advanced number proposals extended program addition missions including manned low earth orbit lunar landing missions second manned program operated nasa consisted seat spacecraft capable maneuvering orbit docking spacecraft allowing crew perform extra activities range applications considered missions including military flights space station crew logistics delivery lunar flights lunar proposals ranged docking systems developed target vehicle powerful upper stages propel spacecraft moon complete modifications enable land lunar surface applications ranged manned lunar apollo ready providing emergency shelters rescue stranded apollo crews replacing apollo program advanced proposals shelf spacecraft original program whilst featured modifications allow spacecraft carry crew dock space stations visit moon perform mission objectives modifications considered included addition wings spacecraft order enable horizontal landing background second american manned program mercury intended demonstrate technologies techniques required apollo program extra activities rendezvous docking maneuvering orbit long duration flight spacecraft built derived earlier mercury spacecraft modified accommodate equipped larger equipment module allowing support longer missions maneuver orbit launched rocket flying cape air force station total missions launched manned following test flights manned flight launched march program concluded november successful recovery applications envisaged spacecraft stages years nasa manned proposals operation considered seriously cases flight hardware constructed prior cancellation case spacecraft launched demonstration flight support program cases technology developed program programs components launched upgrade rockets military applications united_states_air_force intended use spacecraft transport proposed space stations later stations launched rockets spacecraft atop eliminating need rendezvous docking maneuvers purpose modifications capsule including installation hatch heat shield allow access space station order experience programs started program proposed seen fly nasa missions order practice techniques required missions seen cooperative missions nasa air_force missions flying crews composed astronaut nasa followed missions crews performing missions nasa flights air_force flown number missions firstly flown man rendezvous docking mission followed man scientific technology research missions proposed missions included tests astronaut mobility unit designed assist navigation systems flying radar imaging system conducted cape air force station space launch complex test flight launched consisted spacecraft built spacecraft test flight atop space station released trajectory descended earth test modifications heat shield ensure access hatch affect performance continued orbit early stations manned single crew launched station later stations designed support multiple crews delivered additional spacecraft derivatives program cancelled june favour reconnaissance satellites systems developed program later missions space suits development transferred nasa rocket launch flew upgrades built later upgrade rockets stretched second stages core later flights seven segment solid rocket later introduced spacecraft proposed provide transportation crews cargo nasa space stations low earth orbit nasa contracted conduct study modifications needed allow spacecraft support spacecraft envisioned manned spacecraft transport crew stations manned spacecraft cargo module crew cargo delivery dedicated spacecraft resupply station months studies looked required modifications spacecraft docking methods considered use existing docking system missions allowed mission accomplished little modification spacecraft needed crew transfer accomplished means extra activity changes required included strengthening nose installing solid rockets separation burn adding necessary equipment perform transfer providing provisions flight station number retro rockets increased second method seen spacecraft dock way docking spacecraft swung round attached space station tunnel placed allowing crew transfer station performing modifications required final proposed docking method use port mounted rear equipment module allowed crew transfer directly spacecraft space station docking port modified version spacecraft proposed included cargo module attached modified equipment module spacecraft approached station docked backwards port rear cargo module forward docking configurations docking controlled remotely station separating cargo module flying station dock normally different port rear docking simply remained attached cargo module crew boarding station docking controlled crew station cargo module derived spacecraft considered resupply flights involved spacecraft systems manned flight entry landing removed spacecraft docked port spacecraft cargo transferred nose spacecraft entry attitude control system located manned spacecraft spacecraft equipped liquid engine perform rendezvous space station proposal new spacecraft built missions systems possible higher cargo capacity stripped version spacecraft crew cargo supply missions launched aboard saturn saturn combined crew cargo spacecraft increased power saturn spacecraft seats able propel crew far event explosion launch escape tower proposed based mercury spacecraft considered launch heavier spacecraft big big grew proposal called develop enlarged spacecraft docking capability advantage increased capacity offered rockets designed transport space able dock space stations support missions launched heavy lift launch vehicle saturn intended use air_force missions intended nasa missions considered launched smaller version spacecraft lower capacity resupply space stations later program nasa proposed saturn derivatives solid stages alternatives offering similar capacity shape mass spacecraft varied depending rocket launch saturn launched version short conical cargo module total mass kilograms version featured longer cylindrical module total mass kilograms version shorter lighter mass kilograms rocket capacity saturn variant carried crew whilst maximum capacity use nasa variant considered orbit docked space stations apollo docking probe mounted rear cargo module turn mounted rear entry module entry module enlarged accommodate larger crew modifications spacecraft program incorporated including hatch heat shield provide access cargo module event launch failure launch escape system developed apollo spacecraft propel entry module clear rocket big landings land guide runway dry lake edwards air force base landed derived lunar exploration missions number studies investigated sending spacecraft trajectory proposals involved launch architecture spacecraft upper stage orbit upper stages considered included second stage different types including variant developed saturn enlarged burning parallel saturn launch upper stage whilst launch program proposals involved launching spacecraft low earth orbit proceeding moon single launch architecture stage variant saturn proposal predicted able achieve hour flight performed trans lunar injection separating spacecraft concerns raised spacecraft heat shield able protect higher speed associated trajectory required nasa proposed thicker heat shield protect spacecraft modifications spacecraft heavy launched rocket original missions solid rocket motors added allow additional mass flown lunar orbit missions spacecraft stacked upper stages low earth orbit placed trajectory coast reached moon perform lunar orbit following completion activities lunar orbit fired trans earth injection architecture launch spacecraft saturn launching upper stages lunar landing spacecraft manned lunar landing considered early original mercury proposal led program initial proposal lunar orbit rendezvous mission spacecraft lightweight open cockpit launched saturn rocket time lunar orbit rendezvous proposed lunar landing concept spacecraft tested low earth orbit lunar missions launches designed nasa mass kilograms proposals mass low kilograms place heavier proposal intended provide faster lower cost alternative apollo program time proposing direct ascent landing proposal saturn achieve direct ascent mission profile spacecraft consisted module powered engine propel spacecraft trans lunar coast landing initial phases powered descent altitude metres lunar surface second module performed final descent landing spacecraft stayed moon day propelled earth launch trans earth injection performed contained components life support system systems located earth orbit spacecraft module based capsule modified allow atmosphere higher velocity required lunar flight seen effort nasa managers engineers advocated direct ascent mission profile intended cheaper faster safer apollo lunar orbit rendezvous technique apollo rescue risks associated lunar landing number rescue spacecraft proposed allow crew apollo mission return earth safely event problem designs based spacecraft proposals lunar orbit rescue vehicle designed retrieve crew apollo spacecraft stranded orbit moon stretched module accommodate aboard apollo attached modified contained engines lunar orbit trans earth injection life support equipment crew alive returned earth launch trans lunar injection performed spacecraft lunar orbit apollo crew boarded means proposed spacecraft designed sent moon ahead apollo mission landed close planned apollo landing site ascent stage failed crew performed transfer shelter designed landing apollo mission sent collect crew whilst original apollo mission returned earth aboard spacecraft consisted module housed whilst awaited rescue descent stage containing life support systems engine land spacecraft surface rescue spacecraft intended fly direct ascent mission launched saturn descent stages built descent stage reduced spacecraft velocity approached moon configuration service descent stage descent stage performing final landing reused ascent lunar surface trans earth injection configuration descent stages second landing ascent landed close moon apollo crew transferred following apollo fire january nasa conducted safety review apollo program response review proposed version enlarged capsule room rescued intended rescue apollo crew point whilst moon occur designs included seats moon proposal considered rejected lack funds proposals number applications considered spacecraft manned manned proposal manned spacecraft astronomical solar observation larger module proposed big spacecraft launched saturn enlarged module considered spacecraft proposed time rescue crews manned spacecraft stranded low earth orbit launched atop orbit means integrated equipment module larger capsule accommodate crew spacecraft required rescuing rendezvous satellite proposed mission seen spacecraft rendezvous satellite low earth orbit spacecraft launched directly orbit rendezvous lower orbit subsequently docking raise orbit flown crew performed recover piece spacecraft detection panels mission prove rendezvous accomplished spacecraft collect data satellite exposure supporting data satellite returned demonstrate technology military flights inspect hostile satellites missions proposed demonstrate methods landing spacecraft land spacecraft originally designed land set wheels abandoned favor delays development failures testing proposed spacecraft landed way asked nasa consider flying standard spacecraft order test system required operationally winged alternative landing concept air_force proposal attach wings spacecraft proposal arose soon cancellation seen spacecraft attached set wings developed asset program launched rocket unable maneuver orbit proposal saw spacecraft launched maneuvering mission complete spacecraft means solid rocket motors long duration missions proposals use spacecraft conduct long duration missions small purpose built space stations low earth orbit proposal saw space station based provide propulsion attitude control station module docking crew accommodation conduct experiments crew boarded means tunnel spacecraft similar proposal
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