太空电梯的经济学外文文献翻译中英文翻译外文翻译.docx

太空电梯的经济学外文文献翻译中英文翻译外文翻译.docx

《太空电梯的经济学外文文献翻译中英文翻译外文翻译.docx》由会员分享，可在线阅读，更多相关《太空电梯的经济学外文文献翻译中英文翻译外文翻译.docx（9页珍藏版）》请在冰点文库上搜索。

太空电梯的经济学外文文献翻译中英文翻译外文翻译

Spaceelevatoreconomics

Spaceelevatoreconomicscomparedandcontrastedwiththeeconomicsofalternatives,likerockets.

Costsofcurrentsystems（rockets）

Thecostsofusingawell-testedsystemtolaunchpayloadsarehigh.Pricesrangefromabout$4,300/kgforaProtonlaunch[1]toaboutUS$40,000/kgforaPegasuslaunch（2004）.[2][3]Somesystemsunderdevelopment,suchasnewmembersoftheLongMarchCZ-2E,offerratesaslowas$5,000/kg,but（currently）havehighfailurerates（30%inthecaseofthe2E）.Varioussystemsthathavebeenproposedhaveofferedevenlowerrates,buthavefailedtogetsufficientfunding（Roton;SeaDragon）,remainunderdevelopment,ormorecommonly,havefinanciallyunderperformed（asinthecaseoftheSpaceShuttle）.（RocketssuchastheShtil-3a,whichofferscostsaslowas$400/kgrarelylaunchbuthasacomparativelysmallpayload,andispartiallysubsidisedbytheRussiannavyaspartoflaunchexercises.）

GeosynchronousrocketlaunchtechnologiesdelivertwotothreetimessmallerpayloadstogeosynchronousorbitthantoLEO.Theadditionalfuelrequiredtoachievehigherorbitseverelyreducesthepayloadsize.Hence,thecostisproportionatelygreater.Bulkcoststogeosynchronousorbitarecurrentlyabout$20,000/kgforaZenit-3SLlaunch.

Rocketcostshavechangedrelativelylittlesincethe1960s,butthemarkethasbeenveryflat.[3]Itis,however,quitereasonabletoassumethatrocketswillbecheaperinthefuture;particularlyifthemarketforthemincreases.Atthesametime,itisquitereasonabletoassumethemarketwillincrease,particularlyifrocketswillbecomecheaper.

Rocketcostsaresignificantlyaffectedbyproductionvolumesofthesolidpartsoftherocket,andbylaunchsitecosts.Intuitively,sincepropellantisbyfarthelargestpartofarocket,propellantcostswouldbeexpectedtobesignificant,butitturnsoutthatwithhydrocarbonfuelthesecostscanbeunder$50perkgofpayload.Studyafterstudyhasshownthatthemorelaunchesasystemperformsthecheaperitbecomes.Economiesofscalemeanthatlargeproductionrunsofrocketsgreatlyreducecosts,aswithanymanufactureditem,andreuseablerocketsmayalsohelptodoso.Improvingmaterialandpracticalconstructiontechniquesforbuildingrocketscouldalsocontributetothis.Greateruseofcheaplabour（globalisation）andautomationispracticallyguaranteedtoreducemanpowercosts.Othercosts,suchaslaunchpadcosts,canbereducedwithveryfrequentlaunches.

Costestimatesforaspaceelevator

Foraspaceelevator,thecostvariesaccordingtothedesign.Dr.BradleyEdwards,whohasputforthaspaceelevatordesign,hasstatedthat:

"Thefirstspaceelevatorwouldreduceliftcostsimmediatelyto$100perpound"（$220/kg）.[4]However,aswiththeinitialclaimsforthespaceshuttle,thisisonlythemarginalcost,andtheactualcostswouldbehigher.Developmentcostsmightberoughlyequivalent,inrealterms,tothecostofdevelopingtheshuttlesystem.Themarginalorasymptoticcostofatripwouldnotsolelyconsistoftheelectricityrequiredtolifttheelevatorpayload.Maintenance,andone-waydesigns（suchasEdwards'）willaddtothecostoftheelevators.

Thegravitationalpotentialenergyofanyobjectingeosynchronousorbit（GEO）,relativetothesurfaceoftheearth,isabout50MJ（15kWh）ofenergyperkilogram（seegeosynchronousorbitfordetails）.Usingwholesaleelectricitypricesfor2008to2009（7.1NZcentsperkWh）andthecurrent0.5%efficiencyofpowerbeaming,aspaceelevatorwouldrequireUSD220/kgjustinelectricalcosts.Bythetimethespaceelevatorisbuilt,Dr.Edwardsexpectstechnicaladvancestoincreasetheefficiencyto2%（seepowerbeamingfordetails）.Itmayadditionallybepossibletorecoversomeoftheenergytransferredtoeachliftedkilogrambyusingdescendingelevatorstogenerateelectricityastheybrake（suggestedinsomeproposals）,orgeneratedbymassesbrakingastheytraveloutwardfromgeosynchronousorbit（asuggestionbyFreemanDysoninaprivatecommunicationtoRussellJohnstoninthe1980s）.

Forthespaceelevator,theefficiencyofpowertransferisjustonelimitingissue.Thecostofthepowerprovidedtothelaserisalsoanissue.Whilealand-basedanchorpointinmostplacescanusepoweratthegridrate,thisisnotanoptionforamobileocean-goingplatform.Aspeciallybuiltandoperatedpowerplantislikelytobemoreexpensiveup-frontthanexistingcapacityinapre-existingplant.Up-onlyclimberdesignsmustreplaceeachclimberinitsentiretyaftereachtrip.Somedesignsofreturnclimbersmustcarryupenoughfueltoreturnittoearth,apotentiallycostlyventure.

Contrastingrocketswiththespaceelevator

Governmentfundedrocketshavenothistoricallyrepaidtheircapitalcosts.Someofthesunkcostisoftenquotedaspartofthelaunchprice.Acomparisoncanthereforebemadebetweenthemarginalcostsoffullyorpartiallyexpendablerocketlaunchesandspaceelevatormarginalcosts.Itisunclearatpresenthowmanypeoplewouldberequiredtobuild,maintainandruna100,000kmspaceelevatorandconsequentlyhowmuchthatwouldincreasetheelevator'scost.Extrapolatingfromthecurrentcostofcarbonnanotubestothecostofelevatorcableisessentiallyimpossibletodoaccurately.

Spaceelevatorshavehighcapitalcostbutpresumablylowoperatingexpenses,sotheymakethemosteconomicsenseinasituationwheretheywouldbeusedtohandlemanypayloads.Thecurrentlaunchmarketmaynotbelargeenoughtomakeacompellingcaseforaspaceelevator,butadramaticdropinthepriceoflaunchingmaterialtoorbitwouldlikelyresultinnewtypesofspaceactivitiesbecomingeconomicallyfeasible.Inthisregardtheysharesimilaritieswithothertransportationinfrastructureprojectssuchashighwaysorrailroads.Inaddition,launchcostsforprobesandcraftoutsideEarth'sorbitwouldbereduced,asthecomponentscouldbeshippeduptheelevatorandlaunchedoutwardfromthecounterweightsatellite.Thiswouldcostlessinbothfundingandpayload,sincemostprobesdonotlandanywhere.Also,almostalltheprobesthatdolandsomewherehavenoneedtocarryfuelforlaunchawayfromtheirdestination.Mostprobesareonaone-wayjourney.

Fundingofcapitalcosts

Notethatgovernmentsgenerallyhavenothistoricallyeventriedtorepaythecapitalcostsofnewlaunchsystemsfromthelaunchcosts.Severalcaseshavebeenpresented（spaceshuttle,ariane,etc）,documentingthis.RussianspacetourismdoespartiallyfundISSdevelopmentobligations,however.

Ithasbeensuggestedthatgovernmentsarenotusuallywillingtopaythecapitalcostsofanewreplacementlaunchsystem.Anyproposednewsystemmustprovide,orappeartoprovide,awaytoreduceoverallprojectedlaunchcosts.ThiswasthenominalimpetusbehindtheSpaceShuttleprogram.Governmentstendtoprefertocutcostsinmanycases.Spendingmoremoneyissomethingtheyareusuallyloathtodo.

Alternatively,accordingtoapaperpresentedatthe55thInternationalAstronauticalCongress[5]inVancouverinOctober2004,thespaceelevatorcanbeconsideredaprestigemegaprojectandthecurrentestimatedcostofbuildingit（US$6.2billion）isratherfavourablewhencomparedtothecostsofconstructingbridges,pipelines,tunnels,talltowers,highspeedraillinks,maglevsandthelike.Itisalsonotentirelyunfavourablewhencomparedtothecostsofotheraerospacesystemsaswellaslaunchvehicles.[6]

TotalcostofaprivatelyfundedEdwards'SpaceElevator

AspaceelevatorbuiltaccordingtotheEdwardsproposalisestimatedtocost$20billion（$40Bwitha100%contingency）[7].Thisincludesalloperatingandmaintenancecostsforonecable.Ifthisistobefinancedprivately,a15%returnwouldberequired（$6billionannually）.Subsequentelevatorswouldcost$9.3Bandwouldjustifyamuchlowercontingency（$14.3Btotal）.Thespaceelevatorwouldlift2millionkgperyearperelevatorandthecostperkilogrambecomes$3,000foroneelevator,$1,900fortwoelevators,$1,600forthreeelevators.

Forcomparison,inpotentiallythesametimeframeastheelevator,theSkylon,12,000kgcargocapacityspaceplane（notaconventionalrocket）isestimatedtohaveanR&Dandproductioncostofabout$15billion.Thevehiclehasaboutthesame$3,000/kgpricetag.Skylonwouldbesuitabletolaunchcargoandparticularlypeopletolow/mediumEarthorbit.Anearlyspaceelevatorcanmoveonlycargoalthoughitcandosotoamuchwiderrangeofdestinations.[8]

References

1.^SpaceTransportationCosts:

TrendsinPricePerPoundtoOrbit1990-2000（PDF）.Retrievedon2006-03-05.

2.^Pegasus.EncyclopediaAstronautica.Retrievedon2006-03-05.

3.^Theeconomicsofinterfacetransportation（2003）.Retrievedon2006-03-05.

4.^WhatistheSpaceElevator?

.InstituteforScientificResearch,Inc..Retrievedon2006-03-05.

5.^55thInternationalAstronauticalCongress.InstituteforScientificResearch,Inc..Retrievedon2006-03-05.

6.^Raitt,David;BradleyEdwards.THESPACEELEVATOR:

ECONOMICSANDAPPLICATIONS（PDF）.55thInternationalAstronauticalCongress2004-Vancouver,Canada.Retrievedon2006-03-05.

7.^[1]

8.^TheSpaceElevator-Chapter7:

Destinations.Retrievedon2006-03-05.

太空电梯的经济学

太空电梯经济学和火箭经济学的对比与比较。

目前（火箭）系统的成本

使用完善的测试系统发射有效载荷的成本是很高的，2004年其价格范围是从约4300美元每千克发射一个质子到40,000美元每千克发射一个飞马座。

一些处于发展中的系统，如长征系列的新成员长征CZ-2E，其提供的价格低至5000美元每千克，但是它（目前）具有较高的失败率（2E的失败率为30％）。

各种被推荐的系统，有的甚至提供更低的价格，但是未能获得足够的资金支持（如roton;海龙），仍然处于发展之中，或更为普遍，没有财政补助（如太空中的穿梭机一样）。

像shtil-3A型火箭，其成本低至400美元每千克，很少发射，但其有一个相对较小的有效载荷，得到了俄罗斯海军的部分资助，他们将其用于发射演习。

地球同步轨道火箭发射技术向地球同步