NASA recently submitted a permit detailing facility construction and modification plans to support its next Mobile Launch Platform for Space Launch System, the agency’s nearly complete rocket to the Moon. We first have to go back to where SLS all started with the Constellation program to understand why NASA is building a new Mobile Launch Platform.

The current Mobile Launcher, ML-1, was initially built for the Constellation program between 2009 and 2010. When the Constellation program was canned in October 2010, NASA started reworking ML-1 to support their new program for the Space Launch System. With the increased complexity and weight of SLS, issues quickly began to arise.

Mobile Launcher 2

Modifications made to ML-1 would only support SLS Block 1, and the weight of these modifications started to creep up on the safety margin. The SLS Block 1 configuration is not expected to see many flights as NASA plans to introduce Block 1B after the first few flights of Block 1.

The primary difference of Block 1B is the use of the Exploration Upper Stage (EUS) rather than the Interim Cryogenic Propulsion Stage (ICPS). The EUS increases the total height of SLS Block 1B 30 feet (9.14 meters) which would lead to major modifications being required for ML-1 to support it.

After careful research, the decision was made to build Mobile Launcher 2 (ML-2) to support all future versions of Space Launch System. NASA hired contractor Bechtel to design and construct ML-2 between 2019 and 2023.

While ML-2 will have a similar base structure to ML-1, it will have a different service tower with umbilical and support structures located in different locations to support Block 1B and future versions of SLS.

Built for SLS

Rather than being built for Ares launch vehicles and then retrofitted to support SLS like ML-1, ML-2 being built from the ground up to support SLS will allow for better design decisions to be made..

ML-1 and ML-2 look fairly identical at a quick glance, but the two mobile launchers have important differences upon closer inspection. These differences account for increased weight and size of SLS builds.

It is not exactly known what will become of ML-1 once Block 1 SLS is retired. It is possible that NASA will decommission and demolish ML-1 if it doesn’t make sense to attempt another retrofitting effort to have two operational mobile launchers for SLS. Perhaps NASA could gut ML-1 and rebuild its structure to support future SLS versions without eating up safety margin.

Moving forward

In any case, the permit recently filed by NASA reveals that work on the ML-2 project will begin soon. While we will not likely see any hardware being constructed until the new year, we do know that things are moving forward in the Mobile Launcher 2 world.

Page from the plans detailing location of infrastructure

Preparations are underway for the next generation of Artemis rockets. We are still awaiting completion of testing for Artemis 1, the first of SLS launches to begin our journey back to the Moon. Stacking of Artemis 1’s solid rocket booster segments began this weekend, and the critical Green Run test of the first SLS core stage should be complete before Christmas.

[UPDATE] New Permit in Port Canaveral

NASA/Bechtel has filed a permit with the Canaveral Port Authority to support the construction of tower segments for ML-2. They will be using some vacant land just north of SpaceX’s operations in the port.

Construction site can be seen outlined in the white box
Construction Site Overview

The site has been leased to NASA/Bechtel for 20 months starting on August 26th, 2020. The site will have mobile office trailers to serve as offices and training spaces, storage and laydown sites, and other various support structures.

Here is a graphic provided by NASA/Bechtel showing the site where tower sections will be built

The flow of the site goes as follows: The steel structure of the segments will be built outside the membrane tent structure. They will then be moved inside the tent structure to have piping installed, electrical run, and other mechanical systems installed. Once the segment is completed, it will then be transported by Self-Propelled Modular Transporter (SPMT, the same thing SpaceX uses to transport their Starship vehicle around the Boca Chica Facilities) to Kennedy Space Center through Cape Canaveral Space Force Station.

Tower Segment on SPMT

It should be noted that they also outline a water route that could be taken as an alternative, but this water route does not appear to be discussed in the permit documents.

The water route would involve loading a tower segment onto a barge and being tugged through the Canaveral Lock onto the Banana River and up to the Turning Basin at Kennedy Space Center.

Transport Routes for the Tower Segments

Transports taking the road route would occur in the evening as there is less traffic on base and at the port.

A total of 7 tower segments are expected to be constructed measuring 40 feet (12.19 Meters) cubed.

Once construction of the tower segments has been completed, the site will be returned to its vacant state, minus any electrical work that has been done once reviewed by the Port Authority.

Top image: ML-1 rollout to Launch Pad 39B on October 20, 2020

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