Pergamon

v, ww.elsevier.com/locate/actaastro

4cm A stronautica Vol 48, No. 5-12. pp. 737-765. 2001 © 2001 International Astronautical Federation. Published by Elsevier Science Ltd

Printed in Great Britain PII: S0094-5765(01)00081-9 0094-5705101 $- see front matter

SELF-SUSTAINING MARS COLONIES UTILIZING THE NORTH POLAR CAP AND THE MARTIAN ATMOSPHERE

James Powell, George Maise, and John Paniagua Plus Ultra Technologies, Inc. Shoreham, N.Y. 11786 USA

ABSTRACT A revolutionary new concept for the early establishment of robust, self-sustaining Martian colonies is described. The colonies would be located on the North Polar Cap of Mars and utilize readily available water ice and the CO, Martian atmosphere as raw materials to produce all of the propellants, fuel, air, water, plastics, food, and other supplies needed by the colony. The colonists would live in thermally insulated large, comfortable habitats under the ice surface, fully shielded from cosmic rays. The habitats and supplies would be produced by a compact, lightweight (--4 metric tons) nuclear powered robotic unit termed ALPH (Atomic Liberation of Propellant and Habitat), which would land 2 years before the colonists arrived. Using a compact, lightweight 5 MW (th) nuclear reactor/steam turbine (1 MW(e)) power source and small process units (e.g., H20 eleetrolyzer, H2 and O: liquefiers, methanator, plastic polymerizer, food producer, etc.) ALPH would stockpile many hundreds of tons of supplies in melt cavities under the ice. plus insulated habitats, to be in place and ready for use when the colonists landed. With the stockpiled supplies, the colonists would conslruct and operate rovers and flyers to explore the surface of Mars. ALPH greatly reduces the amount of Earth supplied material needed and enables large permanent colonies on Mars. It also greatly reduces human and mission risks and vastly increases the capability not only for exploration of the surrounding Martian surface, but also the ice cap itself. The North Polar Cap is at the center of the vast ancient ocean that covered much of the Martian Northern Hemisphere. Small, nuclear heated robotic probes would travel deep ( I km or more) inside the ice cap. collecting data on its internal structure, the composition and properties of the ancient Martian atmosphere, and possible evidence of ancient life forms (microfossils, traces of DNA. etc.) that were deposited either by wind or as remnants of the ancient ocean. Details of the ALPH system, which is based on existing technology, are presented. ALPH units could be developed and demonstrated on Earth ice sheets within a few years. An Earth-Mars space transport architecture is described, in which Mars produced propellant and supplies for return journeys to Earth would be lifted with relatively low AV to Mars orbit, and from there transported back to Earth orbit, enabling faster and lower cost nips from Earth to Mars. The exploration capability and quality of life in a mature Martian colony

of 500 persons located on the North Polar Cap is outlined. © 2001 International Astronautical Federation. Published by Elsevier Science Ltd.

Studies of the initial stages of the manned exploration of Mars have tended to concentrate on the "multiple mission approach," as illustrated in Figure IA. Individual missions depart from Earth to land at a specific Mars site. exploring it for a short or long period - 30 days or one and a half years depending on whether it is an opposition or conjunction class mission. Each individual mission explores a different site, with the starting point always being Earth.

The exploration of Mars. at least in its initial stages, is thus a long drawn out process involving a sequence of individual mission, each of which has to carry from Earth almost all of the supplies that it needs for a trip to Mars, the exploration itself, and the return trip to Earth. As Zubrin ~ and others have proposed, certain supplies can be produced on Mars (e.g., methane and oxygen from atmospheric CO 2, using hydrogen transported from Earth). However, the amount of supplies thus produced is modest, and does not yield a major reduction in expedition requirements.

Each mission requires lifting at least 500 metric tons into Low Earth Orbit (LEO). Moreover, mission capabilities are constrained, and mission risks increased, by the drive to minimize mission cost and launch requirements. This inevitably drives down margins on the amounts of propellants, consumables, etc. that are carded, decreases operating margins on equipment, and so on.

in the past on Earth. exploration has been the most rapid and successful when explorers have established continuously occupied bases on the new lands, and have used local resources for the bulk of their activities. The same pattern would appear to apply to Mars.

Clearly, if Mars were a habitable and hospitable world, such a pattern of exploration would be followed there. However, the absence of breathable air and water has seemed to prevent this. There has been great interest and speculation about whether or not there is water on Mars,

737

738 51.it IAF Congress

Launch Supplies

from Earth

Potential Approaches for Manned Exploration of Mars Multiple Mission Approach

Time D Next Mission

I,aunch Crev, from Earth

=l Supplies ~l and Crew

Land on -[ Mars

Explore = Local 7 Site

Crev~ Retumg to Earth

F Launch I

Supphes from [ Earth

Limitations/Constraints

• _> 500 Tons IM'LEO required per mtsston

• Minimal use of Martian resources • most supplies come from Earth

• Local exploration ofa fev, sties - no broad exploration program

• Slow pace of exploration

• Safer) mar em~ are hmtted due to mass constraint,

• .Mars cannot se~ e as a base for explorahon of the outer solar s} stem Fi_oure ]

and if so, whether it can be used to support habitats. Curiously, this fascination with finding water has virtually ignored the fact that thousands of cubic kilometers of ice are present in the North Polar regions. and readily accessible to support a colony.

Figure 1 B outlines a different exploration approach, based on the establishment of a robust, continuously staffed colony located on the North Polar Cap of Mars. In contrast to the multiple mission approach, the colon)' would be established at the beginning of the exploration of Mars. not at some point in time that occurred long after a number of individual missions. A compact, lightweight robotic factor)' unit would land on the North Polar Cap at the site of the future colony site. The robotic unit, termed ALPH (Atomic Liberation of Propellant and Habitat) would produce and stockpile essentially all of the supplies (air, water, food. fuel, etc.) plus a large reserve margin, needed for the establishment and operation of the colony before the colonists arrived. The ALPH unit would also create large cavities under the surface of the ice cap that would provide comfortable. shielded habitats for the colonists.

All of the supplies and living space would be in place when the colonists arrived, ready for use. From the stockpiled materials, the colonists would construct rovers and flyers to cart)' out a large scale manned and unmanned exploration of Mars. All portions of Mars

surface would be readily reached from the North Polar colon)', including as far away as the South Polar region. Propellants and supplies would be lifted into Mars orbit and stockpiled in a depot for return trips to Earth, Moreover, additional propellant and supplies would be transported back to a depot in high Earth orbit, to be use{ for outbound trips to Mars.

The above Earth - Mars - Earth transport architecture. plus the production on Mars of virtually of the colony's material needs, would enable the colon)' to rapidly buildup to a level of hundreds of persons with minimum IMLEO launch requirements, as compared to the multipl. mission approach. This advantage, plus the much greater exploration capabilit), make the colony approach extremely attractive for the initial stage of Mars exploration.

FEATURES OF THE NORTH POLAR COLONY CONCEPT

Figure 2 illustrates the advantages oft.he North Polar Car as the base for a Mars colony. First, and most important. there is a plentiful supply of readily accessible H20 locked up as ice. Water is the essential ingredient for a practical Mars colony. Without it, there could be no colon)', and Mars would remain a dead world, visited occasionally by small exploration missions from Earth. With it, and the Martian CO: atlnosphere, vinuall) all of

51st IAF Congress

Potential Approaches for Manned Exploration of Mars (conltnued)

Mars Colony Approach

• Time

739

& Mamufaclures I ~ 1 Mike I ~ l Be~n t.ar~ F'Jqld°r~m°no(Colony RobaucFaclmfiom ~ h s ~ l , ~ , , ~ I s.m,t,. I Fiyers~o, ers I r-~l Scale

Fu'~ ColomsXs / Addl / from ~ ~" C olomm

From Earth

Potion of Colorusts Pomon of Return to Ea~ Colonists ~" - - y

Renan to Earth

Advantages Colony ts largely ~lfsustaming with regard to supplies (propellants. fuels, air. constructio, materials, f0od, etc ) I]

• Minimal r,u, tmal needed from Eau~ once ALPH factories slart opemm8

- Eembl~ Ixoad and rapid ecldonttim program * Robust cokmy with high rmu~n of,u, fe~, " P1~Pelllxit from Mars enables z ~ tTanSpml of colomsts from Earth Addl .--.~4b, " Mars can k,. ~ for explormion ofouler solar system Colomm

From Each

I C~tmu~ E xplorauon

Figure 1

ColomStSBack I Send Propellant Expand to Eanl~ .Mars Traxl, Spon -'~

Earth OrSa

91 . . . . . . . . . . . Potion o f

Colorum Renan

Plenl,hJl ] Marital1

Resources

Habit|is [

Advantages of the North Polar Cap as a Site for a Mars Colony

I Lasd'. A s~,esslble }! .0 Ice

S, uh- surface Melt Ca~.ttlts

Pro'. tde

~ Propella~L~ I H:. 0:. C tG D

114) Plus Fuels IC H.4. CH~. OH,

L Mar~Aun ~ Brcad~beA.rl%.. O:J -1 ICr~ & '~dPlus

Enere.. '~ lelds "" Con~ructton Ma|ena.s ( Plasltcs.

Melais. Composdles p

Food, Prolem. Fats. Carbohydrales}

Spactous Comfomlble Thermally [ ~ J w lmul'ted L'v'nll QmiMers

I ~ " Shtetd,ng From Cosmic Rays(<l Rein Yr.

Underground Lakes for Food Productton a Fish. Shrimp. elc I lind Recreation

Sctemufic Kno~ledet

I Ice ( ores Pro,.le ~lme Histor) of

Marian

.-Mmosphere (Composmon. Meleorolo~ n

Geology. (Dust Composttton. etc t

Bombardment t Meteors [including Eanhl ~,o!ar and Cosmic Aclwit). elc t

Biolog) t Resndual and %'md Bome Mt,:'o::ssds, DNA Traces. etc

Figure 2

740 51st 1.4F Congr¢~.s

the materials needed to comfortably support a major colony can be synthesized.

Moreover, what at first sight appears to be a drawback - the presence of H20 as an ice sheet, rather than as underground water - is a major advantage. It enables robotic units to land and process H~O from the ice into materials that can be easily stored in melt cavities created under the surface, as well as shielded habitats for the colonists when they land. Having the supplies and habitats already in place when the colonists land, rather then having to make them after they land, is a tremendous advantage. It decreases mission risk, since the colonists will not leave Earth until they know that the supplies and habitats are in place, and it greatly reduces the work demands on the colonists when they land, enabling them to concentrate on exploration.

In an odd way, Mars is a mirror image of Earth. On Earth, the vast ice sheets of Antarctica and Greenland, and the pack ice of the Arctic Ocean, are deserts, with the fertile continents being the oases. It is no wonder that these ice deserts were the last places on Earth to be explored.

On Mars, however, the North Polar Cap is the oasis, and the surrounding regions of the planet are its deserts. Logically, it appears wiser to explore the deserts from a robust, capable base located in the oasis, than attempting to set up camps in the inhospitable deserts. Moreover. as illustrated in Figure 2, the North Polar Cap appears to be a veD' attractive site for scientific research b) itself. Samples obtained from inside the ice sheet will provide data on the composition and meteorology of the Martian atmosphere over millions of years, on the geology of the wind borne dust collected by the ice cap, on ancient solar w~nd and cosmic ra) activit), and possibly, evidence of life on Mars, through microtbssils, DNA traces, etc.

The ke) technology elements needed to achieve a successful colony on the North Polar Cap are summarized in Figure 3. First, more detailed information on the internal structure of the ice cap. and of possible landing sites, is needed. There appears to be a relatively small region of pure H,O ice in the cap. This region, estimated to be 837 km" in area and at least 1 km thick -', is surrounded b.v hundreds of thousands of square kilometers of layered polar terrain. Eroded channels in this region exhibit an internal structure of alternating layers of ice and dust. Typically. the ice layers are on the order of I 0 to 30 meters thick, and are separated b.~ thinner layers of dust3 material, probably an ice-dust composite.

Quantitative data on the dust content in this portion of the Ice Cap. both locally and overall, is lacking. Can" :' assumes for purposes of estimating the total inventor) of

H~O on Mars that the average dust/ice content is 50°/o/50%. However, visual indications suggest that the dust content is substantially less than 50%; also, there probably is considerable spatial variation, since one would expect that the more northerly regions would have a smaller dust content, since most of the dust would have been trapped out at lower latitudes.

In general, having a dust)' ice cap rather than a pure ice one would not pose an)' serious problems for the colon)', as long as it did not hinder access to or processing the ice. Dust contents as high as 20 to 30% by volume would not appear to be a problem, since melt channels and cavities could still be created inside the ice sheet. The dust would be filtered or cenlrifuged out, and the purified water then used to make propellants, food. oxygen, etc.

The presence of dust in the ice cap would actuall) be beneficial, since it would be used as a feed material for processes to make aluminum, iron, and other metals, as well as ceramics based on silica, magnesia, etc. This would eliminate the need to make long trips to collect such feed material from sites at lower latitudes.

B,,, landing compact, ultra lightweight mobile robotic devices on the ice cap prior to the establishment of the colony, one would be able to gather detailed data on the internal structure of the cap, including the content and composition of the dust, and how it varied vertically and horizontally within the cap. The small robotic devices. termed MICE (Mars Ice Cap Explorer), would travel verticall) and horizontally through melt channels inside the ice cap. collecting data that would be transmitted back to Earth. Details of the MICE probes are described later.

The second key technology element is a compact. lightweight robotic factor)' unit that would land at the colon)' site two years before the first colonists arrived. The robotic factor)' unit, termed ALPH (Atomic Liberation of Propellant and Habitat) incorporates a small lightweight nuclear reactor that generates heat and electric power, together with a number of small process x essels that produce the desired supplies for the colon), using melt H:O from the ice cap, CO, and N, from Martian atmosphere, and electric power from the reactor. The processes include water electrolysis to produce H, and O,. methanation to produce CH~ and CH:,OH. polymerization to produce polyeth)lene and other plastics, food production by yeasts and bacteria using CH, or CHsOH substrates, and liquefiers to produce and store liquid H,. O:. and CH,.

The third ke) technology element is a compact lightweight nuclear thermal propulsion (NTP) engine tbr transport back and forth between Earth orbit and Mars orbit. Using H, propellant. NTP engines can achieve

51st IAF Congress

Key Technology Elements for a Mars Colony

Ice Cap Exploration In-Situ Production & Supplies

I Technology !

Elements

Compa~ I¢obouc Umt to Explme Under

Ice C~p ( MICE )

- - Small C ~ Nude= Rcucwr

- - WateT Jet Sy~'m for Trtvel ~ Ice Cap

I Mini S~e=m Turbine fm Electric Po~,r

lmtnanent Package

Contsol & C o m m m Ptcbtge

Results

I Spaual Profile of Content Inside

Ice Cap

Mappin~ of Ice Cap Smglm~. Col~pOSIt IOO. Fossils. etc

Compact Robo¢~c FJcto~ to Produce

and Stockpde Supphes for Colony

(ALPH)

I

-+1 I Elements

C O : ' N: - - S ~ I o I

M e l h a a a t o r I

for CI-L. & CHIOH

P o l y m l z e r foP-- Plastics

Yeast & - -

A l t m e

CoP, orator

Compact Nuclear Liquid H: &02 - - Reactor for Return to

Earth Small Steam Turbme for Elecm¢ Power

Sub-Surface - -

H a b l l a l s w,Hea[ & Power

Water .let System to Melt Stontge Air. Wmer & __ Cavmes & Food for Habdats Colonists

H:O Electroly'zer Cmtsmction Materials for

Cryogenic Flyers and Liquefiers Rovers

I R©sults

74]

Liquid C I"1, O~ & CH~OH for Ro~ers & Flyers

Key Technology Elements for a Mars Colony (continued)

Spacecraft Propulsion Earth-Mars Transport

[ Technolog)

Elements

High Specific Impulse

Nuclear Engine tMITEEI

I i - - NUClear Fuel in 3000 K

H: Propellant

- - "LiH Pdode'ratm

- - 10 M'~," L=ter Fuel Elements

I Results I

l - I000 scc Spectfic Impulse

-20 i Thrust to L ~,ete.h! gat]o

- I 0.000 Pound~ Thrust

- - I n s ~ n t P a c k a ~ H: Depot m Earth GEO !Shuttle T ~ s l

I Teclmolog3

Elements

I

Transport H: Propellant from

M m Colon> to Earth GEO

Results

Fuchng Shuttle to Lsfl H: PTopell,tm to Mars Orbtt

H., Depot in Mars Orbit (Shunle Tanks)

2 Way H: Propellant Cargo Vessel Between Mars Orb,t x. Earth GEO

__• Ehmmate ~eed for L]r~m 8 Propellant

increased from Earth Capabdtq.. for Human T ransl:x)n to Mars

Figure 3

742 515t IAF Covgress

specific impulses of about i 000 seconds, over twice that of the best H2/O 2 chemical engines, which deliver only 450 seconds. The higher specific impulse performance of NTP engines greatly reduces the mass of propellant needed for transport between Earth and Mars, as compared to chemical engines. The chemical engines would be used for trips from planetary surface to orbit, both on Earth and Mars.

Over the past 50 years, there has been very extensive R&D on nuclear thermal propulsion engines in the US and the USSIL In the US, successful ground tests of complete NERVA NTP engines were carded out in the 1960's 4 successful tests of portions of NERVA type engines were also carded out in the USSR - up to the 1980's. The NERVA engine, however, was inherently large and massive, with power densities of only a few megawatts per liter, and a mass of several tons.

In the mid 1980's, the US initiated the SNTP program, which aimed at the development of a much smaller and lighter NTP engine based on the Particle Bed Reactor (PBR) for defense applications 2. Goals for the 1000 megawatt PBR NTP engine were a total mass o f -500 kilograms, with a thrust to weight ratio of30/l . The components of the PBR engine were developed and successfully tested at the anticipated operational conditions. Ground tests of complete engine assemblies were planned but not carded out, due to the ending of the SNTP program at the close of the Cold War.

More recently, even smaller and lighter NIP engine designs have been studied for space exploration missions. In particular, the h~llnature ReacTor Engin~ (MITEE) NTP engine mass is projected to be approximately 200 kilograms, with an outer diameter of the 75 megawatt reactor being only 50 centimeters. The MITEE engine, which uses the existing strong technology base on nuclear thermal propulsion, could be developed and applied to space exploration in as little as 5 years, given a strong development program.

The fourth key technology element for a practical Mars colony is an Earth - Mars - Earth transport architecture that minimizes the amount of material that has to be launched into orbit from Earth. An architecture that achieves this goal is described in detail later. As illustrated in Figure 3, a key element of this architecture is the establishment of propellant depots in Mars and high Earth orbit, i.e., at GEO or beyond. Using propellant transported from Mars orbit, spacecraft can travel back and forth between Earth and Mars without having to lift propellant from Earth for the trips. This, plus the ability to manufacture essentially all of the supplies used by the colony from Martian raw materials, reduces the Earth launch requirements to be just those needed to life colonists from Earth's surface to Earth orbit without

having to also lift propellant and supplies for the trip to Mars and the return from it.

Figure 4 illustrates a possible road map for the establishment of the Mars colony. The first ALPH unit would land in 2016, manufacturing and stockpiling supplies for the first colonists, who would land in 2018. The initial landing party would consist of 10 astronauts. Additional groups of colonists would land continue to land at intervals determined by the Earth to Mars launch windows.

The colony would attain a mature population of 500 persons by 2034, sixteens years after the first human landing. A net return to Earth of approximately 20% of the colony population would occur every 2 years. Colonist groups of up to 22 persons would travel in each habitat vehicle that traveled back and forth between Earth and Mars.

MICE Obtaining data on the intemal structure of the ice cap, in particular, the moun t , properties, and spatial distribution of its dust content, is important in the selection of a site for the Mars colony. This data would be obtained from small robotic probes, termed MICE (Mars Ice Cap Explorer) that would land on the surface of the ice cap. Using a compact, ultra lightweight nuclear reactor as a source of heat and electric power, the probe would melt its way down through the ice, collecting data on the dust content and its properties, as well as a wade range of scientific information about the composition of the ancient Martian atmosphere, solar and cosmic ray activity, and possible evidence of Martian life forms, including wind borne microfossils and DNA traces.

Figure 5 shows how MICE would move vertically and horizontally through the ice cap, along a melt channel that it creates using warm water jets powered b,~ heat from the reactor. The MICE reactor/water jet unit tows a small insmunent package behind it. Data from the insmmmnt package is transmitted back to the surface lander/transmitter along a trailing optical fiber. The data is then relayed from the surface/lander back to Earth.

Details of the MICE concept are described elsewhere ~. Figure 6 shows the MICE reactor and instrument package in its melt channel, which is approximatel? I meter in diameter. The melt channel refi-eezes to ice a few meters behind the moving reactor and its instrument package, locking in the optical fiber link to the surface lander. The MICE probe can travel vertically downv~ards or at an angle, with the angle of descent determined b,, appropriate control of the angle and rate of flow from the array of water jets positioned at the base of the reactor.

51st IAF Congrers 743

Road Map for Establishment of a Mars Colony on the North Polar Cap

Exgtore polar cap wdl~ MICE wobes beginning m 2008

Land ALPH facto~ on polar colony sde

2015

Cycler and cargo vehcJes plus fuel depot tanks go to Mars odod

2016 and 2017

5 new groups land at colony sate (100 ps~om)

2019 and 2020

I First group of colonists land at

: colony sae (10 persons)

2018

I ALPH stodq~les supP~ 0~e~ :,,oC~l~ln~ Slit,

Colony saze m 200 pemons 88 new persons arrNe 50 persons leave

2022

i Colony s~ze zs 500 J persons ,f new groups[ • amve (176 persons) I

5 groups deoart I (100 persons, I

2034 I

Colony continues to grow slowly

Figure 4

MICE Operational Modes

Mode 1 (Descent Only) Mode 2 (Descent and Ascent) Nof To Sca~e

Transm~er / Sur~Ice of Polar Cap /

( / 11~"..¢ ~ .o ; . - M*~, ,~ ( / / / . . . o ~ . , ~ ~ , / , / / / ~ / / / / / /

%-~con.nuous ~N:~It~c~r _~ OptK:al F~be, . . . . . F (Me. C.na~ne~ mwrmeomze

No¢ Slmwn) Ice

/ ~ Refr~enMe~ / • ~ / c ~ /

X_..--,~ru.,~,== o,,p ~, /

F i g u r e 5

744 51 st 1,4 F Congress

MICE Reactor With Instrumentation/Control System Package In Melt Channel

Instrumentation and Control

Package

Umbilical Line %

E O4

J_ ( 1 1 t.

Water Jet System f & Buoyancy

Chamber rrr~

Optical Fiber To Sudace

/ Solid Ice

Melt Water

Melt W a t e r Intake

_ Water Circulation ~ Power Qeneratk)n & Buoyancy Chamber

Power Core & Reflector p.

Figure 6

MICE Warm Water Jet Melt System

~ _ r v l J i H m P r D ~ ¢ J f r :

Rear Buoyancy Chamber (Filled w/'H20 During Ascenl.

~uring Descent)

am Turbine and lerator

ermediate Heat changer- Reactor O To Melt Water

St~ Se

• actor Core DH/UH 3, S Tubes w/~20 oolant)

Swivel Joint For Attachment ol Umbilical Line To Instrument Package

Beryllium Pressure Vessel

Warm Water Tubes J L ~ & Jets

Beryllium J~ ~ [ Structure J ~ _ ~ Beryllium

Front Buoyancy Chamber (Filled w/H20 During Descent. Empty Dursng Ascent)

Stand-off

,~ 20 cm

Figure 7,

51st IAF Congrery 745

MICE can also move vertically upwards once it has reached the bottom of its planned downwards trajector)' through the ice cap. MICE simply creates a melt pool several meters in diameter, and by adjusting the balance of its attached buoyancy chambers, reverses its vertical orientation by 180 degrees, so that it starts to travel upwards through the ice sheet instead of downwards. As with the downwards movement, the upwards trajectorT can either be purely vertical or at an angle that is determined by the water jet flow pattern.

MICE probes will thus be able to explore the ice cap over a wide range of vertical and horizontal distances, descending to depths on the order of a kilometer, and traveling horizontally for distances considerably greater than 1 kilometer. A cioseup view of the MICE reactor, its warm water jet system, and its buoyancy chambers is shown in Figure 7. Also present is a mini steam turbine, to generate electric power, which is driven by 200 ° C steam generated by the reactor

Table 1 summarizes the principal design parameters for the MICE probes. The operating conditions are very conservative, and the reactor and power generation components are well within the existing technology base. Development of the MICE instrument package may require some R&D on new instruments.

The integrated MICE probe can be validated by testing on Earth ice sheets, e.g.. Greenland, Antarctica. or glaciers in Alaska, to ensure that it will operate satisfactorily on Mars. A Mars read)' unit could be available in 5 to 6 years given a vigorous development effort.

THE ALPH FACTORY The robotic ALPH factor)' unit is the key to the establishment of a robust self-sustaining colon)' on the North Polar Cap of Mars. Figure 8 depicts how ALPH would be deployed on the ice cap ". After landing of the ALPH unit on the surface of the ice sheet, the ALPH reactor would begin to melt a channel down into the ice, similar in manner to the MICE probe. The ALPH reactor would also be similar in construction to the MICE reactor, though somewhat larger in size (e.g., 50 cm reflector OD, compared to 40 cm for MICE), ~ith a greater thermal power [5 MW(th) vs 200 KW(th)] and a greater electrical power [500 KW(e) vs 3 KW(e)].

Like MICE, the ALPH reactor would be fueled with U- 235 (93.5% enrichment) though with a higher fuel loading and a burnable poison to permit a longer period of operation and a higher power level. After 5 years of operation at full power, the ALPH reactor would have consumed approximately 9 kg of U-235. or about 1/3 of its initial loading. The 3D Monte Carlo neutronic analyses

of MICE and ALPH that have been carried out indicate that they have no reactor criticality or control problems.

During the first few days of operation, the ALPH reactor would sink to a location about 30 meters below the ice surface, where it would remain in place for the balance of its operating life. At this reactor depth, the habitats and storage cavities are fully shielded from radiation emitted by the reactor. After touchdown, the lander also would horizontally deploy flexible lines that circulate warm water from the reactor. These lines sink into the ice, as illustrated in Figure 8. After reaching the desired depth, the warm water circulation pattern is altered to create appropriatel)' sized cavities inside the ice sheet. These cavities would be used to stockpile liquid propellants and supplies produced by ALPH and also as habitats for the colonists.

Figure 9 shows two possible methods for melting a cavity' inside the ice sheet. In both approaches, a flexible, thin wall, collapsed plastic balloon surrounds the warm water melt line at an appropriate point along its length. When the warm water line has melted its way down to the desired depth, additional warm pressurized water is pumped into the collapsed balloon, causing it to expand against, and start to melt, the surrounding ice.

In the warm water filled balloon approach (left picture in Figure 9), the inlet water circulates throughout the whole balloon, while in the heated surface balloon approach (right side of Figure 9), the warm water onl) circulates through the network of flow channels on the surface of the balloon. The interior of the balloon is filled with pressurized water, which keeps the balloon inflated, and its hot surface pressed against the surrounding ice.

The heated skin approach has two advantages. First, it reduces the volume of warm water required: second, after the cavity has been created, the water in the network of surface channels is flushed out and replaced with a thermally insulating gas blanket. The gas would be air, N,, CO,, or H~, depending on the nature and temperature of the cavity contents. Certain materials produced by ALPH would be stored at a lower temperature than the surrounding ice sheet - for example, liquid H 2, liquid 0 2, liquid air, and liquid methane - while other materials would be stored at a higher temperature than the surrounding ice - for example, water, methanol, plastics. and food. The habitats for the colonists would also be kept at a higher temperature than the surrounding ice.

In the first case. the heat leak into the cavity from the ice is minimized by the cellular gas blanket in order to keep the power demand on the cryogenic refrigerators as small as possible. In the second case. the heat leak out of the cavity is kept small, in order to minimize space heating

746 51st IAF Congre~

Table ! MICE Probe Parameters Maximum thermal power Core diameter and height Core moderator Nuclear fuel form U-235 loading Coolant Core geometry Reflector material / thickness Water outlet temperatures

Low temperature tubes High temperature tubes

Power generation system Electric power output Turbine inlet pressure Thermal cycle efficiency

MICE travel rate along 1 meter diameter melt channel MICE mass budget, kilograms

Reactor (core, reflector, coolant, tubes, coolant and control rods) Beryllium pressure vessel Water jets, heat exchangers, and turbo - generator Instrumentation and control package Optical fiber line Contingency

Lander. transmitter and aeroshell Total

200 KW (th) 29 centimeters Lithium -7 hydride Uranium hydride dispersed in ~LiH 2.2 kilograms Water Stainless steel tubes in 'LiH / UH3 block 'LiI-I / 5.0 centimeters

50" C 250 ° C

3 KW(e) 40 Arm 20% 50 meters per day

48 27 15 50

7 50

197 200

397 kg

lJ l . lql A N I L E D I I R A N O H @ o N I q G U I A T I O N

IBq,81111BIT IF I I A I l l l & lilT IMTEII I l U l l l l ~ Iq l~ 181RIIIMTlll

,iiiiiiiii iiiiiii!!i !iii!ii!iiiii!i!iii!iiiiiii! . . . . . . . . I

Figure 8

51st IAF Congres~ 747

Imml~ . I m l

I m I ' ~ c

I , , ~ ~ = i .tL,

P A ~

ALPH PRODUC'IrlON FLOWSHEET

~ W R

i "!

, . -

I-----,

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requirements, and to prevent local melting of the surrounding ice.

Large cavities can be created in a short time using the waste heat from the ALPH nuclear reactor. For example, creating a cylindrical cavity I 0 meters in diameter and 15 meters long would take only 25 days and require about 500 KW(th) of heat. This corresponds to - l 2% of ALPH's reject heat from the steam cycle, so that a total of 8 such cavities could be created in a little more than 3 weeks. After formation, the cavities can be sealed using a freeze seal technique, in which the entrance to the cavity is closed offwith an ice plug created by injection of water and subsequent freezing by the surrounding ice.

Figure l0 shows the ALPH production flowsheet. All of the process units utilize existing technology, with water, CO2 and N 2 as the basic feed materials. The water comes fi'om melting of the local ice, while CO, and N2 came from the Martian amaosphere. The separation into CO, and N z gas streams can be done using either a simple temperature swing absorption (TSA) process with a fixed bed of molecular sieve beads, or by a compressor / liquefaction cycle.

The water electrolysis process would use a high performance solid polymer electrolyte (SPE) with an electrical efficiency on the order of 90%. The O, would

F~gure 9

be liquefied for future use in propulsion engines, fuel cells, etc., or mixed with N., and stored as liquid air for future use as breathable air. Hydrogen and carbon dioxide would be reacted to form methane, methanol, and plastics. Using methane or methanol as substrates for growth of yeasts and bacteria in fermentation vessels to yield food supplies that contain protein, fats, and carbohydrates. Ethanol can also be synthesized for use as a substrate for food production.

Table 2 lists the principal parameters of the ALPH factor5', together with an inventory of the hundreds of tons of supplies that it would produce and stockpile in the 2 year period before the first colonists landed. The total weight of the factory is approximately 4 metric tons. which is tiny compared to the amount of supplies that it would produce.

As with the MICE probes, ALPH would be tested and fully demonstrated on Earth ice sheets located, for example, in Greenland, Antarctica, or Alaska, before it was launched to Mars. Because ALPH is based on existing processes and technologies, it could be full) developed and read)' for use on Mars in a relatively short time, on the order of 7 to 8 years. As discussed earlier, besides offering the ability to support an extremely robust Mars colony. ALPH has the very great advantage that it would have all of the materials that it produced.

74S 51,t IAF Conerc~,

W A R M I N F L A T E D B A L L O N D E S I G N T Y P E S

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T a b l e 2 First ALPH S y s t e m P a r a m e t e r s

Basis: ALPH Unit lands at colony site to produce supplies for initial colonists Time interval between ALPH landing and colonist landings Reactor thermal power Power cycle type Output electric power per unit Inlet steam conditions to turbine Stockpiled supplies aRer 20 months of operation, me~c tons

Liquid hydrogen Liquid oxygen Liuqid methane Methanol Plastics Food

Number/diameter / height of sub-surface habitats for colonists

20 months 5.3 MW(th) Steam turbine (20% efficiency) 1070 KW(e) 250 ° C. 37 Arm

160 1680

60 30 30 10

8 / 9 m ~ 5 m

51st IAF Congress 749

stockpiled in place and ready for use before the colonists ever left Earth.

THE MITEE NUCLEAR PROPULSION SYSTEM As discussed earlier, nuclear propulsion is a key technology element for establishing a Mars colon,,', it greatly reduces the mass of propellant that must be launched into orbit, and shortens the trip time to and from Mars.

Figure I 1 illustrates the design features of the MITEE (Mlnature ReacTor ~ngin~) nuclear engine ~ 9. The reactor core consists of a close packed array of 3 7 separate beryllium metal pressure tubes, each of which contains an inner annular fuel zone which is enclosed by a surrounding outer lithium hydride moderator zone. Cold hydrogen propellant enters at the top end of each pressure tube, and flows longitudinally down through an outer plenum that is located between the pressure tube and moderator region.

As the hydrogen flows down through the plenum, some of it peels offthe main longitudinal flow and flows radially inwards towards the axis of the pressure tube. This radial flow first passes through the outer moderator zone, and then through the inner fuel zone. The local radial flow rate of the hydrogen propellant is controlled by the local effective porosity of the fuel zone, which is fabricated so

that hydrogen exit temperature (-3000 K) out of the fuel region into the central hot gas flow channel is the same at all points inside the reactor. This power to flow matching capability, which allows the mixed mean temperature of the hot exit propellant to reach its maximum possible value, results in the highest specific impulse that can be achieved.

The MITEE-type fuel element enables extremely high power densities in the reactor fuel element, and consequently, very compact and lightweight nuclear propulsion engines. Similar type fuel elements were tested in the SNTP-PBR nuclear propulsion program, and demonstrated the capability to operate at a power densit) of 30 megawatts per liter of fuel region.

The MITEE engine improves on the PRR engine in two important aspects. First, it uses an array of separate individual pressure tubes for the reactor, instead of an array of fuel elements inside a common pressure vessel. This simplifies the construction of the reactor, as well as its development and testing. The development program would concentrate on validating the performance of a single fuel/moderator tube, which would then be replicated to form the complete reactor assembly In contrast, reactors with an integrated core/vessel must test the complete assembl), and require much longer de,elopment time and cost.

THE MITEE REACTOR ASSEMBLY l imtE FUEL REGION FUEL ELEMENT

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750 5/,t IAF Con~,tc~s

Second, the nuclear fuel region inside the MITEE pressure tubes consists of a multi-layer roll of perforated sheets of tungsten - UO 2 metal matrix composite, in place of the packed bed of small fuel particles that was used in the PBR engine. The tungsten -UO2 composite fuel, which was developed in the 1960's, exhibits excellent stability and resistance to high temperature hydrogen corrosion, being able to operate for many hours in 3000 K hydrogen. Moreover, the radial flow of the hydrogen coolant through the perforated fuel sheets can be controlled more precisely than through a random packing of fuel particles, enabling a higher average outlet hydrogen temperature.

Figure 12 illustrates the much larger AV capability, of MITEE engines, as compared to the best H:/O: chemical engines. MITEE can deliver AV's up to ~22 km/sec, vs only about I 0 krn/sec for H,/O2 engines. Applied to unmanned high AV exploration missions, MITEE enables mission performance not achievable by chemical engines. as well as new types of missions that are not even feasible with chemical engines. Applied to the Earth-Mars-Earth architecture described in the following section, MITEE enables a transport capability between the two planets that would be impossible with chemical engines. Put simpl,,, large scale exploration and colonization of Mars can only be done using nuclear propulsion and power.

Table 3 summarizes the principal parameters of the MITEE engine. The small size and weight of M/TEE allows it to perform a wide range of exploration missions, both unmanned and manned a .~. Employed as a single engine that would operate in deep space after a safe orbit had been established, MITEE can propel faster, direct trajectory unmanned exploration missions to the outer planets - e.g., 2 years to Jupiter, 3 years to Saturn, 5 years to Pluto - as well as missions not possible with chemical engines - e.g., Europa sample return, Pluto orbiter, etc. The IMLEO launch vehicles used for these MITEE missions will be considerably smaller than if upper stage chemical engines were used.

In addition to greatly reducing the IMLEO requirements for Earth-Mars transport. MITEE engines have major operational advantages over other nuclear thermal propulsion engines, such as NERVA. MITEE enables a robust multiple engine on the manned space vehicles traveling between Earth and Mars. If one or two of the MITEE engines were to fail, the mission could still be camed out successfully. In contrast, if space vehicles were equipped with much larger, high thrust type NERVA engines, failure of even one engine could prove catastrophic. Moreover. after firing, the small MITEE engine could be detached from the space vehicle eliminating the need to shield from the residual radioactivit 3. In a trip from GEO orbit to Mars orbit, for example, those MITEE engines used/'or the TMI (Trans

Table 3 MITEE Nuclear Engine Parameters Reactor Power

Coolant Pressure

Outlet Temperature

Power Density in Fuel Elements

Moderator ~ Reflector

Core / Reflector OD

Number Fuel Elements ,' Reflector Elements

U-235 Critical Mass

Keff

Reactor Mass

AuxiliaD' Mass

Contingency

Total Engine Mass

Thrust

75 MW(th)

70 Atm

3000 K

I 0 MW / Liter

"LiH

39 / 50 cm

37 /24

23 Kilograms

1.07

100 kg

36 kg

64 kg

200 kg

17.000 Newtons

51st IAF Congress 751

t -

R " t -

6

25

20

15

10

Initial Mass in Low Earth Orbit (IMLEO) as a Function of Mission AV, Engine Type and Tankage Weight Fraction

' I ¢

Tmkage Fraction = ,l k=0.10

Delta Rocket Payfoad

Chemical Engines (H=/O=)

0 5 10

I l t I i

Tankage Fraclion = Tankage Frac'oon = '- k=0.05 k=O.05

Tankage Fracbon = uclear Thermal ~.= 0-.10 Engines

(3000K Hz)

- >, .~ Single Stage Rocket J D 2" 1000 Sec Isp " for Nuclear Thermal

t~ a- ~ ~ for Chem,caJ HalO2

p . : / , . = ~ ~ 0.5 Methc Tons >~ ~- > / ~ for Payload Plus

t r Eng,ne We,ght

Nuclear Electric Propulsion Operating Regime

I -- Nuclear Thermal I = and Nuclear

Electric Rockets ~f t , | I

15 20 25 3O Mission AV, km/sec

as Figure 12

Mars Injection) burn would be detached from the space vehicle and sent onto a non-returning trajector)'. Upon reaching Mars orbit, those engines used for orbit insertion would also be discarded after use. New engines would then be attached at the fueling depot.

Used in this manner, nuclear propulsion reactors do not pose any safety or environmental problems. The residual radioactivity is extremely small - the firing ofa MITEE engine would generate only l i f e oftbe long lived residual radioactivity present in a typical Earth based power reactor, and ! 04 of the radioactivity already present in Earth's biosphere. Moreover, the spent MITEE engines would travel in deep space on non-returning trajectories, and would never impact Earth or Mars.

EARTH-MARS-EARTH STEADY STATE TRANSPORT ARCHITECTURE

Figure ! 3 illus'Wates the proposed architecture for the transport of colonists to and from Mars. Two fueling depots are assumed, the first in high Earth orbit - nominally GEO, though other high orbit locations could be used - and the second in Mars orbit. The depots utilize spent external tanks from space shuttle flights. The extra AV needed for a shuttle tank to achieve LEO is small, on the order of 100 meters per second. After achieving LEO, the tanks would be boosted to GEO or transported to Mars orbit.

Starting from Earth, a habitat vehicle with an attached OTV vehicle is launched by a Saturn V class booster into LEO (Stage l in Figure 13A). The habitat vehicle mass is 93 metric tons, and is sized for a maximum crew capacity of 22 persons. After reaching LEO, the habitat is raised to GEO using its attached OTV, which is powered by 3 MITEE engines. At GEO, the habitat vehicle is mated with a cycler vehicle (Stage 2) which travels back and forth between GEO and Mars orbit. The cycler vehicle is refueled fi'om the GEO depot, using H z propellant which has been transported there from Mars orbit by a cargo propellant vessel. The cycler vehicles then propels the habitat towards Mars. with a 105 day trip time (Stage 3).

Upon reaching Mars, the habitat and cycler separate. The habitat aerobrakes and makes a 2 km/sec controlled burn for land at the colon) site (Stage 4), while the c)'cler does a 4 km/sec burn for orbit capture (Stage 5) and rendezvous with the Martian fueling depot (Stage 6). The cycler remains at the depot until a returning habitat lifts off(Stage 7) from the colon)' site and reaches the depot. (The habitat only uses H2/O_, engines, not nuclear engines, so there are no safety or environmental concerns). There it mates with the cycler (Stage 8) which is refueled with H z propellant lifted up from Mars. The cycler then propels the habitat towards Earth. with a 120 day trip time (Stage 9). Upon reaching Earth. the habitat

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51~t IAF Cot, gress 753

separates, to aerobrake and land on Earth (Stage 10) while the cycler undergoes a 3.7 km/sec burn (Stage 11 ) for GEO insertion. (The habitat also does a 2 km/sec burn to decrease the re-entry velocity to 11 km/sec [Apollo type re-entry] for landing.)

Figure 14 illustrates the propellant transport position of the Earth-Mars-Earth architecture. A fueling shuttle vehicle is used to transport liquid H~ from the Mars colony up to the fueling depot at Mars orbit (Stages 1 and 2). A portion of this liquid H 2 is used to fuel the cycler for its return with the attached habitat to Earth. The remainder is loaded (Stage 3) into the NTCPV (Nuclear Thermal Cargo Propellant Vehicle) which transports liquid H~ back to the GEO fuel depot (Stages 4, 5, and 6). The NTCPV then returns to the Mars depot, using its remaining liquid H~ for the trip (Stage 7).

Table 4 summarizes the propellant flow requirements for a steady state architecture serving a mature Mars colon)' of 500 persons. The colonists turnover rate is assumed to be 20% eveD' 2 years, i.e., 100 persons go to Mars, requiting 5 habitat trips, and i 00 persons return, also requiring 5 habitat trips. The propellant fuel requirements include: 1 ) the liquid H: transported back to the GEO depot to fuel the cycler/habitat vehicles for their outbound trips to Mars; 2) the liquid H 2 consumed by the NTCPV vehicles in their round trips between Earth and Mars depots to deliver the liquid H, cargo to GEO; 3) the liquid H., in Mars depot to fuel the cycler/habitat vehicles for the return trip to Earth: 4) the H2 used by the H2/O_, engines in the habitat vehicles as they lift off from the colon) site into Mars orbit; and 5) the H., used by the H.,/O., engines on the fueling shuttles to deliver liquid H, payloads to the Mars depot.

Figure 15 illustrates the principal features of the habitat, OTV, cycler, fueling shuttle, and NTCPV vehicles used in the Earth-Mars-Earth architecture. All of these are new vehicles and would require substantial development programs. However, the OTV, cycler, and NTCPV vehicles are relatively simple in construction, being essentially propellant tanks with attached engines that operate only in space, and that do not have to land or take off from planetary surfaces.

The total liquid H: production rate of 83.5 tons per year ~ ould require 20 megawatts (thermal) of reactor capacity at the Mars colony site, assuming a power conversion efficiency of 20%, thermal to electric and an operating factor of 90%. This amount of reactor capacity, is easily provided. The oxygen production requires no additional power, since it automaticall) comes along with the H, production.

Other Earth-Mars-Earth architectures are possible and ma) otter even more attractive performance. An

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754 51 ~t IA F Co.,gress

Mars Infrastructure Flotilla Habitat

8m ---,'-

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Weight Empty = 57 Tons

Weight Fu, = 71 Tons

( ~ V = 1 Km/sec)

Weight Fu, = 93 Tons

( ~ V = 2.2 Km/sec)

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New H2/O 2 Engine

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Weight Fu, = 51 0 Tons (No Payload)

Weight Fu, = 144 Tons (With 93 Ton

Habitat Payload)

Isp = 1050sec

MITEE Engine

F i g u r e 15

51st IAF Congress 755

Mars Infrastructure Flotilla Cycler (Both Stages Nuclear)

H2

--f I

I

18m 25 m

Weight Empty = 8.9Tons

Weight Full = 77 Tons (No Payload)

Weight Full = 170 Tons (With 93 Ton

Habitat Payload)

Isp = 1050sec lstStage

MITEE Engines for Each Stage

9 - 0 0 - 9

Mars Infrastructure Flotilla , ' -"- - - 8 m - - - - . -

Propellant Payload

02

H 2

16m

11m

f

Fueling Shuttle

Weight Empty = 10.5 Tons

Weight Full = 155 Tons (No Payload)

Weight Full = 210 Tons (With 55 Ton

Habitat Payload)

Isp = 450 sec

Figure 15

756 51st IAF Congress

Shuttle External

Tank

H2 105 m

58 m

47m I

i

t

!

Mars Infrastructure Flotilla Alternate Cargo Propellant Vehicle

(All Nuclear Stages)

Weight Empty = 41.5 Tons

(Empty Shuttle E.T.)

Weight Full = 251 Tons (No Payload in Shuttle E.T.)

Weight Ful~ = 436 Tons (With 185 Ton

Payload in E.T.)

Isp = 1050sec

MITEE Engine for Each Stage

Figure 15

Table 4 Mars Propellant Flow: Requirements for a Steady State Mars Colony Basis:Mature colony of 500 persons Turnover rate of 20% ever), 2 years

(100 persons to Mars, 100 persons to Earth) 5 habitat trips out every 2 years 5 habitat trips back ever)' 2 years Propellant requirements normalized to an annual basis 5/1 mixture ratio for H:/O., engines

I. Liquid H, transported to GEO depot for 5 habitat trips per 2 years

2. Liquid H., required by NTCPV to transport liquid H2 to GEO depot (2 NTCPV trips per 2 )'ears)

3. Liquid H2 in Mars depot to fuel cyclers tbr habitat trips back to Earth

4. Fuel for HffO~ engines to lift habitats from colon) to Mars depot (5 habitat trips per 2 years)

5. Fuel for H,./O: engines on fueling shuttle to lift liquid H., to Mars depot

Total produced at colon)'

Liquid H2 (Metric Tons/Yr)

175

200

Liquid O: (Metric Tons/Yr)

175

45 230

240 1200

835 1430

51st IAF Congress 757

alternate architecture based on having the Earth fueling depot located in LEO was investigated. This option was not as attractive as the GEO option, however, because of the greater AV requirements for transport to and from Mars, and the requirement to operate nuclear engines for orbit insertion at low orbital altitudes. The GEO depot location eliminates this requirement.

B U l l . n U P T O A S T E A D Y STATE EARTH-MARS- gARTH ARCHITECTURE

The transport requirements for buildup to a steady state architecture have been investigated, assuming a landing of the first colonists in 2018 and a buildup to 500 persons by 2034, as illustrated in Figure 4. Figure 16 shows the numbers of colonists going to Mars and returning to Earth per year (converted to an equivalent annualized basis) as a function of year, together with the number of colonists on Mars, also as a fimction of year.

The buildup rate could be faster or slower, depending on the number of habitats launched every 2 years, and the fraction of the colony that chooses to return to Earth. The 20% return rate at steady state is equivalent to an average stay of 10 years of Mars. Some colonists probably w i l l stay there permanently, whi le others wi l l want to leave utter 2 years. It is not possible to predict what the actual return rate will be, but 20% does not appear unreasonable.

Figure 17 shows the launch mass to Earth orbit per colonist traveling to Mars as a function of Launch year. The value depends slightly on launch year, with an average of 8.6 tons/colonist trip. This is a factor of approximately 10 smaller than the launch mass needed for astronauts exploring Mars using the individual mission approach, in which most of the supplies and propellants for the mission would have to be launched from Earth.

Figure 18 shows the cumulative total integrated mass amount of H2 propellant transported from Mars to the Earth GEO depot as a function of launch year, together with the cumulative buildup of H: propellant in the depot as a function of year. The H, transport rate from Mars to GEO is considerably greater than the amount required by the Earth to Mars trips (otherwise, the cumulative H z buildup would equal zero at all times) A portion of this excess transport can be considered as a reserx e for future trips, while the rest can be sued for other purposes. including propellant for the maintenance of solar power satellite attitude and travel to and fi'om a manned lunar base.

X A N A D U - L I F E IN A M A T U R E M A R T I A N

C O L O N Y Figure 19 illustrates the four main functions and features of life in a mature Martian colony. All are vitally

Number Of Colonists On Mars As A Function Of Time

c O

t - O O o

O

J~ E z o

° ~

E O

5 0 0

4 0 0

3 0 0

2 0 0

1 0 0

2 0 1 8

I I

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I 1 I I

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200 ~

150 "C

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2020 0

2022 2 0 2 4 2 0 2 6 2 0 2 8 2030 2032 2 0 3 4 2 0 3 6 2 0 3 8

Y e a r O f A r r i v a l O n M a r s Figure 16

758 51st 1.4F Co,,etess

Earth To Orbit Launch Mass Required To Transport A Colonist and Supplemental Supplies To Mars

.,., 100 W

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a.:E

c£ ,,., Q.

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i Colony Architecture

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8.4 9.5 6.6 8.1 6.6 8.7

2019 2020 2021 2022 2023 2024 AVG

Year Of Landing Figure 17

Hydrogen Propellant Tonnage Launched From Mars and Returned To Earth As A Function Of Launch Year

7000¸

6000 t

" - 0 G) * . , Q . O

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t ; I I i

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Note: Cumulative Tonnage Values As A Function Of Launch Year Have Been Smoothed From The Actual Stepwise Curves

2021 2022 2023 2024 2025 2026

Year Of Launch

Figure 18

Xanadu Colony

500 Persons

Earth - Mars - Earth Transport

• People • Supplies • Scmnce Materials

51st IAF Congress 759

Functions and A c t i v i t i e s in X a n a d u

/ A ~ r and Water Life Support ~ F o o d - - - - ~ H e a t and Power

/ • Consumables ~ Fuel / • LMng Quarters ~ Construct,on Materials

/ ~ Apartments

aterials Production ~ d l ~ frOm Mars Arm '

I + I ALPH I \ Ma " K , A I \

. Plaslics ' \ ./," ' \ \ ,/b ~ F a t s

e~mm' ~ A J u m i n u m

l P / o " ~ L Exploration ~ C o m b u s t i o n Engines V,i C ~ Rov---'~'v-v-v-v-v-v~ ~ E l e c U ¢ motors

• Robotic nyers f . t l . . . . ~ a . - - - - ~ ~ m a b l e s (air, water, ood) - -,,,,,,,,,,~, ,,]r,;,o ~ S c i e n t i f i c equipment

Figure 19

important to the health and success of the colony. First, virtually all of the life support requirements can be met using the materials produced by ALPH. As shown in Figure 20 and 21, the colonists will be able to live very comfortably, with as good a diet as they would have on Earth, ample Earth type air (I aim, 20% Oz) and water, and living quarters at least as spacious as those for the average American. Moreover, ALPH will provide ample power and space heat, so that the living and work quarters will be well lit and comfortably heated. The one area where there would be consU'aints is the ability to experience and enjoy large surface parks in the open sunlight. Substantial size parks, gardens and lakes could be created under the surface of the ice cap (Coleridge's "caverns measureless to man, down to a sunless sea"), but they would have to artificially, not naturally, lit. Visits to a Iransparent domed enclosed area on the surface would be possible, but not unencumbered walks outside. Any outside visit would essentially require a spacesult.

Second, exploration of Mars would be the driving force behind the colony, and the reason why a colonist would choose to live there - much like the reason that people choose to go to Antarctica. Accordingly, the colony would be very strongly oriented to discovering as much as they could about Mars, and would seek to maximize exploration capabilities. Figure 22 shows 3 main modes for exploring Mars. First, the North Polar region could be extensively explored using manned land rovers over

distances era 1000 kilometers or more out from the colony site. The rovers would not be particularly complicated, and could be fabricated from the plastics and metals produced at the colony, and fueled by methane/oxygen supplies from ALPH. Figure 23 outlines the features and requirements of these manned ice cap rovers. Traveling over frozen ice and permafrost surfaces, they should be able to move at a maximum speed of at least 50 kin/hour (30 mph). A 2 week trip in a pressurized cabin with periodic excursions in space suits onto the surface appears to be a practical exploration regime. A 2000 km round flip would require 70 hours of driving time, or about 5 hours daily, which is reasonable.

The crew would take measurements of local conditions at promising locations, collect samples for return to the colony, and emplace instruments for continuously monitoring and recording data on pressure and temperature, wind speed, dust content, seismic activity. etc. They could also emplace MICE units to travel inside the ice cap to investigate its internal structure, composition, etc.

The second mode of exploration would use unmanned flyers to explore these regions that were beyond the maximum range of the land rovers. As illustrated in Figure 22, the flyers could touch down at a number of locations, nominally on the order of 1000 kilometers

760 51~t IAF C , , n ~ t ~

Several years of stockpiled supphes allow large operatmg margins

Doctors and hospital facility a~ailable

Man.v major discoveries to be made

Shared sense of mlSSIOR

Penodic personnel transfers & continuous ¢ommumcahons ~ ~th Earth

An Excellent Quality of Life in Xanadu is Possible

MmJrnal Rrsks to IndNtdt.kals and Colony

Medical Care

Curbng Edge Soence and Explorat=on

Small Commumty

/ /

Frecluent t, ''/ InterChanges

Between Earth & Mars

" ~ , ~ Xanadu Colony

500 Persons / '

/ / / . / i

/

~L Ean~ Type ~r

20"/, O2.

//

// / f Good Food • 3000 Kcal

/ Vaned D~t /

!i// !i// I Ample Water

> 100 L/Day

"~ "", I S~c=ous Lr~ng [ ',\ \J I - -

',. l - 'ooo e I

| "~ ~'| t Ample Heat and Power

as des~recl

No need to live at sub-atmospheric pressure with high 0~. concentrations

Fish, shrimp, flesh vegetables. etc. will be readily available

Supply can be much more than I00 L/day if desired

Larger than mosl Earth condos and homes. Can be larger if desired

_ _ No constraints on heat and power

Figure 20

Xanadu Co~orq

500 Persons

Life Support Requirements for Xanadu

LMng Quartem

50.000 m ~ Floor Area

Work & Manuf Quarters

100,000 m e Floor Area

Sc~ce Heat for Quarters

12 MW(m)

B a m 2per~ m ( 2 ~ 40~, / I / / i

Air

80 Ton~yr O2 320 Ton/yr N~

Food 0.5 Ton/Day

Walter 50 m~/Day

[0.3 UW(m)]

Basis 100 % los,s/year 3xi0 S m ~ a~r volume Normal air o0ml:osdmn and dens~ 0 2~ k,~tm ~)

Bas~ 3000 k c = ~ day (1/3 fat. 2/3 cadoot~:lratea) 60 O pmtmrt/cllW 30 g fibeffday

i Ba~s 100 L/day per person Heat value s waste heat ecluw

Electnc Power (Not Inc:~de.

Manuf)

2 MW(e) 1 4 ~ ( e ) pe~ person (3 x US avg)

Figure 21

51st IAF Congress 761

~ d

Explorat ion Modes for X a n a d u Manned Surface Rovers Unmanned Flyers

..Mmm ecp~or Pe,o~c ~ Mar~ ~-,,x_

ll4/l'ld I . l ' l l~ l l~# ( - "1= Krrl>/\x x \ ~ 'Xl l l t i C- --'21'~!W

_ ~ IIIusntive N /Note: ~ Can Travel

- By Unrmnned F ~ ~ W,y ~ e So~h F~e

Depot Laying, by Unmanned

L a ~ me Way to

Manned Ryer Exploration Usinq Pre-Esta~L~hed Depots

l.ccmx~ of ~ Matron equmor

\ / "- a ~ - ~ P-~

N~e ManneO F ~ m ~ " ~ . . . . _ j ~ by Manne~ Flyer

Can Travel All the Way

M a n n e d Ice Cap Rover - Features and R e q u i r e m e n t s

Type of Terrain Ice and ice/dust frozen surfaces Flat or moderate angle slopes

X / Crew and Equipment

• 2 or 3 person crew • Pressurized cabin • Surface and sub-surface sample analysis

and collection • Emplace data recorders (MICE, etc.) • 300 kg consumable supplies • 300 kg samples

/ Traction and Propulsion

• Low contact pressure, large balloon tires • Liquid Cl~O~ fuel • Turbine engine with electric drive wheels • 1000 kg empty vehicle mass

Speed and RanRe • 50 km/hour maximum speed • 2000 km maximum range (1000 km out,

1000 km return) • 2 week maximum trip time • 4/10 km per MJ of energy (= 40 mpg

conv. auto) • 450 kg CH4 and 02 per tnp (2000 kin)

762 51~t IAF Congles~

apart, to take measurements and visual records, and to collect samples for return to the colon)'. The flyers. which would be powered by a compact, ultra lightweight nuclear reactor, and use atmospheric CO, for propellant. would have virtually unlimited range. The flyers would be able to visit any location on Mars, even as far away as the South Pole.

Figure 24 lists the principal features of the unrnanned flyer. Using stored outboard liquid CO, propellant, it would be able to land and take off vertically at slow speed, i.e., like a VTOL. Hamer ~'pe jet. After takeoff. it would accelerate to supersonic M = 2 flight (470 meters/sec on Mars), using CO, from the Martian atmosphere as the propellant. The CO., would be directly absorbed in a molecular sieve type of material (e.g., activated carbon or zeolite) and periodically desorbed using hot gas from the reactor heat source. This temperature swing absorption (TSA) cycle would effectively compress the ram intake CO, up to the -10 atmospheres pressure level, where it would then pass through the reactor to be heated to an outlet temperature of ~2000 K.

The reactor thermal power for the flyer is approximatel) 1 megawatt, a modest level readily delivered by a compact gas cooled unit. The diameter of the ram inlet that collects the CO, propellant is only 25 centimeters. The unmanned flyer would not land and take off from the colony site but rather at a site several kilometers distant. to allow the retrieval of samples and maintenance efforts to be carded out remotely. The residual radioactivit), on the reactor would not pose any danger or problems for the colony. The stored liquid CO: inventory on the flyer would be replenished at each touchdown point, using an on-board compressor and liquefier to capture atmosphere CO,. The replenishment process, which would take a fev, hours, enables the flyer to vertically take offand land at its next destination.

The third exploration mode. as illustrated in Figure 22 is by manned flyers. Use of a nuclear propulsion engine for manned flight poses risks, and is not necessar). Instead. the manned flyers would carry liquid methane]oxs gen fuel to heat atmospheric CO: for propulsion. Given the low density of the Martian atmosphere and the consequent inefficiencies of flight in it. it does not appear possible to fly for long distances v,'ith a single load of methane/oxygen fuel. Rather. periodic depots of methane/oxygen fuel would be established using the unlimited range unmanned flyers. The manned flyers would then fly from depot to depot refueling with methane/oxygen at each stop. The depots would be laid out so that each represented a promising site tbr scientific exploration, allowing both the refueling and exploration process to be carried out at the same time. The nominal distance between depots would be about 1000 kilometers.

With sufficient depots, manned flyers could travel all the way to the South Pole, if desired.

Figure 25 outlines an overall exploration program for the Xanadu colony based on the three above exploration modes. This program, which appears will be within the capabilities of a 500 person colony that would not be restricted as to the amount of propellants and supplies available for exploration, would yield an enormous volume of new and exciting knowledge about Martian climatology, geology, meteorology, hydrology, seismolog)., and hopefully, even paleontology.

The third main activity for Xanadu is associated with providing the Earth-Mars-Earth transport architecture. As described previously, this involves refueling habitat vehicles for their trips back to Earth, lifting liquid H 2 payloads to the Mars orbital depot via lyips of the fueling shuttle (approximately 15 trips per year are required), and periodic astronaut trips to the depot to service and maintain the depot.

The fourth main activity for Xanadu is the production of the materials and supplies needed to perform the previously described activities - i.e., life support, exploration of Mars, and maintenance of the Earth-Mars- Earth transport architecture. This production would use ALPH process methods and nuclear reactors. The original ALPH unit used to establish the colon,, was 5 MW(th) (1MW[e]). As the colony grows, the power rating of the individual ALPH reactor will also likel) increase, probably to -10 MW(th). Table 5 summarizes production rates for the principal supplies and material needed for life support, exploration, and Earth-Mars- Earth transport in a 500 person Mars colony. The amount shown are quite generous; however, they could be considerably greater, if desired, without affecting the viability of the colon) concept.

Several conclusions can be drawn fi'om this example. First. the total reactor power required is modest, even for a 500 person colony. Six small 10 MW(th) reactors would supply more than enough electric power, space heat and air and water for the colony, plus all the materials and supplies required, plus a rapidly growing stockpile of food, propellants, oxygen, fuels, etc. that b~ itself could sustain the colony for years. Second. most of the process is required for hydrogen production from water electrolysis, which is an extremely well developed technology. No surprises or problems are anticipated in producing hydrogen, o~'gen, water and air for the colon.~. Third, the electric power generation technology is veD' well developed and available right nov,. The steam cycle efficiency of 20% is extremely conservative; Earth based power plants routinely achieve much higher efficiencies.

5/st IA F Congress 763

Unmanned Flyer Design Features

• Energy source is compact lightweight (I 00 kg) nuclear reactor

• Uses heated (2000 K) atmospheric CO, for propulsive force

• Supersonic flight (M -- 2) in Mars atmosphere @ 470 meters / sec ( ! 050 mph)

• Uses stored on-board liquid CO2 for Harrier Jet type take offand landing

• Captures atmospheric CO, in-flight for propulsion using internal fixed beds of activated carbon particles

~) Bed absorbs CO, at ambient temperature, desorbs at high T

• Flyer mass is 1000 kg unloaded, 1500 kg loaded Wing area is 10 m', L / D = 5 / 1, mco, = 0.5 kg/sec

• Unlimited flight range

• Can land to investigate promising sites with instruments and recover samples (up to 100 kg. Recharge stored CO, for flight to next site.

Figure 24

Illustrative Exploration Program for Xanadu

Manned Ice Rovers • 12 trips pe~ year • 2 week trip time

-10 Iocetions explored per tnp Emplace 12 sub-surface mobile explorers (MICE) Powered by on-board CH,/O a Total 1 ton CH, and 4 tons O~ per year

U m n n e d F l ~ r s for 5upolv Deoots • Lay supply depots for manned flyers

(CH,. 02. consurnables, etc.) • Depots laid at intervals of -1000 km • -5 to 10 flights per manned trip • Powered by compact nuclear reactor that heats

atmosphere CO a f ix propulsion

• -50 trips per year • Ranges up to 10.000 km

(i.e.. as far as South Pole) • 2 weeks trip time • 2 to 3 locations explored per trip • Powered by compact nuclear reactor that heats

atmospheric CO 2 for propulsion

• 12 trips per year • Ranges up to 10.000 km

(,.e.. as far as South Pole) • 1 month trip time • 3 to 4 locations explored per trip • Powered by CHJOa o0¢nbuetion source heating

atmosphehc CO 2 for propulsion

Fimare 25

764 51st 1.4F Con~,tcL~s

Table 5 ALPH Production Rates for Xanadu Colon)' Basis:Average yearl2, production rate

Total reactor thermal power

Total electric generation

Number fo ALPH reactors (10 MW[th])

H~ production, metric tons net ~ ear Liquid Hz for Earth-Mars-Earth transport H, for CH, and CH~OH fuel H, for plastics H, for food substrates H., for stockpile (30%)

O, orodt~¢tion. Metric tons t~er ,.'ear Liquid O: for Earth-Mars-Earth transport O, for breathable air O., for combustible fuels O: for plastics and food O, for stockpile (50%) O., surplus (discarded)

Oentval ~;upo/ies. metric tons oer year Breathable air (80% N2, 20% O:) Water for life support CH, for exploration Fuels for colony Plastics Food (including 50% stockpilel Electric power for life support Space heat for life support

Stead) state colon)' of 500 persons

Total

Total used

20°,0 turnover every 2 )'ears 60 l~fW (th)

12 MW (e)

O

835 40 80 90 30___Q0

1345

1430 80

800 100

1200 8500 3610

400 18.000

15 180 500 270

2 MW(e) 12 MW(th)

Fourth, most (80%) of the oxygen produced is discarded, even after a stockpile equal to 50% of the consumption rate is added. The air losses, which have already been over estimated, could be increased 100 fold without requiring additional oxygen generation. Fifth, to support a substantial colony, a veD' large amount of water, tens of thousands of tons per year, is required, both for life support and for materials production. It is very doubtful that this amount of readily accessible water or sub- surface ice will be available at any location on Mars other than the North Polar Cap. Certainly, the Polar Cap is the logical site for a colon)'. Sixth, nuclear power is a necessity if humanity is to have a substantial colony on Mars. Solar simply cannot supply the amounts of power and heat required by a colony, given the technical difficulty of construction on Mars. the problems of dust, and the substantially reduced solar flux.

Seventh and finally, any significant colony on Mars must be self supporting with only a small fraction of its needs supplied from Earth. Moreover, in addition to supporting itself, it will have to further minimize the remaining transport requirements from Earth by supplying a large fraction of the propellants and supplies needed for trips to and from Mars.

SUMMARY AND CONCLUSIONS A new approach for the large scale exploration of Mars is described. This approach, would establish a permanent

colony on Mars North Polar Cap, where unlimited amounts of water in the form of an extensive, thick ice sheet are readily accessible. A compact robotic factor3.' unit, termed ALPH, would be landed on the ice sheet at the colony site 2 years before the first group of colonists arrived. Using a small, ultra lightweight nuclear reactor to supply heat and electric power, ALPH would manufacture and stockpile hundreds of tons of propellants and supplies that would be ready for use when the colonists arrived. In addition, ALPH would also create large, insulated habitats under the ice surface. in which the colonists would be full,,' shielded from cosmic radiation.

Ample amounts of all of the materials - propellants, fuels. air. water, plastics, and food - required for a large permanent colon.,,' would be produced by ALPH. using ice together with CO: and N: from the Martian atmosphere as raw feed materials. In addition to producing all of the supplies needed by the colon) for life support and a vigorous Mars exploration program. ALPH would also produce large amounts of liquid H: and O,. enabling an Earth-Mars-Earth transport architecture that would not require lifting propellants from Earth. Orbital fueling depots at Mars and Earth GEO would be supplied with propellants and supplies lifted from the Mars colon)'. l 'he only Earth based launch requirements that remain are to lift Mars bound colonists up to GEO orbit.

51~r IAF Congress 765

Propellants and supplies for trips from GEO to Mars and return to Earth would come from Mars, taking advantage of the lower AV requirements.

A strong technology base already exists for the ALPH reactor and process units, as well as the nuclear thermal propulsion engines that would be used for the Earth- Mars-Earth architecture. The ALPH and MITEE propulsion systems can be demonstrated and ready for application within the time flame presently being considered for the initial manned missions to Mars. Based on a first manned landing in 2018, ALPH would have produced and stockpiled hundreds of tons of propellants and supplies at the North Polar landing site.

Following the first landing, the colony could rapidly build up to a mature population of-500 persons by 2034 AD Assuming an average turnover rate equivalent to 20% of the colony population returning to Earth every 2 years, the corresponding Earth launch requirements to sustain the colony would be only 5 habitat vehicle launches to GEO ever}' 2 years, with each habitat weighing -100 tons and carrying 20 persons.

In conclusion, the self-supporting Mars colony exploration approach has major advantages over the conventional individual mission approach. These include: • Much greater Mars exploration capability • Much lower risk. for both the astronauts and the

mission • Greatly reduced Earth launch requirements • Much better living conditions on Mars • Ability to use Mars as a base for exploration of the

outer solar system

Based on these advantages, further investigation of the Mars colony approach appears desirable, including R&D on the key technology elements.

I. Zubrin, R., The Case for Mars. Simon and Schuster. New York (1996).

2. Keiffer, H.H. and Zent, A.P., "'Quasi-Periodic Climate Change on Mars," p. 1180-1233 in Mars, Kieffer, H.H. ed., University of Arizona Press, Tuscon (1992).

3. Cam M-H., Water on Mars, Oxford Universi~, Press 1996).

4. Koenig, D.R., "'Experience Gained from the Space Nuclear Rocket Program," Los Alamos National LaboratoD'. LA- 10062-H (May 1986).

5. Ludewig. H., et al., "'Design of Particle Bed Reactors for the Space Nuclear Thermal Propulsion Program," Prog. In Nuc. Eng.. 30, No. I. p. 1-65 (1996).

6. Powell, J., et al., "MICE: A Compact Light, Near- Term Mobile Robot for Exploration of the Martian Polar Ice Cap," Paper IAA-99-Q.3.08, 50th International Astronautical Congress; Amsterdam, Netherlands, October 4-8, 1999.

7. Poweli, J., et al., "ALPH - A Robotic Precursor to Produce Large Amounts of Supplies for Manned Outposts on Mars," Paper IAF-98-Q.3.08, 49th International Astronautical Congress, Melbourne, Australia, Sept. 28 - Oct. 2, 1998.

8. Powell, J., et al., "An Ultra Lightweight Nuclear Engine for New and Unique Planetary and Science Missions," Paper IAF-98-R, 1.01,49th International Astronautical Congress, Melbourne, Australia, Sept. 28 - Oct. 2, 1998.

9. Powell, J., et al., "'The MITEE Family of Compact, Ultra Lightweight Nuclear Thermal propulsion Engines for Planetary Space Exploration," Paper IAF-99-5.6.03.50th International Astronautical Congress, Amsterdam, Netherlands, October 4-8. 1999.

A C K N O W L E D G E M E N T S

This work has been supported by the NASA Institute of Advanced Concepts (NIAC) Research Grant 07600-053.