The SLS core stage is lifted out of position by the B-2 Test Stand derrick crane on April 19, 2021, to begin the process of returning the unit to the ground.

Credits: NASA/SSC

This summer, Olympic weightlifters broke records pursuing gold medals in Japan. But in early 2020, another historic heavy lift took place on the other side of the world for a prize to advance human space exploration.

A specialized team of professionals at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, defied gravity to lift the core stage of the Space Launch System (SLS) – all 188,000-pounds – to gently position it on the historic B-2 Test Stand, which has tested engines since the Apollo Program.

NASA is building SLS as the world’s most powerful rocket to return humans into deep space, to the Moon, and, eventually, Mars. Through the Artemis program, NASA will send the first woman and person of color to the Moon by 2024.

In January 2020, after the SLS core stage was installed on the B-2 stand, NASA began a series of critical tests called Green Run. The term “Green Run” refers to the testing of new hardware for the first time and in the same way it must operate on a mission. The goals of the tests were to ensure astronaut safety, to increase probability of a successful Moon landing, and to discover and address any stage or systems issues. For the final test of the series, operators fired all four RS-25 engines simultaneously, just as during an actual launch, to generate a combined 1.6 million pounds of thrust.

The testing built on early work of the heavy-lift team. Like any good team before a big event, the lift team practiced to ensure its efforts were successful. The preparation began the summer of 2019 as the team practiced on the core stage pathfinder, a full-scale shape, size, and weight replica of the actual flight unit.

The pathfinder was built to allow NASA teams – including the Stennis heavy-lift crew – to practice handling techniques and procedures needed for the actual core stage. For the Stennis team, this included a detailed rehearsal to practice lift procedures and crane location before the official core stage arrived.

The core stage pathfinder arrived at Stennis in early May 2019. Once it was rolled out on the tarmac, crews practiced small lift procedures and installed equipment needed to perform a full lift and installation. The actual lift-and-installation procedure took place through the night and early morning hours Aug. 23-24, when weather conditions were most optimal.

Once lifted, the pathfinder was carefully positioned into place on the stand, settling on so-called “yellow boxes,” spherical bearings used to anchor the core stage in position on the stand. At one point, a procedural miscalculation resulted in a broken pathfinder aft strut. Once repaired, the lift team implemented more hands-on training in handling procedures to prevent the same mistake from occurring during lift of the core stage.

With the pathfinder replica, the team also discovered a need for cable management. Several cables extended down from the Hydra Set Precision Load Positioner, a device that allows the team to raise and lower the stage in micro increments, and the master link device used to control the test article while it is in the air. To remedy the issue, the team attached an arm to the “spider” – a yellow lifting cap that allows the B-2 Test Stand derrick crane to attach to the forward end of the test article. This addition allowed the team to secure the cables away from the rocket’s body, preventing them from damaging the core stage’s thermal protection system.

“The pathfinder really laid the path for the core stage installation and removal to be more successful,” said Casey Wheeler, the NASA lifting device and equipment manager at Stennis. “It helped us run through processes that you would have not been able to run through completely without actually having a complete mock-up. The practice helped people become more familiar with the procedures and gain confidence with what exactly they were supposed to be doing whenever the multi-billion-dollar test article actually arrived.”

The SLS core stage sits on the B-2 Test Stand tarmac at Stennis Space Center on Jan. 13, 2020. The core stage arrived on NASA’s Pegasus barge, shown docked at the stand, on Jan. 12 and was rolled out soon afterward.

Credits: NASA/SSC

Crews at Stennis Space Center work Jan. 21, 2020, to install the SLS core stage on the B-2 Test Stand for a series of Green Run tests. Operations required crews to lift the stage from a horizontal position into a vertical orientation, a procedure known as “break over.”

Credits: NASA/SSC

The derrick crane atop the B-2 Test Stand at Stennis Space Center hoists the SLS core stage into a vertical orientation Jan. 21, 2020, as part of the unit’s installation process. Once oriented, crews tied the core stage in place to await favorable wind conditions to lift it into the stand.

Credits: NASA/SSC

The SLS core stage is shown suspended from the B-2 Test Stand derrick crane at Stennis Space Center early on the morning of April 20, 2021. As soon as wind conditions allowed, Stennis crews completed the removal process by “breaking over” the stage into a horizontal position as it was lowered to the ground.

Credits: NASA/SSC

The SLS core stage is shown installed on the B-2 Test Stand on Jan. 22, 2020, in preparation for a series of Green Run test of its sophisticated systems.

Credits: NASA/SSC