Mobile launcher platform

The Space Shuttle Atlantis is carried atop the MLP-1 in the lead-up to STS-79

Construction of the Mobile Launcher Platform-1 (MLP-1) (formerly called the Mobile Launcher-3 or ML-3) began in 1964 and was completed with the installation of the Launch Umbilical Tower hammerhead crane on 1 March 1965.[6] The swing arms were added at a later date.

The ML-3 was used for five crewed Apollo launches; Apollo 10, Apollo 13, Apollo 15, Apollo 16 and Apollo 17.

Following the launch of Apollo 17, the ML-3 was the first of the Mobile Launchers to be converted for use by the Space Shuttle. The Launch Umbilical Tower was dismantled and later partially reassembled on LC-39A[7] as that pad's Fixed Service Structure (FSS) and the base of the launch platform was modified to accommodate the locations of engines on the Shuttle. The platform was redesignated MLP-1.

In total, the MLP-1 was used for 52 Shuttle launches between 1981 and 2009. It was used for the first Space Shuttle launch, STS-1, in April 1981. Following the launch of STS-119 in March 2009, it was transferred to the Constellation program. The platform was used only for the Ares I-X and the MLP-1 suffered substantial damage. The canceled Ares I-Y would have used the same MLP.[8][9] However, the Constellation program was canceled and the MLP was left unused.

Following the STS-135, usable parts from the MLP-1 were removed and stored in the Vehicle Assembly Building, with no plans to use the MLP again.[10]

In 2021, NASA began rolling out Mobile Launch Platform-1 on Crawler transporter-2 with a concrete ballast on the top to condition the crawlerway to handle the combined weight of the Space Launch System and Orion spacecraft in the future.[11] NASA stated that re-conditioning of the crawlerway will be required periodically in the future, and MLP-1 will be retained for that purpose. MLP-1 will be stored in High Bay 1 of the Vehicle Assembly Building when not in use for crawlerway maintenance.[12][13]

The Space Shuttle Atlantis is carried atop the MLP-2 in the lead-up to STS-117

Mobile Launcher Platform-2 (MLP-2) (formerly called the Mobile Launcher-2 or ML-2) was used for the uncrewed Apollo 6 mission, followed by three crewed Apollo launches; Apollo 9, Apollo 12 and Apollo 14. It was subsequently used for the launch of Skylab on a Saturn V in 1973.

Following the launch of Skylab, ML-2 was the second of the Mobile Launchers to be converted for use by the Space Shuttle. The Launch Umbilical Tower was dismantled and partially reassembled to become the LC-39B[14] Fixed Service Structure (FSS), and the base of the launch platform was modified to accommodate the locations of engines on the Shuttle. The platform was redesignated MLP-2.

In total, MLP-2 was used for 44 Shuttle launches, starting in 1983. All of the orbiters except Columbia made their maiden flights from MLP-2. It was also the launch site for the ill-fated STS-51L mission, when Space Shuttle Challenger disintegrated shortly after launch, killing all seven crew members.[15]

Following the Space Shuttle retirement, NASA kept the MLP-2 for liquid-propellant rockets,[10] but in January 2021, NASA announced that due to lack of storage space, the massive structure would be demolished.[16]

A Saturn V is carried atop the ML-1 in the lead-up to Apollo 11

The first launch from the Mobile Launcher Platform-3 (MLP-3) (formerly called the Mobile Launcher-1 or ML-1) was the maiden flight of the Saturn V, and the first launch from LC-39, Apollo 4. Following this, it was used for two crewed Apollo launches: Apollo 8 and Apollo 11. After NASA decided to move Saturn IB launches from LC-34 to LC-39B, the ML-1 was modified by the addition of a structure known as the Milkstool, which allowed the Saturn IB to use the same Launch Umbilical Tower as the much larger Saturn V. Three manned flights to Skylab, and the Apollo launch for the Apollo-Soyuz Test Project, were conducted from the ML-1 using the Milkstool.

Prior to the scrapping of the LUT in 2004, there was a campaign to rebuild and preserve it as a memorial to Project Apollo.[17] The crew access arm is preserved at the Kennedy Space Center Visitor Complex on the upper level of the gift shop.[18]

Following the launch of Apollo-Soyuz, ML-1 was the last Mobile Launcher to be converted for use by the Space Shuttle. The LUT and Milkstool were dismantled and placed into storage, and the base of the launch platform was modified to accommodate the locations of engines on the shuttle. The platform was redesignated MLP-3.

In total, MLP-3 was used for 29 Shuttle launches, starting in 1990. It was the least used of the three MLPs. Following the Space Shuttle retirement, NASA kept the MLP-3 for solid-propellant rockets.[10]

Usage of MLP-3 to launch the OmegA rocket was granted to Orbital ATK (later bought out by Northrop Grumman) following discussions in 2016,[19] and later formalized through a Reimbursable Space Act Agreement in August 2019.[20] Under the Agreement, Vehicle Assembly Building High Bay 2 would be used to assemble the rocket, while MLP-3 and crawler-transporter 1 would be used to move the rocket to LC-39B for launch. From 2019 to 2020, the OmegA launch tower was under construction on MLP-3. Following the cancellation of OmegA in September 2020, work began to demolish the half-completed launch tower.[21] As of January 2021, MLP-3 is planned to be placed in storage in High Bay 2 of the Vehicle Assembly Building.[12][13]

The SLS Mobile Launcher-1 in 2015

Between 2009 and 2010, a mobile launcher platform called the Mobile Launcher-1 (ML-1) was constructed as part of the Constellation program. Since the cancellation of the program in 2010, ML-1 was converted for the Space Launch System Block 1, with various phases of construction between 2013 and 2018. The total cost of the ML-1 is estimated to be $1 billion.[22]

The biggest modification to the ML-1 was on the platform's base, where engineers increased the size of a 22 square feet (2.0 m²) exhaust duct to a rectangle stretching 60 by 30 feet (18.3 by 9.1 m) and strengthened the surrounding structure. SLS weighs more than twice as much as the planned Ares I rocket. The Ares I rocket would have featured a single solid-fueled first stage, while the SLS includes two large solid rocket boosters and a powerful core with four RS-25 engines. The base of the ML-1 is 25 feet (7.6 m) high, 158 feet (48 m) long, and 133 feet (41 m) wide.[23] The ML-1 also features a 355-foot-tall (108 m) Launch Umbilical Tower (LUT) with several arms that permit servicing of the SLS on the launch pad, and swing away from it at launch.

Rendering of the Space Launch System Block 1B, on Mobile Launcher-2 with tower

In June 2019, NASA awarded a contract for the design and construction of the Mobile Launcher-2 (ML-2) for SLS Block 1B.[23] Construction of the ML-2 began in July 2020, with the planned completion in 2023. The total cost of the ML-2 is estimated to be $450 million.[22]

The Atlas V utilizes an MLP when launching from SLC-41. The rocket is stacked on its MLP in the 280-foot-tall (85.4 m) Vertical Integration Facility (VIF), and is then rolled-out over 600 yards (550 m) to the launch pad.[24] The design of this MLP is derived from the MLPs used by the Titan III and IV rockets.

Titan III and Titan IV rockets launched from SLC-40 and SLC-41 utilized MLPs to decouple assembly of the launch vehicle from launch. This was meant to enable simultaneous assembly of multiple launch vehicles as part of the Titan's Integrate-Transfer-Launch (ITL) concept, allowing a high flight rate from a small number of launch pads.[25]

United Launch Alliance's Vulcan will use an MLP similar in design to the one used by the Atlas V when launching from SLC-41, altered to support the former's larger design. The VLP (Vulcan Launch Platform)[26] stands 183 ft (56 m) tall, and when complete will weigh 1.3 million pounds (590 tonnes). It will be equipped with various electronics, power-lines, and cables to support and control the rocket. For the initial Vulcan-Centaur configuration, the MLP will supply liquefied natural gas and liquid oxygen to the first stage, and liquid hydrogen and liquid oxygen to the Centaur upper stage. As of October 24, 2019, the basic structure has been completed, but the umbilicals and equipment have yet to be installed.[27]