Gemini Program

7/30/2019 Gemini Program

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FACT SHEET #291FEBRUARY 1965GEMINI PROGRAM

The National Aeronautics an d Space Administrationannounced December 7, 1961, a plan to extend themanned spaceflight effort by development of a two-manspacecraft. On January 3, 1962, the program was offi-cially designated "Gemini" an d named after the thirdconstellation of the zodiac, featuring the twin starsCastor and Pollux.

OBJECTIVESThe Gemini Program is managed by the Manned

Spacecraft Center, Houston, Texas, under the directionof th e Office of Manned Space Flight, NASA Headquarters, Wasllington, D. C .

.Primary objectives of the Gemini program, which. were decided upon after it became evident to NASA

officials that an intermediate step between Mercuryan d Apollo was required, are:

*To provide a logical follow-up program to Mercurywith a minimum of time and expense.

*To subject two men and supporting equipment tolong duration flights, a research an d experience requirement for projected later trips to the moon ordeeper space.

*To effect rendezvous an d docking with anotherorbiting vehicles; an d to maneuver the combined spacecraft in space, utilizing the propulsion system of thetarget vehicle for such maneuvers.

*To experiment with astronauts leaving the Geminispacecraft while in orbit and determining their abilityto perform extravehicular activities such as mechanicalor other type tasks.

*To perfect methods of reentry and landing thespacecraft at a pre-selected landing area.

*To gain additional information concerning theeffects of weightlessness, an d physiological reactionsof crew members during long duration missions, an dother medical data required in preparation for thelunar missions of the Apollo Program.

*To provide the astronauts with required zero-gravity an d rendezvous an d docking experience.

GEMINI SPACECRAFTThe Gemini spacecraft is similar to th e Mercury

spacecraft in shape bu t is, of necessity, considerablylarger. Th e reentry module alone is ll-feet high and7lh-feet in diameter at the base as compared to the

nine-feet high, six-feet in diameter Mercury spacecraft.The combined weight of th e Gemini spacecraft an d

it s adapter module, which is about 19-feet high, isapproximately 7,000 pounds as compared to Mercury's

THE GEMINI SPACECRAFT, on a dolly, is shown as it arrives atHangar AI' af Cape Kennedy, Florida.


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4,000 pOill1ds. The cabin section ha s about 50 percEmtmore volume than was available in Mercury.

There ar e many other major changes incorporatedin th e Gemini spacecraft as compared to Mercury.Since Mercury was primarily a research and development vehicle, it was designed to provide completelyautomatic control from the although it ha dbuilt-in capabilities for switchover to pilot control. Du eto difficulties encolh'1tered in the various systems inProject Mercury flights, and the fact th e astronautscapably handled such difficulties, the Gemini spacecraft is primarily designed to be controlled by th eastronauts throughout th e flight.

Another major difference betwe en th e two spacecraftis the type and placement of sub-systems and components. In Project Mercury, most of th e systems werein the pilot's cabin, with many components stacked in"layer-cake" fashion, an d when troubles were encountered it was sometimes necessary to disturb a nmnberof systems to ge t at the one causing trouble. By comparison, in Gemini, th e systems are modularized byplacing all pieces of each system in compact packages.Packages are so arranged that an y system ca n beremoved without tampering with any other system, an dspare packages ar e completely checked and kept readyfor rapid replacement if an y troubles OCCUI'. Thesepackages ar e located on th e outer waH of th epressurized cabin, permitting easy access in the eventreplacement is necessary. Only th e visual instruments,controls, conmmnications equipment an d Hfe

equipment and materials such as food, water, wastehandling equipment, survival gear and breathing apparatus is located in the pilots' cabin section.

Another major change between th e spacecraft concept of America's first two-malliled space program isth e difference in approach to safety should anabort occur. l\1:ercury had an escape while inthe G'3mini Program ejection seats will be used. Theuse of ejection seats is made possible in Gemini because th e fuel used by th e Gemini launch vehicle, amodified Air Force Titan II , burns on contact with th eoxidizer rather than exploding as did th e fuel used byth e Atlas launch vehicle in th e Mercury program. Th eejection seat method provides an additional benefit inthat it can be utilized during reentry at low altitudesI I I case trouble develops that phase of th ennSSlOn.

of a retrogradean d the reentry

H "UUCW : ; , , " V H N i ~ C ' H O of th e rendezvous and recovery sec-th e reentry control and the cabin section.

Th e heat shield is attached to the cabin section. Anose fairing, attached to the forward en d of th e rendezvous and recovery section, is ejected during the launchphase of th e mission.

I t is not practical to list al l of th e components andsystems housed in these sections of th e spacecraft forsuch would mount into th e hundreds, bu t followingar e some of the major itenls in each:

A M O C K ~ U P OF l i r ' n ~ Gemini spo:ee.:rr:!!T1l' is shown ~ H < @ k e f i de.nvn ~ ~ c l i t : ~ ' e 5 E H ' ~ ~ ' k m 5 'she spGrcel;:["ofto from ~ e f ~ i ' J s ' 5 ~ ~ ~ ' ewe 'the t 1 d c s p ~ e rmodule S e d ~ O i l 1 , 'the c d q j p ~ @ ? modt1lje 5 " e ~ r g r v d e s e d ~ t ' H ' ~ F a:Jncl -ehe n ~ : e ~ l I t i i " ) r M@duk:: v,Fhich i : @ n s ~ s t s ::+w f.:iUbii1 s e ~ * k H l , riH::i!1fY cCil11ro;

5 e d k ~ ! i 1 f rendezvovs O'nd ret :avery 5 e ~ ~ i o i n .


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*Rendezvous an d Recovery Section: radar equipment for use in rendezvous missions, an d the droguean d main parachutes.

*Reentry Control Section: fuel an d oxidizer tanks,valves, tube assemblies, and thrust chamber assembliesfo r th e reentry control system.

*Cabin Section: an internal pressure vessel servingas the crew station an d including those items mentioned previously. This pressurized compartment isballasted to provide th e correct water flotation position.The space between th e pressurized crew station andth e external skin of th e cabin section houses instrumentation packages an d electronic gear among otheritems. The cabin also incorporates two hatches symmetrically spaced on the to p side. These hatches arehinged on the outside an d each is manually operatedby means of a handle an d mechanical latching mechanism. Both of the hatches have visual observation 'Nin-dows consisted of an inner and outer glass assembly.

*Retrograde Section: provides spaces for the installation of the four retrograde rockets an d six orbitalattitude maneuvering thrust chamber assemblies.

*Adapter Equipment Section: th e part of the spacecraft which is mated to th e launch vehicle, an d alsohouses the primary oxygen supply, batteries and/orfuel cells, coolant, electrical an d electronic components.Ten orbital attitude maneuver thrust chamber assemblies are mounted on th e large diameter end of thissection.

GEMINI LAUNCH VEHiCLE(TITAN I i)The Gemini Launch Vehicle (GLV) is the Air Force

Titan I I , modified to fit th e needs of the Gemini program. By using this proven vehicle, NASA ha s again,as in the Mercury program, utilized existing hardwareto the maximum rather than developing alaunch vehicle for the program.

The GLV is a two-stage vehicle which uses storablehypergolic propellent (the fuel an d oxidizer burn oncontact). Th e height of th e GL V without th e spacecraft is 90 feet an d it is 10 feet in diameter. The liftoffweight of the total configuration is approximately 150tons. Th e two first stage engines provide 430,000pounds of thrust at sea level; an d the single secondstage engine provides 100,000 pounds of thrust at it signition altitude (the first stage engines burn ou t an dth e second stage engine ignited at approximately200,000 feet) .

In order to assure th e reliability an d safety requirements fo r use of th e Titan II in the Gemini program,th e following modifications were developed an d made:

*A malfunction detection system (MDS) to senseVUH:"UO in any of th e vital launch systems, an d trans

mi t this information to the astronaut crew.

*A redundant flight control system which can takeover th e job of th e primary system if it should failin flight.

*Redundancy in the electrical system with neces-sary changes to provide power for such added launchvehicle equipment as the MDS.

*Substitution of radio guidance for th e inertial guid-ance to provide weight reduction.

t4. Clfft\VlIAV G R A F H ~ C H i u s t r a ~ s o r " 0';: the GemiUl; k n ~ ~ ( h e c n f ~ 9 U r t ' & k H ' 1 lShOW!fil'8 some major wems of hardware.


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* A new truss in th e second stage of the launchvehicle to hold much of the new flight control, MDS,and guidance equipment.

*New Stage II forward oxidizer skirt assembly tomate th e rocket with the Gemini spacecraft insteadof a warhead.

*Redundancy in the hydraulic systems to assurepilot safety, such as installa,tion of dual hydraulicactuators for engine gimbaling.

*Instrumentation to provide additional data duringpreflight checkout an d flight.

AGENA DA modified Agena D vehicle will be used as the target vehicle for Gemini rerrdezvous an d docking missions. This vehicle will be launched by a standardizedspace launch vehicle, and following burnout of theAtlas, it s propulsion system will be turned on until itattains an altitude of approximately 181 statute miles.The Agena will then be placed into a circular orbitand its power shut down to be turned on again formaneuvering following completion of docking with thespacecraft.

The Agena D, as inserted in orbit with its nose coneis 32-feet long; without th e nose cone, which is jettisoned after being in orbit, it is about 241;2-feet longwithout th e adapter. Th e Agena is five-feet in diameteran d also uses storable hypergolics to develop its capability of 15,000 pounds of thrust. Its engine will be atth e opposite end from th e docking adapter, an d whenthe astronauts start the Agena engine to maneuver thetwo spacecraft as a .single unit, they will be propelledbackward.

Modifications made to th e Agena D to make it suitable as the target vehicle f.or the Gemini rendezvousmissions included:

addition of a secondary propulsion system-increase in length to accommodate larger fuel

tanks provision for restart capability in the main pro

pulsion system electronics for command signals an d docking

maneuvers a docking adapter to permit mooring of th e space

craft and th e targetFLIGHT PROGRAM

The Gemini flight program was started on April 8,1964, with th e successful launching of GT-1 (GeminiTitan I) from Cape Kennedy, Florida, following aflawless five-hour countdown. Primary objectives ofthe mission were to check overall dynamic loads on astructural shell spacecraft during th e launch phase an dto demonstrate the structural compatability of thespacecraft and launch vehicle.

Since recovery of th e spacecraft an d separation of

the Gemini from the Titan's second stage were no tplanned, these two pieces of hardware went into anelliptical orbit with a perigee (low point) of about 100statute miles and an apogee (high point) of 204 statute miles, with an orbit time of 89.27 minutes. Velocityachieved during this mission was more than 17,500miles pe r hour.GT-1 reentered the earth's atmosphere over th eSouth Atlantic an d burned up on it s 64th orbit.

The Gemini flight schedule, beginning with the startof calendar year 1965 calls for one flight each quarter,barring difficulties which may be a result of natural ortechnical causes or both. An example of this previousstatement might best be presented by the story ofGT-2, which was originally scheduled to have beenflown during the third quarter of 1964.

The Gemini launch vehicle used in GT-2 wasshipped to Cape Kennedy July 10, 1964, following inspection an d acceptance at Martin Company's Balti-

GEMINI 2 is shown split seconds after liftoff from Pad 19 at CapeKennedy, Florida, January 19, 1965.


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more, Maryland plant, and its erection at th e Cape'sPad 19 complex was completed July 14. On August 17,th e launch vehicle ','vas exposed to lightning strikesnear th e Pa d area, causing a delay while necessaryrepairs were made an d systems revalidated. Late inAugust, it was determined necessary to de-erect thesecond stage of the launch vehicle as Hurricane Cleobattered the Florida Coastline. Another hurricane,Dora, hi t the area in September and this time bothstages were de-erected.

Three days later the launch vehicle was re-erectedfo r the last time an d work started toward completingnecessary work to make it ready for the launch. OnNovember 5, the Gemini spacecraft was mated to thelaunch vehicle and it seemed that, finally, th e secondan d last of the planned unmaIl11ed Gemini tests vilOuldbe completed early in December. With th e lauIlchfinally se t for December 9, th e countdown progressednormally and, when th e countdown reached zero thestage one engines were ignited. Th e Malfunction Detection System detected technical troubles due to aloss of hydraulic pressure and shut down the enginesabout T plus 1 second. After an inspection of the

vehicle by NASA, Air Force and associated contractor officials to determine the cause of th e difficulty,it was decided to re-schedule th e GT-2 launch fo rJanuary 1965.

GT-2 was launched from Pad 19 on January 19,1965, at about 9:04 a.m., EST. The mission, a suborbita l flight, lasted a little more than 19 minutes. Theprimary objective of th e flight, last of the unmannedtests scheduled in th e Gemini Program, was to flightqualify the total spacecraft as an integrated systemfor manned space flight.

A major item under careful observation was th ereentry module's heat protection equipment during th emaximum heating rate reentry situation planned.

Other requirements identified as primary missionobjective were th e satisfactory performance of th e following spacecraft systems - reentry control, retrograde rocket, parachute recovery, pyrotechnics, communications, electrical, sequential, environmental control, spacecraft displays, orbital attitude an d maneuveran d associated electronics, inertial measuring unit(during th e launch an d reentry phases), inertial guidance (during tum-around an d retro maneuvers),


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spacecraft recovery aids, tracking and data transmission, check-out and launch procedures, an d backupguidance steering signals throughout the launch phase.

During the flight th e maximum altitude attainedwas about 99 statute miles, an d the maximum earthfixed velocity was 16,709 miles pe r hour. Other majorevents followed the planned pattern closely. For instance, the planned exit g-force was estimated at 7.57and th e actual g-force during that phase was indicatedat 7.5; the reentry g-force was estimated at 9.576 an dth e data recorded indicated it was 9.6.

The GT-2 spacecraft was lifted out of the water at10:45 a.m., EST, by the aircraft carrier Lake Champlain, the same carrier which retrieved Astronaut AlanB. Shepard Jr., the first American to go into space.

FLIGHT CREWSFlight crews for the manned Gemini mISSIOn are

named well in advance of th e scheduled flight times.Since NASA originally planned the first mannedGemini flight for late 1964, th e crew was selected onApril 13. Astronauts Virgil 1. Grissom an d John W.

Young were named prime crew command pilot an dpilot, respectively, with Astronauts Walter M. Schirra,Jr., and Thomas P. Stafford as th e back-up crew in thesame positions.

On July 27, 1964, th e crew members for th e secondmanned Gemini mission were named. They are Astronauts James A. McDivitt and Edward H. White II , asth e prime command pilot and pilot, respectively, an dFrank Borman and James A. Lovell as th e back-upcrew.

From the time these crews are named they practically "live" with the spacecraft assigned to their particular mission. They spend much time at the McDonnell Aircraft Corporation plant in St . Louis, Missouri,where th e spacecraft is assembled an d keep an almostcontinuous check on it as well as participate in th espacecraft testing during all phases of assembly.

Additionally, they are at the Cape for the mating ofth e spacecraft and the launch vehicle an d participatein many simulations and tests prior to an d followingthat mating procedure. Th e crews spend literally hundreds of hours training for their mission. A major part

THE INSTRUMENT PANEL OF THE Gemini spacecraft is pictured above. The center panel is located between the two astronauts, the panel at theleft is in front of the command pilot, an d the panel at the right in front af the pilot.


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THE GEMINI translation an d docking simulator is shown in use abovewith Astronaut Richard F. Gordon Jr. at th e controls, at the left. Thissimulator is used by all the astronauts to gain experience for rendez-vous an d docking maneuvers in space with a target vehicle. Below isa picture of the Gemini Mission Simulator at Manned Spacecraft Centerat Clear Lake. This is one of tw o such training devices built for NASAby the McDonnell Aircraft Corporation. The other such simulator islocated in the Mission Control Center at Cape Kennedy, Florida. Thecrew station of ' he simulator is shown at the left, an d the instructor'sconsole's an d related equipment take the remainder of the space. Byuse of this simulator, assigned flight crews run through many simula-tions of their missions an d th e instructors are able to "insert" varioussystems failures an d other unexpected events in the flight simulationsequences in order that the pilots might gain experience in reacting tosuch situations. The simulators ar e also capable of being used in test-ing the Manned Spaceflight Network prior to actual missions byrunning the various mission simulations through the computer whiletied into the network. In addition to providing flight training for theastronauts, this training device is able to provide almost every con-tingency an d flight condition with th e exception of zero gravity.


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of this time is spent in simulated mission runs in theGemini Mission Simulator at Cape Kennedy, with eachastronaut spending more than 100 hours in this typetraining. Other refresher training for the selected crewsincludes such areas as abort training, egress activities,star identification an d familiarization with the constellation above the planned orbital path, parachute landings, centrifuge, restraint system procedures an d controls an d displays. All this training is accomplished toassure that th e crews are at a peak of efficiency atflight time. Th e many hours in simulated missions alsoprovides them with th e opportunity of working withflight controllers, network personnel, an d other personnel who support them on the ground during th emissions.

TYPICAL MISSION PROFILESThere are two typical mission profiles for Gemini

manned flights. I t might be more true to say there isone flight profile which pertains to all flights an d anadditional profile for th e rendezvous missions.

First, le t us consider th e non-rendezvous type missions which will start with three orbits and then graduate to longer flights later in the program with someflights being up to a 14-day duration.

Gemini flights really consist of a number of phasesprelaunch, launch, orbit, retrograde, reentry, landing,an d recovery.

The following series of 14 photos ar e the artist's concept of variousimportant activities during 0 Gemini mission. In Picture 1, above, theliftoff phase is shown with th e launch vehicle's 430,000 pounds ofthrust pushing the tolal Gemini configuration skyward.

Th e prelaunch phase begins with the arrival of thelaunch vehicle and th e spacecraft at Cape Kennedy.This is followed by the launch vehicle erection; continuing checks of both launch vehicle an d spacecraftsystems; physical mating of th e launch vehicle an dspacecraft; simulations to give further assurance thateverything is in working order; an d finally, the countdown on launch day.

When the Gemini configuration lifts off th e pad, th elaunch phase starts and continues through th e pointwhen the spacecraft is separated from th e launch vehicle's second stage approximately six minutes after liftoff. During this phase of th e mission, many vitalactions are required for a successful mission to takeplace. The roll program is completed (this is necessaryto reach proper altitude for orbital insertion) ; th e stageone engines are shut down about 21f2-minutes followinglaunch at an altitude of about 230,000 feet; the stagetwo engine is ignited an d following this ignition, stagesone an d two ar e separated. When the orbital insertionpoint is approached, th e astronauts cu t off the secondstage engine an d fire explosive charges which separateth e spacecraft from th e launch vehicle.

When these actions are completed, the orbital phaseof th e flight begins, and the activities from that pointon depend upon th e specific flight plan, and theplanned length of the mission. Typical actions duringth e orbital phase of flight include a continuous check

Picture 2 shows the separotion of the second stage of the launchvehicle an d the spacecraft from th e first stage following first stageburnout an d ignition of the second stage.


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of spacecraft systems, trfu"1s1ational and out-af-planeorbital maneuvering, completion of experiments assigned to the mission, possible egress of one of th eastronauts while in space, taping comments at specifiedtimes, communications with network stations, updating information in the computer, an d performing otherrequired pilot functions.

At a specific point in th e orbital phase of flight, th eastronauts will turn their spacecraft around so that th elarge en d is forward in flight in th e proper reentryattitude. They will then jettison the equipment sectionof th e adapter module, thereby exposing th e four retrograde rockets. Meanwhile, ground tracking stationswill transmit data indicating orbital position an d trackwhich the pilot will insert into the on-board computer.The computer will then determine when the plannedlanding point is within range of the spacecraft an d indicate th e time th e astronauts should fire the retrorockets to reach that point. The retrorockets will s-u.fficiently slow the spacecraft's orbital velocity to apoint where it will gradually from it s orbit. Th eretrograde section is jettisoned following retrofire, andthe spacecraft starts the reentry phase.

During reentry, th e computer continues to assess th eflight path; directs the crew to roll th e spacecraft withattitude control jets to position it properly to takeadvantage of it s lift capability an d to fly right or left

P ~ d Y : r e 3 in ?he ! 5 e r ~ 0 - 5 shOrtS th e 5eo::ol1d si'a!)e fHi 'fne s""cec,",n "' .;t nears th e i ' b i t c ~ i n S ( H " ~ 1 0 n pf.)int an d just pdor to ihe

setond slh'lge e n 8 ~ n e .

or to lengthen or shorten the descent as necessary toto the planned landing point. The Gemini space

craft can be "flown" in this manner to a point withina lO-mile circle in a 28,000 square mile area. Whenthe spacecraft reaches a point where a non-lifting trajectory will carry it to th e landing area, th e computervvill direct th e crew to establish a continuous roB toeliminate th e lift effect on th e spacecraft path. Aerodynamic drag then ultimately slows th e spacecraft tonear sonic speed.

At approximately 60,000 feet, the astronauts willdeploy a drogue chute which will further slow theirdescent an d stabilize th e spacecraft. At approximately10,000 feet, a large ring-sail parachute will be deployedan d the spacecraft will make a water landing.

The Department of Defense plays a major role inthe recovery phase of th e mission. Ships, aircraft, an dpersonnel are deployed to many parts of th e world torasure as a recovery as possible eithera or contingency landing.

The bulk of th e recovery forces ar e located acrossthe Atlantic Ocean, along th e plaI'illed orbital insertionpath in th e event of a high-altitude abort situation an din the primary planned hmding areas such as in th ecase of a three-orbit mission, are located at the en d ofth e first, second and third orbits. In this case severald,esiroyers are located in th e area at the end of the first

sage of the kH . CiYief r : i s t n : n ~ ~ ! ! , ! l ~ S ~ 1 l ' 1 { G fired C2fi e j { p ~ @ ..shre d1ClrSS i-o h d ~ h : ' l t e 5uq:h action.


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Pichne .s shows an ash'of/uHlit steppnng OU'{ ~ n t c space dUh"!ng a H g g h ~prior to aH'empting some e x t i " a ~ v e h i c u i O J r adiviiies.

and. second. orbits an d an aircraft carrier (the primerecovery vessel) an d a destroyer in th e area plannedfor landing at th e en d of a nominal three-orbit flighL

During other missions, there will be prime landingareas in both the Atlantic an d Pacific Oceans as wenas preferred contingency landing areas. This will require additional Department of Defense support, particularly in the number of Navy ships required tosupport the particular mission. However, in all cases,the bulk of th e recovery forces "win still be locatedacross th e Atlantic Ocean.

In addition, the Department of Defense has severalships an d aircraft with special equipment which areused in tracking operations an d these ships are capable, as well, of certain communication capabilities withth e spacecraft.

Following the spacecraft landing and the exact location determined by aircraft, pararescue men aredropped fron'! aircraft or helicopters an d install a flotation collar th e spacecraft to aid in keeping itafloat until a ship with special retrieval equipmentarrives an d completes the recovery operation.

The flight profile of th e spacecraft is much the samefo r rendezvous missions with some differences - theoxbital plane may be adjusted slightly by varying th eazimuth in order to place th e spacecraft into an orbitalpath which will most nearly compare to the path ofthe Agena D vehicle launched at an earlier time.

Picture 6 shaws the ash'@ru::n,ri's IlJsing thrust maneuvering rackets todose En on the t a w g e ~ vehDde dl!J6"Hng lfhe reS1lclezVCH,iS mission.

Pidures If 8 eind 9 show il'he app-E'@cdll of $ p C E ( e c i r ~ f ~docki"g with ' ' ' ' 'get !he two vehides i " ,10"

an d he [lv/cry ~ r o m whe * ~ r g 0 ~ vehide


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Picture 10 shows th e e'l"ipm"'"'t sedio" " f th e ",


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r j i c t U l ~ e 13 shows the spocecro'it En *he f i l J ] a ~ destent p h ~ s e ' 1 : ~ r i e ~ ther ~ r g e ring",stllul PCH'q::h::hu'ie is depi@yed ~ b C H J i ' Hl,OOO feei1.

ance system. I t is on e of the major sub-systems whichhas been incorporated in th e Gemini program, both toaid in th e rendezvous an d missions an d for th ereentry phase of al l missions.

When th e spacecraft closes to within 20 miles of th eAgena, the astronauts will be able to see a intensity flashing light to help them in their rendez


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ing are al l on a single circuit. The suits are connectedin parallel to this circuit and fitted with individualregulators so that each astronaut can select th e oxygenflow rate he desires.

Oxygen enters the suit just below th e chest fu'1d isrouted to th e face area, th e ann areas, th e legareas, then out an e::dnust line to be purified for reuse.

ELECTRICAL SYSTEMTh e major components of the prLmary electrical

power system consist of two fuel cells, five silver zincbatteries, utilization of grou,'1d power prior to liftoff,an d necessary switches an d controls for distribution ofA-C an d D-C power. On some flights batteries may beused as the primary electrical

j Q h ~Gzwain SP;;'lIk' $ U ~ t .

system.

Gewjni is th e first space vehicle to utilize th e fuelcell as a primary source of electrical power. Fromlaunch through orbital phases, until the equipmentsection is jettisoned these cells will be used as a primary power source. Through th e chemical reactionof oxygen an d hydrogen, each cell will also produce apint of pure drinking water for th e crew each kilowatthour of operation. This is a valuable by-product sinceit drastically cuts down the total water supply onboardat launch time, an d weight in Gemini as in al l spaceprograms is a prime consideration.

CONTROL AND TRACKiNGAlthough th e Gemini spacecraft will be controlled by

the pilots throughout the flight, there are a number ofdecisions which ar e made by flight controllers whichdirect th e actions of th e flight crew. The flight controllers are stationed in the Mission Control Centeran d this team of specialists continually monitors th evarious systems of both the launch vehicle and th espacecraft throughout al l phases of the fiight.

The Mission Control Center at Cape Kennedy hasbeen used for the unmanned Gemini flights an d willcontinue there through the early manned missions.Another Mission Control Center is being completed atth e Manned Spacecraft Center at Houston, Texas, andprobably, starting with th e third manned Gemini flight,control following liftoff will be shifted to that facilityfo r the remainder of th e Gemini missions an d al lApollo missions.

Prior to launch date, a mission readiness review isheld an d al l aspects of the launch vehicle, spacecraft,crew, manned spaceflight communications network,an d the weather are thoroughly reviewed as to theirflight readiness. At the conclusion of this review th eGemini Operations Director makes a Go/No Go deci-

based upon th e reports submitted.The flight date an d time is established th e

Director serious problemsm an y of the aforementioned

areas during th e interim period, the schedule is fo1-lovved. many hardware tests an d simulated

as well as :flight-readiness tests of both thespacecraft an d launch vehicle are prior to thermSSlOn there is always the possibility that, insuch a complex operation, troubles might crop up dur-

the final countdov'ffi which might necessitate "hold-the mission fo r minutes or even days, depending

on the trouble area and the length of time requiredfor corrective action. Such trouble areas might, forexample, be in major launch vehicle or spacecraftsystems, status of a downrange network station, orweather conditions.

director Control Center ha sfor th e mission from liftoff

upon information furnished


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him by his group of flight controllers concerning th evarious systems an d the nominal parameters for suchsystems, he must decide whether to permit the missionto continue as planned in case of an y serious systemsdeficiencies or to terminate th e mission. I t is antici-pated that during Gemini th e crew members ma y beable to make most necessary corrective actions.The manned spaceflight commullications networkplays a vital role in al l missions, both in tracking th espacecraft an d in relaying information from th e space-craft to Mission Control Center and from MissionControl Center to th e spacecraft.

The network presently consists of tracking stationslocated at Cape Kennedy; Grand Bahama Island;Grand Turk Island; Ascension Island; Bermuda; GrandCanary Island; Kano; Nigeria, Tananarive, Malagasy;Indian Ocean Ship; Carnarvon, Australia; CantonIsland; Kauai, Hawaii; two Pacific Ocean ships; PointArguello, California; Guaymas, Mexico; White Sands,

New Mexico; an d Corpus Christi, Texas. In additionto the three ships which have been specially modifiedfor the tracking duties, the Department of Defensehas also converted several aircraft to provide additionaltracking capability.

Two ]\;HSTRAM (missle tracking measurement)stations, Eleuthera an d Valkaria, may be used duringth e powered phase of flight to obtain additionaltrajectory data.

The Mission Control Center uses both digital com-mand and tone command systems an d can remotethese commands through some of the network stations.

High speed data is provided through the GroundOperational Support Systems Network through a com-bination of submarine cable, land lines an d radio. Untilcontrol is shifted to th e Mission Control Center(MCC) at Houston, al l this data is processed atGoddard Space Flight Center, Greenbelt, Maryland,then transmitted to the Cape. After control has been


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switched to the Houston MCC much of the information will be relayed through the Goddard facility inraw form an d will be processed at Houston. This willresult in a money-saving since the existing communications network is established and will require onlyextending the lines from Goddard to Houston.

Data received via the network and data originatingat the Control Center for transmission to the spacecraft is processed an d displayed in real-time, that iswithin several seconds of th e time of transmission.Through this exceptional communications system boththe flight controllers and the astronauts have vitalinformation concerning th e systems which is updatedon a continuing basis.

Following each flight, all of the data recorded isthoroughly reviewed an d a comprehensive report prepared. Th e information gathered from these reports isused by the engineers in the development of plans forfuture spaceflight missions.

The picture above shows a cutaway impression of the sectionsof th e Gemini adapter module an d the picture below shows a similarimpression of the sections of the reentry module.

AN ARTIST'S conception of an astronaut egressing from the spacecraftduring a Gemini flight an d attempting extra-vehicular experimentswith specially designed tools.


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A GEMINI SPACECRAFT is shown at P"d 19 at Cape Kennedy "s it is lifted to the top of the gantry prior to being mated with its launch vehicle.This activity takes place after static firing of both stages of the launch vehicle an d subsequent checks of "II systems of the spacecraft and thelaunch vehicle. Many other tests an d simulations ar e conducted following the mating procedure before the flight is made.

Documents

Gemini Program