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. The crew access arm is preserved at the Kennedy Space Center Visitor Complex on the upper level of the gift shop. 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. Usage of MLP-3 to launch the OmegA rocket was granted to Orbital ATK (later bought out by Northrop Grumman) following discussions in 2016, and later formalized through a Reimbursable Space Act Agreement in August 2019. 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. As of January 2021, MLP-3 is planned to be placed in storage in High Bay 2 of the Vehicle Assembly Building. Space Launch System 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. The biggest modification to the ML-1 was on the platform's base, where engineers increased the