Space 
The Space ShuttleA program which ran thirty years between 1981 and 2011, the Space Shuttle program was the way the USA acceded to the orbit during last decades. The Space Shuttle was a new concept allowing a launch with partly reusable parts and a landing after the atmospheric re-entry. During 30 years, the Space Shuttle program successfully carried people into orbit repeatedly, launched, recovered and repaired satellites, conducted cutting-edge research and built the International Space Station (note: a large part of that tutorial, or the texts linked to, are written at the present time; such passages and texts should be read at the past as the Space Shuttle program ended by the summer of 2011, as those texts might be, or not, adapted in a near future)
| About the Space Shuttle How a Flight Does Unfold? | Missions Archive |
About the Space Shuttle| History | Structure |
History | shuttle Discovery, mission STS-103. picture NASA |
The Space Shuttle program was launched as soon as 1972 as it was by the time of the Apollo 16 mission moonwalks that the U.S. Congress had passed funding for the Space Shuttle program. It was President Richard M. Nixon who announced on Jan. 5, 1972, his decision for NASA to build the Space Shuttle, stating that 'it would revolutionize transportation into near space.' Once Congress authorized the funds, NASA on July 26 awarded the contract to the North American Rockwell Corporation of Downey, California, to begin construction of the first orbital vehicle. It was more or less derived from a 1960's hypersonic weapon program. Various companies were awarded the making of the Shuttle's various parts in 1972 and 1974, as the first Shuttle was designed for test purposes only and not for real space use. It was named "Enterprise," from the famous "Star Trek" Starship (the name Enterprise had been given, with the approval of President Gerald R. Ford, after fans of the Star Trek series letter to NASA and the U.S. space agency since saw several other reference to that inclusive-minded series or involvement with). It eventually flew in September 1976 and began a series of 13 test flights. Such flights ranged from captive, manned or unmanned flights atop a Boeing 747, to manned, landing, free flights as a first landing occurred at the Redstone Army Airfield, in Alabama. The Challenger orbiter (OV-099) was another test-vehicle built and completed by 1978 to serve to test a lighter weight orbiter and to ensure the lighter airframe could handle the stress of space flight as computer software at the time wasn't yet advanced enough to accurately predict how the new, optimized design would respond to intense heat and stress. The best solution was to submit the vehicle to a year of intensive vibration and thermal testing. Columbia eventually became the first shuttle to really fly in space (STS-1), in April 1981. The first flight of the Space Shuttle interestingly occurred, April 12th, 1981, which is exactly twenty years after Yuri Gagarin first manned spaceflight in April 1961. The STS-1 flight hold two crewmembers only, with astronaut John Young, a veteran of four previous spaceflights including a walk on the moon in 1972, commander, and Navy test pilot Bob Crippen pilot. At the difference of the previous manned programs, no unmanned test flight had been performed! The Shuttle may be considered NASA's next main step following the Apollo program. The first four shuttle flights were considered test flights however as it was not until the fifth flight that shuttle missions were considered operational. Shuttles were built at Boeing's Palmdale, Calif. The NASA chose the Space Shuttle astronauts mostly from the Air Force as they had reckoned that they would need Air Force support for the flights. Some of those came from the 'Manned Orbital Laboratory' (MOL) program, a undercover reconnaissance satellite one. The Space Shuttle total have cost over 40 years $196 billion for the design, construction, 5 orbiters, and 135 flights, which is some more above what the Apollo program, at $156 billion. It allowed for a continuous access to space by the USA as some however point to a 'magnificent failure,', the program failing to meet the target of a easy, safe and frequent access to space, with two orbiters lost in flights and 9 flights performed in average a year instead of 50. The Space Shuttle had to satisfy both NASA and the Department of Defense, which imposed the exact shape of wings or the size of the payload bay. During the formative years of the space shuttle program, NASA Dryden F-15 and F-104 jets were used to flight-test in atmospheric conditions only various advanced Thermal Protection System (TPS) materials for the shuttles. Up until the space shuttle, only disposable, one-use-only ablative materials were used as TPS materials on spacecraft. The idea of using reusable materials was radical. With the US space vehicles before, and after the Space Shuttle program, disposable, cheeper capsules some also deem that the program might have been a diversion from the natural evolution of rocketry! The concept behind the Space Shuttle was a three-step plan to space, in replacement of what to do after the Apollo program, a reusable orbiter allowing to a space station as the latter to Mars
The Space Shuttle program eventually ended by the summary of 2011 with shuttle Atlantis landing a last time on Thursday, July 21st, 2011, returning from a mission to the International Space Station. The 30-year endeavour thus came to a end. After a interruption of the Space Shuttle program following the dramatic loss of the Columbia shuttle by February 2003 when it was flying back Earth, missions took back by September 2006 only with the STS-115 mission. US President Bush, by 2004, had laid down a new space program of the U.S.A. as it was scheduling the retirement of the space shuttles in 2010. When President Obama acceded to presidency, he radically changed that program and the shuttles eventually were retired during the summer of 2011. The last years of the space shuttle mainly was dedicated to the completion of the orbital outpost, or marred with the loss of shuttle Columbia in February 2003 and the technological failures and new procedures affecting the last flight of the orbiters' fleet. Fundings had prevented NASA to a second-generation shuttle and, despite updates, forced to use the 1960's and 1970's tech vehicles during a lapse of 30 years! The Space Shuttle program allowed to science in orbit, US-Soviet cooperation, repair of satellites or defense missions. Shuttles were built at Boeing's Palmdale, Calif. as the total cost over 40 years of the program was $196 billion, 5 orbiters, 135 flights, 543 million miles in more than 21,000 orbits. 1,333 days will have been passed in space through 355 crewmembers, mostly Americans. Some point to that the program did not met its targets with 9 flights performed in average a year instead of 50. Two shuttles also were lost in flight, Columbia in February 2003 and Challenger by 1986. Only 3 orbiters were still in use by the last years of the program, Discovery, Atlantis and Endeavour namely. With the retirement of those, the USA, on a other hand, are left with no access to Earth's orbit and to depend upon Russian Soyuz during some years as any new US space program mostly lies in limbo and a object of debate and questionment. Even the Russian Roskosmos agency ironically stated the day of the landing of the last flight of the Space Shuttle program: 'So long [the Space Shuttle], and thanks for the help,' as 'from today, the era of the Soyuz has started in manned space flight, the era of reliability.'
Here following is a list of more details about the five NASA orbiters which flew like space shuttles of the Space Shuttle program. Enterprise, or the OV-101, never was intended for spaceflight and is now on display at the Dulles Airport outside of Washington, D.C. (by order of delivery like a active spaceship to the Kennedy Space Center, Fla; OV stands for 'Orbital Vehicle')
Columbia was in charge of the program first flight, the Orbital Flight Test Program or the missions STS-1 through STS-4 as it recovered too the Long Duration Exposure Facility (LDEF) satellite from orbit (mission STS-32, January 1990) or performed the STS-40 Spacelab Life Sciences mission in June 1991 - the first manned Spacelab mission totally dedicated to human medical research. Shuttle Challenger performed her maiden flight, the STS-6, on April 4, 1983 with the first spacewalk of the program and the deployment of the first satellite in the Tracking and Data Relay System constellation. The first American woman, Sally Ride, flew aboard Challenger too on the STS-7 mission as the orbiter was the first too to carry two U.S. female astronauts on the STS-41-G mission. Challenger was the first orbiter to launch and land at night during the STS-8 mission and was the first orbiter to land at the Kennedy Space Center, by the end of the STS-41-B. Spacelabs 2 and 3 flew aboard the ship on missions STS-51-F and STS-51-B, as did the first German-dedicated Spacelab on STS-61-A. Discovery has her first flight during the STS-41-D mission, on August 30, 1984. Discovery milestones include the deployment of the Hubble Space Telescope on the STS-31 mission in April 1990 or the launching of the Ulysses spacecraft to explore the sun's polar regions on the STS-41 in October 1990 Atlantis lifted off on its maiden voyage on Oct. 3, 1985, on the STS-51-J mission, which was the second dedicated Department of Defense flight. Later missions included the launch of the Galileo probe to Jupiter on the STS-34 in October 1989, or the STS-37 mission with the Gamma Ray Observatory in April 1991. Endeavour, NASA's newest orbiter began flight operations in 1992 on the STS-49 mission, a Intelsat VI repair mission
->Challenger Space Shuttle First Flight
In early 1983, after five flights of the Space Shuttle Columbia successfully completed, based on lessons learned, Challenger used a lighter airframe and employed lighter blankets instead of tiles for thermal protection in certain areas of the vehicle, saving 2,486 pounds in overall weight. For additional launch performance, Challenger’s main engines were rated to 104% maximum thrust versus Columbia’s 100%. The maiden flight of Challenger also marked the first use of a lightweight External Tank (ET), weighing about 10,000 pounds less than the tank flown on the first Shuttle flight, and the use of lighter Solid Rocket Booster (SRB) motor casings. All these improvements resulted in an increased payload mass capability. The Shuttle would deploy the TDRS satellite as another major objective of STS 6 was to conduct the first Extra-Vehicular Activity (EVA) or space walk from the Space Shuttle, and indeed the first US EVA since Skylab in 1974
StructureAt launch time, the Space Shuttle is an ensemble of three components, that is the orbiter itself, an expendable external fuel tank (External Tank, ET) and two lateral, reusable solid propellant boosters (Solid Rocket Boosters, SRBs). The terms "Space Shuttle", specifically, apply to the system in the launch configuration (the orbiter, the External Tank, the two boosters). "Orbiter" is used for the manned vehicle, which eventually goes orbital. The two boosters are providing 80 percent of the boost during launch, as they separate 2 minutes into the flight, at an altitude of 24 NM (44 km). The relay is taken by the three shuttle's main engines which continue to push. The two SRBs are parachute-splashing and recovered in the ocean to be refurbished and reused for next launches. It's NASA's Marshall Space Flight Center (MSFC), Huntsville, Ala. which is managing the SRBs -their recovery and refurbishment included. The rust-colored External Tank (ET) is 27.6-feet (9-m) wide and 154-feet (45-m) tall. It's providing 535,000 gallons of liquid hydrogen and liquid oxygen to the shuttle's main engines during the first 8½ minutes of flight. It's then jettisoned. The External Tank is managed by the Space Shuttle Propulsion Office at NASA's Marshall Space Flight Center, as it's Lockheed Martin Space Systems Co., New Orleans, which is the primary contractor. The Shuttle may orbit between 115 and 400 miles high (185-640 kilometers) at a speed of 17,321 mph (27,800 km/h). The Shuttle may deliver a maximum cargo of 63,500 pounds (29 tons) into orbit, as the orbiter itself weighs 180,000-pounds (about 82 tons). Three Auxiliary Power Units (APUs) provide hydraulic power to steer the vehicle during ascent and entry. The crew may range from two (this was the case for the first missions) to eight, as the average manning is between five and seven. The Shuttle, over the 20 years during which it worked, has evolved and it is significantly different today than it was when first launched. Four shuttles have been built from 1981 to 1985: Columbia, Challenger, Discovery, and Atlantis. Shuttle Challenger exploded 73 seconds after take-off in January 1986. Endeavour was built to replace it. Shuttle Columbia was lost in February 2003
 | click to a view of the Shuttle's panel (a heavier picture is available for flightsimmers). picture NASA/KSC |
The Shuttle's Panel. Just like in a commercial airliner, the Shuttle's panel is a 'glass cockpit' one. That occurred with the installation of the Multifunction Electronic Display System (MEDS) or 'glass cockpit' replacing several cathode ray (CRT) tube displays, gauges and electromechanical displays with 11 active matrix liquid crystal flat-panel, full-color displays in the shuttle cockpit. Nine flat-panel screens are located in the forward cockpit and two in the aft cockpit. Previous displays were old green screens with no graphics and very few capabilities and the other instruments were actually mechanical airplane cockpit meters and hard to replace with replacement parts as they were designed in the 60s, built in the 70s and by the mid-80s the companies that built those meters had gone out of business. By as soon as the 1970's NASA Langley Research Center worked with aircraft industry partners to develop a concept for a fully electronic glass cockpit flight display system as aircraft industry hardly was beginning to use CRTs. The Boeing Co. eventually developed the first glass cockpit for its 767 aircraft in 1982. A glass cockpit is lighter and less power-consuming as it improves the crew-orbiter interaction with easy-to-read graphics of key flight indicators, such as attitude, altitude and speed. Atlantis was the first orbiter to be modified by 1998, followed by Columbia by those same years as Discovery and Endeavour were by about 2005. Each orbiter MEDS is configured differently for every mission, according to what the astronauts want to see displayed in each window as the MEDS is tested before each transfer to the launch pad, from the firing room to ensure the correct displays work. The next cockpit improvment will be "smart cockpits", reducing the pilot's workload during critical periods
It takes rail to move the reusable boosters four 150-ton segments from manufacturer ATK plant in Promontory, Utah to the Kennedy Space Center during a seven-day trip. Each incoming shuttle-booster segment, which is already filled with its solid explosives, rests on a cradle in a custom-built railcar as a clamshell-like cover, hinged at the top, protects the hardware. The route involves commercial rail companies such as Union Pacific, Kansas City Southern, Norfolk Southern, CSX and Florida East Coast Railway (FEC) and then the Kennedy railroad crew takes charge. At the northern end of the space center, the NASA Railroad splits into two nine-mile stretches of track. Kennedy's mainline runs South, past the Vehicle Assembly Building and other Launch Complex 39 facilities before reaching the center's Industrial Area. To the East, a second line of track extends to the Cape Canaveral Air Force Station. Although the train has to traverse a drawbridge spanning the Indian River, the bridge is not strong enough to hold a train with so many heavy cars. The solution: Empty "spacer" cars are added between the segments to distribute the weight over the individual spans of the bridge, so the weight on the bridge is manageable. Speed into KSC, generally, must not exceed 25 mph. The segments are then disembarked into the booster Rotation, Processing and Surge Facility, where they are rotated to vertical and prepared for stacking. Kennedy Space Center railroad was upgraded by the 1980s to materials allowing a better resistance to the tropical climate there, like were locomotives too with 1,500-horsepower locomotives used today and closing to 4 1/2 to 5 million pounds with one motor. In addition to shuttle boosters, NASA Railroad carries to nitrogen tetroxide, an oxidizer used as rocket propellant or Air Force Titan rockets, Navy Trident missiles. Spent solid rocket booster casings are sent back to the ATK plant the other way
One of the most carefully choreographed aspects of preparing a shuttle for launch involves placing three 7,700 pound main engines into the back of the spacecraft. The engines face slightly up toward the rudder, they have to be installed at an angle. The main engines are taken out soon after a shuttle returns so their components can be inspected closely and without the engines in the way, processing for the orbiter is safer and quicker. The main engines however originally were not planned like that removal and the initial five missions were inspected in-place without removal. Thus procedures or machinery involved now were deviced by experience. Some of the launches during the early part of the Space Shuttle Program were scrubbed a few seconds before liftoff, after the main engines had ignited but were shut down for a problem. Called a 'pad abort,' the situation meant a mandatory engine change at the launch pad, with the shuttle in its launch position. The installation of the main engines, generally, takes about four hours
The accident of shuttle Columbia, in February 2003, as it was returning Earth, has led to the shuttles' fleet undergoing 41 major modifications following the recommendations of an investigation board. Among them are devices to allow the inspection and possible repair of the Shuttle's heat shield in space, like the Orbiter Boom Sensor System, cameras, and laser systems, sensors installed in the wings' leading edge to monitor the wings for debris impacts during launch, a new digital camera to view the External Tank at this same moment. As far as the External Tank (ET) is concerned, it has been modified with two forward bipod heaters there where the tank connects to the Orbiter. Two NASA jets, at last, are imaging the Shuttle launching from a distance of 15 to 20 miles (24-32 km) during 150 seconds from liftoff to separation of the Solid Rocket Boosters. Launches, now, occur in daylight only as, in case of a docking to the International Space Station (ISS), a "Rendezvous Pitch Maneuver" is performed. One hour before the docking occurs, the Shuttle pauses 600 ft below the ISS and flips end over end, by 180°, rotating at 3/4 of a degree per second. This allows the ISS residents to further assess the Shuttle's thermal protection during 93 seconds
 | click to a view of the Shuttle's stack and the mobile service structure. diagram site 'Amateur Astronomy' based on a picture NASA/KSC |
Five general purpose computers computers, or GPCs with a storage capacity of one megabyte and a speed of 1.4 million instructions per second serve as the brains of the space shuttle, collecting the signals from the orbiter, External Tank and solid rocket boosters' myriad sensors and controling the orbiter varied moves and motions which constitute the Space Shuttle's computer-driven flight control system. The networked computers are set up so that four are operational and one is a backup that could fly the launch and entry if the others failed. The shuttle's primary flight software contains about 400,000 lines of code. For comparison, a Windows operating system package includes millions of lines of source code as shuttle programmers focus solely on what the software must do for a mission to succeed. A single shuttle flight requires a series of software sets to operate at different times on the computers. There are overlays for pre-launch, launch, in-orbit operations, in-orbit checkout and entry. The GPCs were upgraded by 1991, from their original design. The current 1 megabyte allows programmers to more efficiently add, or replace, into the code. Although the GPCs run the spacecraft during a mission, astronauts take a number of relatively modern computers with them into orbit in the form of laptops, like modified IBM ThinkPad A31p computers for rendezvous assistance, entry and landing simulations and e-mailing Earth, with that modernity having a trade-off that the laptops are not nearly as reliable as the GPCs due to radiation effects and use of less critical commercial off-the-shelf software, as they do not work on life-support or high-criticality systems that require the reliability found in the GPCs. Laptops are susceptible to radiation particles, to badly written software or vibration during takeoff, as with a laptop two to three memory changes due to radiation occur during the time the Space Shuttle take to fly to ISS. During a mission, higher, to the Hubble Space Telescope, such changes occur up to 30 times. Laptops too crash when the shuttle passes through the "South Atlantic Anomaly," which is an area where the magnetic field draws in to Earth, offering less radiation filtering. The GPCs don't crash for radiation concerns because the GPC hardware includes a memory scrubber that prevents the system from reading radiation-changed memory. GPCs are not set up for performance-intensive work such as complex graphical displays and word processing as astronauts started through fold-up computers originally made by GRiD. Using more-powerful Thinkpads and developing modifications and custom software laptops allows to show the astronauts where they are in space to help them navigate to the space station and dock with a graphical display. A Thinkpad launched for the first time in December 1993 aboard Endeavour for the first repair mission to NASA's Hubble Space Telescope. The most recent reseach in the domain will be able to be used aboard following craft once the Shuttle retired, like putting all of the shuttle's GPC software onto a computer chip weighing only a couple ounces
Carbon dioxide from the shuttle’s cabin atmosphere is removed through lithium hydroxide canisters. That are not needed while a orbiter is docked to the International Space Station as the station’s systems are removing carbon dioxide from the entire docked complex. Communications with the orbiter occurs through its S-band antenna
How a Flight Does Unfold?| Preparation to Flight Launch Docking and Undocking Operations in Case of a Mission to The ISS | Back Earth |
Preparation to FlightThe preparation of a shuttle for a flight is taking place at the Kennedy Space Center, Fla. The Orbiter Processing Facility (OPF) and the famed, tall, Vehicle Assembly Building (VAB) are used. The orbiter is prepared at the Orbiter Processing Facility. It's there that its main engines are attached, or that, after the manipulator positioning mechanisme, these pedestals that hold the robotic arm in place in the payload bay, the said robotic arm (the "orbiter boom sensor system") is installed. It's also in the Orbiter Processing Facility that the Shuttle's thermal protection is checked and possibly cured. Several months of work are needed to safe a orbiter for a new flight a process know like the 'processing flow.' Orbiter Processing Facilities (OPFs), also called bays or hangars, consist into three custom-built, 29,000-square-foot buildings at the Kennedy Space Center. OPFs are to be seen like the highest-tech garages on the planet and the place where a orbiter is towed after landing. OPF-1 and OPF-2, which are connected by a 233-foot-long low bay, have recently been the residence of Atlantis and Endeavour, respectively as OPF-3 is the home base of Discovery. As removing hazardous chemicals like fuel, drying the engines and opening the door panels to gain access is performed first, then the payload is removed and, during a three-month work the heat shield tiles are checked, the orbiter's main engines, or SSMEs, swapped out and the vehicle's structural, mechanical and electrical integrity assessed. Each orbiter is assigned its specific team of engineers, each directed by the 'flow director' on the NASA side and the 'flow manager' on the government side. Cranes and bridges are helping to the work as a appropriate environment is secured. Before a process called 'densification' was invented, tiles had to be all removed in bay 1 and densified again in bay 2 before reapplication. In the VAB, meanwhile, a huge, two-story tall, mobile platform, the Mobile Launcher Platform (MLP), is used as a basis on which the External Tank and the two Solid Rocket Boosters (SRBs) are stacked together. Each SRB is 149 ft high/12 ft wide (45 m/3.6 m), producing a 2.65 million pounds thrust at launch (about 5.8 tons). Each booster is composed of 4 parts: the solid propellant, the solid rocket motors, a nose cone, and an aft skirt, as the skirt is fixed first onto the mobile platform. The rest is craned upon. The SRBs are further linked to the External Tank. Once the orbiter's preparation is completed, it's moved to the VAB - a move called 'rollover'- where it comes to join the External Tank and the SRBs. A test of electrical and mechanical attachments between the orbiter and the ET is performed, umbilical checks and an interface verification test are performed. Checks are monitored from the Space Center's Firing Room facility. Then, about just a week later, the fully assembled "Space Shuttle Vehicle" -also said the "stack", consisting of the orbiter, the External Tank (ET) and the two SRBs, mounted on the Mobile Launcher Platform, is mounted on a crawler transporter int the purpose of moving it to the launch pad. The crawler is moving at a speed of barely 1 mph. Shuttles' launch pads are the LC 39A or the LC 39B. Such a roll to the launch pad is performed about two to three weeks before the launch. The External Tank, the Solid Rocket Boosters, the Space Shuttle Main Engine and the Propulsion Systems Engineering and Integration are managed at Marshall Space Flight Center, Huntsville, Ala, by the Space Shuttle Propulsion Office, as Shuttle's main engines are tested at the Stennis Space Center, in southern Mississipi and the External tanks are manufactured (by Lockheed Martin) at the Michoud Assembly Facility, in New Orleans, La. The External Tank for a mission, once completed, as too large to be delivered by train or truck, is transported into Florida, from Gulfport, on a Pegasus barge tugged during a 6-day delivery journey by a NASA's recovery ship which also is used to retrieve the Solid Rocket Boosters after a launch
->More About The Crawler Transporter! check more about the Space Shuttle program crawler transporter
At the launch pad, the shuttle is enveloped into the Rotating Service Structure (RSS), which looks like a launch tower of sort but which is better a servicing structure used to protect the Shuttle from inclement weather until launch, to install payloads into the orbiter's cargo bay, to perform various tests and loadings at the spaceship, and, of course, to allow the crew in on the day of launch. The Shuttle, at the launch pad, is further prepared, tested, and checked. These operations are performed by the ground crew, as the launch team is taking the opportunity to inspect hardware too. The External Tank is filled-tested it with its cryo-propellants (liquid oxygen and liquid hydrogen), with a check of how the orbiter, the External Tank, both Solid Rocket Boosters, and ground systems are performing under "cryo-load". The tanking test includes a simulated countdown through the T minus 31 second hold. The orbiter's main propulsion system is prepared too as the overall operation of ground systems is evaluated. Operability of the Remote Manipulator System (Shuttle arm) and of the new Orbiter Boom Sensor System is checked as is the flight readiness of the three main engines. The two additional thrusters systems of the Shuttle are loaded with their hypergolic propellants (monomethyl hydrazine and nitrogen tetroxide), that is the Orbiter Maneuvering System (used to nudge the Shuttle into orbit, for major orbital maneuvers, and for the deorbit burn) and the Forward Reaction Control System (thrusters system used for providing attitude control while in orbit)
Hot-fire tests of power units on both the orbiter and one of the SRBs are performed (this requires the Rotating Service Structure to be rotated away from the vehicle). Further required engineering analysis, validation, and verification testing occur. Final preparations, at last, occur like the loading of the Extravehicular Mobility Units (EMU) used for possible spacewalks, or the installation of the "lockers", the seats of the astronauts, at mid-deck
For each mission, Shuttle crews practise training comprising a mix of specifically crew tools trainings, mock spacewalk in the Neutral Buoyancy Lab (NBL) pool, classroom lessons, mockup training, simulations, and T-38 flights! The "integrated simulations" or "long sims" are involving Mission Control and other teams, as the Crew Equipment Interface Test (CEIT) is giving the crews a hands-on look at the payloads they will have to deal on with in orbit, or about the orbiter, generally. The three-day Terminal Countdown Demonstration Test (TCDT) takes place when the shuttle is at the launch pad, as it includes a launch pad safety training (emergency egress practice) and other prelaunch activities, of them a countdown dress rehearsal along with the launch team in the Launch Control Center. The countdown activities run up to main engine cutoff. The commander and pilot, on the other hand, practise aboard a Grumman American Aviation-built, modified Gulf Stream II jet to allow for the same flight sensations than the orbiter during the atmospheric part of its return flight. The Kennedy Space Center fire training crew teaches astronauts how to handle emergencies on the launch pad or on the ground following a problem, like use the slidewire basket which directly slide crew down to ground from the highest level of the rotating structure or how to drive on of the yellow M113 armored personnel carriers which allow to drive out of harm's way. The M113, a Vietnam era, 10-tons armored army vehicle serves for the emergency firefighters to reach to the launch pad in case of a emergency as they will then evacuate the orbiter, the closeout crew in it. NASA began using surplus Army M113s during the Apollo Program in case an emergency developed with the spacecraft or the gigantic Saturn V rocket. Three are on hand on launch day. Two stand by less than a mile from the launch pad, each with a complement of firefighters on board. A other M113 sits empty with its back ramp open facing the door of an emergency bunker near the pad. If the astronauts have to take the slidewire baskets to get away from the pad, they would get out of the baskets and into the bunker. Then they can get inside the M113, close the ramp and drive to safety. All crews practice those processes during the Terminal Countdown Demonstration Test, or TCDT a launch rehearsal occurring during the lead to actual launch as any of those may have to drive the vehicle. The Army designed the M113 too to float and drive through rivers and the like
Generally, each shuttle regularly undergoes an Orbiter Major Modification (OMM) period, which lasts about 2½ years, during which technicians procede to additional modifications which are enhancing safety and performance, and infusing new technology
As far as a mission's payload is concerned, a 'payload mission manager' is managing and directing the efforts of a 'mission processing team' -a group of multidisciplinary engineers and technicians who assemble and test station components and experiments flying aboard a shuttle. The payload mission manager is working in coordination with the concerned ISS offices, in the Johnson Space Center -in case the mission is headed to the ISS (via the ISS buildings -especially the Space Station Processing Facility- at the Kennedy Space Center). All such a work leads to the closure of the canister into which the payloads are loaded. Such a canister (from the Shuttle program proper, or from the ISS one) then is placed into a canister fit to the shuttle's payload bay. The canister itself is rotated into a vertical position in the Canister Rotation Facility, then placed on a transporter and transported to the launch pad shortly before that the Space Shuttle is rolled there, where they are filled into the Payload Changeout Room or PCR, which is part of the Rotating Service Structure. Thence, the canisters, about 2 days after the Space Shuttle rolled to the pad, from the Vehicle Assembly Building, is transferred into the orbiter's payload bay. Close outs and tests are performed once the installation performed as the payload bay doors are closed, after that, for flight. The orbiter main propulsion system is pressurized following the closure of the spacecraft's payload bay doors. NASA is filling extra space in the shuttle’s cargo bay using the Shuttle Small Payloads Project (SSPP), based at the Goddard Space Flight Center, with hooks and power buses built into the shuttle bays allowing hundreds of small, modular experiments and technology test units to make the best use of missions cargo capabilities as, between 1982 and 2003, more than 200 of these projects, including Get-Away Special (GAS) Cannisters, Hitchhikers and Spartans, flew in 108 missions
Aerospace technicians called spacecraft operators (SCOs) also participate into the preparation of a flight, as they check the more than 2,000 switches and displays and controls panels inside the cockpit of the orbiter from the Orbiter Processing Facility to launch pad, verifying how any system responds to commands from a remote controller through radio or cables, for example. They then also check systems inside the Vehicle Assembly Building and when, about three days before liftoff, the countdown officially begins and the orbiter is powered up the entire time, SCOs also check in the cockpit before the Astronaut Support Person (ASP) climbs in to configure the cockpit switches prior to crew boarding. Some SCOs also are present with the so-called 'Closeout Crew' helping the astronauts install aboard or configuring the White Room, a airlock to the cabin. SCOs at last are also present on landing day and some of the first people to approach a orbiter just returned from space. After the crew module has been cleared, control of the ship is transferred from NASA's Johnson Space Center in Houston back to Kennedy as two SCOs settle into the cockpit and begin monitoring systems, flipping switches and installing guards on switches that need to stay in their current position. They stay on board until the shuttle is towed back to the processing facility as the procedure is the same at Edwards Air Force Base, Calif.
Launch | a shuttle launching. picture NASA |
The initial launch date selection process is of the responsability of the NASA Headquarters and the Shuttle and the International Space Station (ISS) Programs. Once the Shuttle at the launch pad, from the Vehicle Assembly Building, three major reviews are required prior to launch. The Design Certification Review (DCR), the Debris Verification Review (DVR), and the Flight Readiness Review (FRR), as the later terminates by assessing the Shuttle's readiness to flight and with the selection of a definitive launch date. It's the 'Shuttle Mission Management Team' which conducts the Flight Readiness Review two weeks prior to launch. The group thoroughly evaluates all activities and elements necessary for the safe and successful performance of shuttle mission operations -- from the prelaunch phase through post-landing -- including the readiness of the vehicle, flight crew and payloads. Then the NASA officials OKay the launch of the mission, after a two-day flight readiness review at the Kennedy Space Center. Helping to the designation of the launch date are too the flight dynamics officers (FDOs), in case of a flight to the International Space Station (ISS), and, in any case, the chief of the National Weather Service Spaceflight Meteorology Group (SMG), both located at the Johnson Space Center. The FDOs make sure that two requirements are respected. The launch has to occur within 5 minutes of the plane of the ISS being over the launch site, with, moreover, an ascent trajectory South-North, as sufficient sunlight must be provided for the newly implemented, various monitoring systems. As far as the weather is concerned, it's not as much important in case of a launch to the ISS, as the launch windows are restricted to about 5 or 10 minutes. In all cases, the weather is monitored and forecasted for the launch site ("Launch Commit Criteria" -LCC), but for the abort landing locations too. These are runways located under the Shuttle trajectory, in Spain or France, for example, where the orbiter can land in case an emergency occurs. A launch from the Kennedy Space Center has to be performed when the Earth's rotation carries the KSC into the plane of the ISS' orbit. In case of a nighttime launch, the launch may be seen all along the Atlantic coast of the U.S.A. The orbiter and its three engines running, after that the 3 SRBs have been jettisoned are reaching the -2nd magnitude, rivaling Sirius. Further, more technical, conditions are needed for a Space Shuttle's launch, like, for example the Sun angles at the ISS while a shuttle is docked there, with a risk of the orbiter made too hot. The launch date is also chosen in consideration of what's called a beta-angle constraint, which limits the times the space shuttle can visit the space station based on sun angles to the station's solar arrays. Mission managers also weigh the schedule of the other rockets that must lift off from the same launch range. Launch countdown is beginning three days before the launch date in one of the Firing Rooms of the Launch Control Center (LCC), as the final "go" or "no go" decision is taken two days before the launch and belongs to the flight director, the launch director, and, ultimately, to the Deputy Shuttle Program Manager who is chairing the Mission Management Team. The mission's crew is arriving at KSC, from Houston, three days before launch as NASA Test Director and the mission's Payload Manager are announcing their go/no go for launch. The Launch Weather Officer keeps monitoring the weather conditions. The last preparations occur in the countdown, as the crew enters the Shuttle on the day of launch about 4 hours before launch. see more about the crew preparations on launch day. The Rotating Service Structure (RSS) is eventually rolled back -usually about 24 hours before launch, the External Tank is loaded with its cryogenic propellants... and the launch proceeds. It's to be noted that the Vehicle Assembly Building's doors are being closed about 2 ½ hrs in preparation for launch, as new safety processes are now at work for each Shuttle's launch. A pair of WB-57 aircraft are flying off the coast, about 25 minutes before launch, from where they provide images of the Shuttle's ascent, or a new robotic arm, adjusted to the one of the Shuttle is able to check the thermal tiles of the orbiter once in orbit. Further checks are performed from the International Space Station in case of a flight there, as, generally, tiles repair techniques are at the crew's disposal in case of any failure. NASA's two Solid Rocket Booster retrieval ships, the "Freedom Star" and the "Liberty Star" are heading on station, 140 nautical miles out in the Atlantic Ocean to the east of Jacksonville, Fla. The ships, from there, are towing the boosters back to KSC Kennedy Space Center following each SRB's 7-minute descent into the ocean. Due to Florida's Atlantic Coast weather specificities, launch pads at the Kennedy Space Center face some of the most extreme weather conditions of any launch complex as a new comprehensive weather instrumentation system on Launch Pad 39B, as installed by 2011, is now providing up-to-the-second and extremely accurate measurements close to the pad through 500-ft lightning prevention towers which hold too sensors, two more weather stations to come, and nine down-conductors, and other stations that can identify whether lightning struck and where, or its strength was. All stations are sending their data down to computers in the Pad Terminal Connection Room, or PTCR, a basement-type area below the surface of the pad. Kennedy's Weather Office is to share this new data with the U.S. Air Force's 45th Weather Squadron at nearby Patrick Air Force Base, which usually provides to NASA weather services and 'go' or 'no-go' decisions for launches based on weather constraints
Before the launch, three elite teams are intervening, with the 'Ice Team' -or 'Final Inspection Team', which inspects the launch stack, as a team is preparing the cabin, with the last team, the 'Crusaders' helping the crewmember to get seated into. This elite team, also termed the Closeout Crew comprises two suit technicians from Johnson Space Center in Houston, along with a astronaut support person, a active astronaut who is not on the flight crew. There are three additional USA employees from Kennedy as well as a NASA quality inspector. That crew is gathering about three hours before they're due at the launch site to prepare their equipment as, during the T-3 hour built-in hold, they ride to the pad in a van specially equipped. They then, in the 'White Room,' a corridor giving access to the orbiter, help the astronauts in and with a parachute pack. The Crusaders owe their name of "Cape Crusaders" to that they are assigned to NASA's Kennedy Space Center as they are also named ASPs (for 'Astronaut Support Personnels'), or C-squareds (because of both Cs in their name). The crew, for launch or reentry is wearing partial pressure suits, those well-known bulky, orange flight suits that are designed to help the crew survive an emergency, or more commonly referred to as 'pumpkin suits' as they are featuring numerous fittings and connections that have to be prepped before liftoff. Once the crew is safely inside, the orbiter test conductor in the Launch Control Center gives the Closeout Crew a 'go' to close the hatch. The crewmembers, on the other hand, may decide to procede by themselves to further checks of the launch stack, just before launch. In 2011, the Propellants North Administrative and Maintenance Facility, or Propellants North facility was inaugurated, as it controls the flow of fueling chemicals to shuttles and rockets in the Launch Complex 39 area
It's the Mission Management Team (MMT) -a team composed of high-ranking NASA managers, who ultimately manages the mission during the flight from the Houston Control Center. The important decisions, like postponing a mission launch or landing are of their responsability. The mission control, generally is located at the Houston Control Center, under the form of the space shuttle flight control room of the Johnson Space Center's Mission Control Center (MCC). The Network Integration Center and Flight Dynamics Facility at NASA's Goddard Space Flight Center also support a shuttle flight as it provides tracking, data and voice communications. As far as the Shuttle's thermal protection system is concerned, it's the Payload Operations Control Center at the Johnson Space Center which is screening the images and videos for possible damages
Image taking, generally, plays a critical role in shuttle flight safety as it begins long before the main engines fire and the solid rocket boosters ignite, with the entire shuttle stack has been photographed and monitored with TV cameras. The Final Inspection Team plays a large part in providing prelaunch imagery and analysis once the External Fuel Tank filled with fuels, singling out any trouble. Large teleobjectives, further, at 135 different camera locations, with standard, infrared, higher and lower speed cameras are able to film the orbiter several minutes into the flight. Such a variety of trackers used allows for short, medium and long-range tracking. For miles up and down the coast, tracking cameras and long-range optical tracking systems capture ascent imagery. At sea, ship-mounted wideband and Doppler radar tracking systems are used to detect debris during launch and ascent. Cameras at last mounted aboard the shuttle stack itself help give a close-up view of the climb as the boosters and external tank perform their jobs and then fall away as the shuttle achieves orbit. All that imagery also are part, or stands in complement, of the new imaging obligations which were instituted by NASA following the accident of shuttle Columbia by February 2003
. a video which swiftly summarizes the main steps of a liftoff is available (2.3 Mb)!
Once taken off, the Shuttle is passing from standing still on the launch pad to more than 17,000 mph (27,300 km/h) in just eight minutes ½! Check the following sequence of the events
| T-6.5 sec | the 3 main engines ignite |
| T-0 | the two Solid Rocket Boosters (SRBs) ignite; the Shuttle is released |
| Half a minute into the flight | the main engines are throttled back to about 72 percent to reduce the aerodynamics load ("Q") due to the thick lower atmosphere. Engines are throttled back up to 104 percent about one minute into the flight, when the atmosphere becomes thinner, just before the Shuttle pack passes through maximum aerodynamic pressure known as 'Max Q' |
| T+2:00 mn | SRBs burn out. Throttle back again to ease the SRBs being jettisoned. Small rockets help to disconnect them, and push them away, from the shuttle and the External Tank. The main engines alone continue to push (the acceleration reaches its maximum of 3 G), as the throttle is controlled to reduce stress on the shuttle's structure and passengers |
| T+2:15 mn | the orbital maneuvering system engines begin firing for just under three minutes to provide additional thrust |
| T+3:00 mn | the Space Shuttle is now speeding at 4,000 mph (6,400 km/h) at 53 miles of altitude! |
| T+4:00 mn | the Space Shuttle is now at the point of negative return |
| T+5:47 mn | the Space Shuttle begins to roll back to a heads-up position |
| T+6:00 mn | the Space Shuttle now rolls to a heads up position |
| T+7:00 mn | the Space Shuttle is speeding at 14,000 mph (22,500 km/h), more than 4 miles a second |
| T+8:30 | main engines shut down (Main Engine Cutoff, MECO), as the External Tank is jettisoned 20 seconds later. The shuttle is short of orbital speed, running at 17,000 mph (27,300 km/h). This move is done to ensure that the tank doesn't go orbital, but falls back instead and burns into the atmosphere. The Shuttle then is in an elliptical orbit of 137x36 statute miles (220 par 58 km) |
| MECO+45 | after 45 mn coasting, the shuttle fires two small Orbital Maneuvering System engines during two minutes. This is giving the final nudge to orbit due to that it raises the perigee of the orbit. The shuttle is now on an orbit of 143x116 statute miles (230 by 186 km) |
| further into the mission | when it's heading to a rendezvous with the International Space Station (ISS), the Shuttle has its orbit further raised and circularized to reach the ISS, which is, as far as it is concerned, at an altitude of 218 miles (350 km) |
->What in Case Of an Aborted Launch? NASA is maintaining 3 "Transoceanic Abord Landing" (TAL) sites on the other side of the Atlantic Ocean to assure the best launch safety. see more
Docking and Undocking Operations in Case of a Mission to The ISSA Space Shuttle launch is precisely timed to lead to a link up with the ISS about 220 miles above the Earth. A series of engine firings during the first two days of the mission is bringing the orbiter to a point about 50,000 feet behind the Station. Thence it begins its final approach. About 2.5 hours before docking, the shuttle’s jets are fired during what is called the terminal initiation burn as the orbiter eventually covers the final distance to the ISS with the next orbit. As it moves closer, its rendezvous radar system and trajectory control sensor are provide crew with range and closing-rate data. Several small correction burns place the shuttle about 1,000 feet below the station. The Commander with help from Pilot and other crew members manually flies the shuttle for the remainder of the approach and docking. He stops the orbiter about 600 feet below the station. Timing the next steps to occur with proper lighting, he then maneuvers the shuttle through an approximate 8-minute back flip called the Rendezvous Pitch Maneuver, or the R-bar Pitch Maneuver since the shuttle is in line with an imaginary vertical R-bar directly below the station, allowing ISS crew members to image the shuttle's upper and lower surfaces through windows of the Zvezda Service Module, a 800 mm lens to provide up to one-inch resolution and a 400 mm lens providing three-inch resolution. When the orbiter has completed its back flip, it is back where it started with its payload bay facing the station. The Commander then flies the shuttle through a quarter circle to a position about 400 feet directly in front of the Station and from that point, he begins the final approach to docking. Shuttle crew members then operate laptop computers that process the navigational data, the laser range systems and orbiter's docking mechanism. Using a video camera mounted in the center of the orbiter docking system, the Commander lines up the docking ports of the two spacecraft. If necessary, he can pause the shuttle 30 feet from the station to ensure the proper alignment of the docking mechanisms, maintaining the shuttle’s speed relative to the station at about one-tenth of a foot per second, while both craft are moving by 17,500 mph above the Earth. The docking mechanisms have to be kept aligned to a tolerance of three inches. When the orbiter makes contact with the Station, preliminary latches automatically link the two spacecraft. Shuttle’s steering jets are deactivated to reduce the forces acting at the docking interface. Shock absorber springs in the docking mechanism dampen any relative motion between the shuttle and ISS. Once motion between the shuttle and the Station has been stopped, the docking ring is retracted to close a final set of latches between the two vehicles! As far undocking, separation and departure maneuvers are concerned, hooks and latches are opened at undocking time and springs push the space shuttle away from the ISS. Undocking maneuvers mostly occur under the mission's pilot's responsability. Shuttle's steering jets are shut off to avoid any inadvertent firings during the initial separation. Once the shuttle is about two feet from the station and the docking devices are clear of one another, the steering jets are turned back on and the orbiter becomes manually controlled within a tight corridor as it separates from the ISS. Moving to a distance of about 450 feet, the orbiter then begins to fly around the Station, circling at a distance of 600-700 feet. Once 1.5 revolutions of the complex completed, the orbiter's jets are fired to leave the area. The shuttle then begins to increase its distance behind the ISS with each orbit performed around the Earth while the crew conducts one last inspection of the heat shield using the Orbiter Boom Sensor System. The distance remains close enough to allow the shuttle to return to the ISS in the event that the heat shield is damaged, preventing a safe re-entry. About a other domain of activites, when a spacewalk – also called extravehicular activity (EVA) for short – is being conducted, one crew member inside the International Space Station is assigned the job of Intravehicular (IV) officer, or spacewalk choreographer. When the Station’s 58-foot-long robotic arm is to be used during a spacewalk, it is controlled from the inside by astronauts who have remained there. The IV officer is also coordinating communications between the spacewalkers and Mission Control in Houston as several 'Robotic Work Stations' are available at the ISS to allow for help or monitoring to a spacewalk. Exiting the pressurized environment of the ISS needs one of several airlocks of the space station. Astronauts either spend a night, or 'campout' inside the lock with their spacesuits to accomodate, or a new procedure, which is less consuming of the ISS oxygen supply and called 'Suit Light Exercise protocol' or ISLE, a technique first used by 2011, consists into to wait until before the spacewalk and breathe pure oxygen through air masks for an hour as the air pressure inside the airlock is lowered to 10.2 pounds per square inch. After that, astronauts don their spacesuits and perform light exercise, moving their legs inside the suits for 50 minutes to raise their metabolic rate and purge nitrogen from their bloodstreams. Spacewalks may be performed together by, for example, crew from a Space Shuttle mission and a member of a Expedition crew present aboard the ISS. Astronauts during a spacewalk may walk their way by themselves or be maneuvered through the ISS robotic arm as operated from inside by two astronauts
Back EarthThe Space Shuttle usually lands at the Shuttle Landing Facility (SLF) of the Kennedy Space Center, Florida, as two other runways are at its disposal, one at the Edwards Air Force Base in California, the other at the White Sands Space Harbor, New Mexico. The "go" for one of the Shuttle's three landing sites may be given up to about ½ hr before the deorbit burn, that is about 90 minutes in all before landing. Initially, all Shuttle landings were conducted at the Edwards AFB. The first landing at KSC took place in 1984. Today, it's Kennedy which is considered the prime landing site. The Space Shuttle can't land in rainy weather. The weather-resistant coating burns off the white thermal protection tiles on the orbiter during launch and reentry, and if any moisture were to find its way underneath a tile, it could be trapped there and could cause a tile to buckle and fall off
->we have a fine tutorial about how the Shuttle is returning Earth
In case the Shuttle lands at the Kennedy Space Center, the operations just consists into the towing of it, by a diesel-powered tractor, along a two-mile tow-way strip, from the Shuttle Landing Facility (SLF) into the Orbiter Processing Facility (OPF) where the Shuttle is unloaded of the materials it may have brought back from the International Space Station (in case of such a flight) or is directly readied for its next flight. It's there, when the Shuttle is in the OPF, that a mission is officially considered over. When the landing in Florida occurs by nighttime, the 3-mile (4.8-km)-long runway of the SLF is lighted with xenon lights. In the case that the Space Shuttle is forced, for whatever reason, to a landing at one of its two other runways, it has to be brought back to KSC, as the Shuttle can not fly on its own in the usual aerial domain. This is done by one of the two NASA's modified Boeing 747 Shuttle Carrier Aircraft (SCA). Such a craft, when the flight is, for example, from California to Florida, is journeying a two-days (or better, a one-week), three-stop, cross-country flight. At the effect the stringent flight weather conditions be met (in order to safeguard the thermal tiles of the Space Shuttle from the rain, cold, or turbulences), a "pathfinder" KC-135 aircraft is flying 100 miles ahead the Shuttle Carrier Aircraft, monitoring the weather on the flight path. The Space Shuttle is installed and de-installed from, the carrier craft through a Mate/Demate Device (MDD) located both at the departure and the arrival locations. The MDD, at KSC, is located at the SLF. The MDD allows, for a mating for example, to lift the Shuttle and to have the craft moved under. And the contrary for demating. The Shuttle is maintained aloft as the carrier craft is removed; the Shuttle is then lowered down. The rest of the process is the same than when the Shuttle lands at KSC, that is to be towed to the Orbiter Processing Facility. NASA 911, one of both those modified Boeing 747s was retired from service by February 2012 landing at Air Force Plant 42 in Palmdale, Calif. after a short hop from NASA's Dryden Flight Research Center at Edwards Air Force Base. The converted jetliner will be retired and used as a source of parts to keep NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) Boeing 747SP aircraft and the remaining Shuttle Carrier Aircraft, NASA 905, flying. NASA 905 will be used to ferry the remaining space shuttles to the cities of their final display venues. NASA 911, a Boeing 747-100SR short-range version, was the second shuttle carrier aircraft. It was built in November 1973 and was flown in commercial airline service by Japan Air Lines for about 15 year and first flying for NASA by 1990 during 21 years. It flew 386 flights after it was converted to a shuttle carrier aircraft, including 66 flights carrying a space shuttle on a ferry flight. Although less utilized, NASA 905 may have had the more exotic career, however, teaming up with Enterprise between February and November 1977 for the shuttle program's Approach and Landing Tests at the Dryden Flight Research Center in California. NASA 905 also accompanied Enterprise on a European tour in 1983 in Germany, at the Paris Air Show and outside London. SCA pilots and flight engineers practice flights in an SCA about every three weeks and simulator training twice a year
To prevent any unwanted rush, a week before every launch, more than 40 NASA and contractor employees fly out to the alternate landing sites, staying the entire mission, supplied with 8 more folks to White Sands and 75 to the Edwards AFB when the landing time is coming. Just one flight took use of the White Sands landing facility, in March 1982, an alternate site, at that time, to the default Edwards AFB, The winds were so high, dust and sand added weeks of cleaning time to processing. As far as the turnaround operations are concerned, 40 members of the deorbit burn team will fly out of Orlando International Airport the day of landing and flying to the alternate landing site, and a team of about 180 Kennedy employees is chartering an aircraft the next day to support turnaround operations. In case of a landing at Edwards AFB, the orbiter is towed to the Dryden AFB, where the Mate-Demate Device is located. The weather constraints for a landing of the Space Shuttle needs those alternate site because rain can deteriorate the shuttle's protective thermal shield and rain further can cause the re-entering orbiter to loose momentum and potentially not reach its intended landing site. All this leads to that there can't be any showers within 30 miles of the landing site, with the visibility at its best for the pilot being able to safely guide the orbiter to a touchdown
Missions ArchiveWe have at your disposal two different archives to the missions of the Space Shuttle program
->The Numbering System of The Space Shuttle Missions
From STS-1 to STS-9 Shuttle missions -- 'STS' for 'Space Transportation System' -- were simply numbered in sequential order as after that NASA changed its flight designation system starting in 1984 in response to the growing complexity of its launch manifest. The new system of designation tried to pack more information into the flight number than a simple sequential ordering could. STS still stood for Space Transportation System but the numbers took on new meaning. The first number represented the fiscal year in which the Shuttle launched (like 4 for the year 1984; in the United States fiscal year runs from October 1 to September 30); the second number (which was originally intended to designate from which location the Shuttle would launch, a 1 for the Kennedy Space Center and a 2 for the Vandenberg AFB) finally marked the Shuttle’s launch sequence for that fiscal year as it turned into letters (a B, for example, denoting the second planned launch for the fiscal year concerned). Some source also state that the new system was created solely to avoid then-NASA Administrator James Beggs fear of the number 13. He didn't ever want any mission be numbered 13 (which would also explain why the astronauts who flew on STS-41C, what would have been STS-13, created their own 'Black Cat' mission patch -- as they also ended landing on a Friday, 13th). In reality, NASA anticipated a much greater frequency of launches as the Space Shuttle system moved into full operations at two sites as plans called for up to 50 polar orbit launches per year with Vandenberg AFB and equatorial orbits from the Kennedy Space Center. On top of that, NASA was planning the payloads and launch dates for the Shuttles years in advance, with delays and cancelations threatening to push the Shuttles out of sequential order anyway. The new system was designed to prevent that (shuttles however were still launched out of order, i.e., STS-51B launched a full three months after STS-51C, and some designations were never used at all. For example, although there was an STS-41G, there was never an STS-41E or STS-41F). The new system was finally overturned after January 28, 1986 because the tragic flight of the Space Shuttle Challenger (STS-51L) forced NASA to reconsider its launching plans, and, in the interest of safety, fewer launches were planned (even the launch site at Vandenberg, Space Launch Complex-6 was abandoned). Thence the need for that complicated flight designation system evaporated and when the Shuttle returned to flight on September 29, 1988, the mission was simply designated as STS-26. From there, NASA came back to the original numbering system and relied on a sequential flight designation system for the rest of the Space Shuttle program. Making the switch did create a few inconsistencies. For example, the Shuttle flight manifest not only shows STS-41B, -41C, -41D, and -41G flown in 1984, but also STS-41 flown in 1990. The same goes for STS-51 and STS-61. That return reduced confusion but it did not resolve the issue of Shuttle missions launching out of numerical order. STS-94 launched a full two years before STS-93 launched. Still, the straightforward numbering system was the preferred method. The Shuttles and their payloads were assigned their flight designations when the mission was planned, not when the mission would be launched. Interestingly enough, NASA considered at one point changing the designations as the launch order changed, but officials quickly realized that this would have confused too much of the mission paperwork. Once the flight designation was assigned, no more changes could be made. That way, no matter what delays or reschedulings moved the launch around, the designation for a mission would be the same—from the day it was first planned to the day it landed
for more see the official Shuttle page at NASA
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