Space shuttle program
- This article refers to American space shuttles. There was a cancelled Russian space shuttle project, whose features can be found in Transbordador Buran, and another cancelled European ferry project, which can be consulted in Transbordador Hermes.
Space Shuttle Programme  | ||
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| Commemorative badge of space shuttle | ||
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| Atlantis space shuttle on the launch platform during STS-135, the latest of the shuttle program (NASA) | ||
| Organization: | NASA | |
| Programme duration: | 1981-2011 | |
| Primary tasks: | Triple access to low orbit; placement of satellites and interplanetary probes, logistical support and maintenance; assembly and re-provision of the ISS. | |
| Launch sites: |
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| Shuttle fleet (space broadcasts): |
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| Total number of missions: | 135 | |
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The space shuttle or space shuttle (in English Space Shuttle) of NASA, officially called the Space Transportation System (STS), translated "Space Transportation System", was the only space vehicle used for the transport of astronauts by the United States between 1981 and 2011. The most remarkable thing about it is that it was partially reusable.
Since the takeoff of the first space shuttle mission (STS-1) launched on April 12, 1981, these spacecraft have been used to transport large loads to various orbits, to supply and place orbital modules in the International Space Station (ISS) and to perform maintenance missions (such as the Hubble Space Telescope). A use that, initially, was foreseen but that was not carried out, was to bring satellites back to Earth to be repaired. However, since the existence of the ISS, large loads were brought back with the shuttle, something that the Soyuz could not do due to their more limited capacity.
The vehicle was initially scheduled to perform approximately 100 flights.
The space shuttle program began in the late 1960s and became NASA's top priority in the 1970s. In January 1986, a shocking Challenger accident that killed all seven crew members halted two years. the launch schedule. Similarly, after the Columbia disaster in 2003, there were no more flights for the next two years. In January 2004, NASA announced that it would retire the entire fleet of shuttles and replace them in 2010. The return of flights with the STS-114 mission was initially scheduled in July 2005, but due to problems with an external tank sensor, the discarded. After more than two years of suspension, on July 26, 2005, Discovery resumed operations with the International Space Station (ISS) for the transfer of material and supplies. During the re-entry to Earth, there were technical problems with the tracking of the spacecraft due to bad weather on August 9.
Since in a single mission the orbiter could not combine the transport of modules to the ISS and continue the maintenance of the Hubble Space Telescope, and having previously canceled these missions to Hubble, NASA announced that it would carry out one mission, the last made to the telescope, on May 11, 2009.
According to the speech given by US President George W. Bush on January 14, 2004, the use of the space shuttle would be concentrated entirely on the assembly of the ISS until 2010, the year in which it would have to be replaced by the vehicle Orion, at that time under development and currently abandoned. The last launch of a shuttle occurred on July 8, 2011, on mission STS-135, after which the program was cancelled.
History
Design
The Space Shuttle Program was designed primarily as a successor to the Apollo missions to provide NASA with a low-cost manned space program due to its "reuse" in the 1980s.
NASA wanted to cut costs and needed a multifunctional spacecraft. One of its uses would be to bring the satellites that were launched into space for repair in the event of a failure. Another function would be that it be reusable to avoid the loss of billions of dollars in rockets that were separated into smaller phases and once discarded burned up during reentry into the atmosphere. Finally, it would be used as transportation to the space station that NASA planned to build.
With all these principles during the 1960s, NASA had outlined a series of paper projects on reusable space vehicles to replace single-use systems such as Project Mercury, Project Gemini and the Apollo Program. The United States Air Force (USAF) was also interested in smaller, more maneuverable systems and was pursuing its own spaceplane project, called the X-20 Dyna-Soar. In order to develop a state of the art on the matter, both teams worked together.
In the second half of the 1960s, the effort to improve Apollo was fading, and NASA began looking into the future of the space program. His vision was for an ambitious program that envisioned the development of a huge space station that would be launched with large rockets, and would be maintained by a "space shuttle" reusable spacecraft that could service a permanent lunar colony and eventually transport people to Mars.
However, the reality was different, since NASA's budget dwindled rapidly. Instead of going backwards and reshaping its future based on its new financial situation, the agency tried to salvage as much of its projects as possible. The mission to Mars was scrapped, but both the space station and the shuttle were still standing. Eventually only one of them could be saved, which was the shuttle for economic and logistical reasons, since without this system a space station could not be built.
A number of designs were then proposed, many of them complex and different from one another. Maxime Faget, designer of the Mercury capsule, among others, created the "DC-3", a small aircraft capable of carrying a payload of 9,070 kg or less, four crew members, albeit with limited maneuverability. The DC-3 became the basic platform against which the other designs would be compared.
Desperate to see their latest project saved, NASA asked the blessing of the United States Air Force (USAF). The agency made a request that future USAF launches be made with the shuttle instead of the expendable launchers that were being used, such as the Titan II rocket. In return, the USAF would see significant savings in building and upgrading its launchers, since the shuttle would have more than enough capacity to accomplish the objectives.
Without much enthusiasm, the USAF agreed, but not before asking for a significant increase in capacity to allow it to launch its planned spy satellites. These were large, weighing approximately 18,144 kg, and would have to be put into polar orbits, which takes more energy than is required to put an object into low orbit (LEO). The vehicle would also have to have the ability to maneuver to either side of its orbital footprint to adjust for the rotational drift of the launch point while in polar orbit - for example, in a 90-minute orbit, Vandenberg AFB in California., the US would have a drift of 1600 km, whereas in orbits more aligned with the equator, the drift would be less than 400 km. To achieve the above, the vehicle would have to have bigger and heavier wings.
This took the simple DC-3 out of the equation due to its reduced payload capacity and maneuverability. In fact, all the designs were insufficient. All new drawings would have to incorporate a delta wing. And that was not the only drawback, with the increase in the capacity of the vehicle, the thrusters also had to be much more powerful. Suddenly, the system had grown to be taller than the Saturn V rocket, and its costs and complexity were beyond all expectations.
While all this was going on, other people suggested a different approach: NASA use the existing Saturn to launch the space station, which would be maintained by modified Gemini capsules that would go on USAF Titan II-M rockets. The cost would probably be lower, and it would reach the goal of the international station sooner.
The answer was immediate: a reusable shuttle would more than pay the cost of developing it, when compared to the expense of launching single-use rockets. Another factor in the analysis was inflation, which was so high in the 1970s that any replacement of the cost of development had to be quick. A launch rate was then needed to make the system economically plausible. These conditions were not met by the space station or the USAF payloads. The recommendation was, then, to make the launches from the shuttle, once it was built. The cost of launching the shuttle would have to be less than any other system, small and very large rockets excepted.
With the issue of plausibility resolved, NASA set about obtaining funds for the five years that the development of the project would take, an undertaking that was not easy at all. Inflation and the Vietnam War threatened to kill off the shuttle, but it was the only viable project, and stopping it meant the US would not have a manned space program in the 1980s. Budgets had to be tightened, however, Which led back to the drawing board. The reusable rocket project was abandoned in favor of a simple rocket that would detach and be later recovered. The fuel was removed from the orbiter to an external tank, which allowed to increase the cargo capacity at the cost of scrapping the tank.
The last design stumbling block was the nature of the thrusters. At least four solutions were proposed, and the one that contemplated two solid rockets (instead of one large one) was finally chosen, due to lower design costs (an aspect that was permanently present in the shuttle design).
Despite the goal of reducing costs, once the shuttle was in operation, it cost more than $50,000 dollars to get each kilogram of payload on it to orbit.
Development
Shuttle development became official on January 5, 1972, when President Richard Nixon announced that NASA would begin creating a low-cost, reusable shuttle system. Due to budget caps, the project was already doomed to take longer than originally anticipated. However, the work started quickly, and a couple of years later there were already several test articles.
Of these, the most notable was the first complete Orbiter, originally to be known as "Constitution". However, a massive letter campaign from Star Trek fans convinced the White House to rename the orbiter "Enterprise". To great fanfare, the Enterprise took its first taxi on September 17, 1976 and began a series of successful tests that were the first real validation of the design.
The first fully functional orbiter, Columbia, was built in Palmdale, California, and shipped to the Kennedy Space Center on March 25, 1979. Two crew members were on Columbia's maiden voyage on April 12, 1981. In In July 1982 the CEK saw the Challenger” arrive. In November 1983 Discovery arrived, and Atlantis in April 1985. Over time the crews grew: the first crew of five astronauts was in the STS-7 in 1983 and the six was on STS-9 at the end of the same year. The first crew of 7 was on STS 41-C in 1984 and the record eight was in 1985 aboard STS 61-A.
Due to the large crews, the astronauts were divided into two groups: pilots, responsible for the flight and maintenance of the orbiter; and the mission specialists, in charge of the experiments and the payload. Finally, another category was created: cargo specialists, who do not necessarily have to take an astronaut course. These deal with experiments on board.
The second part of the project, the so-called Freedom Space Station, announced in 1984, became, with modifications and reductions, the Alpha Space Station and later the International Space Station. On the morning of January 28, 1986, Challenger exploded 73 seconds after takeoff (mission STS-51-L). The problem was due to a leak in a gasket on the booster rockets. The crew of seven lost their lives. To replace it, the Endeavour was built, which arrived in May 1991. Meanwhile, in 1988, the Soviets launched the Buran shuttle, similar to the American one.
In 1995 the space shuttle was prepared for the conception of the International Space Station, which is why it made a series of dockings with the Russians at the Mir station. Finally, and due to budget delays from the Russian space agency, the construction of the ISS began in 1998.
On February 1, 2003, another tragic accident rocked NASA's family of space shuttles when Columbia disintegrated in the skies during reentry, returning from the successful completion of STS-107.
NASA has suspended all scheduled shuttle flights while it investigates what happened. The result was that the Columbia disaster was caused by a piece of foam from the external tank, which broke off during launch and struck the shuttle wing at about 800 km/h, producing a hole that then it would be fatal. As the shuttle re-entered the atmosphere, the damage allowed hot atmospheric gases to penetrate and destroy the internal structure of the wing, causing the spacecraft to become unstable and gradually break up, killing all crew members.
Flights restarted with the takeoff of Discovery two and a half years later, on July 26, 2005, to carry out the STS-114 mission, which was carried out without having completely resolved the external tank problem, Discovery returned home on August 9, 2005 at Edwards Air Force Base in California. The next Shuttle mission was carried out in July 2006 with the launch of Discovery. The mission included a trip to the International Space Station and safety tests.
Conclusion
The shuttle has required significant technological advances for its development, including thousands of heat shield tiles, capable of withstanding the heat of reentry over the course of multiple missions, as well as sophisticated engines that could be used over and over again. without being discarded. The aircraft-shaped orbiter has three of these main engines, which burn hydrogen and liquid oxygen that are stored in the external tank. Attached to the external tank are two solid rocket boosters, or SRBs, which provide most of the thrust during takeoff. The "boosters" are turned off and thrown into the ocean to be recovered, refilled and ready for the next use. Once the solid rockets have been jettisoned, the orbiter's three main engines continue to burn fuel from the external tank until approximately eight minutes into the flight.
The STS introduced many tools that are used in space: the Remote Manipulation System, a 50-foot-long arm built by the Canadian Space Agency, is capable of moving large, heavy objects to and from the hold of the shuttle, which measures about 18.29 meters long. The Spacelab module, built by the European Space Agency (ESA), provides a pressurized and fully equipped laboratory for scientists to carry out various experiments, covering a wide spectrum of research: from astronomy, the creation of new materials, the observation of the Earth, the study of physical phenomena and even biomedical research. The Maneuverable Flight Unit (MMU) allows astronauts to move freely in space without being connected to the Shuttle using small rockets attached to the chair-shaped structure for movement.
Most of the missions have been scientific and defense. Among the most important scientific projects are the launching of the Hubble Space Telescope, the Galileo spacecraft that made important discoveries, the Gamma Ray Observatory, and the transport of modules and supplies for the construction of the International Space Station (ISS).
NASA Space Shuttle Fleet
- Test vehicles, not suitable for orbital flights:
- Lost in accidents:
- Currently withdrawn from the service:
STS Program Missions
Fuel sources
The Shuttle has two sources of fuel: the External Tank and two Solid Rocket Boosters (SRBs). The orbiter also stores hypergolic fuels that are used during the stay in space.
The combined momentum is such that in 0 to 8.5 s the shuttle reaches a speed of 250 m/s (900 km/h). This is equivalent to about 3 G, that is, more than 3 times the force exerted by the earth.
External tank
The Outer Tank arrives at the Vehicle Assembly Building in a huge boat. Once in this facility, it is processed and placed upright to be attached to the orbiter.
The External Tank is the largest and heaviest element of the space shuttle. In addition to powering the Orbiter's three main engines, the Tank serves as the Shuttle's backbone by absorbing thrust charges during launch. It is ejected 10 s after the shutdown of the shuttle's main engines, re-entering the Earth's atmosphere and impacting the Indian or Pacific Ocean, depending on the type of mission. It is not reusable.
In the first two missions it was painted white but after STS-3 it was no longer painted to reduce weight. Since then it presented that characteristic orange color.
Main Engines
It has three, and they provide the necessary thrust to reach orbital speed. The main engines are located in the lower part of the orbiter and before being installed in the orbiter, they must have undergone a firing test at the Dennis Space Center in Mississippi, from where they are transported by truck to the vehicle's assembly building.
The engines are about 4.2m tall and each weigh about 2t. The power they produce is tremendous: 12 million horsepower, enough to power 10,000 homes. The main element of the engines is the turbopump which is responsible for feeding propellant to the combustion chamber. The power of the turbopump is also enormous, since with only the size of a V-8 engine it has the power of 28 locomotives, so if it were to explode it would send a column of hydrogen 58 km in all directions. When turned on, the turbopump consumes 1 t/s of fuel.
The main engines use LOX and LH2 which are ignited in the combustion chamber which is no more than 25cm in diameter at a temperature of 3300°C giving it high pressure. Once released, the hot gases are expelled through the nozzle. After the separation of the boosters, the main engines remain on for several minutes. The main engines are reusable for 55 takeoffs and operate with a maximum efficiency of 104%.
Solid booster rockets
The space shuttle uses the world's largest solid-propellant rocket. Each booster rocket contains 453,600 kg of propellant in the form of a solid substance with the consistency of an eraser. The Solid Booster Rocket (SRB) has four central sections that contain propellant. The top has a star-shaped hole that extends two-thirds down to form a cylinder. When ignited all exposed surfaces react violently providing the necessary impulse. Once they are ignited, they cannot be turned off. Due to the star shape of the upper segment, the driving efficiency is much higher than with a cylindrical shape.
After providing a thrust equivalent to a third of the total, the SRBs separate at 2:12 min of flight. They fall into the Atlantic Ocean, with the help of a parachute, from where they are rescued and later reused.
Propellants
The fuel used by the space shuttle comes from the External Tank and the rocket boosters or also known as Boosters. The propellant used in the boosters is ammonium perchlorate and has a solid consistency; Regarding the External Tank, the opposite happens here since it is divided into two tanks, the upper one contains liquid oxygen (LOX) and the second tank contains liquid hydrogen (LH2) which are mixed in the combustion chamber of the main engines of the space shuttle. providing combustion.
An important characteristic of fuels is their specific impulse, which is used to measure the efficiency of rocket propellants in terms of seconds. The higher the number, the “hotter” the propellant.
NASA uses four types of propellants: petroleum, cryogenic, hypergolic, and solid.
Petrol is actually a type of kerosene similar to that burned in lamps and stoves. However, in this case it is a type called RP-1 (Refined Petroleum) that is burned with liquid oxygen (oxidant) to provide impulse. The RP-un is only used in the Delta, Atlas-Centauro rockets and was also used in the first stages of the Saturn IB and the Saturn 5.
No oil is used in the Shuttle program, except for satellite stages. At takeoff, the space shuttle uses the cryogenic and solid type, while in orbit it makes use of the hypergolic types.
Cryogenics
Cryogenic engines are based on the union of liquid oxygen (LOX), which is used as an oxidant, and liquid hydrogen (LH2) which is the fuel. LOX remains liquid at –183 °C and LH2 at –253 °C.
In their gaseous state, oxygen and hydrogen have such low densities that huge tanks would be required for their storage. For this reason they must be cooled and compressed to be stored in the rocket tanks. Due to the permanent tendency of cryogenics to return to their natural gaseous state, their use is less frequent in military rockets because these must remain in the launching pads for long periods of time.
Despite the difficulties associated with storage, the LOX-LH2 combination is highly efficient. Hydrogen has a power 40% greater than other fuels, being very light (density of 0.071 g/cm³). Oxygen is 16 times as dense (1.14 g/cm³ density).
The high-efficiency engines aboard the orbiter use hydrogen and liquid oxygen achieving a specific impulse of 455 seconds, which is a huge improvement over the Saturn 5's F-1 engines, which reached 260 s. Fuel cells aboard the orbiter use these two liquids to produce electrical power in a process known as reverse electrolysis. The burning of LOX with LH2 occurs without producing toxic gases, leaving only water vapor as a by-product.
Hypergolic
Hypergolics are combustibles and oxidizers that ignite when simply in contact, so they don't need an ignition source. This ability to fire makes them especially useful in maneuvering systems, both manned and unmanned. Another of its advantages is its ease of storage, since they do not need extremely low temperatures like cryogenic ones.
The fuel is monomethylhydrazine (MMH) and the oxidizer is nitrogen tetroxide (N2O4). Hydrazine is a compound of nitrogen and hydrogen with a very strong odor similar to ammonia. Nitrogen tetroxide is reddish in color and has a foul odor. Because both are highly toxic, they are handled under extremely safe conditions.
The orbiter uses hypergolics for the Orbital Maneuvering System (OMS) for orbit entry, orbital maneuvering, and deorbiting. The reaction control system uses hypergolics for attitude control.
The efficiency of the MMH/N2O4 combination in the orbiter is 260 to 280 seconds in the SCR and 313 seconds in the OMS. The greater efficiency of the OMS is explained by the greater expansion of the nozzles and the high pressures in the combustion chambers.
Solid
Solid propellants are the simplest of all. Its use does not require turbopumps or complex propellant feeding systems. Its ignition occurs with a long jet of flames produced from the tip of the rocket which produces immediate ignition. Solid fuels, made up of a metal and different chemical mixtures, are more stable and allow better storage. On the other hand, the great disadvantage that they present is that solid propellants, once ignited, cannot be extinguished.
Solid propellants are used in a wide variety of spacecraft and systems such as the Payload Assist Module (PAM) and Inertial Upper Stage (IUS) that provide the boost necessary for satellites to reach geosynchronous orbits or to enter in planetary orbits. The IUS is used on the Space Shuttle.
A solid propellant always has its own source of oxygen. The oxidizer in the space shuttle's solid propellant is ammonium perchlorate, which makes up 63.93% of the mixture. The fuel is a powdered form of aluminum (16%) with a powdered iron oxidizer (0.07%) as a catalyst. The fixative that holds the mixture together is polybutadiene acrylonitrile acid (12.04%). In addition, the mixture contains an epoxy protection agent (1.96%). Both the fixer and the epoxy agent burn along with the rest of the propellant, contributing to thrust.
The specific impulse of the Space Shuttle SRBs is 242 seconds at sea level and 268.6 seconds in a vacuum.
NASA facilities for the space shuttle program
The Kennedy Space Center is NASA's primary facility for testing, checking, and launching the space shuttle and its payloads. The center is also one of the landing sites for the Shuttle.
The Shuttles take off from Launch Complex 39 located on Merrit Island, Florida, north of Cape Canaveral. The facilities of Complex 39 have undergone modifications since the time of the Apollo missions in order to adapt to the technology of the Space Shuttle Program.
Shuttle Landing Facility
The runway for the space shuttle is one of the largest in the world. The Kennedy Space Center runway is located about three kilometers northwest of the Assembly Building, on a northwest/southeast alignment. The runway is twice the length of commercial airport runways. It measures approximately 4,752 meters long and 91.4 meters wide, and is 406 millimeters thick at the center. At each end there is a space of 305 meters for security purposes. On each side of the track run small grooves 0.63 cm wide and deep.
Because the orbiter, once it has re-entered the atmosphere, lacks its own propulsion system, it has to rely on aerodynamic suspension provided by the air. The landing speed varies between 343 and 364 kilometers per hour.
To achieve a perfect landing, the orbiter needs navigation aids, which are both on the ground and aboard the same spacecraft. The landing system's microwave scanner is used for the final approach and directs the orbiter to a certain point on the runway.
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Landings are made from northwest to southeast (Runway 15) or southeast to northeast (Runway 33). The track is not perfectly flat as it has a 61cm slope from the center line to the edge. This slope together with the furrows constitute an effective method of dispersing water. The grooves are also useful for surface slip resistance. Subsequent modifications to the runway increased its length, so that it is currently about 5,182 meters long.
Orbiter Processing Facility
Hours after landing the orbiter is transported to the processing building at the space center. The building has three hangars, each 60 m long, 46 m wide and 29 m high, occupying an area of 2,694 m². The lower hangar connects to hangars 1 and 2. It is 71 m long, 30 m wide and about 8 m high. Hangar 3 is located to the north and east of the first two; it also has an adjacent lower hangar.
Other annexes and structures provide the necessary space to carry out maintenance on the orbiter. Each upper hangar is accompanied by a crane arm weighing 27 t with an approximate height of 20 m. A series of platforms, a main access bridge and two powered movable bridges provide access to the orbiter. The upper hangars have an emergency escape system in the event of a hypergolic escape. The lower hangar has electrical and mechanical equipment, a communications room, offices and control supervision rooms. All hangars have fire protection systems.
Post-flight control and improvements, in addition to the installation of loads in a horizontal position, are carried out in this building. Upright satellites are normally installed on the launch pad.
After processing, the orbiter is towed to the assembly building through the large door at the north end of the upper hangar.
Installation of the thermal protection system
A Thermal Protection System, made up of a network of tiles, filters and insulation blankets, protects the interior of each orbiter from the heat produced during takeoff and reentry, as well as the low temperatures of space. These materials can withstand some damage within flight time and must be inspected, repaired, or sometimes replaced for the next mission.
Repair and final fabrication of thermal protection system materials takes place at the thermal protection system facility, a 2-story building with an area of 4,088 square meters. The building is located across the street from the orbiter processing complex.
Logistics Installation
The Logistics Complex, with an area of 30,159 square meters, is located to the south of the assembly building. It contains nearly 160,000 space shuttle spare parts and more than 500 NASA and contract company workers. One of the notable features of this building is the existence of the parts retrieval system, which automatically finds and removes specific parts from the Shuttle.
Solid Rocket Accelerator Processing Facilities
After 2 minutes of launch, the SRBs separate from the external tank thanks to the firing of retrorockets and open their parachutes to fall into the north of the Atlantic Ocean where they are rescued by special ships that transport them to the Air Force station from Cape Canaveral.
Facility for disarming the Solid Booster Rocket
Corresponds to the area in and around the AF hangar that together with the building form the disarmament facility for the Accelerator Rocket. Special elevators behind the AF hangar lift the SRBs out of the water. There they go through an initial wash and each rocket is separated into its four sections and upper and lower assemblies. The core segments are returned to the launch complex at the Kennedy Space Center aboard rail vehicles for shipment to the manufacturer and propellant refilling.
Facility for reconditioning and assembly of the Solid Rocket Accelerator
The refurbishment and installation of the upper and lower sections takes place in this building located to the south of the assembly building. This complex consists of five buildings: construction, engineering, service, lower section test or fire test and the cooling facility. The three-story building for construction has an automatic control system, a 24 X 61 meter crane in the upper hangar and three crane robots, the latter being among the largest in the world.
Installation for the rotation and exit process
Located north of the assembly building, this facility receives propellant-filled SRB segments via a rail system from the manufacturer. The complex includes a processing building and two dispatch buildings. Inspection, rotation, and assembly of the bottom of the booster occurs in the processing building. The other two dispatch buildings are used to store the segments loaded with propellants and remain there until they are transported to the assembly building to be integrated into the other parts of the booster ready for the next flight.
Installation for the reconditioning of the parachute
After the two boosters fall into the Atlantic Ocean, two vessels retrieve them and also remove the parachutes which are rolled onto huge rollers which are sent to this facility. Once there, the parachutes are washed, dried and stored in tanks for future use.
Vehicle Assembly Building
Here, the boosters are attached to the external tank and the orbiter for transport to the launch pad.
Located in the center of Launch Complex 39, the vehicle assembly building is one of the largest in the world, covering an area of 3.24 ha and with a volume of approximately 3,884,460 m³. The building is 160 m high, 218 m long and 158 m wide.
The structure can withstand 125 km/h winds and is reinforced with 406 mm diameter steel beams to a depth of 49 m.
The upper hangar is 160 m high and the lower hangar is 64 m. To the east are upper hangars 1 and 3 where the space shuttle components are attached upright on the launch pad. To the west are hangars 2 and 4 where the external tank is checked and is also where storage is carried out.
This building has more than 70 lifting devices including two 227 t cranes.
Once assembly of the space shuttle is complete, the massive doors of the building are opened to allow entry of the tracked transporter which travels under the Mobile Launch Pad and carries them - with the assembled Shuttle - to the launch site. launch.
Launch Control Center
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It is a four-story building connected to the eastern part of the assembly building via a high enclosed bridge. The control center has two operations rooms and two other support rooms, each equipped with the launch processing system – an automatic computerized operation system – which monitors and controls the space shuttle assembly, control and launch operations. launch.
The countdown to the space shuttle takes about 43 hours thanks to the launch processing system, otherwise it would take more than 80 hours, like the Apollo missions.
On the other hand, the use of the launch processing system requires the presence of 225 to 230 people in the launch room, unlike the Apollo missions that required about 450 people.
Once the solid-boost rockets ignite for liftoff, control automatically passes to the mission control center at the Johnson Space Center in Houston, Texas.
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Transportable equipment and facilities
Mobile Launch Pad
It is a two-story steel structure that provides a transportable launch pad for the space shuttle. The main body of the platform is 7.6 m high, 49 m long and 41 m wide. The platform rests on six 6.7 m high pedestals.
Unladen, a platform weighs about 3,730 t. With a Shuttle without fuel, it weighs about 5000 t.
The main body of the platform has three outlets: one for the gases expelled by the solid propulsion rockets and another located in the middle, for the three main engines.
On the structure there are two devices of considerable size on each side of the exhaust shaft of the main engines. These devices called "rear service masts" they provide several umbilical connections to the orbiter including a liquid oxygen line through one and a liquid hydrogen line through the other. These cryogenic fuels are fed to the external tank through these connections from the platform. At the time of launch these umbilicals are retracted to the masts where they are protected from the flames of the engines by a rotating cover.
Each mast is 4.5m long, 2.7m wide and rises about 9.4m high above the platform floor.
Other umbilicals carry helium and nitrogen, as well as electrical power and communication links.
Eight bolts, four at each SRB base, hold the space shuttle on the launch pad. These bolts fit with other opposing bolts on the two exhaust holes of the SRBs. The ship is disconnected from the platform by pyrotechnics that break the links of these bolts.
Each launch platform contains two internal levels that provide electrical, test, and propellant-loading equipment.
Caterpillar Conveyor
These special vehicles transport the space shuttle mounted on the launch pad from the assembly building to the launch site. These are two caterpillars (name given to vehicles whose traction is given on mobile belts such as war tanks) that are 6.1 meters high, 40 m long and 34.7 m wide. Each one weighs about 2,700 t without load. Such a vehicle has six tracks with 57 sections each. Each set of wheels contained in the track weighs about 907 kg.
The caterpillar's top speed with the shuttle on board is 1.6 km/h, while without a load it has a top speed of 3.2 km/h.
The caterpillar has a leveling system to counteract the 5 degree inclination to the launch site and also has a laser beam system that allows it to locate itself in a precise position.
Each track is powered by two 2,750 hp diesel engines. The motors control 1000 kW generators that provide electrical power to the 16 traction motors.
Path of the caterpillar transporter
A 39.6 m wide road is used by the tracked transporter on a path from the assembly building to the launch pad that are about 4.8 km apart.
The road consists of two 12-meter lanes separated by a 15-meter central strip. To support the weight of the total load (about 7,700 t) the road is made up of four layers. The upper part is a layer of river gravel of 20.3 cm in the curves and 10.2 cm in the straight sections. The other layers —in a descending direction— are: 1.2 m of compressed rock, 76 cm of a select fill and 30 cm of a compact fill.
The distance from the assembly building to platform 39A is about 5.5 km and to platform 39B about 6.8 km.
Cargo Container
This container mounts payloads vertically and operates in multiple facilities. In the orbiter processing facility it serves for horizontally positioned payloads.
Each container is hermetically sealed and can carry loads up to 4.5m in diameter and 18.3m in length. The maximum weight allowed is approximately 22.68 t.
Cargo Container Transporter
It is a 48 wheeler truck that can transport the container either vertically or horizontally. The Transporter is about 19.8m long and 7m wide, with a platform that can be raised or lowered from 1.5m to 2.1m.
Each wheel has an independent axis which allows it to move freely in any direction. A diesel engine drives the transporter in outdoor activities, but when it is inside a facility it is powered by an electric motor.
When fully loaded it has a maximum speed of 8 km/h, but it can also travel at speeds of the order of 0.636 centimeters per second (or what is the same: 0.022 km/h) for loads that need a precision movement.
Launch Pads 39A and 39B
Platforms A and B of the Launch Complex are nearly octagonal in size. Each covers an area of 0.65 km². The central part of Platform A is located at about 14.6 meters above sea level, and Platform B at 16.8 m. Before the return to flight in 1988 after the tragic Challenger mission, the Complex underwent 105 modifications. The modifications were made to improve the inspection of the systems.
The top of each Platform measures 119 X 99 m. The two main structures of each launch pad are the Fixed Service Structure and the Rotating Service Structure.
Fixed service structure
It is located north of each launch pad. It is an open structure of about 12.2 square meters. A crane at the top provides access for pro-launch operations. The structure has 12 working floors at intervals of 6.1 m each. The height of the structure is 75 m. While the height to the top crane is 81 m above all is the lightning rod: a cylindrical fiberglass structure with a length of 24 m. With the lightning rod, the structure has a height of 106 m.
The fixed structure has three service arms:
- Access to the orbiter: This arm extends to allow the access of specialized personnel to the crew compartment in the orbiter. The extreme part of this arm includes a section called “white quartz”. This small room allows access to a maximum of six people and allows access to the hatch through which astronauts are located in their positions.
The access arm remains in the extended position until 7 min 24 s prior to launch to provide an emergency exit for the crew. It measures 19.8m in length, 1.5m in width and 2.4m in height. This arm is fixed to the Fixed Service Structure at a level of 44.8 m above the surface.
In an emergency, the arm can be extended mechanically or manually in about 15 s.
- Access line arm for the hydrogen ventilation of the external tank: This arm allows the union of the umbilical lines of the external tank with the facilities of the platform in addition to providing access for work in the tank area. This arm retracts several hours before the launch leaving the umbilical cables attached to the tank which are cut at the moment the boosters turn on. The cables return to the tower of the structure where they are protected from the flames of the engines thanks to a water curtain.
The access line arm for the hydrogen vent of the external tank is 48 m long and is attached to the fixed service structure at a level of 51 m.
- Gaseous oxygen vent from the external tank: This arm extends to the top of the outer tank where a cobertor or cocoon drops at the end of the tank. The cocoon contains heated gaseous nitrogen that runs through this deck to prevent the vapours of the vent from condense by forming ice that can be detached and thus damage the ship during takeoff. The ventilation arm system is 24.4 m long, 1.5 m wide and 2.4 m high. This arm is attached to the Fixed Service Structure between the levels corresponding to 63 and 69 m.
The cover is removed from the air vent at 2 min 30 s prior to launch and the arm is retracted to the tower structure and can be returned to its extended position if the countdown is stopped.
Rotating service structure
Provides protection to the ferry and access to the cargo hold for the installation and service of cargo on the platform. The structure rotates from a third of a circle to 120° so that the doors of the cargo change room can be coupled with the orbiter's cargo bay. The body of this structure begins at a level of 18 meters and extends to a level of 57.6 m providing access to five levels. The revolving structure moves in 8 cars on rails. The rotating body is 31 m long, 15 m wide and 40 m high.
The main purpose of the rotating structure is to install payloads in the orbiter's hold. It is only responsible for the installation of light loads, for heavier cases such as compartments, laboratories, etc. are performed in the orbiter's processing facility.
The cargo exchange room is located in the central part of this structure and constitutes a sealed room that receives the cargoes from the cargo container. The cleanliness of these loads is maintained thanks to covers that prevent the devices from being exposed to the open air.
Orbiter central umbilical unit
This unit allows access and work in the central area of the orbiter. It extends from the Rotating Service Structure from levels 48 to 53.6 m. This unit is 6.7 m long, 4 m wide and 6 m high. An extension platform and a manual panning mechanism allow access to the orbiter's central body door.
This unit is used to feed hydrogen and liquid oxygen to fuel cells, and gases such as nitrogen and helium.
Umbilical system of hypergolics
The system transports the hypergolic fuel and oxidizer, as well as service lines for hydrogen and helium from the fixed service structure to the space shuttle. This system also allows the rapid connection of the lines and their disconnection from the vehicle. Six umbilical units are manually operated on the platform. These units are located on each side of the bottom of the orbiter. These units serve the orbital maneuvering system and reaction control system, as well as the cargo hold and nose area of the orbiter.
Climate protection system
This system located on platforms A and B serves to protect the orbiter from inclement weather such as hail, downpours, and wind-borne debris that could damage the thermal protection system and insulation blankets.
The revolving structure when closed covers most of the orbiter, and a weather protection system covers the free spaces.
Sliding doors that slide between the orbiter's belly and the external tank provide protection for the lower part of the orbiter. These doors, which are 16 m long and 11.6 m high, weigh about 20,866 kg. The doors are connected to the revolving structure and the Fixed Service Structure. The doors move on opposite sides on rails.
An inflatable seal protecting the top of the orbiter extends from the cargo-switching room, forming a semicircle that covers a 90-degree arc between the vehicle and the external tank. A series of 20 or more 24.4 by 1.2 meter double metal doors extend from the cargo exchange room in the Rotating Service Structure to cover the side areas between the external tank and the orbiter.
Flame deflector system
The system serves to protect the vehicle and platform structures from launch fire.
A flame deflector is an inverted V-shaped structure that serves to deflect launch flames and direct them through openings in the launch pad to the pits below. The walls of this structure curve as they move away from the central area and reach an almost horizontal slope.
This baffle structure is 149 m long, 18 m wide, and 12 m high. The deflector system used by the space shuttle is double as one side of the inverted V receives the flames from the main engines, while the opposite side receives the flames from the solid-propellant rockets.
The orbiter's baffles and rocket boosters are constructed of steel and covered with a 127mm-thick ablation material. Each baffle weighs more than 453.6 t.
In addition to the fixed baffles, there are also two baffles that move over the pit to provide additional protection from rocket booster flames.
Exhaust system
Provides an escape route for orbiter astronauts and technicians in the Fixed Service Structure until the last 30 seconds of the countdown. The system is made up of seven cables that extend from the Fixed Service Structure to the level of the Orbiter Access Arm whose paths end on the ground.
In case of an emergency, astronauts enter a bucket-shaped structure made of steel and surrounded by netting. Each bucket can serve three people. The cable extends some 366 m to a shelter bunker located to the west of the Fixed Service Structure. The descent lasts about 35 s and braking is carried out thanks to a net and a chain braking system.
Lightning rod
The lightning rod extends from the top of the fixed structure and provides protection to the vehicle and platform structures. The lightning rod is connected to a cable that is attached to an anchor 335 m south of the structure and another cable extends the same distance to the north. A lightning strike that strikes the tip runs through this cable to the ground, in this way, the mast of the lightning rod works as an electrical insulator, keeping the cable isolated from the fixed structure. The mast together with the accompanying structure raises the cable about 30.5 m above the structure.
Water system for sound suppression
This platform-mounted system protects the orbiter and its payloads from damage caused by acoustic energy and flares ejected by solid rockets in the baffle pit and launch pad.
The sound suppression system includes a water tank with a capacity of 1,135,620 L. The tank is 88 m high and is located in an elevated position adjacent to each platform. The water is released just before the ignition of the space shuttle engines and flows through pipes with a diameter of 2.1 m. The journey is made in about 20 s. Water is ejected through 16 nozzles above the flame deflectors and through openings in the launch pad shaft for the orbiter's main engines, beginning at T minus 6.6 s (T corresponds to time (time, in English) that defines the precise moment of the launch).
By the time the SRBs ignite, a torrent of water covers the launch pad thanks to six huge nozzles or sprinklers attached to its surface.
The sprinklers are 3.7 m high. The two central ones measure 107 cm in diameter; the remaining four are 76 cm in diameter.
The point of greatest water flow occurs 9 seconds after takeoff with 3,406,860 L from all sources.
Sound levels are highest when the shuttle is about 300m above the launch pad. The danger decreases at an altitude of 305 m.
Solid Rocket Accelerator Stress Suppression System
This system belongs to the sound suppression system. In this case, it is responsible for reducing the effects of the reflected pressures that occur when the booster rockets ignite. Without the suppression system the pressure would put a lot of stress on the wings and orbiter control surfaces.
There are two main components to this acoustic energy suppression system:
- A system of water sprayers that provides a water mattress which is aimed at the flame pit directly below each booster.
- A series of water bags distributed around the flame holes provide a mass of water that facilitates the absorption of the reflected pressure pulse.
Used together, this water barrier prevents the passage of booster pressure waves, reducing their intensity.
In the event of an aborted mission, a post-shutdown flooding system would take over to cool the bottom of the orbiter. It also controls the burning of residual hydrogen gas after the engines have been shut down with the vehicle on the apron. There are 22 hydrants around the exhaust shaft for the main engines inside the launch pad. The water is fed by a supply line with a diameter of 15 cm, making the water flow at 9,463.5 L/min.
Main Engine Hydrogen Removal System
Hydrogen vapors that are produced during the start of the ignition sequence are expelled at the engine nozzles just prior to ignition. As a result, a hydrogen-rich atmosphere is obtained inside the nozzles. To prevent damage to the engines, six removal pre-starters are installed on the rear mast. Just prior to ignition of the main engines these pre-igniters are activated and ignite any remaining hydrogen in the area below the nozzles. This process avoids a sudden combustion in the ignition of the main engines.
Propellant storage facilities
These facilities are located on the two launch pads. A 3,406,860 L tank located at the northwest end of each platform stores liquid oxygen (LOX) that is used as the oxidizer for the orbiter's main engines.
These tanks are actually huge vacuum bottles. These keep the LOX at temperatures of –183 °C. Two pumps supplying 4,540 L oxidant/min (each) transfer the LOX from the storage tank to the orbiter's external tank.
Similar vacuum bottles with a capacity of 3,217,590 L and located at the northeast end of the platforms, store the hydrogen for the orbiter's three main engines. In this case, no pumps are needed to move the LH2 to the external tank during fueling operations, since some of the hydrogen first evaporates and this action creates a gas pressure at the top of the tank that moves the light fuel. through transfer lines.
Transfer lines carry super-cooled propellants to the launch pad and feed the external tank through the rear masts.
Hypergolic propellants used by the orbital maneuvering engines and attitude control rockets are also stored on the platforms, in well-separated areas. A facility located at the southeast end of each platform contains the fuel monomethyl hydrazine. A facility in the far southwest stores the oxidizer, nitrogen tetroxide. These propellants are stored by transfer lines to the fixed structure and continue to the hypergolic umbilical system of the rotating structure, with its three pairs of umbilical lines connected to the orbiter.
Launch pad interface and launch processing system
Elements located in the pad's Terminal Connection Room provide the vital links between the launch processing system in the launch control center, the ground support team, and the shuttle's flight devices. This room resides below the elevated position of the platform.
Fonts
- Information Summaries: Countdown! NASA Launch Vehicles and Facilities(NASA PMS 018-B (KSC), October 1991).
- U.S. Human Spaceflight: A Record of Achievement, 1961-1998. NASA - Monographs in Aerospace History #9, July 1998.