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SHUTTLE LANDING OPERATIONS<\/p>\n
When a mission’s planned in-orbit operations have been accomplished,
\nthe emphasis on board the orbiter turns to the task of preparing the
\nvehicle for its return to Earth. Usually, the last full day in orbit
\nis devoted primarily to stowing equipment, cleaning up the living
\nareas and making final systems configurations which will facilitate
\npost-landing processing.<\/p>\n
The crew schedule, or timeline, is designed such that crew members
\nare awake and into their “work day” 6 to 8 hours before landing. At
\nabout 4 hours before deorbit maneuvers are scheduled, the crew and
\nflight controllers have finished with the Crew Activity Plan for that
\nmission. They now work from the mission’s Deorbit Prep handbook,
\nwhich covers the major deorbit events leading up to touchdown. Major
\nevents include the “go” from MCC to close the payload bay doors, and
\nthe final OK to perform the deorbit burn which will bring the orbiter
\nback to Earth.<\/p>\n
However, before the deorbit burn is performed, the orbiter is turned
\nto a tail-first attitude. (That is, the aft end of the orbiter faces
\nthe direction of travel.) At a predesignated time, the OMS engines
\nare fired to slow the orbiter down and to permit deorbit. The RCS
\nthrusters are then used to turn the orbiter back into a nose-first
\nattitude. These thrusters are used during much of the reentry pitch,
\nroll and yaw maneuvering until the orbiter’s aerodynamic,
\naircraft-like control surfaces encounter enough atmospheric drag to
\ncontrol the landing. This is called Entry Interface (EI) and usually
\noccurs 30 minutes before touchdown at about 400,000 ft. At this
\ntime, a communications blackout occurs as the orbiter is enveloped in
\na sheath of plasma caused by electromagnetic forces generated from
\nthe high heat experienced during entry into the atmosphere.<\/p>\n
As the orbiter glides toward a landing, initially at a velocity of
\n25,000 feet per second at the EI point, its velocity is gradually
\nslowed by a series of banks and roll reversals. As the atmospheric
\ndensity increases, the forward RCS thrusters are turned off, while
\nthe aft RCS jets continue to maneuver the orbiter until a dynamic
\npressure of 10 lb. per square foot is sensed by instruments on board.
\n At this point, the ailerons on orbiter’s delta-shaped wings begin to
\noperate and the aft RCS roll thrusters are stopped.<\/p>\n
When the dynamic pressure reaches 20 lb. per square foot, the
\norbiter’s wing elevators become operational and the RCS pitch
\nthrusters are stopped. A speed brake on the vertical tail opens when
\nthe orbiter’s velocity falls below Mach 10. Then, at Mach 3.5, the
\nrudder is activated and the final RCS burns — the yaw jets — are
\nstopped. The orbiter is now at an altitude of 45,000 ft., and is
\nbeginning what are called “area energy management maneuvers” which
\nenable it to intercept the landing approach corridor at the desired
\naltitude and velocity.<\/p>\n
As it nears the landing site, the orbiter is steered into the
\nnearest of two heading alignment circles called HACs. Each has a
\nradius of 18,000 ft. The orbiter is now in subsonic flight, at
\n49,000 ft., and about 22 mile from its touchdown point.<\/p>\n
In the future, final approach and landing will be controlled at this
\npoint the commander takes over control of the orbiter for final
\napproach and landing maneuvers by the Microwave Scanning Beam Landing
\nSystem (MSBLS) — called autoland — which will take over control 2
\nminutes before touchdown while the orbiter is at an altitude of
\n15,489 ft., 9.8 mile from the runway touchdown point, traveling at a
\nspeed of 410 mph. This phase of the flight will be completely
\nautomatic and the crew’s main task will be to monitor the MSBLS.<\/p>\n
The initial orbiter landing approach is at a glide slope of 19
\ndegrees. This is six times steeper than the 3-degree glide slope of
\na typical commercial jet airliner as it approaches landing.<\/p>\n
Just before the orbiter touches down, flare or pull-up maneuvers are
\nrequired to bring it into its final landing glide slope of l.5
\ndegrees. At touchdown — nominally about 2,500 ft. beyond the runway
\nthreshold — the orbiter is traveling at a speed ranging from 213 to
\n226 mph.<\/p>\n
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POST-LANDING OPERATIONS<\/p>\n
Once the orbiter has rolled to a stop on the runway, post-landing
\nactivities get underway involving the Orbiter Recovery Convoy.
\nMission responsibility has shifted from the Johnson Space Center back
\nto the Kennedy Space Center.<\/p>\n
Recovery Convoy. The Orbiter Recovery Convoy consists of a number
\nof specially-designed vehicles and a team of specialists who safe and
\nservice the orbiter and assist in crew egress. Included in the
\nconvoy are ll special vehicles and units. A brief description of
\nthese follows.<\/p>\n
Scape Trailer . Self-Contained Atmospheric Protection Ensemble
\n(SCAPE), vehicle, parked at a midfield location during landing,
\ncontains the equipment necessary to support recovery including
\nrecovery crew SCAPE suits, liquid air packs, and a crew who assist
\nrecovery personnel in suiting-up in protective clothing.<\/p>\n
Vapor Dispersal Unit. The Vapor Dispersal Unit is a mobile
\nwind-making machine able to produce a directed wind stream of up to
\n45 mph. It is an adaptation of a standard 14-ft. agricultural wind
\nmachine designed to protect fragile agricultural crops from frost
\ndamage or freezing. It is used by the recovery team to blow away
\ntoxic or explosive gases that may occur in or around the orbiter
\nafter landing. The fan can move 200,000 square feet of air a minute.<\/p>\n
Coolant Umbilical Access. This apparatus is a stair and platform
\nunit mounted on a truck bed which permits access to the aft port side
\nof the orbiter where ground support crews attach coolant lines from
\nthe Orbiter Coolant Transporter.<\/p>\n
Orbiter Coolant Transporters. This unit is a tractor-trailer
\ncarrying a refrigeration unit that provides Freon ll4 through the
\norbiter’s T-O umbilical into its cooling system.<\/p>\n
Purge Umbilical Access Vehicle. This vehicle is similar to the
\nCoolant Umbilical Access Vehicle in that it has an access stairway
\nand platform allowing crews to attach purge air lines to the orbiter
\non its aft starboard side.<\/p>\n
Orbiter Purge Transporter. This vehicle is a tractor-trailer which
\ncarries an air conditioning unit powered by two 300 KW, 60 Hz
\nelectric generators. The unit blows cool or dehumidified air into
\nthe payload bay to remove possible residual explosive or toxic gases.<\/p>\n
Cres Hatch Access Vehicle. The Crew Hatch Access Vehicle consists
\nof a stairway and platform on which is located a white room equipped
\nwith special orbiter interface seals. It contains pressurized
\nfiltered air to keep toxic or explosive gases, airborne dust or other
\ncontaminants from getting into the orbiter during crew egress.<\/p>\n
Astronaut Transporter Van. As its name implies, this van is used to
\ntransport the flight crew from the landing area. It is a modified
\nrecreational vehicle in which the crew can remove their flight suits
\nand be examined by a physician while enroute.<\/p>\n
Helium Tube Bank. This specialized vehicle is a trailer on which is
\nmounted a 12-tube bank container which provides helium to purge
\nhydrogen from the orbiter’s main engines and lines. The bank
\ncontains 85,000 cubic feet of helium at 6,000 psi.<\/p>\n
Orbiter Tow Vehicle. This unit is very much like the typical towing
\nunits used for large aircraft. However, it is equipped with a
\nspecial towing bar designed specifically for the orbiter. It is used
\nto move the orbiter from the landing facility to the OPF. It also is
\nused for moving the orbiter from the OPF to the VAB.<\/p>\n
Mobile Ground Power Unit. The final special vehicle for orbiter
\npost-landing operations is the Mobile Ground Power Unit which
\nprovides power to the orbiter if the fuel cells have to be shut down.
\nIt can deliver a nominal load of 10 of direct power to the orbiter.<\/p>\n
Augmenting these special orbiter recovery convoy vehicles are various
\nconventional command and emergency vehicles.<\/p>\n
Recovery Convoy Operations. The main job of the recovery convoy is
\nto service the orbiter, prepare it for towing, assist the crew in
\nleaving the orbiter and finally to tow it to servicing facilities.<\/p>\n
Even before the Shuttle is launched, the recovery convoy begins its
\npost-landing preparations by warming up coolant and purge equipment,
\nreadying ground service equipment and carrying out extensive
\ncommunications checks.<\/p>\n
During the Shuttle flight, the recovery convoy is on call in the
\nevent an earlier than planned landing is necessary.<\/p>\n
Major activity begins at about 2 hours before the orbiter is
\nscheduled to land. At this time chilldown of the purge and coolant
\nunits begins. About 1 hour, 40 minutes before landing, the recovery
\ncrew puts on their SCAPE suits and makes final communications checks.
\n At 5 minutes before touchdown, the recovery convoy is ready to go to
\nwork.<\/p>\n
After landing, the first staging position of the convoy is 200 ft.
\nup wind from the orbiter. The safety assessment team in the SCAPE
\nvan moves to about 100 ft. of the port side of the orbiter. A
\nSCAPE-dressed crew then moves to the rear of the orbiter using a high
\nrange flammability vapor detector to obtain vapor level readings and
\nto test for possible explosive hazards and toxic gases. Two readings
\nfrom three different locations are made to determine concentrations
\nof hydrogen, monomethyl hydrazine, and hydrazine and ammonia. If
\nthey find that high levels of gases are present, and if wind
\nconditions are calm, the Vapor Dispersal Unit — the mobile wind
\nmachine — moves into place and blows away the potentially dangerous
\ngases.<\/p>\n
Meanwhile, the Purge and Coolant Umbilical Access Vehicles are moved
\nbehind the orbiter and the safety assessment team continues to
\ndetermine whether hazardous gases are present in the area. Once the
\numbilical access vehicles are in position, and as soon as it is
\npossible to connect up to the liquid hydrogen T-O umbilical on the
\norbiter, the ground half of the on board hydrogen detection sample
\nlines are connected to determine the hydrogen concentration. If the
\nconcentration is less than 4 percent, convoy operations continue.
\nHowever, if it should be greater than 4 percent, an emergency power
\ndown of the orbiter is ordered. The flight crew is evacuated from
\nthe orbiter immediately and the convoy personnel clear the area and
\nwait for the hydrogen to disperse.<\/p>\n
If the hydrogen level is below 4 percent, the carrier plate for the
\nstarboard liquid oxygen T-O umbilical is attached to permit insertion
\nof purge air ducts. After the carrier plates have been installed,
\nthe Freon line and purge duct connections are completed and the flow
\nof coolant and purge air through the umbilical lines begins.<\/p>\n
Purge air provides cool and humidified air conditioning to the
\npayload bay and other cavities thereby removing any residual
\nexplosive or toxic fumes.<\/p>\n
When it is determined that the area around and in the orbiter is
\nsafe, non-SCAPE suit operations begin. First, in the forward orbiter
\narea, the priority is to assist the flight crew off the orbiter.<\/p>\n
The Crew Hatch Access Vehicle moves to the hatch side of the
\norbiter. When the access white room is secured, the orbiter hatch is
\nopened and a physician boards the orbiter to make a brief preliminary
\nmedical examination of the crew. The crew then leaves the orbiter
\nand departs in the Astronaut Transporter Van.<\/p>\n
The flight crew is replaced on board the orbiter by an exchange crew
\nwho make preparations for ground towing operations, installing switch
\nguards and removing data packages from onboard experiments, if
\nrequired.<\/p>\n
Meanwhile, after allowing for a 30-minute orbiter tire cool down,
\nthe Tow Vehicle crew installs the landing gear lock pins, and
\ndisconnects the nose landing gear drag link. The Tow Vehicle is
\npositioned in front of the orbiter and the tow bar connection is
\nmade. Finally, about two hours after landing the orbiter is towed
\noff the runway.<\/p>\n
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SOLID ROCKET BOOSTER RETRIEVAL OPERATIONS<\/p>\n
After the Space Shuttle is launched, the Solid Rocket Boosters (SRB)
\nare jettisoned at 2 minutes, 7 seconds into the flight. They are
\nretrieved from the Atlantic Ocean by special recovery vessels and
\nreturned for refurbishment and eventual reuse on future Shuttle
\nflights.<\/p>\n
SRB separation occurs at an altitude of about 30 miles The
\nseparated boosters then coast up to an altitude of 47 miles and
\nfree-fall into an impact zone in the ocean about 158 miles downrange.
\n The so-called splash “footprint” is in an area about 7 miles wide
\nand about 10 miles long.<\/p>\n
When a free-falling booster reaches an altitude of about 3 miles its
\nnose cap is jettisoned and the SRB pilot parachute pops open. The
\npilot parachute then pulls out the 54-ft. diameter, l,100-lb. drogue
\nparachute. The drogue parachute stabilizes and slows down the
\ndescent to the ocean.<\/p>\n
At an altitude of 6,240 ft., the frustum, a truncated cone at the
\ntop of the SRB where it joins the nose cap, is separated from the
\nforward skirt, causing the three main parachutes to pop out. These
\nparachutes are 115 ft. in diameter and have a dry weight of about
\nl,500 lb. each. When wet with sea water they weight about 3,000 lb.<\/p>\n
At 6 minute and 44 seconds after liftoff, the spent SRBs, weighing
\nabout 165,000 lb., have slowed their descent speed to about 62 mph
\nand splashdown takes place in the predetermined area.<\/p>\n
The parachutes remain attached to the boosters until they are
\ndetached by recovery personnel.<\/p>\n
Waiting near the impact area are two 176-ft.-long,
\nspecially-designed SRB recovery vessels. Their first job is to
\nrecover the main SRB parachutes. Each vessel is equipped with four 5
\nft. 6 in. -diameter reels which wind the parachute winch lines onto
\nthe reel similar to the way line is wound onto a fishing reel.<\/p>\n
The frustum-drogue parachute also is reeled in until the 5,000-lb.
\nfrustum is about 100 ft. from the recovery ship. The drogue
\nparachute lines are then reeled in until the frustum can be lifted
\nout of the ocean by a 10-ton-capacity crane.<\/p>\n
Next, the empty SRB casings are recovered using a special device
\ncalled the Diver Operated Plug (DOP). This procedure calls for a
\nteam of underwater divers to descend to a depth of about 110 ft. and
\nplace the DOP into the nozzle of the casing. A 2,000-ft.-long air
\nline attached to the DOP is plugged into an air compressor on the
\nrecovery vessel. Air is pumped into the booster at 120 psi to empty
\nwater from the casing — a procedure called “dewatering.”<\/p>\n
Under ideal weather and sea conditions, the retrieval operation
\ntakes about 5 and 1\/2 hours. The recovery ships with the retrieved
\nSRBs in tow, sail to Port Canaveral, travel north up the Banana River
\nand dock near Hangar AF at the Cape Canaveral Air Force Station,
\ntheir mission completed.<\/p>\n
SRB Disassembly Operations. The retrieval ships take the SRBs to a
\ndock at the Solid Rocket Booster Disassembly Facility (SRBDF) located
\nat Hangar AF — a building originally used for Project Mercury, the
\nfirst U.S. manned space program.<\/p>\n
The SRBs are unloaded onto a hoisting slip and mobile gantry cranes
\nlift them onto tracked dollies where they are safed and undergo their
\nfirst washing.<\/p>\n
The casings are then taken to the SRBDF for disassembly into their
\nfour main segments: two aft skirt and two forward skirt assemblies.
\nThe main casing segments undergo further cleaning, after which they
\nare placed on railroad cars and shipped to the manufacturing plant in
\nUtah where they undergo final refurbishment and are again loaded with
\npropellant.<\/p>\n
Meanwhile, the nose cone frustums and parachutes are processed at
\nthe Parachute Refurbishment Facility in the KSC Industrial Area.<\/p>\n
Parachute Refurbishment . The SRB Parachute Refurbishment Facility
\n(PRF) was originally built to process the parachutes used in the
\nGemini manned space program and was modified for the Shuttle program.<\/p>\n
The SRB parachutes are taken to the PRF for refurbishment on the
\nreels from the recovery vessels. The PRF also receives and stores
\nnew parachutes and hardware for the SRBs.<\/p>\n
Specific procedures for refurbishment of the SRB parachutes include
\nuntangling the lines, and hanging them on an overhead monorail and
\nautomatically washing and drying them. When this is completed, and
\nfinal inspections are conducted, the parachutes are folded on
\n64-ft.-long tables and stored in canisters for eventual reuse.<\/p>\n
