pale blue dot -carl sagan- 第50节

Once　upon　a　time　it　was　thought；　on　the　basis　of　econometric　models；　that　for　every　dollar　invested　in　NASA　many　dollars　were　pumped　into　the　U。S。　economy。　If　this　multiplier　effect　applied　more　to　NASA　than　to　most　government　agencies；　it　would　provide　a　potent　fiscal　and　social　justification　for　the　space　program。　NASA　supporters　were　not　shy　about　appealing　to　this　argument。　But　a　1994　Congressional　Budget　Office　study　found　it　to　be　a　delusion。　While　NASA　spending　benefits　some　production　segments　of　the　U。S。　economy—especially　the　aerospace　industry—there　is　no　preferential　multiplier　effect。　Likewise；　while　NASA　spending　certainly　creates　or　maintains　jobs　and　profits；　it　does　so　no　more　efficiently　than　many　other　government　agencies。

Then　there's　education；　an　argument　that　has　proved　from　time　to　time　very　attractive　in　the　White　House。　Doctorates　in　science　peaked　somewhere　around　the　time　of　Apollo　11；　maybe　even　with　the　proper　phase　lag　after　the　start　of　the　Apollo　program。　The　cause…and…effect　relationship　is　perhaps　undemonstrated；　although　not　implausible。　But　so　what？　If　we're　interested　in　improving　education；　is　going　to　Mars　the　best　route？　Think　of　what　we　could　do　with　100　billion　for　teacher　training　and　salaries；　school　laboratories　and　libraries；　scholarships　for　disadvantaged　students；　research　facilities；　and　graduate　fellowships。　Is　it　really　true　that　the　best　way　to　promote　science　education　is　to　go　to　Mars？

Another　argument　is　that　human　missions　to　Mars　will　occupy　the　military…industrial　plex；　diffusing　the　temptation　to　use　its　considerable　political　muscle　to　exaggerate　external　threats　and　pump　up　defense　funding。　The　other　side　of　this　particular　coin　is　that　by　going　to　Mars　we　maintain　a　standby　technological　capacity　that　might　be　important　for　future　military　contingencies。　Of　course；　we　might　simply　ask　those　guys　to　do　something　directly　useful　for　the　civilian　economy。　But　as　we　saw　in　the　1970s　with　Grumman　buses　and　Boeing/Vertol　muter　trains；　the　aerospace　industry　experiences　real　difficulty　in　producing　petitively　for　the　civilian　economy。　Certainly　a　tank　may　travel　1；000　miles　a　year　and　a　bus　1；000　miles　a　week；　so　the　basic　designs　must　be　different。　But　on　matters　of　reliability　at　least；　the　Defense　Department　seems　to　be　much　less　demanding。

Cooperation　in　space；　as　I've　already　mentioned；　is　being　an　instrument　of　international　cooperation—for　example；　in　slowing　the　proliferation　of　strategic　weapons　to　new　nations。　Rockets　demissioned　because　of　the　end　of　the　Cold　War　might　be　gainfully　employed　in　missions　to　Earth　orbit；　the　Moon；　the　planets；　asteroids；　and　ets。　But　all　this　can　be　acplished　without　human　missions　to　Mars。

Other　justifications　are　offered。　It　is　argued　that　the　ultimate　solution　to　world　energy　problems　is　to　strip…mine　the　Moon；　return　the　solar…wind…implanted　helium…3　back　to　Earth；　and　use　it　in　fusion　reactors。　What　fusion　reactors？　Even　if　this　were　possible；　even　if　it　were　cost…effective；　it　is　a　technology　50　or　100　years　away。　Our　energy　problems　need　to　be　solved　at　a　less　leisurely　pace。

Even　stranger　is　the　argument　that　we　have　to　send　human　beings　into　space　in　order　to　solve　the　world　population　crisis。　But　some　250；000　more　people　are　born　than　die　every　day—

which　means　cans　that　we　would　have　to　launch　250；000　people　per　day　into　space　to　maintain　world　population　at　its　present　levels。　This　appears　to　be　beyond　our　present　capability。



I　RUN　THROUGH　such　a　list　and　try　to　add　up　the　pros　and　cons；　bearing　in　mind　the　other　urgent　claims　on　the　federal　budget。　To　me；　the　argument　so　far　es　down　to　this　question：　Can　the　sum　of　a　large　number　of　individually　inadequate　Justifications　add　up　to　an　adequate　justification？

I　don't　think　any　of　the　items　on　my　list　of　purported　justifications　is　demonstrably　worth　500　billion　or　even　100　billion；　certainly　not　in　the　short　term。　On　the　other　hand；　most　of　them　are　worth　something；　and　if　I　have　five　items　each　worth　20　billion；　maybe　it　adds　up　to　100　billion。　If　we　can　be　clever　about　reducing　costs　and　making　true　international　partnerships；　the　justifications　bee　more　pelling。

Until　a　national　debate　on　this　topic　has　transpired；　until　we　have　a　better　idea　of　the　rationale　and　the　cost/benefit　ratio　of　human　missions　to　Mars；　what　should　we　do？　My　suggestion　is　that　we　pursue　research　and　development　projects　that　can　be　justified　on　their　own　merits　or　by　their　relevance　to　other　goals；　but　that　can　also　contribute　to　human　missions　to　Mars　should　we　later　decide　to　go。　Such　an　agenda　would　include：

·U。S。　astronauts　on　the　Russian　space　station　Mir　for　joint　flights　of　gradually　increasing　duration；　aiming　at　one　to　two　years；　the　Mars　flight　time。

·Configuration　of　the　international　space　station　so　its　principal　function　is　to　study　the　long…term　effects　of　the　space　environment　on　humans。

·Early　implementation　of　a　rotating　or　tethered　〃artificial　gravity〃　module　on　the　international　space　station；　for　other　animals　and　then　for　humans。

·Enhanced　studies　of　the　Sun；　including　a　distributed　set　of　robot　probes　in　orbit　about　the　Sun；　to　monitor　solar　activity　and　give　the　earliest　possible　warning　to　astronauts　of　hazardous　〃solar　flares〃—mass　ejections　of　electrons　and　protons　from　the　Sun's　corona。

·U。S。/Russian　and　multilateral　development　of　Energiya　and　Proton　rocket　technology　for　the　U。S。　and　international　space　programs。　Although　the　United　States　is　unlikely　to　depend　primarily　on　a　Soviet　booster；　Energiya　has　roughly　the　lift　of　the　Saturn　V　that　sent　the　Apollo　astronauts　to　the　Moon。　The　United　States　let　the　Saturn　V　assembly　line　die；　and　it　cannot　readily　be　resuscitated。　Proton　is　the　most　reliable　large　booster　now　in　service。　Russia　is　eager　to　sell　this　technology　for　hard　currency。

·Joint　projects　with　NASDA　（the　Japanese　space　agency）　and　Tokyo　University；　the　European　Space　Agency；　and　the　Russian　Space　Agency；　along　with　Canada　and　other　nations。　In　most　cases　these　should　be　equal　partnerships；　not　the　United　States　insisting　on　calling　the　shots。　For　the　robotic　exploration　of　Mars；　such　programs　are　already　under　way。　For　human　flight；　the　chief　such　activity　is　clearly　the　international　space　station。　Eventually；　we　might　muster　joint　simulated　planetary　missions　in　low　Earth　orbit。　One　of　the　principal　objectives　of　these　programs　should　be　to　build　a　tradition　of　cooperative　technical　excellence。

·Technological　development—using　state…of…the…art　robotics　and　artificial　intelligence—of　rovers；　balloons；　and　aircraft　for　the　exploration　of　Mars；　and　implementation　of　the　first　international　return　sample　mission。　Robotic　spacecraft　that　can　return　samples　from　Mars　can　be　tested　on　near…Earth　asteroids　and　the　Moon。　Samples　returned　from　carefully　selected　regions　of　the　Moon　can　have　their　ages　determined　and　contribute　in　a　fundamental　way　to　our　understanding　of　the　early　history　of　the　Earth。

·Further　development　of　technologies　to　manufacture　fuel　and　oxidizer　out　of　Martian　materials。　In　one　estimate；　based　on　a　prototype　instrument　designed　by　Robert　Zubrin　and　colleagues　at　the　Martin　Marietta　Corporation；　several　kilograms　of　Martian　soil　can　be　automatically　returned　to　Earth　using　a　modest　and　reliable　Delta　launch　vehicle；　all　for　no　more　than　a　song　（paratively　speaking）。

·Simulations　on　Earth　of　long…duration　trips　to　Mars；　concentrating　on　potential　social　and　psychological　problems。

·Vigorous　pursuit　of　new　technologies　such　as　constant…thrust　propulsion　to　get　us　to　Mars　quickly；　this　may　be　essential　if　the　radiation　or　microgravity　hazards　make　one…year　（or　longer）　flight　times　too　risky。

·Intensive　study　of　near…Earth　asteroids；　which　may　provide　superior　intermediate…timescale　objectives　for　human　exploration　than　does　the　Moon。

·A　greater　emphasis　on　science—including　the　fundamental　sciences　behind　space　exploration；　and　the　thorough　analysis　of　data　already　obtained—by　NASA　and　other　space　agencies。

These　remendations　add　up　to　a　fraction　of　the　full　cost　of　a　human　mission　to　Mars　and—spread　out　over　a　decade　or　so　and　done　jointly　with