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ALUNAR MINING FACILITY harvests oxygen from the soil of Mare Serenitatis. The Moon's abundant

resources will help open up the entire solar system for human exploration. NASA; ILLUSTRATION BY PAT RAWLINGS

The next goal for human space flight should be the same asthe first: Earth's Moon. / / / PAUL D. SPUDIS

Four reasons to returnThe first motivation to revisit the Moonis that its rocks hold the early history ofour own planet and the solar system.Next, its unique environment and prop­erties make it an ideal vantage point forobserving the universe. The Moon is alsoa natural space station where we canlearn how to live off-planet. And finally,it gives us an extraterrestrial fillingstation, with resources to use bothlocally and in near-Earth space.

Often pictured as a simple, primitivebody, the Moon is actually a small planetof surprising complexity. The periodwhen it was most active geologically,between 4 billion and 3 billion years ago,corresponds to a missing chapter of

significant goal, the space program willcircle aimlessly in a deteriorating orbit.

One outstanding target awaits in ourbackyard. The Moon offers scientific andtechnical benefits, as well as more tangi­ble ones. [n the 1960s, we raced to theMoon because it was a fence thought tobe just jumpable. When we return, we'llgo for different reasons - not to provethat we can do it, but because we under­stand the Moon's true value.

More than half the people now alivewere born after America last went to theMoon. Yet if asked, today's studentswould probably say that existing tech­nology could get us there and land on thesurface. In reality, the hardware, soft­ware, and know-how needed for lunarflight were dismantled almost 30 yearsago. America stopped going to the Moonbecause the reason to go had been satis­fied. We went to beat the Soviets - andwe stopped going because once a battle iswon, you don't keep fighting it.

Fixing the problems that caused theloss of the Shuttle Columbia has NASA'sfull attention at present. But the agencymust move forward, and soon it, likeeveryone else involved in space, will befocusing on what the next goal might be.

ASA has advanced studies examiningpossible directions. Build large astro­nomical instruments in deep space? Visitan asteroid? Send people to Mars?

The urge to explore beyond familiarhorizons is one of humanity's greatestdrives. We need a new challenge in space.It must be difficult yet achievable,substantial yet manageable. It shouldencourage new technology, yet be attain­able on a limited budget. Without such a

Harvest the ~PLOMTION

Earth's history. The processes that trans­formed the Moon - impact, volcanism,and tectonism (crustal deformation) ­affect all the rocky bodies of the innersolar system. Because the Moon has noatmosphere or flowing water, the geolog­ical story of its ancient surface can beread clearly. And as Earth's companion,it retains a record of the history in thiscorner of the solar system, vital knowl­edge unavailable on any other object.

we can turn to the ancient lunar surface,which still holds its impact histolY

For astronomical observations, theMoon offers a premier place: It has noatmosphere and is a quiet, stable body.The lack of an atmosphere permits clearviewing with no opaque portions of thespectrum to contend with - all ofnature's radiation can be viewed from theMoon's surface. Because one lunar daylasts 709 hours, or 29.5 terrestrial days,

humans or robots?", we should be asking:"How can we use both most effectively?"

Exploring any planet is a job forgenerations, but efficient ways to do ite:-.ist. The Moon is a natural laboratoryfor discovering the best strategies.

Yet resources may well prove the mostimportant reason to return. Materialsand energy available on the Moon willopen up the space frontier. Shadowedareas near the lunar poles can do more

It once took a gigantic Saturn Vbooster to get us to the Moon'ssurface, We now have cheaper and far better ways to gO,

The biggest scientific benefit of theApollo program was learning the impor­tance that impact cratering had in theevolution of planets. This new under­standing turned out to have profoundconsequences. Scientists now know thatimpacts of large bodies periodically wipeout species on Earth, most notably65 million years ago when the dinosaursand many others met their demise. TheMoon taught us how to spot the telltaleresidue of large impacts in Earth's past,but our knowledge remains incomplete.While Earth's surface record has beenerased by erosion and crustal recycling,

Paul D. Spudis is a planetary scientist and authorof The Once and Future Moon, published by theSmithsonian Institution Press. His new book isThe Clementine Atlas of the Moon, to be publishedby Cambridge University Press.

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there are long periods of near-continuoussunlight and darkness. Even during thelunar day, brighter sky objects remainvisible in a black sky. The far side of theMoon is permanently shielded from thedin of civilization's electromagnetic noise.And near the lunar poles lie areas ofperpetual darkness and sunlight. Thedark regions remain very cold, only afew tens of degrees above absolute zero,providing natural cold-traps that cancool infrared detectors for free.

The Moon also beckons as anotherhome for humanity - not for territorialexpansion, but as a laboratory wherehumans can learn to survive and thriveoff-Earth. Exploration is a task that weonly think. we understand. The endlessdebate between advocates of human androbotic space flight highlight this igno­rance. Instead of asking, "Which is better:

than cool telescopes: They contain vastdeposits of water ice, emplaced by asteady rain of comets over billions ofyears. Scientists estimate that more than10 billion metric tons of water exist inthese regions. Vital for human life, watercan also be broken down into hydrogenand oxygen to make rocket propellant.Water from lunar cold-traps can thushelp create our first space filling station.

It's true that hydrogen and oxygen canbe extracted directly from lunar soil. Thesolar wind implants hydrogen on the dustgrains, and oxygen is locked in the min­erals. This means rocket propellant andwater could, in principle, come directlyfr0111 the bone-dry dust. Yet such proc­essing would be difficult and costly. Polarwater is already in a concentrated, usefulform, greatly simplifying the scenariosfor lunar return and habitation.

The lunar poles have uses from yetanother resource perspective - the areasof permanent darkness lie close to areasof near-permanent sunlight. The Moonhas no seasons to speak of because itsrotation axis stands nearly perpendicularto the plane of Earth's orbit. This meansthe Sun always appears on or near thehorizon at the poles.

Scientists have identified several polarregions that receive sunlight for morethan 75 percent of the lunar day. Thus, anoutpost in these areas will have amplesunlight to generate electrical power viasolar cells. They also have a benign ther­mal environment because sunlight strikesthe polar ground at a shallow angle.Surface temperatures never reach those

found at noon on the lunar equator(about 212° Fahrenheit or 100° Celsius).The lunar poles make inviting oases innear-Earth space.

Using off-planet resources presents uswith a challenge and a worthwhile goal.If Earth is our only source of materials,we'll never go very far in space. We haveto cut the umbilical cord with Earth.Having a Moon endowed with usableresources opens up the solar system ­yet we have to learn how to use theseresources before we go farther.

An architecture for returnForty years ago, America built themighty Saturn V booster rocket tolaunch men and machines to the Moon

in a single leap. Indeed, this brute-forceapproach was so successful it has domi­nated lunar-return plans ever since.Nearly every Moon-mission scheme ofthe past 20 years starts with rebuildingthe heavy-launch capability of the SaturnVOl' its equivalent. This thinking, how­ever, has technological tunnel vision.

Parts of the Saturn V were literallyhand-made, making it hugely expensive,and developing any new launch vehicle isenormously costly. What's needed is amission design with the least amount ofnew development we can get away with.Such a plan would let us concentrateenergies on the most important missionaspects: learning how to use lunarresources to support space flight.

AHUGE RESERVOIR OF WATER ICE lingers in permanently shadowed regions at the Moon's south pole. The ice can provide hydrogen and oxygen to fuel

spacecraft as well as air and water for future lunar inhabitants. NASA: ILLUSTRATION BY PAT RAWLINGS

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The Office of Exploration at NASA'sJohnson Space Center in Houston, Texas,has devised a clever architecture for lunarreturn that uses the Space Shuttle, aug­mented by existing expendable boosters.Thus, right from the start, it eliminatesone of the biggest costs, the demand fora new launch vehicle.

TheJohnson plan uses existing DeltaIV expendable boosters to deliver thecargo clements of the lunar return to low

gradually passing through the intenseradiation belts t11at surround Earth.

The crew, however, would be launchedseparately. From Earth orbit they'd use achemically fueled vehicle for a quicktransfer to the Lr depot, taking just a fewdays to get there to avoid lingering in theradiation belts. The crew then movesinto the lunar lander and habitat vehicle,continues on to the Moon, descends tothe surface, and begins exploring.

needed. We conduct the lunar missionfrom the Space Station and return to itafterward, making the Station an essen­tial component of the migration into thesolar system. Placing a staging depot atthe Lr point makes it easy (in terms ofenergy) to go to the Moon - and it'salmost as easy to go nearly anywhere elsein the solar system, too. Using ion-drivepropulsion for cargo vehicles pushestechnology but doesn't require any great

Returning to the Moon can in truth) must - be done on a time-scalesimilar to political terms of office: four to six years.

Earth orbit: a lander, a habitat, and atransfer stage. Assembled into a packagein Earth orbit, these items are then sentto a point in space about 80 percent ofthe way to the Moon. This point, calledthe Moon-Earth Lagrangian point I (Lrfor short), is dynamically stable. It orbitsEarth with the Moon such that it appearsfixed in space from both bodies. Its place­ment relative to the two worlds lets ussit tight and wait for favorable alignmentsof these bodies and the Space Stationduring various phases of the mission.

As Apollo showed, direct flight fromEarth to the Moon involves high veloci­ties, short travel times, and loads of fuel.But with the LI plan there's no need forspeed. Cargo rockets can use innovativelow-thrust technologies such as ion drives(used on the Deep Space r probe) tomake long, spiraling trips out to LI. Thejourney there might take several months,

The preferred landing site lies nearthe Moon's south pole, the most attrac­tive spot for both science and operations.The goal of the mission is to build amanned base where we can learn to minelunar resources on ever-larger scales.Each trip brings new components to thesurface, and the size and capability of thelunar outpost grows over time.

On return, the Lr depot provides asafe haven for the crew while they waitfor the orbital plane of the Space Stationto align with the trajectory of the returnvehicle. Rather than entering the atmos­phere directly and landing as Apollo did,the crew's return craft would skim theatmosphere, using friction to brake intoorbit for rendezvous with the Station.Refueled, the vehicle would remain avail­able for the next mission out to Ll.

This architecture offers importantbenefits. No new heavy-lift booster is

leaps. Technjcal innovations will emergeas a byproduct of the program, but thearchitecture doesn't depend on them.

Space scientists often disparage theShuttle and Space Station, but they playa key role in this plan. The reason:money. The costs of people and infra­structure almost completely dominatethe price of space flight, and creating anew manned launch system would beenormously expensive. Since the Shuttleand the Space Station already exist, itmakes sense to use them as much as pos­sible and focus new efforts on finding,processing, and using lunar resources.

Reasons to return nowThis mission plan makes sense fromtechnical and fiscal perspectives. Butdoes it make political sense? Mter all,no large-scale project will get funded bythe federal government without a solid

THE MOON'S POLES harbor vast quantities of water ice in craters where the Sun never shines. These

mosaics from the Clementine spacecraft show the Moon's north pole [left] and south pole (right).

The blue zones trace the extent of ice found by the Lunar Prospector spacecraft. NASAlBMDD

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SUNLIGHT AT THE SOUTH POLE ranges from non­

existent in deep craters to nearly continuous on a

sliver of the rim of the crater Shackleton. NASA

THE FAR SIDE OF THE MOON offers the best vantage point in the solar system for astronomers studying radio emissions from deep space. No other loca­

tion remains totally shielded from the electromagnetic noise streaming from our home planet. NASA,ILLUSTRATION BY PAT RAWLINGS

political rationale. Here's where thepicture grows murkier.

The history of the United Statesshows that only two kinds of big engi­neering projects enjoy long-term fundingstability: those related to nationaldefense (the Panama Canal, the Apolloprogram) and those that build andmaintain the economic infrastructure(the Tennessee Valley Authority, theinterstate highway system).

Unfortunately, neither the search forworlds around other stars nor a searchfor extraterrestrial life fits these cate­gories. So it's unlikely that pure scienceprojects will be funded well enough toallow a great deal of human space flight.This outcome poses a constant threat for

ASA. If people are not flying in space- an activity that crystallizes publicsupport for the space program - ASAwill wither away.

Ifyou ask anyone at NASA what theirnext big goal is, they'll answer "Mars."

ASA scientists have detailed plans forexploring the Red Planet, culminating ina series of robotic sample-return missionslate in the 20IOS as prelude to humanjourneys. Advanced studies focus almostexclusively on manned Mars missions andon the search for evidence of former orexisting martian life.

The problem is, a human mission toMars won't happen. No matter how ithas been approached, scaled-back, orreinvented, the reality is that such

missions cost hundreds of billions of dol­lars and need time spans lasting decades.The national budget simply won't stretchfor a project of this magnitude.

Can international cooperation makeMars affordable? Our experience withthe Space Station suggests not. Large­scale international missions invest moreresources in bureaucracy than in spacehardware. Consensus management andorganizational in-fighting produce delaysand increase costs, and projects becomehostages to other countries' budgetfights, too. The result is a mission that'sless capable, more expensive, and moredelayed than if it had been done from thestart by one nation with a vision.

But even a space program undertakenby a single nation has no guarantee ofsuccess. The best programs are thoseundertaken with clear aims and well­chosen goals, and which are done undersome schedule pressure. They also musthave a clear political rationale. To getlong-term funding, a technical projectmust relate to some national priority, andit must produce a payback on time-scalesroughly equal to political terms of office- that is, four to six years.

Mars is out of the question underthese conditions. But a lunar return isachievable within five years, at a costone-tenth that of a manned Marsmission. Moreover, by developing thecapability to operate on the Moon, wegain routine manned access to all levels

of Earth orbit, including geosynchronousorbit. (This is where a satellite circlesonce every 24 hours, remaining fixed inthe sky over a given point on Earth.)

At 23,000 miles high, geosynchronousorbit is where all of Earth's communica­tion satellites reside. The ability to sendpeople there is important because thenext generation of col11ll1unication satel­lites will need to be gigantic, complexmachines, requiring megawatts of power.Too expensive to abandon when theymalfunction, such satellites will requireoccasional maintenance.

Going to the Moon to mine itsabundant water ice for use as rocketpropellant will provide routine access togeosynchronous orbit and other zones ofnear-Earth space. With this capability,worth trillions of dollars, we can build,maintain, and operate the service satel­lites of the new century.

Unlike Mars, a return to the Moonprovides us an excellent opportunity to

accomplish important national goals.This mission will aid our national secu­rity by giving the United States access tovaluable lunar resources (our first, off­world "El Dorado"). It will also boost ourexpanding economic infrastructure byteaching us how to use all the orbitallevels of near-Earth space. A lunar returnties the space program to importantnational priorities - and it gives NASAan exciting, vigorous mission that pavesthe way to the planets beyond. iii

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