Game Killer/Game_Killer.bin/911.WATER.DOC

Text File | 1990-05-25 | 17KB | 292 lines

MARTIAN COLONY WATER SIMULATOR

by Alan Meiss,

copyright 1989



Background

     The Martian Colony Water Simulator is the product of the 1989 Engineering
Design Student Challenge, a competition recently held at Purdue University,
sponsored by the Engineering Student Council and the General Electric
corporation.  Students formed teams with members from a variety of engineering
disciplines, with the purpose of creating a general plan for a manned outpost
on the planet Mars, and then selecting a particular subsystem of such a colony
for in-depth examination, such as power systems, construction, materials,
transportation, and so forth.  My team after much deliberation selected the
water acclamation and distribution subsystem for concentrated study, and the
Water Simulator is the centerpiece of a project that received first place in
the competition.
     Though full appreciation of the simulation may be difficult without the
text of the competition report, I've chosen to release the program for the
benefit of any interested in the subject material and/or the competition.
The entire empirical basis of the simulation cannot be detailed here, but I'll
try to make clear the purpose and function of the simulation, and how the user
can manipulate and interpret its various elements.



Running the Simulation

     The program consists of the following files:

WATER.EXE          The simulator.
WATER.PIC          Simulation graphics.
TITLE.PIC          Title screen.
NUM.DAT            Some more graphics information.
WATER.DOC          What you're now reading.

Note that the graphics files are necessary to run the program.
     To run the simulation, enter water and hit return.  The title will appear
shortly, and, after a keypress, you will be asked to choose one of four
initial conditions for simulation; option two serves as a good example (these
will be explained shortly).



What the Display Means

     The display you see when the simulation is running is fairly complex, and
rather bewildering without some explanation.  The schematic presented on the
screen is an abstract representation of the water distribution system of the
hypothetical colony.  Each major water reservoir or significant use in the
system (described later) is represented on the screen by a shape; circles
represent storage facilities, rectangles indicate processors or uses, and
cloud shapes are atmospheric concentrations.  Connecting these are lines
representing pipes that show where water can flow between the various
elements, with red arrows indicating the direction of flow.  Dashed lines on
the right side of the screen indicate the paths of evaporation of water.
Valves along the "pipe" connections are marked by blue shapes; all are open as
the simulation begins.
     The simulation time progresses in minutes, about 10 simulation minutes to
one real-time second on a turbo-speed (8Mhz) computer.  The elapsed time is
displayed in a box in the lower left; note that it is based on the 24 hour
Earth day rather than the slightly longer Martian day.
     In most of the labelled shapes representing the reservoirs, processors,
and areas of use, you will see numbers in smaller rectangles that indicate how
many of each particular unit are involved in the system; for example, a 5 in
the grey storage tank area would indicate that 5 storage tanks are available
to hold water, and a 4 in the humidifier area would indicate that 4
humidifying units are currently engaged in the system.  Below this in most
elements are two white brackets, each set containing a blue bar that moves
slowly to indicate water capacity; the area between the brackets represents
the total water holding or processing capacity of that part of the system, and
the blue bar indicates what fraction is filled.  For example, a very short bar
indicates the presense of little water, and a long bar much water.  A
completely filled bar between the two brackets would thus indicate completely
filled capacity.  As water flows through the system, the various bars with
shift as water levels change.
     Keep in mind the abstract nature of the arrangement shown for the system.
Like a circuit diagram or a flow chart (so to speak), it simply shows the
relationships between units in the system, not the actual placement or
geometry that would be used in laying out the water units in the settlement.



What It's Doing

     What you see when running the simulation and watching the display is a
continuous series of transfers of imaginary "water" between the elements of
the system that forms a circular distribution cycle, where water is stored,
processed, used, collected, purified and recycling, and again stored, with
supplemental water input from the Martian environment.  The computer acts as a
"water accountant", transferring amounts of water each minute between the
various units operating in the system.  There are about 100 different flows
occurring each minute in the system (many described later), and each is
represented by some transfer of water between the units or applications, the
large shapes you see on the screen.  The computer knows what quantities to
transfer between successive elements each minute for each flow, for example,
how much water to send to the hydroponics from grey storage or how much to
send to the colonists' showers.
     A considerable amount of judgement is made by the computer in performing
these transfers; no flows are made if the water is unavailable or the next
unit is full, preventing spills or sinks.  There is also a small amount of
active regulation done; the computer will manipulate valves to balance the
content of the hydroponics section and the water vapor content of the colony's
internal atmosphere (assumed 40% relative humidity), the optimal capacities of
which are indicated by tick-marks on their capacity bars.



The Functions of the Elements in the System

     Here I'll tell briefly the functions of each of the elements in the
system, beginning with the grey water storage tanks and proceeding roughly
clockwise through the diagram.
     The grey water storage tanks contain water that has been cleaned well
enough for agricultural use or washing, but is not intended for consumption
(drinking) by humans.  Total cleaning of all the colony's water to the point
where it would be drinkable would be an incredible drain of resources, as only
a small fraction is actually ingested, and many applications do not require
pure water.  All storage tank in the system envisioned by our team are spheres
of one meter radius, as spheres were calculated to require the least amount of
material for storage of a given amount of water.
     The "TIME" purifier prepares that portion of the water that must be clean
enough for human consumption or possible laboratory use.  TIME is an acronym
for Thermoelectric Integrated Membrane Evaporation system, a complex purifying
apparatus that filters, distills, and treats the input grey water. (The
simulation treats the TIME unit simply as a box with water moving in and out,
not modelling the complicated processes within it.)  Pure water thus produced
is then stored until required in the pure storage tanks.
     Human water use is a general category that includes more than a dozen
different flows, not only drinking and washing uses, but also subtler flows
such as latent water absorbed while bathing and water evaporation from laundry.
The direct human water uses follow a schedule; rather than having colonists
consume water at a uniform rate throughout the day, demand is highest during
meal times and minimal during early morning, and the schedule is adjusted for
the slightly longer Martian day.  It should be noted that, while a realistic
colony would likely involve 10-20 settlers initially, our design team, freed
from economic constraints by contest rules, postulated an (ambitious) 500
person settlement, the figure which the simulation is (flexibly) based on.
     Industrial use introduces a random variable into the simulation.  Such
uses would involve research and construction applications that are not
definite, would change with the colony's needs, and might place erratic
demands upon the system.  Thus the inputs to and from this element are
conducted randomly, with red markers indicating when water is flowing through
the two input and one output connections.
     The hydroponics section, where the colony's vegetarian diet is produced
(sorry, steak lovers), is a significant water reservoir.  The system the team
envisioned for hydroponics is one named "Phytofarm", a privately developed
conveyor system in which plants mature quickly and efficiently, currently in
use in an Illinois facility and being investigated for space colony
applications.  The water in this section is actively balanced by the computer,
as a fairly constant level is needed.
     Inputs into the colony's internal atmosphere consist of evaporation in
the form of water vapor.  Surpisingly, this is the major water concentration
in the entire system, aside from storage;  bringing the air to 40% humidity
requires an enormous amount of water.  This content is adjusted
(automatically) by the humidity control system, whose direction of operation
is indicated by a red arrow above the respective box; a left arrow indicates
dehumidification and output to storage, a right arrow humidification and
release of water vapor into the internal atmosphere.  Because little water
vapor is lost from the largely sealed colony into the outside Martian
environment, the primary task of the humidity control system eventually
becomes dehumidification, as human respiration constantly introduces water
vapor.
     Wastes from these applications are collected in waste storage tanks, and
then introduced into the slow sand filter.  This unit filters waste and sewage
through sand columns, and performs general treatment to prevent bacterial and
chemical contamination.  Water thus treat is input to storage as fresh grey
water, and the cycle again commences.
     The atmospheric compressors provide a small amount of water to replenish
the system by condensing the thin Martian atmosphere during the local night.
This, however, is only regarded as a supplement; given present knowledge, our
team planned that the bulk of the colony's water would be brought with them
and scrupulously conserved.  While significant amounts of Martian water are
thought to lie in subsurface permafrost, the northern polar ice cap, and
chemical water of hydration in soil, these are all hypothetical sources; it
would be reckless without more definite information to propose them as primary
sources, as their use is still a subject of (vital) research.  The
condensation of atmospheric water vapor, while providing relatively small
input, is nonetheless a proven and measureable source, and thus was
tentatively chosen for our design.
     A final element, airlock ingassing, is included.  It would be foolish to
release colony atmosphere to the environment when opening airlocks, given the
great amount of water it contains, and thus this air is retrieved, and
considered as input to the compressors (for conceptual ease).



Simulation Commands:  How to Run the Show

     Many options are available to you to change the parameters of the
simulation and direct the flow of the system.  The following commands are
supported:

   v - Switch valve.  Each blue valve is labelled with a number and can be
toggled on or off; press v, and then enter the valve's number (preface single
digit valves with a zero, for example, type "v" and then "05" to switch valve
five.)  A black square marks a shut valve, solid blue open.


   a,f,g,h,p,s,t,u - Increment/decrement units engaged in the system.
Elements that have quantities shown in attached boxes can be changed by
pressing the letter highlighted in red in that particular element's label.
The sign after the word "mod" in the lower right indicates whether units will
be added or removed.  Note that when you change the number of units available
of a particular element, you change that element's water storage/processing
capacity, and the blue bar may jump abruptly to reflect this recalculation.
Also, you can't remove elements that are holding water, ie, removing an
element and leaving greater than 100% filled capacity in those left.

   +,- - Pressing plus or minus changes the "mod" value in the lower right,
which determines whether units will be added or removed.

   Shift + letter - Pressing, simultaneously, shift and any of the letters
highlighted in red will bring up a graph of a particular element's water usage
with time and pause the simulation.  Pressing the space bar will let the
simulation proceed and keep the graph window open as a moving "chart
recorder"; any other key will remove the graph and proceed.  The last 50
values of each element's fractional capacity are displayed by the graph.

   r - Change sampling rate for the graphs.  This number, displayed in the far
lower right, shows how many minutes elapse between the content values that are
saved for each element, and can be varied between 1 and 9 minutes.  A large
number will in effect compress the graphs, as data is then taken less often.
Sampling every minute is the default.

   q - quit the program, with the option of restarting.



Miscellaneous

     Obviously this documentation cannot serve as a full treatment of the
subject, nor can the simulation be regarded as a concrete plan for
implementing such a water system.  It does, however, provide an interesting
conceptual model of such a system, and endeavours to be as accurate as
possible.  Many assumptions are made, such as instantaneous transfer between
units, negligible water content of pipes, and a rough estimate of colony
atmospheric volume.  The bulk of the program, however, is firmly founded in
extensive empirical research, and can be used to predict the relationships
between units and areas where increased/decreased capacity is needed in
response to changing conditions.  It should at least prove intriguing for
those interested in such things, and give some ideas for anyone involved in
writing simulations with human-user interfaces.
     I hope you enjoy the program, and find it of some interest.  If you have
questions or comments about the program, the project, or the competition in
which it was entered, I can be reached at the addresses below.  I would be
happy to provide copies of the accompanying full report and program source
were it not for the fact that both are rather lengthy, and the report is
stuck, at least for now, in MacWrite format on a Macintosh disk.  I cannot
promise speedy reply with a full class load going on, but if you are
particularly interested in these materials, arrangements can be made for
postage and so forth.

Home:   Alan Meiss
        2626 Parkwood Drive
        Speedway, IN  46224

Current Campus:   Box 278, Shreve Hall
                  Purdue University
                  W. Lafayette, IN  47906       (may change)

Internet, etc:   [e-mail]       (perhaps swiftest route)



Anecdotal

     As with most such things, work proceeds most feverishly as a deadline
looms closer, and, believe it or not, this simulation was written from scratch
in about two or three painful weeks, the bulk in three days of a sacrificed
October break.
     Bugs after release are probably a programmer's worst nightmare, all the
more so if they occur during presentation of a program.  One of the project's
exhibitions was made at the Midwest Space Development Conference held at
Purdue, and I had to give a presentation of the simulation for an audience.
Time was tight, and we had just long enough to set up a teammate's computer,
start the program running, and shut the monitor off before even seeing the
title screen.  Despite having made a few code changes only an hour before, I
had the harrowing task of flipping the monitor on and nonchalantly proceeding
with my talk, hoping that the program was running successfully and not
presenting "ERROR AT ..." to the audience.  It worked fine, but it was a
nerve-wracking leap of faith to put so much trust in one's own program.

Alan Meiss, 1-5-89