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Mobile Launcher Platform

Mobile Launcher Platform

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The Mobile Launcher Platform or MLP is one of three two-story structures used by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 to support the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 stack during its transportation from the Vehicle Assembly Building
Vehicle Assembly Building
The Vehicle Assembly Building, or VAB, at NASA's Kennedy Space Center was used to assemble and house American manned launch vehicles from 1968-2011. It is the fourth largest building in the world by volume...

 (VAB) to Launch Pad 39-A at the Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

 as well as serve as the vehicle's launch platform. NASA's three MLPs were originally constructed for the Apollo Program to launch the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 rockets in the 1960s and 1970s, and have remained in service to this day, with substantial alterations.

Function


Each MLP weighs 8230000 pounds (3,733,065.2 kg) unloaded and roughly 11000000 pounds (4,989,516.1 kg) with an unfueled Shuttle aboard, measures 160 feet (48.8 m) by 135 feet (41.1 m), and is 25 feet (7.6 m) high. It is powered by a Crawler-Transporter
Crawler-Transporter
The crawler-transporters are a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building along the Crawlerway to Launch Complex 39. They were originally used to transport the Saturn IB and Saturn V rockets during the Apollo, Skylab and Apollo–Soyuz programs....

, which measures 131 feet (39.9 m) by 114 feet (34.7 m), and is 20 feet (6.1 m) high. Each Crawler weighs about 6000000 pounds (2,721,554.2 kg) unloaded, has a maximum speed of about 1 miles (1.6 km) per hour loaded, and has a leveling system designed to keep the Space Shuttle vertical while negotiating the 5 percent grade leading to the top of the launch pad. Two 2750 hp diesel engines power each Crawler.

Originally designated the "Mobile Launcher", the MLP was designed as part of NASA's strategy for vertical assembly and transport of space vehicles. Vertical assembly allows the preparation of the spacecraft in a ready-for-launch position, and avoids the additional step of lifting or craning a horizontally-assembled vehicle onto the launchpad (as the engineers of the Soviet space program chose to do).

The Mobile Launcher Platform is set atop six legs inside the massive Vehicle Assembly building. The Solid Rocket Boosters are mounted on top of the MLP. The External Tank is then lowered between the two boosters and attached to them. After that, the Orbiter is lowered into position and attached to the External Tank. The Crawler-Transporter then carries the combined platform and vehicle to the launch site, and deposits them there together. Once the launch has been completed, the Crawler-Transporter retrieves the empty MLP from the pad to be readied for its next use.

Evolution



Apollo


The MLP was originally constructed for the use of transporting and launching the Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 rocket for the Apollo program lunar landing missions of the 1960s and 1970s. Each MLP originally had a single exhaust vent for the Saturn V's motors. The MLPs also featured the distinctive 400 feet (121.9 m) launch umbilical tower (LUT) with arms that permitted the servicing of the rocket on the launch pad. The arms swung away from the Saturn V at launch. For Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...

 and Apollo-Soyuz
Apollo-Soyuz Test Project
-Backup crew:-Crew notes:Jack Swigert had originally been assigned as the command module pilot for the ASTP prime crew, but prior to the official announcement he was removed as punishment for his involvement in the Apollo 15 postage stamp scandal.-Soyuz crew:...

, MLP #1 was modified with a so-called "milkstool" pedestal that allowed the shorter Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

 rocket to use the Saturn V tower and service arms, and Saturn V Ground Support Equipment (GSE) was removed or de-activated and Saturn IB GSE equipment was installed.

Space Shuttle


In the post-Apollo years, the umbilical towers from Mobile Launchers 2 and 3 were removed. Portions of these tower structures were erected at the two Space Shuttle (or STS, for Space Transport System) launch pads, Pads 39 A and B. These permanent structures are now known as the "Fixed Service Structure" or in NASA's language of acronyms, FSS. The umbilical tower from Mobile Launcher 1 (which was the platform used for the most significant Apollo Missions) was taken apart and stored in the Kennedy Space Center's industrial area. Efforts to preserve it in the 1990s failed, however, for lack of funding and it was scrapped.

In addition to removal of the umbilical towers, each Shuttle-era MLP was extensively reconfigured with the addition of two Tail Service Masts, one on either side of the Main Engine exhaust vent. These 31 feet (9.4 m) masts contain the feed lines through which liquid hydrogen (LH2) and liquid oxygen (LOX) are loaded into the shuttle's external fuel tank, as well as electrical hookups and flares that are used to burn off any ambient hydrogen vapors at the launch site immediately prior to Main Engine start.

The Space Shuttle Main Engine
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...

 (SSME) vents its exhaust through the original opening used for the Saturn rocket exhaust. Two additional holes were added to vent exhaust from the Solid Rocket Boosters
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...

 that flank the external fuel tank.

The Space Shuttle assembly is held to the MLP through the use of eight attach posts, also called "hold-down bolts", four on the aft skirt of each Solid Rocket Booster. Immediately before SRB ignition, frangible
Frangible
A material is said to be frangible if through deformation it tends to break up into fragments, rather than deforming plastically and retaining its cohesion as a single object...

 nuts attached to the top of these bolts are detonated, releasing the assembly from the platform.

When NASA began launching shuttle missions, it became clear that the MLP might inadvertently pose a danger to the crew or the vehicle: massive acoustic shock waves and rocket exhaust can bounce off the platform and hit the shuttle as it lifts off. This was true for the Saturn V launches as well, but there was less risk because the Apollo Modules, atop the 363 feet (110.6 m) stack, were much farther away from the engines. Because the shuttle is about half the height of the Saturn, the crew-cabin and payload bay are much closer to the platform and much more vulnerable to the tremendous forces bouncing back off the MLP - on the first mission, STS-1
STS-1
STS-1 was the first orbital flight of NASA's Space Shuttle program. Space Shuttle Columbia launched on 12 April 1981, and returned to Earth on 14 April, having orbited the Earth 37 times during the 54.5-hour mission. It was the first American manned space flight since the Apollo-Soyuz Test Project...

, the shock waves damaged many of the protective thermal tiles
Space Shuttle thermal protection system
The Space Shuttle thermal protection system is the barrier that protects the Space Shuttle Orbiter during the searing heat of atmospheric reentry...

.

NASA's solution to this danger is to cushion the MLP at every launch with a flood of flowing water. Starting 6.6 seconds before engine ignition, a 300000 gallons (1,135.6 m³) water tank at the launch site begins dumping water down a pipeline and into the exhaust vents of the MLP. Next, six 12 feet (3.7 m)-high towers known as "rainbirds" begin to spray water over the MLP and into the flame deflector trenches below it. The water absorbs some of the bruising forces of the acoustic waves, and discourages fires that might be caused by the rocket exhaust. This water-dumping mechanism, known as the Sound Suppression System, empties the launch pad tank in around 41 seconds. The giant white clouds that billow around the shuttle at each launch are not smoke, but water vapor generated as the rocket exhaust boils away huge quantities of water. The suppression system reduces the acoustic sound level to approx 142 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...

.

Constellation



With the retirement of the Shuttle in 2011 and its planned replacement Orion spacecraft and its Ares I
Ares I
Ares I was the crew launch vehicle that was being developed by NASA as part of the Constellation Program. The name "Ares" refers to the Greek deity Ares, who is identified with the Roman god Mars...

 launcher in the design and test phase, NASA is converting LC-39B from Shuttle operations to support Ares I launches. The Ares I-X
Ares I-X
Ares I-X was the first stage prototype and design concept demonstrator in the Ares I program, a launch system for human spaceflight developed by the United States space agency, NASA. Ares I-X was successfully launched on October 28, 2009...

 suborbital mission (using a five-segment solid-fueled first stage
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...

 with four active and one dummy segments and a boilerplate second stage and spacecraft) utilized MLP 1, the same MLP used for Apollo 11
Apollo 11
In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...

, to support the stacking and launch operations. The cancelled Ares I-Y
Ares I-Y
Ares I-Y was to be a structural test flight in the Ares I spacecraft development program. The test flight vehicle would have been similar to the Ares I-X mission, launched on October 28, 2009...

 (using a full five-segment first stage, production second stage, and boilerplate Orion spacecraft with an active Launch Abort System) would have used the same MLP.

Starting with Orion 1, NASA would utilize one of three new MLPs, designed by ASRC Aerospace (under the University-Affiliated Spaceport Technology Development Contract [USTDC]) that will support the "stick-like" Orion-Ares I configuration, its launch umbilical tower, and escape equipment. At a weight of about 9.5 million pounds (4,300 metric tons), the new MLPs would allow NASA to utilize the Crawler-Transporter in its current configuration.

The existing Apollo and Shuttle MLPs, after the retirement of the Shuttle, will be overhauled and modified, along with LC-39A, for support of the planned Ares V
Ares V
The Ares V was the planned cargo launch component of the Constellation program, which was to have replaced the Space Shuttle after its retirement in 2011. Ares V was also planned to carry supplies for a human presence on Mars...

 rocket, the Altair spacecraft, and its launch umbilical tower. The three exhaust ports, in a "triangular" arrangement (due to the "piggyback" nature of the Shuttle stack) would be modified for the in-line nature of the Ares V, and the compartments would be strengthened to support the heavier weight of the launch vehicle. At the same time, NASA would either modify the existing Crawler-Transporters, or even construct replacements, that will allow them to carry both an Orion-Ares I and Altair-Ares V stack from the Vehicle Assembly Building
Vehicle Assembly Building
The Vehicle Assembly Building, or VAB, at NASA's Kennedy Space Center was used to assemble and house American manned launch vehicles from 1968-2011. It is the fourth largest building in the world by volume...

to their respective launch pads if lunar landing missions commence after 2018.

External links