciding presence [DEC] in theinformation domain. The human presence is tying together both the mass-energy
dimensions and the information dimensions at the cognitive peak of mass-energy and
information control loops by simultaneously fulfilling both the roles of producer [PRD]
and decider [DEC]. Due to the data bandwidth communicated and then time criticality ofthat data, or control bandwidth, a local presence for the control loops of all of these
dimensions (mass, energy, and data) is the main contribution of a human presence in
space exploration, and is an additional rationale for the inclusion of the local in situhuman element in spaceflight activities. This area could benefit from further study by
quantifying the impact of [PRD] and [DEC] roles on needed control loops in HSF
mission control areas with and without a local human presence.
1.4 Categories that Process Mass-Energy and Information
Finally we discuss the last two LST categories, those that process both matter-energy andinformation. The first of these is the boundary [BND], the dividing line that separates any
systems interior from its exterior. This is important from a matter-energy point of view
in that it delineates and defines what constitutes system structures and energy contentfrom external structures and energy sources. From an information point of view it divides
the information that resides within the system from the information not contained by (or
known by) the system in question. The second and final category that processes mass,energy, and information is reproduction [REP]. For a system to reproduce itself in must
reproduce not only a subset of the mass and energy it contains, but also a critical subset
of the information it contains, that subset required to perpetuate life.
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2. LST CONTEXT DIAGRAMS FOR MISSIONS TO MARS
2.1 Problem Statement
How can LST categories help with requirements development? Like any other functional
decomposition LST categories serve as a useful inventory of possible needs of a given
system. In the case of LST, the typical design patterns associated with supporting andsustaining life will give rise to needs or requirements in nearly all of these categories.
The first step in revealing requirements through functional decomposition is to define the
context in which the system will operate, which in turn helps to reveal the system itself.
For the case of missions to Mars, four contexts are examined: a deep space Transhabcontext in section 2.2, a Mars Surfacehab context in section 2.3, a deep space EMU
spacewalking context in section 2.4.1, and a Martian surface SMU exploration suit
context in section 2.4.2.
2.2 Transhab LST Context
In this section we develop the Transhab context, summarized in figure 2.2-1.
Figure 2.2-1, Transhab LST Context Diagram
We first note that there is the context of the Transhab itself in relation to both sunlit and
shaded space. Within the Transhab is the crew, which may collectively be taken togetherin relation to the Transhab. There is therefore in figure 2.2-1 two nested context
diagrams, one for the Transhab in space, and one for the crew in the Transhab.
Taking the outer context first, aside from crew ingress (not shown) there is very little
mass-energy input into the Transhab. Only solar energy is ingested [ING]. In the
Sunlit Space
Crew
Transhab
Shaded Space
SolarEnergy
Info:Com,Nav,Time,
Sensors
Info:Com,Nav,
Status
O2
H2O
Food
CO2
H2Ovaporwaste
Info:C3I
RadiativeCooling
Ventedwaste
Solidwaste
Info:C3I,CSS
C3I = Commed Cmd, Control, and IntelCSS = Commed Sensors & Status
Sunlit Space
Crew
Transhab
Shaded Space
SolarEnergy
Info:Com,Nav,Time,
Sensors
Info:Com,Nav,
Status
O2
H2O
Food
CO2
H2Ovaporwaste
Info:C3I
RadiativeCooling
Ventedwaste
Solidwaste
Info:C3I,CSS
C3I = Commed Cmd, Control, and IntelCSS = Commed Sensors & Status
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information domain communication, navigation, timing, and sensors for situational
awareness (such as cameras) need to be provided [INT].
On the output side, waste heat must be extruded [EXT] or emitted to space, and
command, control, and status information must be communicated to Martian surface
elements and back to Earth as an output [OUT].
Within the Transhab there must be a habitable boundary [BND] and structure [SUP] ofsufficient volume to maintain a living space commensurate with NASA long duration
mission standards [6]. The Transhab must supply the crew with the oxygen, water, and
food needed to sustain life. These inputs are quantified in section 4.2. Likewise the
Transhab must be able to accept waste products from the crew, including CO2, watervapor, and so on, and to the extent possible recycle these products for reuse as life
sustaining inputs, so as to minimize the need for stored provisions [STR].
2.3 Surface LST Context
Sustaining the crew on the surface of Mars is presented in the nested context diagram offigure 2.3-1 for the case of the Surfacehab.
Figure 2.3-1, Surfacehab LST Context Diagram
In dwelling on the differences between the Transhab and Surfacehab cases, we may first
note that there is now a much greater presence of resources, in the form of Martianatmosphere and regolith. These resources may be leveraged to great effect externally to
the Surfacehab in the form of a greenhouse, of potentially lesser atmospheric pressure
and at a reduced temperature, for the ingestion [ING] of organic produce. Likewise both
Martian Atmosphere
Martian Regolith
Surfacehab
Crew
SolarEnergy
Info:
Com, Nav,Time, Sensors
Info:Com,Nav,
Status
O2
H2O
Food
CO2
H2Ovaporwaste
Info:C3I
ConvectiveCooling
Ventedwaste
Solidwaste
Info:C3I,CSS
C3I = Commed Cmd, Control, and IntelCSS = Commed Sensors & Status
Atmosphere
GreenhouseFood
RegolithDerived H2O Conductive
Cooling
Martian Atmosphere
Martian Regolith
Surfacehab
Crew
SolarEnergy
Info:
Com, Nav,Time, Sensors
Info:Com,Nav,
Status
O2
H2O
Food
CO2
H2Ovaporwaste
Info:C3I
ConvectiveCooling
Ventedwaste
Solidwaste
Info:C3I,CSS
C3I = Commed Cmd, Control, and IntelCSS = Commed Sensors & Status
Atmosphere
GreenhouseFood
RegolithDerived H2O Conductive
Cooling
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atmosphere and potentially regolith may be externally preprocessed to provide many of
the life support resources needed by the Surfacehab such as H2O and O2.
On the mass-energy output side [EXT], the cooling will be simpler: rather than the space
radiators of the Transhab, exploiting the options of conductive cooling to the soil or
convective cooling to the atmosphere will greatly simplify the cooling design associated
with the thermal control of the Surfacehab.
2.4 Spacesuit Context Diagrams
The case of an astronaut in a deep space spacesuit is substantially different from the case
of a Martian surface habitant in a surface exploration suit. Context diagrams for these two
cases are therefore handled separately in sections 2.4.1 and 2.4.2.
2.4.1 EMU for use with Transhab
Figure 2.4.1-1 is the context diagram for an astronaut in an EMU. The EMU itself willneed to provide access for the astronaut, and yet must maintain pressure during the
spacewalk. Visual situational awareness must be provided, either through the use of a
visor and/or the use of cameras small with monitors or eye-projectors, (such as Google-glasses). External lighting will be required for illumination in shaded space, (not shown).
Figure 2.4.1-1, EMU LST Context Diagram
Mechanical manipulation and vectored movement must be provided and must be under
positive control from within the suit via a natural feeling interface, (such as joysticks orrollerballs). All of these functions have been demonstrated for generations by NASA, but
for Mars missions an unprecedented level of reliability and flexibility will be required, as
spares will be at a premium for mission durations that will extend into multiple years.
Sunlit Space
Shaded Space
Astronaut
Extravehicular
Mobility
Unit
Info:Com, Nav,
Time, Sensors
Access
VisualSit
Awareness
A/Vs
O2, H2O
Support,Pressure
Voice
Touch cmdw/ feedback
WasteStorage
Info:C3I
MechanicalManipulation
ThrustVectoring
Sunlit Space
Shaded Space
Astronaut
Extravehicular
Mobility
Unit
Info:Com, Nav,
Time, Sensors
Access
VisualSit
Awareness
A/Vs
O2, H2O
Support,Pressure
Voice
Touch cmdw/ feedback
WasteStorage
Info:C3I
MechanicalManipulation
ThrustVectoring
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2.4.2 SMU for use with Surfacehab
A Surface Mobility Unit (or surface exploration suit) for Mars will be challenging. Thereis less precedence for such as design. The suit must either be light enough to be able to
flex and move under human power, or it must be self-powered through the use of stored
portable battery power. It must still maintain nominal atmospheric pressure for the
occupant, and must provide the oxygen and water needed by the occupant, all whilesafely removing, immobilizing, and/or storing waste products the occupant generates for
the duration of the exploration service period.
The suit must provide all of the com, nav, visual inputs, and voice encoded outputs that
are associated with the much larger spaceborne EMU, while in a higher dust, static, andpotentially higher RF interference environment.
The suit must also be durable enough to endure the repeated mechanical manipulation
and friction contact with Martian surface features and human rated tools, while reliably
maintaining internal pressure and internal systems integrity.
Figure 2.4.2-1, SMU LST Context Diagram
Martian Atmosphere
Martian Regolith
SurfaceMobilityUnit
Surf InhabitantInfo:
Com, Nav,Time, Sensors
Access
VisualInput
A/Vs
O2, H2O
Support,Pressure
Voice
Touchcmd
WasteStorage
Info:C3I
Mechanical
Manipulation
ContactThrust
Net ThrustForce
C2O
Martian Atmosphere
Martian Regolith
SurfaceMobilityUnit
Surf InhabitantInfo:
Com, Nav,Time, Sensors
Access
VisualInput
A/Vs
O2, H2O
Support,Pressure
Voice
Touchcmd
WasteStorage
Info:C3I
Mechanical
Manipulation
ContactThrust
Net ThrustForce
C2O
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3. HATLEY-PIRBHAI (HP) TEMPLATES FOR MISSIONS TO MARS
The Hatley-Pirbhai (HP) diagram may be used to further organize functional concepts,
including Living System Theory (LST) functions, for a more coherent utilitarian view of
how functions interrelate, and for auditing the interfaces between LST functions. The
general form of an HP diagram is shown in figure 3-1.
Figure 3-1, The General Form of the Hatley-Pirbhai (HP) Diagram [5]
The Hatley-Pirbhai (HP) context diagram divides functionality according the how it
relates to system externals. It is a variant of a context diagram in the sense that it definesa system in the context of its external interfaces. Input and output processing have their
own categories, as do user facing interfaces. Inward facing internal monitoring functions
also have their own category, maintenance and self test, and all processing not engagedin either outward facing or inward facing data processing is considered to be part of
central processing.
3.1 Generalized ME HP Template
If we use the preceding guidelines to map mass-energy LST categories to HP diagrams,
we achieve the results shown in figure 3.1-1. Following the convention that inputs are on
the left, user interfaces are on top, outputs are to the right, maintenance and self test
(overhead, or inward facing) functions are on the bottom, and central processingfunctions are in the middle, figure 3.1-1 shows how matter-energy living system theory
functional categories map to an H-P context diagram.
As expected, [ING] appears on the left, and [EXT] and [REP] appear on the right. [PRD]
generally represents the user, and is shown on top, but can also be a central processingfunction. Most motorized functions [MOT] are overhead in nature, and are therefore
represented on the bottom, but can be an output as well, as in attitude control or
propulsion functions. Support [SUP], boundary [BND] and matter energy distribution
InputProcess
Central Processing
OutputProcess
User Interface Processing
Maint. and Self Test
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Figure 3.2-1, ME HP Example for Transhab ECLSS [3]
3.3 Generalized IP HP Template
If we use the preceding guidelines to map information processing LST categories to HP
diagrams, we achieve the results shown in figure 3.3-1. Input [INT] and decoding [DCD]functions appear on the left, output [OUT] and encoding [ECD] functions appear on the
right, the decider [DEC] functions here generally represent user interfaces shown on top,
and overhead functions shown on the bottom include internal transducers [ITL] andautonomous association functions [ASC]. This leaves network [NET], timing [TIM], and
memory [MEM] functions as central.
While LST categories predate the invention of the internet and were far in advance of
cloud computing architectures, the parallel to modern network based architectures isstriking. The boundary [BND] label is not included in the figure but could be thought of
as two boundaries, an outer one surrounding the entire diagram, and an inner information
assurance enclave, that includes the core functions surrounding the network [NET],memory [MEM], and time keeping function [TIM].
ING: AirRecircluation
DST: CabinAir Return
EXT: TraceContaminate
Removal
STR: Air
MOT:Cabin Air
Circ
CNV:Oxygen
Generation
PRD: AirTemp &
HumidityControl
EXT: H2Overboard
Venting
AirSupply
LSS Users: Crew
H2OSupply
ING:
Condensate
ING: UrineRecovery
STR: H2O
PRD: PotableWater
Processing
ContaminationRemoval
O2 System
EnvironmentalControlSystem
MOT:Water
Pumps
Key:
EXT: CO2Removal
Solids
STR:
Nutrition
EXT:Waste Mgt
STR:Spare
Oxygen
Input Output
User I/F
Processing
Overhead
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Inputs [INT] and outputs [OUT] are composed of communication devices and sensors,
supported by the necessary decoders [DCD] and encoders [ECD] respectively,presumably over which navigation and timing data is made available and from which nav
and timing may be derived.
The network [NET], time-keeping [TIM], and memory [MEM] reside in the inner
processing enclave, and the ECLSS monitoring [ITL] and any Kalman filtering or otherprocessing needed to derive navigation solutions [ASC] are in the housekeeping and
overhead enclave. In the user interface is the crew with their controls and displays, cast in
the role of the decision element, or decider [DEC].
4. FLOW REQUREMENTS FOR MISSIONS TO MARS
4.1 People Flow as defined by Mission Profile
Personnel flow is now briefly considered here to help bring clarity to the missioncontexts. As depicted in figure 4.1-1, the flow of personnel for the typical mission can be
divided into three mission segments: and outbound transit segment, during which theTranshab will sustain the lives of the crew, a surface visit segment, during which the
Surfacehab must sustain the crew, and the return transit segment, during which theTranshab must again be depended upon for sustenance.
Figure 4.1-1, Mission Directed Personnel Flow, Time and Distance
The periods of time over which each of these segment last will need to be integrated intime to determine the provisions and consumables required by the crew, and is heavily
distance from Earth
time
Outbound
TransitSegment
SurfaceVisit
Segment
ReturnTransit
Segment
launch
TMI burn
Mars landing
Mars ascent
Earth reentry
E M
distance from Earth
time
Outbound
TransitSegment
SurfaceVisit
Segment
ReturnTransit
Segment
launch
TMI burn
Mars landing
Mars ascent
Earth reentry
distance from Earth
time
distance from Earth
time
Outbound
TransitSegment
SurfaceVisit
Segment
ReturnTransit
Segment
launch
TMI burn
Mars landing
Mars ascent
Earth reentry
E M
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dependent on the amount of recycling that is possible in each habitat, as well as in situ
resource utilization on the Martian surface during the surface stay and possibly also forreturn transit use, if launched from the Martian surface with the returning crew.
4.2 ME Flows in the Transhab Context
Give the period of time the Transhab will be occupied during the transit segments the
mass and energy flows occurring in the Transhab will be very significant for sustainingthe lives of the crew. The major flows of mass and energy needed for ECLSS is shown in
figure 4.2-1. Collection [ING] of solar energy will be through the use of solar panels.
Typically these panels convert solar energy to voltage and current, used to chargebatteries or fuel cells for energy storage [STR]. The energy will be used to power
propulsion, ECLSS, and IP systems. Waste energy in the form of excess heat must be
disposed of via passive high emissivity radiative panels which radiate thermal photons
directly into space [EXT]. In the ECLSS context the major mass flows are the O2 to CO2loop, shown at the top, and the clean water to waster water loop shown on the bottom of
the diagram. Both loops should maximize recycling [CNV] to minimize storage [STR]requirements.
Figure 4.2-1, Mass-Energy Flows in the Transhab Context
O2, H2O, and food are the key consumables. It is necessary to quantify the consumables
needed to support a crews metabolism and resupply in order to size life support systems
and determine needed supplies. This is captured in table 4.2-1.
Sunlit SpaceTranshab
Shaded Space
CrewCrew
O2 STR CO2 CNV
EnergySTR
FoodSTR
H2OSTR
WasteCNV
Crew
INGsolarpanel EXT
otherwasteheat
EXTwasteeject
EXTradiativecooling
Sunlit SpaceTranshab
Shaded Space
CrewCrew
O2 STR CO2 CNV
EnergySTR
FoodSTR
H2OSTR
WasteCNV
Crew
INGsolarpanel EXT
otherwasteheat
EXTwasteeject
EXTradiativecooling
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Table 4.2-1, Consumables needed to support a crew [6]
Consumable Requirement (kg/person-day)
Portable Water (includes food rehydrationwater) 1.6 - 3.6
Hygiene Water (toilet, shower, clothing wash) 5 - 25
Oxygen 0.6 - 1
Buffer gas leakage 0.5 - 2
CO2 production (for removal) 0.7 - 3
Food (containing 2/3rds bound water) 1.5 - 2
Cooling water for EVAs 3.5 - 5.5 (kg/person-EVA hour)
One readily observes from the table that the range of required consumables is highly
variable, depending on the mass and metabolism of the individual astronaut, the range ofactivities they are performing, and the availability and application of various resource
handling technologies.
4.3 ME Flows in the Surface Hab Context
The mass-energy flows expected in the Surfacehab context are shown in figure 4.3-1.
Figure 4.3-1, Mass-Energy Flows in the Surfacehab Context
Martian Atmosphere
Crew
Surfacehab
Martian Regolith
Crew
O2 STR CO2 CNV
EnergySTR
FoodSTR
H2OSTR
WasteCNV
Crew
INGsolarpanel
EXTconvectivecooling
INGgreen
houseproduce
EXT
otherwasteheat
CNVsanitizer
RegolithCNV
INGmined
regolith
EXTwasteeject
Martian Atmosphere
Crew
Surfacehab
Martian Regolith
Crew
O2 STR CO2 CNV
EnergySTR
FoodSTR
H2OSTR
WasteCNV
Crew
INGsolarpanel
EXTconvectivecooling
INGgreen
houseproduce
EXT
otherwasteheat
CNVsanitizer
RegolithCNV
INGmined
regolith
EXTwasteeject
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The energy flow on Mars will be less than a comparable system on Earth due to the
reduced solar flux. The solar panels will therefore have to be scaled up accordingly. Butthe consumables picture in the Surfacehab context is considerably more promising. Due
the relatively extensive resources of the Martian atmosphere and regolith, mass flows
[ING] should be and will be substantial so as to lessen the storage requirements [STR].
While recycling [CNV] will still be important, the efficiency of the recycling will notneed to be as high given the resources available for food, water, and even potentially
oxygen replenishment.
These mass flow contexts may be further decomposed using LST functional categories asshown in figure 4.3-2 for the example of a waste treatment CNV function. Each step
depicts both the activity type, such as screening and aeration, as well as the LST
stereotype, such as [DST] and [CNV]. Ideally a UML/SysML modeling language (suchas SparxEATM) should be used for functional decomposition of this nature so that the
resultant requirements can be captured and ported to a requirements management tool
such as DOORSTM, and subsystem requirements can be shared and negotiated withbiotechnology vendors just as they are now with aerospace hardware vendors.
In this instantiation there is reclaimed water separated first and then additional treatment
applied to reclaim drinking quality water, but in practice it may simplify the process and
reduce steps to just treat all reclaimed water to drinking quality.
Figure 4.3-2, Typical Wastewater Recycling Process Flow in the Surfacehab Context
ScreeningDST
Waste CNV
(sludge to dewatering fordisinfection & disposal)
EXT H2O:Class A
reclaimedwater
EXT H2O:Drinking
qualitywater
SeparationDST
ING Raw Waste Influent
EXT solidwaste
disposal(and / or
composting)
PrimaryDisinfection
CNV
OzoneTreatment
CNV
Flocculation &Clarification
CNV
ZeeweedTM (
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5. CONCLUSIONS
From the observations, analysis, and discussions of this paper we conclude that:
There is utility in the use LST categories for modeling and developing therequirements of sustaining living systems, such as in human space flight missions,
in all their various contexts. Hatley-Pirbhai (HP) Diagrams may be useful for organizing and categorizing LST
categories in both the Mass-Energy domain and in the Information Processing
domain.
The following activities are recommended as future work areas:
Derive detailed mass, energy, and information budgets as a function of crew sizefor various Transhab and Surfacehab contexts.
Begin partitioning the context diagrams presented by splitting functionality intoservice modules and living quarters, and document the associated interfaces.
Develop dynamic models and simulations of ECLSS using Living Systems
Theory (LST) that incorporate diurnal and activity induced variations in loading. Recommend LST categories as standard functional stereotypes for UML and /or
SysML to the OMG, in order to better enable more uniform system modeling for
Human Spaceflight Systems in general, and ECLSS systems in particular.
6. ACKNOWLEDGMENTS & DISCLAIMERS
Approval for the publication of this paper by the LinQuest Corporation is gratefully
acknowledged. Disclaimer: This paper represents one approach to life support systemsmodeling and should not be construed as design guidance for ECLSS or any life support
system. The views expressed in this paper are solely the authors and do not represent the
position or views of the LinQuest Corporation, the United States Air Force, or any otherorganization.
7. REFERENCES
[1] Miller, James Grier, Living systems. (1978). New York: McGraw-Hill. ISBN 0-
87081-363-3.
[2] Miller, James Grier, Applications of Living Systems Theory to Life in Space,Presented at the NASA-NSF conference Experience in Antarctica: Applications to
Life in Space, (1987) Sunnyvale, CA: NTRS Ascension ID 93N16865.
[3] Stephenson, Gary Van, Redeployment Options for the International Space Station,
Master of Engineering Thesis, (2011) Stevens Institute of Technology.[4] Buede, Dennis M, The Engineering Design of Systems: Models and Methods. (2000).
New York: John Wiley & Sons, Inc. pp. 188-189. ISBN 0-471-28225-1.[5] Hatley, Derek, et al., (2000). Process for System Architecture and Requirements
Engineering. New York, NY: Dorset House Publishing. p. 434. ISBN 0-932633-41-2.
[6] Larson, W. J., and Pranke, L. K., Human Spaceflight Mission Analysis and Design.(2007). McGraw-Hill, Inc. p. 149, p. 459. ISBN 978-0-07-236811-6.