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 Altered Trajectory

Jamie Groh M.Ed. 

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Out for a Walk


Illustration Credit: NASA

In recent weeks if you had the opportunity to visit Kennedy Space Center in central Florida you would’ve likely seen the crawler-transporter out for one of it’s monthly “walks.” We had the opportunity to visit on a few different occasions and got to witness the crawler in various locations on it’s 4.4 mile journey from the Vehicle Assembly Building (VAB) and Launch Complex 39B (LC-39B). This turned out to have been part of a practice walk to work out any kinks and fine tune all operating systems with crawler-transporter 2 (CT2) because it would soon be called to duty.

In the first week of September NASA’s Exploration Ground Systems engineers affixed the upcoming Space Launch System(SLS) program’s towering 380 foot tall Mobile Launcher (ML) atop of CT2. The ML is the structure that will serve as the backbone for the SLS rocket during assembly, processing, and launch. This was a major milestone in program advancement as this is the first step in testing for the ML to support the SLS rocket. Eventually, SLS will be what sends humans and habitats to Mars for NASA.


Photo Credit: NASA

The SLS needs such a structure as the ML because the pad at Launch Complex 39B is what’s known as a “clean pad” meaning that the rocket and supporting launch structures are not affixed to the launch pad itself, rather, they are transported to the pad as needed. This will allow for assembly procedures to be conducted inside of NASA’s VAB and will decrease the time that the rocket needs to be on the pad for launch preparations to 10 days or less. This also opens up the possibility for other launching systems to use the pad when not in use by the SLS.

Once ground crew teams got the ML mated with CT-2 preparations began for the first ever SLS support system’s walk to Pad 39A. The ML and CT-2 have been mated together and made the walk to LC-39B previously as part of preparations for the Ares I crew launch vehicle for the now cancelled Constellation program in 2011, but has since been undergoing refurbishments to support SLS. The ML now sports a new crew access arm and umbilicals that will eventually connect to SLS for launch preparations and procedures.

Once mated properly CT2 and the ML were on the move to complete the walk to LC-39B escorted by a water truck. The two day trek was watched through streaming webcams and commentated by many online reporting outlets and space enthusiasts alike. This progress is seen as a good indicator that the the SLS program is fully on it’s way to completion and will soon be returning humans to space from the United States, something that hasn’t occurred since 2011.


Photo Credit: NASA

The walk out to LC-39B took almost a full work day and ended the first day of operation at about the halfway mark. The following day ground crews were back at work and CT-2 rolled the ML around the left hand turn towards LC-39B and to the ramp of its final destination atop of the raised launch pad. CT-2 is specially equipped for this exact job with laser guidance and leveling systems to keep the ML, and SLS, perfectly level while it rolls up the 5% incline. The CT-2 successfully delivered the ML to it’s parking place and teams than began with the on-pad testing. It was assumed that the Laser Docking System would be used to help guide with the hard down procedures, however time constraints did not allow for use. The ground teams did however, achieve a successful hard down within an inch of accuracy which has been described as an amazing milestone achievement in the overall process to get SLS up and running. CT-2 was rolled off of the ramp and parked nearby while testing commenced. It remained nearby to once again pick up the ML and commence a walk, this time back to the VAB.

One important test that was completed on pad while the ML was there was the water deluge test. The water deluge system is an integral part of launching procedures as it delivers thousands of gallons of water to suppress acoustic vibrations and high temperatures. This system is necessary to protect the pad, the rocket, and payload all from the combined 8.4 million pounds of thrust and associated heat and noise that will be produced during launch of the SLS. This is the second test of the sound suppression water deluge test. An impressive release of about 600,000 gallons of water was conducted in January of this year ahead of the CT-2’s delivery of the ML.

Photo Credit: NASA

Once pad tests were complete the CT-2 was back to work picking up the ML once again. This time Ct-2 and ML would complete the 4.4 mile journey back to the VAB in one day arriving at the doors just in time for the end of work day. NASA’s Exploration Ground Systems, along with invited members of media and guests, early the next morning to deliver the ML to it’s final resting point in one of the HB3 inside the VAB.


Photo Credit: NASA

The event was highly publicized because delivery of the ML inside the VAB now initiates the next step in testing and preparations for launch of the SLS currently slated for 2020. Teams were able to test the swing out of the Crew Access Arm before rolling the ML inside. The Laser Docking System finally did get it’s moment to shine when it was used to aid with rolling the ML inside High Bay 3 (HB3) of the VAB. This was the final element of the move testing phase and teams were able to conclude all moving procedures early in the day. The ML now will reside inside HB3 for an estimated 7 months to complete various tests.


Illustration Credit: NASA


Following this initial testing period the ML will ride once again atop of CT-2 to initiate an expected 4 month long visit to LC-39B for another round of on-pad testing. Once ML has gone through the nearly year long testing phase it is expected to be mated with SLS and rolled to the pad for the launch of NASA’s currently planned Exploration Mission 1 which will catapult an uncrewed Orion capsule around the moon and back.


Illustration Credit: NASA