pale blue dot -carl sagan-第48章

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term　direction　for　the　U。S。　space　program。　Called　the　Space　Exploration　Initiative　（SEI）；　it　proposed　a　sequence　of　goals　including　a　U。S。　space　station；　a　return　of　humans　to　the　Moon；　and　the　first　landing　of　humans　on　Mars。　In　a　later　statement；　Mr。　Bush　set　2019　as　the　target　date　for　the　first　footfall　on　that　planet。

And　yet　the　Space　Exploration　Initiative；　despite　clear　direction　from　the　top；　foundered。　Four　years　after　it　was　mandated；　it　did　not　even　have　a　NASA　office　dedicated　to　it。　Small　and　inexpensive　lunar　robotic　missions—that　otherwise　might　well　have　been　approved—were　canceled　by　Congress　because　of　guilt　by　association　with　SEI。　What　went　wrong？

One　problem　was　the　timescale。　SEI　extended　five　or　so　presidential　terms　of　office　into　the　future　（taking　the　average　presidency　as　one　and　a　half　terms）。　That　makes　it　easy　for　a　president　to　attempt　to　mit　his　successors；　but　leaves　in　considerable　doubt　how　reliable　such　a　mitment　might　be。　SEI　contrasted　dramatically　with　the　Apollo　program—which；　it　might　have　been　conjectured　at　the　time　it　began；　could　have　triumphed　when　President　Kennedy　or　his　immediate　political　heir　was　still　in　office。

Second；　there　was　concern　about　whether　NASA；　which　had　recently　experienced　great　difficulty　in　safely　lifting　a　few　astronauts　200　miles　above　the　Earth；　could　send　astronauts　on　an　arcing　year…long　trajectory　to　a　destination　100　million　miles　away　and　bring　them　back　alive。

Third；　the　program　was　conceived　exclusively　in　nationalist　terms。　Cooperation　with　other　nations　was　not　fundamental　to　either　design　or　execution。　Vice　President　Dan　Quayle；　who　had　nominal　responsibility　for　space；　justified　the　space　station　as　a　demonstration　that　the　United　States　was　〃the　world's　only　superpower。〃　But　since　the　Soviet　Union　had　an　operational　space　station　that　was　a　decade　ahead　of　the　United　States；　Mr。　Quayle's　argument　proved　difficult　to　follow。

Finally；　there　was　the　question　of　where；　in　terms　of　practical　politics；　the　money　was　supposed　to　e　from。　The　costs　of　getting　the　first　humans　to　Mars　had　been　variously　estimated；　ranging　as　high　as　500　billion。

Of　course；　it's　impossible　to　predict　costs　before　you　have　a　mission　design。　And　the　mission　design　depends　on　such　matters　as　the　size　of　the　crew；　the　extent　to　which　you　take　mitigating　steps　against　solar　and　cosmic　radiation　hazards；　or　zero　gravity；　and　what　other　risks　you　are　willing　to　accept　with　the　lives　of　the　men　and　women　on　board。　If　every　crew　member　has　one　essential　specialty；　what　happens　if　one　of　them　falls　ill？　The　larger　the　crew；　the　more　reliable　the　backups。　You　would　almost　certainly　not　send　a　full…time　oral　surgeon；　but　what　happens　if　you　need　root　canal　work　and　you're　a　hundred　million　miles　from　the　nearest　dentist？　Or　could　it　be　done　by　an　endodontist　on　Earth；　using　telepresence？

Wernher　von　Braun　was　the　Nazi…American　engineer　who；　more　than　anyone　else；　actually　took　us　into　space。　His　1952　book　Das　Marsprojekt　envisioned　a　first　mission　with　10　interplanetary　spacecraft；　70　crew　members；　and　3　〃landing　boats。〃　Redundancy　was　uppermost　in　his　mind。　The　logistical　requirements；　he　wrote；　〃are　no　greater　than　those　for　a　minor　military　operation　extending　over　a　limited　theater　of　war。〃　He　meant　to　〃explode　once　and　for　all　the　theory　of　the　solitary　space　rocket　and　its　little　band　of　bold　interplanetary　adventurers；〃　and　appealed　to　Columbus'　three　ships　without　which　〃history　tends　to　prove　that　he　might　never　have　returned　to　Spanish　shores。〃　Modern　Mars　mission　designs　have　ignored　this　advice。　They　are　much　less　ambitious　than　yon　Braun's；　typically　calling　for　one　or　two　spacecraft　crewed　by　three　to　eight　astronauts；　with　another　robotic　cargo　ship　or　two。　The　solitary　rocket　and　the　little　band　of　adventurers　are　still　with　us。

Other　uncertainties　affecting　mission　design　and　cost　include　whether　you　pre…emplace　supplies　from　Earth　and　launch　humans　to　Mars　only　after　the　supplies　are　safely　landed；　whether　you　can　use　Martian　materials　to　generate　oxygen　to　breathe；　water　to　drink；　and　rocket　propellants　to　get　home；　whether　you　land　using　the　thin　Martian　atmosphere　for　aerobraking；　the　degree　of　redundancy　in　equipment　thought　prudent；　the　extent　to　which　you　use　closed　ecological　systems　or　just　depend　on　the　food；　water；　and　waste　disposal　facilities　you've　brought　from　Earth；　the　design　of　roving　vehicles　for　the　crew　to　explore　the　Martian　landscape；　and　how　much　equipment　you're　willing　to　carry　to　test　our　ability　to　live　off　the　land　in　later　voyages。

Until　such　questions　are　decided；　it's　absurd　to　accept　any　figure　for　the　cost　of　the　program。　On　the　other　hand；　it　was　equally　clear　that　SEI　would　be　extremely　expensive。　For　all　these　reasons；　the　program　was　a　nonstarter。　It　was　stillborn。

There　was　no　effective　attempt　by　the　Bush　Administration　to　spend　political　capital　to　get　SEI　going。

The　lesson　to　me　seems　clear：　There　may　be　no　way　to　Send　humans　to　Mars　in　the　paratively　near　future—despite　the　fact　that　it　is　entirely　within　our　technological　capability。　Governments　do　not　spend　these　vast　sums　just　for　science；　or　merely　to　explore。　They　need　another　purpose；　and　it　must　make　real　political　sense。

It　may　be　impossible　to　go　just　yet；　but　when　it　is　possible；　the　mission；　I　think；　must　be　international　from　the　start；　with　costs　and　responsibilities　equitably　shared　and　the　expertise　of　many　nations　tapped；　the　price　must　be　reasonable；　the　time　from　approval　to　launch　must　fit　within　practical　political　timescales；　and　the　space　agencies　concerned　must　demonstrate　their　ability　to　muster　pioneering　exploratory　missions　with　human　crews　safely；　on　time；　and　on　budget。　If　it　were　possible　to　imagine　such　a　mission　for　less　than　100　billion；　and　for　a　time　from　approval　to　launch　less　than　15　years；　maybe　it　would　be　feasible。　（In　terms　of　cost；　this　would　represent　only　a　fraction　of　the　annual　civilian　space　budgets　of　the　present　spacefaring　nations。）　With　aerobraking　and　manufacturing　fuel　and　oxygen　for　the　return　trip　out　of　Martian　air；　it's　now　beginning　to　look　as　if　such　a　budget　and　such　a　timescale　might　actually　be　realistic。

The　cheaper　and　quicker　the　mission　is；　necessarily　the　more　risk　we　must　be　willing　to　take　with　the　lives　of　the　astronauts　and　cosmonauts　aboard。　But　as　is　illustrated；　among　countless　examples；　by　the　samurai　of　medieval　Japan；　there　are　always　petent　volunteers　for　highly　dangerous　missions　in　what　is　perceived　as　a　great　cause。　No　budget；　no　timeline　can　be　really　reliable　when　we　attempt　to　do　something　on　so　grand　a　scale；　something　that　has　never　been　done　before。　The　more　leeway　we　ask；　the　greater　is　the　cost　and　the　longer　it　takes　to　get　there。　Finding　the　right　promise　between　political　feasibility　and　mission　success　may　be　tricky。



IT'S　NOT　ENOUGH　to　go　to　Mars　because　some　of　us　have　dreamt　of　doing　so　since　childhood；　or　because　it　seems　to　us　the　obvious　long…term　exploratory　goal　for　the　human　species。　If　we're　talking　about　spending　this　much　money；　we　must　justify　the　expense。

There　are　now　other　matters—clear；　crying　national　needs—that　cannot　be　addressed　without　major　expenditures；　at　the　same　time；　the　discretionary　federal　budget　has　bee　painfully　constrained。　Disposal　of　chemical　and　radioactive　poisons；　energy　efficiency；　alternatives　to　fossil　fuels；　declining　rates　of　technological　innovation；　the　collapsing　urban　infrastructure；　the　AIDS　epidemic；　a　witches'　brew　of　cancers；　homelessness；　malnutrition；　infant　mortality；　education；　jobs；　health　care—there　is　a　painfully　long　list。　Ignoring　them　will　endanger　the　well…being　of　the　nation。　A　similar　dilemma　faces　all　the　spacefaring　nations。

Nearly　every　one　of　these　matters　could　cost　hundreds　of　billions　of　dollars　or　more　to　address。　Fixing　infrastructure　will　cost　several　trillion　dollars。　Alternatives　to　the　fossil…fuel　economy　clearly　represent　a　multitrillion…dollar　investment　worldwide；　if　we　can　do　it。　These　projects；　we　are　sometimes　told；　are　beyond　our　ability　to　pay。　How　then　can　we　afford　to　go　to　Mars？

If　there　were　20　percent　more　discretionary　funds　in　the　U。S。