Article by Joey Vars – The Talk of Titusville
With the arrival of ten Solid Rocket Booster segments to Kennedy Space Center June 12, most of the major vehicle components for the maiden flight of NASA’s Space Launch System are now at the launch site. The first flight-worthy booster will launch an Orion capsule on a nearly monthlong deep space shakedown cruise, and is expected to launch no earlier than November, 2021.
NASA announced back in May that, due to in part to the COVID-19 pandemic gripping America, the target date for the booster’s maiden flight would occur in ‘late 2021.’ On Friday, July 17, NASA Administrator Jim Bridenstine gave an update saying the agency was targeting ‘no earlier than November.’
Components for both of the rocket’s twin Solid Rocket Boosters arrived June 12 from Northrup Grumman’s facility in Promontory, Utah. Ten segments, each measuring nearly 30 feet in length, arrived via railcar to the Rotation, Processing and Surge Facility near the Vehicle Assembly Building.
Their arrival marks the first major propulsive element of the heavy-lift booster to arrive at the Kennedy assembly site. Teams at the RPSF unloaded the booster segments from their specialized railcars and are currently in the process of inspecting their joints and installing sensors. They will also paint NASA’s iconic ‘worm’ logotype on some of the segments, continuing the logo’s reemergence following appearing on the side of May’s historic DM-2 Falcon 9 booster.
Motor segments on the aft and forward portions of each booster will undergo specialized hardware installation, such as the aft skirt and forward dome. Teams will then wait for the arrival of the SLS core stage before beginning to stack the booster segments atop the Mobile Launcher. Solid rocket boosters such as those employed on SLS can only be stacked for twelve months before they need to be disassembled and inspected. NASA is awaiting the completion of Green Run testing before proceeding with SRB assembly.
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Development of the core stage has been the biggest benchmark for the Artemis I processing flow; once testing is complete and arrives at Kennedy, teams can solidify the remainder of the prelaunch processing schedule.
The path to flight readiness – Green Run testing
Since Artemis I is the maiden flight of the SLS vehicle, development and checkout of the core stage has been the biggest benchmark for preflight processing. Boeing and NASA engineers must first verify that each of the booster’s subassemblies are performing as expected under simulated flight conditions.
Installed at Stennis Space Center’s historic B-2 test stand in January, the SLS core stage will undergo eight major tests before being certified for flight. As of early July, NASA has completed the first three of the eight test objectives. These focussed on the vehicle’s overall structure and avionics, with the remainder of test objectives focusing on the propulsion systems and countdown protocols. The next phase of testing, known as Green Run 4, is expected to last until late August. These will test the primary elements and subassemblies of the propulsion system.
All these objectives culminate in a full-duration static firing of the booster’s four RS-25 engines and is expected for October. Known as a ‘hot fire’, this will mark the first time all four first stage engines will be fired in unison as well as the first time they are fired for a full flight duration of eight minutes.
NASA will then refurbish the core stage before shipping it to Kennedy Space Center, where SLS integration and stacking will begin.
John Shannon, Boeing’s SLS Program Manager stated at an industry conference in early July that ‘so far the design has held up pretty well. We’ve had no issues with power ups or checks.”
LVSA and ICPS
Arriving at Kennedy the same day the agency launched the Perseverance rover to Mars, NASA’s Pegasus barge delivered the final structural component of the SLS booster from the Marshall Space Flight Center in Alabama. Mounted atop the core stage tank, the Launch Vehicle Stage Adapter acts as the structural connection between the core stage and the Interim Cryogenic Propulsion Stage. Technicians loaded the component on Pegasus July 17 and arrived at Kennedy’s Turning Basin 13 days later. It is currently stored in the VAB’s High Bay 4 awaiting integration.
The Interim Cryogenic Propulsion Stage was the first component of the Artemis 1 SLS to arrive at Kennedy Space Center. Since the ICPS is derived from the Delta Cryogenic Second Stage that has been flown on the Delta IV family of rockets, the ICPS underwent modifications at ULA’s facilities at nearby Cape Canaveral Space Force Station. It arrived at Kennedy’s Space Station Processing Facility in February, 2018, where it has been awaiting stacking with the SLS vehicle. NASA expects to use the ICPS for at least the first three SLS block I flights before upgrading to the Exploration Upper Stage for the SLS 1b variant.
Once the core stage arrives and is integrated with the LVSA and ICPS, Lockheed Martin teams at the Neil Armstrong Operations and Checkout Building will perform final checkouts on the Orion capsule. This includes fueling tanks in both the capsule and the European Service Module and integration with the Launch Abort System. The combined Artemis I payload will then be transported to the Vehicle Assembly Building for integration with the SLS stack.