KENNEDY SPACE CENTER, FL – The 212 foot long core stage pathfinder mock-up for NASA’s Space Launch System (SLS) megarocket was offloaded from the agency’s one-of-a-kind Pegasus barge Monday, Sept 30, at the Kennedy Space Center (KSC) in Florida where it will serve as a test article for critical lifting and stacking maneuvers inside the iconic Vehicle Assembly Building (VAB) for the next 4 weeks in support of the Artemismoon exploration program aimed at landing US astronauts on the lunar south pole by 2024.
Pegasus and Pathfinder had sailed into and docked at the Turn Basin by the world famous countdown clock at Kennedy three days ago on Friday afternoon, Sept. 27 after being towed by ocean-going and river-going tugboats for a nearly 1000-mile and week-long trek from NASA’s Stennis Space Center in Mississippi to KSC.
Technicians started offloading the 212-foot-long cylindrical Pathfinder from the 310-foot-long Pegasus bargeon Monday morning, Sept. 30 and then move a day later, Tuesday, Oct. 1 a short distance to the iconic Vehicle Assembly Building (VAB) for a month of maneuvering and stacking practice by NASA’s Exploration Ground Systems (EGS) team and contractor Jacobsbefore the first real SLS core stage arrives sometime in mid-2020 for eventual launch on the Artemis 1 mission in late 2020 or early 2021.
Media including Space UpClose were invited to attend both last Friday and Monday. Watch our on site coverage from today and last week.
The 228,000 pound SLS core stage pathfinderis a full-scale mockup test article that is identical to the core stage in shape, size and weight. But the 27.6 foot diameter cylinder is hollow and lacking fuel tanks, built from stainless steel and has 4 wire rim replica engine placeholders in place of the real RS-25 engines.
“This will help ensure that all core stage engineers and technicians are trained and certified in preparation for the flight core stage processing,” said Jim Bolton, EGS core stage element operations manager at Kennedy.
“It’s a very significant milestone that will demonstrate the capabilities and ability for KSC to receive, process and integrate that flight hardware.”
Pegasus had to be lengthened approx. 50 feetto accommodate Pathfinder compared to the shorter Shuttle External tanks it previously transported from NASA Michoud to KSC.
The NASA/contractor team started rolling off the Pathfinder mockup from the Pegasus barge using two WHEELLIFT transporters around 11 a.m. ET this morning – base first with the 4 replica engines exposed.
After about a quarter of the test article was out the team stopped to assess procedures, weights, balances and torques on the wheeled transporter and cradles to ensure all was within specification.
By 2 p.m. the mammoth 21 story tall core stagepathfinder was fully rolled off horizontally from Pegasus.
By 4 p.m. they had rolled the lengthy cylinder back onto Pegasus for the night.
Overall the teams spent the day practicing rolling the pathfinder off and on Pegasus and making 3 point turns to prepare for transport into the VAB on Tuesday, Oct. 1.
The purpose of shipping the SLS pathfinder test article to KSC is for use by NASA engineers and contractors for the next four weeks to practice stacking the hardware in the VAB High Bay 3 using the same procedures needed to stack the real hardware for the Artemis I mission.
This month long work period is the only time Pathfinder will be present at KSC. The NASA EGS team told me it was always planned for Pathfinder to travel to KSC for these stacking exercises as part of preparations for launch of the Artemis 1 mission.
The SLS core stage mock-up will be transported into the transfer aisle of the VAB for the stacking maneuvers.
Once in the VAB crane crews will then lift it vertically for placement into High Bay 3 – minus the Mobile Launcher which currently resides atop Launch Complex 39B at KSC.
Crane crews will then lift the long cylindrical test article off the transporter and raise it nearly 200 into the vertical position using the bridge cranes on the VAB roof.
The base of Pathfinder will be hoisted up and over the 16th floor walkway, 196 feet high, in the VAB transfer aisle and then maneuver it sideways over to High Bay 3.
Then it will be lowered by crane back to where the mobile launcher would normally reside.
Basically, this involves the same lifting and stacking procedures as were done for the Space Shuttle External Tank (ET).
And the crane crew is highly experienced says NASA and is comprised largely of the same folks who worked on the shuttle ET – which was last launched in 2011.
However the SLS core stage is more than 50 feet longer then the ET.
NASA and Jacobs teams will practice the same stacking exercises on the pathfinder mock-up as if it were a real core stage.
About 40 to 50 people will be working on pathfinder operations inside the VAB at any one time.
If deemed necessary to gain added practice and confidence they will practice the same lifting and stacking maneuvers up to two more times in the VAB – before exiting and departing.
“The pathfinder, though not actual flight hardware, will provide the SLS program, Exploration Ground Systems (EGS) team with the opportunity to practice stacking maneuvers and certify the new system inside the Vehicle Assembly Building (VAB) High Bay 3 before Artemis flight hardware arrives next year,” say NASA officials.
“Over the next several months, pathfinder will be used to validate ground support equipment and demonstrate how the core stage will be integrated in the VAB – the same process the actual core stage will undergo when being processed for Artemis I.”
The pathfinder exercises will be completed by Oct 31.
Pegasus is NASA’s one of a kind and football field sized barge used to transport the space vehicle hardware between NASA centers for testing and eventually to the launch site at the Kennedy Space Center in Florida.
The SLS core stage pathfinder was transported from NASA’s Stennis Space Center in Mississippi where it recently completed fit check testing for the upcoming ‘green run’ test of the first real SLS core stage for the Artemis 1 mission.
Last Friday Sept 27 Pegasus and Pathfinder arrived by way of Port Canaveral and the Banana River -accompanied by a KSC tracking ship and heading towards inland water ways to KSC Launch Complex 39 and the VAB. The inland path was dredged decades ago by NASA to open up access to the VAB at the KSC Turn Basin and Press site.
The 310 foot long Pegasus followed the same route used by NASA vessels decades earlier to ship Apollo moon rocket stages and Space Shuttle External tanks and solid rocket boosters.
NASA will conduct a full duration ‘green run’ engine fire test of the completed core stage at Stennis to fully confirm its readiness for flight on Artemis 1. But that test will require six months of intense work by NASA and contractor teams.
Watch for Ken’s continuing onsite coverage of NASA, SpaceX, ULA, Boeing, Lockheed Martin, Northrop Grumman and more space and mission reports direct from Kennedy Space Center and Cape Canaveral Air Force Station in Florida and Wallops Flight Facility in Virginia. Stay tuned here for Ken's continuing Earth and Planetary science and human spaceflight news. Dr. Kremer is a research scientist and journalist based in the KSC area, active in outreach and interviewed regularly on TV and radio about space topics. Ken’s photos are for sale and he is available for lectures and outreach events.