NASA Facts Manned Space Flight Projects Mercury and Gemini 1966

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    Vol. II. No.8(Rev. Jan . 1966)

    PageNASA F CTSAn Educational Services Publication of the

    National Aeronautics and Space Administration

    MANNED SPACE FLIGHTPROJECTS MERCURY AND GEMINI

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    Astronouts Virgil I. Grissom (left) and John W. Young (right) in pressure suits climb into the Gemini ProcedureTrainer for a flight test profile and training session in preparation fo r the first manned Gemini flight.

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    Page 2

    MANNED SPACE FLIGHTA major goal of the United States space pro

    gram is manned space flight to the moon, andsafe return to earth of the astronauts, before theend of this decade.NASA's manned space flight program hasbeen divided into three big steps, or projectsMercury, Gemini, and Apollo.

    Already accomplished, Project Mercury pavedthe way by using experimental one-man vehiclesand proving that men could be sent into spaceand returned safely to earth.

    Project Gemini's two-man spacecraft will fulfill a two-part plan: first, extending orbit missionsup to 2 weeks at a time; second, developing thetechnique of rendezvous and docking, duringwhich two space vehicles are maneuvered closetogether and finally joined, or "docked."

    That same technique of orbit rendezvous-butaround the moon instead of earth-will enableastronauts in the three-man Project Apollo spacecraft to achieve lunar landings.

    PROJECT MERCURY

    Project Mercury became an official program ofNASA on November 26, 1958. A Space TaskGroup to initiate this neW venture was formedat Langley Field, Virginia. This group evolvedinto th e Manned Spacecraft Center, Houston,Texas and after a nationwide call fo r je t pilotvolunteers, seven astronauts were chosen inApril 1959.

    The one-man Mercury spacecraft was designedand built with a maximum orbiting weight ofabout 3,200 pounds. Shaped somewhat like abell (truncated cone), the craft is 74.5 incheswide across the bottom and about 9 feet tall.The astronaut escape tower on top adds another17 feet for an overall length of approximately26 feet at launch. Two boosters were chosenthe Army's Redstone (78,000 Ibs. thrust) an d AirForce's Atlas (360,000 Ibs. thrust)-for suborbitaland orbital flights, respectively. Before themanned flights began, Ham, the chimp, success-

    Vol. II, No.8

    Mercury one-man spacecraft alongside mock-up oftwo-man Gemini.

    fully achieved a suborbital Mercury-Redstone 2(MR-2) flight on January 31, 1961.

    Then all was ready for the historic MR-3 flightof May 5, 1961, as Astronaut Alan B. Shepard,Jr., made the first U.S. manned space flight. Hissuborbital mission of 19 minutes took his Freedom7 spacecraft 116 miles high into space.

    After another countdown for MR-4 on July 21,1961, the Redstone booster hurled AstronautVirgil I. "Gus" Grissom through the second ballistic (suborbital) flight in the Liberty Bell 7.

    This ended the Redstone non-orbital tests asth e Mercury-Atlas series of flights advanced toorbital missions. Again preceding the firstmanned attempt the chimp Enos made an orbitalflight (MA-5) on November 29, 1961.

    An MA-6 space milestone, on February 20 ,1962, made Astronaut John H. Glenn, Jr., thefirst American in orbit, completing three circuitsin Friendship 7.

    On the MA-7 mission of May 24, 1962, Astronaut M. Scott Carpenter in Aurora 7 completed another three-orbit flight.

    MA-8 of October 3, 1962, doubled the flighttime in space as Astronaut Walter M. Schirra, Jr.,orbited six times, landing Sigma 7 in the Pacificrecovery area, instead of the Atlantic.

    Finally, on May 15-16, 1963, AstronautL. Gordon Cooper, Jr.'s Faith 7 completed a 22-orbit mission of 34 1/2 hours, triumphantly concluding the flight phase of Project Mercury. Thetechnical report, "Mercury Project Summary" waspublished in October 1963, five years after theproject began.

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    Vol. II, No.8Originally, Project Mercury was assigned only

    two broad missions by NASA-f i rs t , to investigateman's ability to survive and perform in the spaceenvironment; and second, to develop the basicspace technology and hardware for mannedspace flight programs to come.

    Beyond these basic goals, Mercury accomplished the following: developed a NASA man-agement system to car ryon more advancedmanned space flight ventures; explored the fundamentals of spacecraft reentry; started a familyof launch vehicles from existing rockets that ledto new booster designs; expanded the aerospaceindustry by NASA contracting; set up an earthgirdling tracking system; trained a pool ofastronauts easily augmented for future spaceexploration programs.

    PROJECT GEMINIProject Gemini was named after the twin stars

    Castor and Pollux in the constellation Gemini.NASA decided to follow the Mercury's basic

    "capsule" design fo r Gemini spacecraft, savingtime and engineering efforts. But the two-mancraft is wider (7.5 feet), taller (11.5 feet), andmore than twice as heavy (7700 Ibs.). Thesedimensions give 50 percent more cabin space,making room fo r much new equipment and withit for greater performance flexibility.

    Since Mercury's Redstone an d Atlas boosterslacked the power to orbit the heavier two-man

    Page craft, a modified version of the military Titanbecame the Gemini Launch Vehicle (GLV), witha total thrust of 530,000 pounds (first stage430,000 pounds). The hypergolic (self-ignitingp r o p ~ l I a n t s used are non-explosive, an astronausafety factor.

    Chosen fo r Gemini's prime mission of orbitarendezvous an d docking was the Agena-D "target" vehicle, a new version of the reliableAgena-B second-stage that, with Thor or Atlaboosters, had orbited many satellites and

    . launched Mariner an d Ranger probes. Agena's"stop-and-restart" rocket engine, capable ocutoff and retgnition at least four times, is important for r e n d ~ z v o u s maneuvers with GeminiThe hypergolic propellants are hydrazine annitrogen tetroxide.

    Agena-D is 32 feet long and 5 feet in diameter, is shaped like a cylinder and tapered at thefront end to a blunt point.

    FIRST GEMINI-TITAN FLIGHT (GT -1 )The first Gemini-Titan test fl ight (GT-1) on

    April 8, 1964, was an almost perfect lift-off, asTitan boosted the unmanned Gemini craft intoorbit from Launch Complex 19 at Cape Kennedy,Fla.

    Gemini's apogee (high point of orbit) was 204miles, perigee (low point) 99.6 miles, and therevolution period around the earth was 89.27minutes.

    EQUIPMENT RETROGRADE RE ENTRYMODULE

    DOCKING

    Separated segments of Gemini mock-up. At right is docking structure of Agena whichcontains appara tus for l ink-up of spacecraft and rocket.

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    Page 4._ . ~ - .... ~ - . - - - - - . - - - ... .

    Gemini-Titan launch at Cape Kennedy.

    Vol. II, No.8In orbit 4 days, the craft came down as cal

    culated on April 12. There was no attempt atrecovery since the flight was mainly a structuralintegrity test for the booster / spacecraft combination, and for its guidance system.

    GEMINI EXPERIMENTSFollowing GT-1 , NASA scheduled a series of

    scientific, biological, and technological experiments for subsequent Gemini flights. Separatebioastronautics (space medicine) experiments in-volve the physiological reactions of the astronautsin space.

    In "extravehicular activities" experiments, theGemini astronauts, each in turn, will leave theirspacecraft and practice getting around and working in empty space. It is planned that thisactivity will include tests of specially designedspace tools that a weightless astronaut can usewithout twisting effect.

    Capability to leave the craft is afforded bylife-support features of the Gemini space suit.While outside of the spacecraft, the astronaut,in effect, will be a "human satellite."

    GEMINI SPACECRAFTThe Gemini craft is designed to be piloted byits two-man crew. After an automated launch,

    the Gemini spacemen take over : turning, changing speed, even shifting orbits.

    The spacecraft consists of two major portions-the reentry module (package) and theadapter module. The latter, in turn, also hastw o separate sections, so that Gemini, aslaunched, is actually a three-part structure.

    Only the reentry module returns to earth.This module contains the " living" section wherethe tw o astronauts ride.

    The life-supporting cabin is double-walledwith an inner shell around the crew's pressurizedcompartment and an outer shell as the craft'sexternal hull.

    Between these shells is a storage space forelectronic gear and other apparatus-a technological improvement over the Mercury craft,whose components (parts) were "stacked" upon

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    Vol. /I, No. 8one another inside the crowded pilot's compartment. In contrast, much Gemini equipment isin the double-walled storage area, where it canbe easily checked, adjusted, replaced, even whenGemini is in place atop Titan on the launch pad.

    The aft (rear) section contains more equipment, and bottommost is the ablative (meltingand evaporating) heat shield that protects thereentry module from air-friction heat on earthreturn.

    One purpose of the two-part adapter module,which tapers and flares out from 7 112 feet to 10feet in diameter, is to "adapt " (fit) the narrowGemini to the Titon booster's broad top. Sec-ondly, the adapter's 90-inch deep volume isanother housing area fo r equipment.

    The adapter section adjacent to the crew'sreentry module is the retrograde assemblage,holding two sets of engines-retrorockets (forreducing speed) an d space-maneuvering thrusters.

    The adapter's aft part, the equipment section,holds fuel cells, attitude controls, radio units,and a l iquid-coolant radiator to dissipate internalspacecraft heat away into open space.

    The lower end of this two-part adapter ismated, by means of a metal collar, to the top ofthe Titan launch rocket.

    EJECTION SEATBased on a jetplane technique, Gemini's light

    weight ejection seats can, in emergency, catapultthe astronauts out of two large hinged hatchesthat open mechanically.

    Unlike Mercury's automatic ejection sensors,Gemini's system relies entirely upon the astronaut crew's quick reflexes, because Titan's nonexplosive propellants merely burn and allow timefor human reactions .

    COMPUTERAmong Gemini innovations is a "shoebox"

    computer, weighing only 57.6 Ibs. and occupyin g a mere cubic foot of cabin space, yet able tomake the computations for the intricate rendezvous and docking maneuvers with the orbitingAgena-D.

    Page FUEL CELL

    Another "space f irst" is Gemini's fuel celgenerating electrical power by chemical meansMuch l ighter than the equivalent batteries thereplace, two groups of fuel cells provide 1,00watts each, supplying the spacecraft's totaelectrical needs.

    GUIDANCE SYSTEMAboard Gemini is an ingenious inertial guid

    ance system which records and totals every bof progress forward, backward, and sidewaysfrom the earth-launch starting point to the spacedesti nation .

    l inked into the guidance system during orbitamaneuvers are other units-computer, radarelectronic controls, attitude thrusters, propulsionunits-so that the astronauts' m a ~ t e r conrols canaccurately achieve rendezvous and docking withAgena.

    RENDEZVOUS RADARGemini's high-definition radar gives the range

    (distance), bearing (direction and angle of approach), and closing speeds of the chase andtarget vehicles, with data starting when they are250 miles apart.

    Later, the high-intensity flashes of Agena'sl ight beacon become visible to the astronauts, aa maximum range of 50 miles. These opticaobservations, plus radar tracking, are then combined, as manual controls guide Gemini towardrendezvous with Agena.

    Undoubtedly, the Gemini astronauts wi" eventually blend their own intuitive skills with computer data, and gain the know-how to swing thetw o vehicles around in space with the routineease of parking cars on earth.

    COMMUNICATIONS SYSTEMSThree major communications systems are car

    ried aboard Gemini: the voice system, which in-cludes an intercom connection between theastronauts; the receiver of command signals andupdated orbit information from Manned FlighControl; data collection tapes and their relaytransmitters for automatic transmission of reportsto earth.

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    Vol. II , No.8

    Gemini spacecraft is raised to top of gantry fo r mating to Titan launch vehicle .

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    Vol. II, No. 8ENVIRONMENTAL CONTROL SYSTEM (ECS)

    The Gemini Environmental Control System in the reentry module's cabin compartment sustains

    the astronaut pilots and permits them to carryou t their duties.

    Though the Gemini l i fe-support system is simi lar to the Mercury ECS, major engineeringchanges have gone into it . Each astronaut hastwo parallel suit circuits for oxygen, plus the option of using the cabin's habitable (purified) atmosphere while being partially unsuited fo r morefreedom of action.

    Mercury ' s bottled gas has been replaced inGemini by a liquid oxygen supply, requiring lessstorage volume for the maximum 14-day supply.

    lhe third major ECS change is an improvedmethod of d issipating unwanted heat into space.

    FOOD AND WATERBesides being a body fuel, food is important

    to man as a psychological " uplift. "A basic diet of 2,550 calories per man will be

    fulfilled by freeze-dried foods including meats, soups, desserts, an d fruits. Water restores

    them to their original form .Water will be recovered from the atmosphere

    within the spacecraft, also will be derived as afuel cell byproduct.

    GEMINI LAUNCH VEHICLEThe Gemini launch vehicle is a modification

    of the military Titan II. Fueled by stable andstorable propellants, it is 10 feet wide and 89feet long (first stage booster 70 feet). The combined Gemini-Titan stands 108 feet high.

    An important new Gemini launch vehicle device is the Malfunction Detection System, whoseelectronic monitors watch the vehicle 's performance during launch for possible booster trouble.Warning signals allow ample time fo r the astronauts to abort (cut short) th e mission, i f necessary, by using their ejection seats.

    AGENA-D TARGET VEHICLEIn the rendezvous of Agena-D and Gemini,

    the two spacecraft will be joined nose to nose.Hence, after first being orbited, the Agena turns

    Page 7around and goes backwards. Its fore end ithus in docking position as the later-launchGemini arrives nose first.

    Bringing the front ends of t wo spacecraft together, while whirling around earth at nearl18,000 mph, is much more difficult than mid-airefueling between a jetplane and a tankerHence, the mid -space meeting of rocket vehiclemust feature the quickest and most reliable contact via easy-fitting docking devices .

    At the Agena ' s forward end, the target dockin g adapter (TDA) is a cylindrical collar, withinwhich is a docking cone i l lum inated by two approach lights. Self-adjusting mechanisms locfirmly to the inserted nose of Gemini and mooth e two vehicles.

    Prior to docking, an invaluable aid to theastronauts is the lighted status display panelmounted outside Agena's lOA. Its visual monitors reveal the Agena equipment's operationareadiness by means of nine l ights and threedials. Typical are green lights for " OK todock, " "PPS TIME " (primary propulsion system)which clocks the amount of burning time left fothe main rockets before fuel depletion.

    STANDARDIZED SPACELAUNCH VEHICLE

    Historically fa mous as the booster fo r sixhighly sucessful Mercury space flights, the Atlaswill also serve as the Agena launch rocket inGemini's rendezvous experiments .

    Known as the Standardized Space launchVehicle (SSLV), this 62-foot booster is poweredby five conventional liquid rocket engines. Atlaspower alone cannot orbit the Agena, and atbooster burnout, pyrotechnic devices (explosivebolts) at the SSl V-adapter's forward end releasethe Agena, whose own eng ine fires to gainorbital velocity.

    LAUNCH CHECKOUTSPrior to a scheduled Gemini rendezvous mis

    sion, all the hardware of two complete launchvehicles and two spacecraft is meticulouslychecked an d rechecked many times over. Because the failure of the tiniest relay or switch

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    Page 8can ruin an entire multimillion dollar space ven-ture-and also risk two human l ives-this tediously painstaking checkout procedure is vitallynecessary.

    Al l the major vehicles arrive at Cape Kennedybroken down into modules an d sections. Afterdozens of checkouts until all modules are matedinto full vehicles, 7 days remain before lift-off.In that week, the final tests include: radio andradar circuits; simulated flight via computer; sim-ulated launch with the two astronauts aboard thespacecraft; servicing an d fueling of Titan withcheckout of engine systems; complete check oftotal Gemini Titan equipment; 300-minute dressrehearsal countdown; final 2-day servicing andcheckout.

    Only after this long parade of cross-checkcheck-outs does the real countdown start.

    Sharing in all main tests, the tw o Gemini astro-nauts gain full confidence that the Titan boosteran d Gemini spacecraft will successfully bear theminto orbit, and safely return them to earth.

    The Mission Control Center of MSC, at CapeKennedy, monitored the early Gemini flights. Inlater missions, the f l ight phase has been moni tored by a new Mission Control Center at theManned Spacecraft Center, Houston, Tex.; thelaunch phase still being conducted by the CapeKennedy team.

    TRACKING NETWORKExpanded from the former Mercury network,

    the Gemini tracking system comprises 13 landstations an d tw o tracking ships, the latter fillinglandless gaps in the Pacific Ocean.

    Besides tracking equipment, all stations havetwo-way communications with the Gemini space-

    Some have additional telemetry equipment or command signal transmitters.

    GEMINI RENDEZVOUS MISSIONA Gemini rendezvous mission calls fo r send-

    g up the Agena target vehicle from CapeLaunch Complex 14 approximately

    4 hours prior to the Gemini chase vehicle's liftff from Launch Complex 19.

    Vol. II, No. 8The Agena is propelled into a circular orbit

    185 miles up, after which precise velocity andtrajectory elements are calculate d. About 24hours later Gemini blasts off, within the specified"launch window" - the time interval during whichlaunch will produce an orbit permitting the twocraft to meet.

    Gemini's orbit must be in the same plane(slant toward equator) as Agena's. This restrictsthe Gemini launch window to about 2 hours ineach 24, for the 5-day period the target vehiclecan wait for rendezvous. Certain orbit-correctingmaneuvers by the Agena, before Gemini launch,can double the launch window.

    The basic plan is to maneuver the Gemini intoa circular orbit whose altitude is approximately23 miles less than the Agena.

    TARGET CAPTUREWhen the distance between vehicles is 250

    miles, radar is switched on. As the gap closesto 50 miles, the Gemini astronauts pick up theAgena's flashing beacon and take over themanual controls.

    Aiding the astronauts is the status displaypanel outwardly mounted on the Agena-D, giving visuol data on Agena fuel reserves, electricalpower, attitude position, al l of which is processedthrough the computer along with the Geminicraft's own movements.

    During these maneuvers the relative speeddifference between the vehicles has been cut toless than a 2 mph drift rate so that their nosestouch gently.

    I f the first docking maneuver is imperfect, theAgena is merely bumped away and no harm isdone. The astronauts simply back off fo r an-other try. In a successful contact, the Gemini'snarrow end enters the Agena's target dockingadapter, whose latches clamp shut to preventthe tw o vehicles from slipping apart. Then amotorized Agena unit pulls the Gemini noseconeinward 011 the way.

    Once the two craft are tightly moored, match-in g electrical contacts meet and give the Geminiastronauts direct control of Agena's onboardequipment-guidance, propulsion, attitude con-trol, relay switches, and the rest.

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    __ _ ___________ ___ __________.. PageVol. II, No. 8

    Union of the tw o vehicles results in a larger REENTRY AND RECOVERYGemini / Agena spacecraft almost 50 feet long, Their rendezvous maneuver completed, the

    astronauts unhook their Gemini craft from theAgena (left in orbit) and prepare fo r earth-returnThey first ascertain that upon f iring the retrorockets, their downward trajectory will land themin a designated recovery area . This may require orbi t corrections by means of theipropulsion units .

    much more powerful an d versatile than either ofthe tw o original craft. With the main Geminirockets in back and the Agena thrusters in thefront, the two-part Gemini-Agena spacecraft canmove either forward or backward without havingto turn around. The doubled rocket power alsoallows fo r unique space performances throughthe series of manned Gemini missions.

    PAINTING BY DAVIS MELTZER, ItESEA,RCH n GEORGE W . aEAITY () N .G .

    Scanning the dark sky, Gemini 's radar locates Agena a t a distance of 250 miles and holdsthe quarry in view (far left). Gemini's computer determines th e approach speed and pointa t which the tw o craf t will meet . An 8-foo t boom an tenna on the t arget craft receivesradio signals from the astronauts , wha order Agena to assume a stabilized position. Guidedby flashing beacons, the astronauts speed up their vehicle and maneuver it toward Agena'scone-shaped docking collar . Though the two craf t t ravel 17,500 miles an hour, theirdifference in speed is only a little more than one mile an hour a t final closure. Crewmenmaneuver Gemini 's nose into a V-slot in Agena's collar; then mechanical latching fingerssnap the craft together. Th e space-mated couple turn around, placing Agena's restartableengine in posit ion to propel the vehicle into a new orbital path so that the astronauts canprobe deeper into space. They will detach Agena before re-entering earth 's a tmosphere.

    FLIGHT ASTRONAUTSGT-3 Virgil I. GrissomJohn W. YoungGT-4 James A. McDivitt

    Edward H. WhiteGT-5 Charles Conrad, Jr .

    L. Gordon C_pe rGT-7 Frank Borman

    James Loven

    HIGHLIGHTS OF PROJECT GEMINI MANNED SPACE FLIGHTSDATE FLIGHT TIME REVOLUTIONS REMARKS

    3/23/65 04 hrs. 54 min. 3 America's first two-manned flight.6 /3 /65 97 hrs. 59 min.

    8/21/65 190hrs . 56 min.12/4 /65 33 0 hrs. 35 min.

    62

    12 020 6

    First "walk in space" by an American as t ronaut . First extensive maneuver of spacecraftby a pilot.Eight-day flight proved man 's capacity fo rsustained functioning In space environment .World 's longest manned orbi tal flight.

    GT-6 Walter M. Schlrra, Jr . 12/15/65 25 hrs. 51 min. 16 World's first successful space rendezvous.Thomas Stafford

    GT-8 Nell A. ArmstrongDavid R. Scott

    3 /16 /66 10 hrs. 44 min. 6 World's first successful docking in space .

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    Vol. II, No.8 Page 11

    Gemini spacecraft mockup being checked out by Astronaut.

    DEFINITIONSAPOGEE: In an orbit about the earth, the point at whichthe satellite is farthest from the earth; the highest alt itudereached by a sounding rocket.ASTRONAUTICS: The art, skill, or activity of operatingspace vehicles. In a broader sense, the science of spaceflight.ATTITUDE: The position or orientation of an aircraft,spacecraft, etc., either in motion or at rest, as determinedby the relationship between its axes an d some referencel ine or plane such as the horizon.BALLISTIC TRAJECTORY: The trajectory followed by abody being acted upon only by gravitational forces andthe resistance of the medium through which it passes .

    BOOSTER ROCKET: A rocket engine, e ither solid orl iquid fuel, that assists th e normal propulsive system orsustainer engine of a rocket or aeronaut ical vehicle insome phase of its f l ight . A rocket used to set a missilevehicle in motion before another engine takes over .DOCKING: The process of bringing tw o spacecraft to -gether while in space .HYPERGOLlC: Propellants, fuel and oxidizer, which ignitespontaneously upon contact; hydrazine and nitrogentetroxide are examples.MODULE: A self-contained unit of a launch vehicle orspacecraft which serves as a building block fo r the overallstructure. The module is usually designated by its primary

    (Continued on page 12)

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    ~

    Page 12 Vol. II, No .8

    Gemini Docking Simulator.

    DEFINITIONS- (Continlled from page 11 )function as "command module", lunar landing module, etc .A one-package assembly of funct ionally associated electranic parts; usually a plug-in unit .PERIGEE: That orbital point nearest th e earth when theearth is the center af attraction .PITCH: The movement of an aircraft or spacecraft aboutits lateral (nose going up or down) axis.PROPELLANT: Any agent used fo r consumption or combustion in a rocket and from which the racket derives itsthrust, such as a fuel , oxidizer , additive, catalyst , or an ycompound or mixture of these.REACTION, ENGINE: An engine that develops thrust byits reaction to ejection of a substance from it ; specifically,such on engine that ejects a je t or stream of gases createdby the burning of fuel within the engine .REENTRY: The event occurring when a spacecraft orother object comes bock into the sensible atmosphere afterbeing rocketed to altitudes above the sensible atmosphere ;the action involved in this event.RETROROCKET: A rocket fitted on or in a spacecraft, satel lite, or the like to produce thrust opposed to forwardmotion.

    NASA FACTS format is designed fo r bulletin-board displayuncut, or for 8 x lOY, looseleaf notebook insert ion whencu t along dot ted l ines and folded a long solid lines. Fornotebook ring insertion , punch a t solid dots in th e margins.

    ROLL: The rotational or oscillatory movement of on aircroft or similar body which tokes place about a longitudinalaxis through the body-ca l led " ro" " fo r any amount ofsuch rotation.SENSOR: The component of on instrument that canverts oninput signal into a quantity which is measured by anotherpart of the instrument. Also cal led " sensing element. "SUBORBITAL: Non-orbit ing or ball ist ic f l ight trajectoryfrom launch point to target point.TRAJECTORY: In general, the path traced by any body,as a rocket, moving as a result of externally applied forces .WEIGHTLESSNESS: A condition in which no acceleration,whether of gravity or other force can be detected by onobserver within th e system in question . A condition inwhich gravitat ional an d other external forces acting on abody produce no stress, either internal or external, in thebody .YAW: The lateral rotational or oscil latory movement ofan aircraft , rocket, or the l ike about a transverse axis.The amount of this movement, i.e., the angle of yaw .

    NASA FACTS is an educational publicat ion of NASA's Educational Programs and Services Office . It will be mailed toaddressees who request it from: NASA, Educational Publicat ions Distribution Center , FAD-I, WaShington, D.C., : : Z u ~ 4 6 .

    U. S. GOVERNMENT PRINTING OFF ICE : 1966 OF-208 -860For safe by the Superintendent of Documents , U.S. Government Printing Office

    Washington, D.C. , 20402 - Price 20 cents pe r copy

    -,