NASA Facts Space Shuttle Operations in Near-Earth Orbit

8/6/2019 NASA Facts Space Shuttle Operations in Near-Earth Orbit

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An Educational Publcatlonof theNational Aeronautics andSpace Administration

Space Shuttle:Operations In Near-Earth Orbitby Robert Haynes

Performing Useful Tasks In Space Items in and out of the cargo bay and fllght at Kltty Hawk more than 80 years

NASA's Space Shuttle is the first from place to place in the vlcrnjty of the ago. Shuttle routinely travels up to 320

space-flight system that can be Shuttle. Spacelab, built and paid for by kilometers (200 miles) above the Earth

reused. Much more than a launchthe European Space Agency (ESA), and can orbrt there for as long as 10

vehicle, it not only delivers cargoes to Can be car r ied in th e bay and days On a typical 7-day mlssion,

space, but can return them to Earth, 1ts has expanded the Shuttle's capab~l~ty Shuttle lets sc~entists each beyond the

versatile design lets it take off like a to perform scientific operations ~n planet's surface to perform regular

rocket, fly in Earth's atmosphere and Space. The modular form of Spacelab studres and observations, learnlng

gravity like an airplane, and behave in a~lows t o fly in many configurations to Important I ~ S S O ~ Shat will benefit thelr

space like a spacecraft, gulded by meet different needs. Rockets attached d~sciplines.

reaction thrusters. to space vehicles launched from

The Shuttle has already proven itself bay propel payloads

a space-worthy craft, turning missions into higher orbits or toward their

that might have been fallures into missions in deeper space.

successes. For example, after the Space Shuttle will play a major role

multi-million dollar Solar Maximum in shaping the U.S. space efforts for the

satellite failed to operate properly in rest of this century. Many lessons have

space, shuttle crew members repaired been learned since that first 12-second

it in orbit and returned it to fulloperation. The Shuttle retrieved twoother satellites (Westar and Palapa-B)and returned them to Earth forrefurbishing.

Crew members have an array ofsophisticated computers andmachinery at their fingertips. A RemoteManipulator System (RMS) moves

Shut t le on ded ica ted Space lab mission. When Spacelab occu pies the lul l caigo bay.Shui i le 's mission wi ll be dedicated to scient~ l ic perat ions. Boih 01 Spacelab 's malnelements are shown here. a iong h abi iabie module and two pal ie(s



Designed for Hard Work

The Shuttle Orbiter is a r el ia ~l e ndreusable workhorse that carriespayloads and crew s routinely to andfrom space. O n the launc h pad, it ismated to two solid fuel rocket boostersand a large external fuel tank. Theboosters help lift the assemblage awayfrom Earth's gravitational pull and fallinto a designated oc ean area whe rethey are retrieved for reuse. Theexternal fuel tank h olds prope llants thatpower the three main engines.

The only part of the launchconfiguration that is not reused is theexternal tank. It holds a total of 72 0,000kilograms (1,584,000 pounds) ofpropellants, consisting of liquidhydrogen (fuel) and liquid oxygen(oxidizer). Fuel from the externa l tankdrives Shuttle to a poin t just sho rt of its

final orbit, where the tank separates

and drops back to Earth. The tankbreaks up in the atmosphere and fallsinto a predetermined remote oceanarea. Shuttle coasts a few secondsand then fires its two o rbitalmaneuvering engines to position it inorbit.

The O rbiter is about the same lengthand weight as a comm ercial DC-9airplane. It measures 37 meters (122feet) long and 17 meters (57 feet) high,has a wingspan of 24 meters (78 feet),and weighs abo ut 77,300 kilograms(170,000 pounds) without fuel orpayload. Its appearance, however, ismarkedly different. High performance

double-delta (or triangular) wings and alarge cargo bay (where passengerswould sit on a n airplane) give Shuttle achubby appearance.

Another difference when comparedwith a conventional airplane is theShuttle's thermal p rotection system.

Every part of Shuttle's external shell isshielded by some type of th'ermalprotection. Most notable are the rigidsilica tiles that p rotect areas of intenseheat when O rbiter reenters Ea rth'satmosphere. White tiles co vering theupper and forward fuselage sectionsand the tops of wings can absorb heatas h igh at 650°C (120 0°F). Black tiles



on the underside absorb highertemperatures, up to 1260°C (2300°F).Areas that receive the most heat onreentry, such a s the no se and leadingedges of wings, are covered with blackpanels made of reinforced carbon-carbon (RCC).These p anels soak up

heat in excess of 1260 °C (2300 °F).The engines that push Shuttle into

an Earth orbit and steer it on its wayhave been tested in successive flights.They will lift continuously heavierpayloads un til their full lifting capacity is

payloads until their full lifting capacity isreached . Payload capacity is not onlyaffected by ca rgo we ight, but also bythe weight of fuel necessary to lift it, theorbital azimuth and length of mission inspace, and the size of the cre w andconsumables needed to support them.

The three main engines are designedfor reuse on more than 50 missions,and the two maneuvering engines, oneither side, for about 100 missions.

While the Orbiter is in space,thrusters in its nose and aft sectionscontrol its attitude. The nose con tains14 thrusters, called primary reactioncontrol engines, and 2 vernier enginesfor fine tuning. In the tail or aft section,each pod contains 12 primary enginesand 2 vernier engines. All primarythrusters and vernier engines weredesigned for a 100-mission lifespan.

From launch to landing. On the launchpad, the Shuttle Orbiter is mated to twosolid fuel booster rockets and a large fueltank. At ab out 24 nautical miles after lift off,the two booster rockets are lettso ned .They fall in an a rc, slowed by parach utes,

to a remote ocea n area, where they areretrieved for later use. Shortly before orbitalinjection, the main engines are shut do wn,and the external tank is separated. Thetank tumbles to Earth, falling in p~e ce s veran u ntraveled ocean area. T he Orbitercoasts a few secon ds, then maneuveringrocke ts fire to position its orbit. Cargo baydoors op en, and the crew performs itsmission. Whe n mission is comple te, thebay doors close and the Shuttle leavesorbit wlth thcust from its m aneu vering.rockets. It reenters the atmosphere andlands on a runway like an airplane.

The O rbiter cabin, a 71.5-cu bic-meter (2 500 cu . ft.) area, normallyhouses a 4- to 7-member crew. It ispressurized to Ea rth's air pres sure atsea leve l. Temperatures are keptbetween 18" and 26°C (65-80°F) andliving quarters below the flight deck

offer sleeping, hygiene, and foodprepa ration facilities.

Heavy-duty hydraulic systemsprovide power for the Orbiter's ascent,reentry, and landing operations. Thehydraulic system is powered by threeindependent auxiliary pow er units,fueled by monopropellant hydrazine.Hydraulic actuators move wingaerodynamic control surfaces, a bodyflap, and the rudder. They also operatevalves, lower landing gear, control mainengine thrust direction, and providepower for Orbiter brakes.

Electrical pow er operates everythingelse. Electricity is provided by threefuel cells. The cells provide 20-30kilowatts during ascent, when most ofthe pa yload equipment is turned off,and 14-36 kilowatts while payloadmachinery is in use during orbit. Abyproduct of the fuel cells is potablewater, used for drinking , hygiene, andonboard experiments.

All Shuttle subsystems aremonitored by a unique five-computernetwork configured in a redundantoperating group (four operate at all

times and one is a backup ). Theysimultaneously process data fromvirtually every a rea of the Shuttle, eac h"communicating" with the others andcomp aring data. If the com putersdisagree , they, in effect, vote betweenthemselves, and the data from theoutvoted computer are ignored.

Spacelab will be carried insideOrbiter's cargo bay on a s many asthree or more missions per year.Spacelab consists of two mainelements, which c an be flownseparately or together: a pressurizedhabitable module, where experimentsare cond ucted in a shirtsleeveenvironment; and p allets, on whichexperiments ca n be m ounted forexpos ure to space. As many as fivepallets can be flown at a time. Whenonly pallets are flown, essentialsubsystems are normally carried in an8-foot-long cannister called an igloo.The igloo houses subsystems for



operating experiments, includingcom ma nd, data management, andelectrical power subsystems, which onother missions are located in thehabitable module.

Shuttle Is Tested

Shuttle Orbiter

On April 12,1981, John Young andRobe rt Crippen stepped aboard theShuttle Columbia for the first mannedflight of a reusable spacecra ft. But longbefore their maiden voyage, this newveh icle had been tested and retested.

In the mid-1970s, after the ba sicaerodynamic delta design had beendec ided , wind-tunnel tests began. Oneby o ne, Shuttle's components weretested and pronounced ready. In 1977,the first manned Orbiter, nam ed

Dep loying a nd re trieving satellites . On e of the Shuttle's useful features is the RemoteManipulator System (th e remote a rm). Here it is show n lifting a satellite into orbit from thecargo bay. But the arm may also help in retrieving objects from space and in moving themabout the vicinity of the Shuttle while in orbit.

Enterprise, was released from its How Shu ttle com pare s with a irplane s. Although Shuttle is about the same length and"pi gg yb ac k" perch atop a carrier weight as a DC-9 irplane, it do esn't look like one. Th e Shuttle is a high-performan ceBo ein g 747 aircraft five times to test its craft, and its modified delta design and wide carg o bay give it a chubby appearance .



aeronautical capabilities on approachand landing. Engines were groundtested as were compu ters, the heat-resistant tiles, and all linkages joiningthe assemblage.

But it was not until mid-April 1981that Shuttle p roved to b e an integrated

space transportation system. It was thefirst of four test flights with mannedcrew s, dubbed th e Orbital Flight Test(OFT) progra m. During OFT, crewscond ucted more than 1100 carefullyoutlined tests and data collections.OFT was declared a su ccess. After thefourth flight lande d on July 4, 1982,Shuttle was declared operational.

Airline To Space

Shuttle c an b e thought of as theairline that will transport humankind to

a future habitat in space. Accelerationis lim~tedo less than 3 t ~ m e sheacceleration of gravity during ascent,and less than 2 .5 t~ m es uring reentry(with 1 g being the acceleration ofgravity at sea lev el). This me ans m enand women not spec~allyra~ned s

astronauts c an travel in it, experiencingabout the same acceleration as onsome carnival r~d es . y comparison,crew s of Apollo had to withstand asmuc h as 8 1 g during reentry IntoEarth's atmosphere.

While riding the Shuttle, travelers liveand work In a shirtsleeve env ironment,without cumbersome spacesuits andbreathing apparatus. The main thing towhich sp ace travelers w ~ ll ave to getaccustom ed is the near absence ofgravity (microgravity),which candras t~cally hange the way they work,

sleep, and eat. Howev er, microgravity(near weightlessness) itself IS anessential element for certainexpe r~me nts huttle crews will conducwhile in orb~t.

Looking To Th e FutureOn one of its upcoming missions,

Shuttle will carry Spac e Telescope in~ t s argo bay a nd plac e it in orbit.Unhindered by Earth's distort~ngatmosphere, th ~selescope will be ableto study objects in the universe 50times fainter and 7 times farther aw aythan even the large 200-inch Earth-bound telescope at Mt. Palomar,California.

Space Telescope In cargo bay. Called the Hubble Telescope, this orbiting observaiorywill be launched into an Earth orbit from the Shuttle's cargo bay



Space Telescope will reveal objectswe have never be fore viewed. It willscan the very edge of the universe,looking back toward the b eg~n ning ftime for possible clues abo ut theunive rse's origin. By simply lettingscientists view 350 times more space

than they do now, it is expected toreveal extraordinary and unanticipatedphenomena.

Shuttle m akes building a mannedSpac e Station possible. As currentlyenvisioned, modules and othercomponents of the station will bedelivered into space on 6 to 8 Shuttlefllghts. Astronauts will asse mble theseelements In orbit using the Shuttle as awork platform. This flrst phase of theSpa ce Station, called the "initialoperational capa bility,' ' 1s sched uled forthe early 1990s. Once the Space

Station is built, Shuttle will periodically

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revisit it, replenishing expendablesupplies, such as fluids, oxyg en, food,clothing, and spare parts forexperiments.

Also on board Shuttle will beSpacelab, flying either as "m ixedcargo" or on "dedicated" missions

occupying ih e whole cargo bay. InOctober 1985, he German Spacelabmission D-1 was a dedicated Spacelabflight, uslng a long habitable module toconduct experiments in life sciencesand materials sciences. Germanydeveloped the payload and wasresponsible for mission ope rations. TheUnited States flew only one experimenton this Octob er 1985 rnisslon.

Spacelab specialists perform thekinds of tasks better done In spacethan on Earth. Scientists have alreadystudied the Earth from s pace . They

have chec ked on weather conditions,

land u ses, air pollution, and lake sllting,and exp lored the depths of our solarsystem and b eyond through orbitingtelescopes (without Earth'satmosphere to obscure their view).Experiments on board Spacelab haveincluded growing large near-perfect

crystals, developing pure alloys, drugs,and lenses of a purity unatta~n ableunder the influ ence of Earth's gravity.

As inha bitants of Earth, we are n olonger restricted to living on our nativeplane t. We are well on our wa y tobecoming permanent residents andworkers in spa ce. Already regularvisitors to thls formerly hostrleenvironme nt, we will soon be able toperform in frlendly surround ings,stretching the limlts of our knowledgeand understanding.

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NASA Facts Space Shuttle Operations in Near-Earth Orbit