SLS Rocket Pathfinders Prepare Teams for One-of-a-Kind Hardware Prior to Moon Mission

NASA's Pegasus barge arrived Sept. 27 at the agency's Kennedy Space Center in Florida with the core stage pathfinder for NASA's Space Launch System (SLS) rocket. The pathfinder will be used for lift and transport practice techniques inside Kennedy's Vehicle Assembly Building to prepare for the first lunar mission of SLS and NASA's Orion spacecraft, Artemis I. The core stage pathfinder is one of three pathfinder structures used by NASA to train lift crews on best practices for moving and handling the SLS rocket flight hardware. In addition to the core stage pathfinder, there is an RS-25 engine pathfinder and a solid rocket booster pathfinder. Designed as full-scale mockups of the flight hardware, the three SLS pathfinders each reflect the shape and size of the individual components of the rocket. The number of pathfinders for the rocket allow multiple teams to use the pathfinders for different operations and procedures at several processing locations. After teams at Kennedy practice with the core stage pathfinder in the VAB, NASA's Exploration Ground Systems will begin stacking operations with the booster pathfinder structures to simulate an aft booster assembly and bottom center segment stacking operation. All this practice prepares teams for the same upcoming tasks with the actual flight hardware. Engineers previously used the core stage pathfinder in August at NASA's Stennis Space Center near Bay St. Louis, Mississippi, where crews practiced similar lift and handling procedures into the B-2 Test Stand ahead of the Green Run test series for the core stage.

"After the pathfinder lift operations were complete, the unit was installed into the B-2 Test Stand at Stennis," said Barry Robinson, B-2 Test Stand core stage test project manager at Stennis. "Among other things, the exercise helped us identify minor facility modifications early enough to provide the time needed to make the corrections prior to the arrival of the core stage flight hardware."

Equipped with the largest rocket stage NASA has ever produced and the largest twin boosters ever built for flight, the SLS rocket for the Artemis missions will be the most powerful rocket in the world, enabling astronauts in Orion to travel to the Moon's south pole. The two massive propellant tanks in the rocket's 212-foot-tall core stage power the four RS-25 engines at the bottom of the rocket. On either side of the core stage are two, five-segment solid rocket boosters. Together, the engines and the boosters will produce a combined thrust of 8.8 million pounds during launch and flight. The rocket for Artemis I will tower at 322 feet.

"Practicing operations with pathfinders offers teams hands-on experience for managing and handling the immense structures before this one-of-a-kind flight hardware arrives," Robinson said.

Because the pathfinders replicate the flight hardware, the various pathfinders validate ground support equipment, and flight hardware access techniques as well as train handlers to transport the equipment on a variety of terrains with different vehicles, like the Pegasus barge and Kennedy's mobile launcher, and demonstrate how the equipment can be integrated within facilities.

"Experience is the best teacher," said Jim Bolton, EGS core stage operations manager. "Pathfinders allow crews to practice lifting, accessing and transporting techniques that we prefer not to do for the first time with the flight hardware. Practicing with a pathfinder reduces risk and builds confidence."

As crews at Kennedy use the SLS booster and core stage pathfinders for the same processes the actual flight hardware will undergo when processed at Kennedy for Artemis I, completed flight hardware for SLS and Orion will also be delivered.

"NASA's first Artemis mission flight hardware has progressed into final assembly and integration, moving well beyond the early design and manufacturing stages of development," said Mark Prill, SLS core stage pathfinder lead. "Flight hardware for both the SLS rocket and the Orion spacecraft will continue to be delivered to Kennedy as NASA prepares for the launch of Artemis I."

NASA is working to land the first woman and the next man on the Moon by 2024. SLS, along with Orion and the Gateway in orbit around the Moon, are NASA's backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

Space Launch System Intertank completes functional testing

The intertank that will be flown on Exploration Mission-1 as part of NASA's new rocket, the Space Launch System, has completed its avionics functional testing, at the Michoud Assembly Center in New Orleans. The avionics, shown here inside the intertank structure, guide the vehicle and direct its power during flight. The intertank houses critical electronics that "talk to" the flight computers in the forward skirt. The intertank, forward skirt, two colossal fuel tanks and the engine section make up the massive core stage of the SLS rocket. The avionics units on the core stage work with the rocket's flight software to perform various functions during the first eight minutes of flight. Now that the intertank and forward skirt have passed avionics testing, they are ready to be mechanically joined and tested to verify they can successfully work together. To prepare for the first mission, engineers from Boeing, the prime contractor from Huntsville, Alabama, building the SLS core stage, are currently checking out the avionics systems for the entire rocket at the systems integration laboratory at NASA's Marshall Space Flight Center in Huntsville.

They are verifying that the core stage avionics can use the flight software to operate and communicate with all the parts of the rocket as well as to Orion and to ground control computers.

NASA tests engine part to reduce costs

NASA redesigned and tested a key component for the RS-25 engine that powers the agency's new deep space rocket, the Space Launch System (SLS), by incorporating modern manufacturing techniques that significantly reduce both cost and fabrication time. The redesigned main combustion chamber, which is the heart of the engine, has performed well during two tests in flight-like conditions. During the tests, temperatures reached 6,000 degrees Fahrenheit, and the part experienced 3,000 pounds of pressure as the engine fired up in a test stand at NASA's Stennis Space Center in Bay St. Louis, Mississippi. When SLS launches, four RS-25 engines will produce two million pounds of thrust to help send SLS to space for missions to the Moon and beyond. "We're testing propulsion parts like the main combustion chamber, one of the most complex and critical components for engine operations, to show it can be made less expensively without sacrificing reliability, safety or performance," said Steve Wofford, SLS liquid engines manager. "The SLS rocket will be the most powerful rocket in the world, and these tests show engines can be made with modern manufacturing techniques and still provide the power to safely send astronauts to the Moon."

Inside the chamber, the fuel and oxidizer combust and flow through the nozzle, to turn the high-pressure combustion into the 500,000 pounds of thrust that each engine produces. The new chamber design reduces the complexity of the part by eliminating 29 welds. The chamber is made in less time for less money with a bonding technique called Hot Isostatic Pressure - or HIP - bonding. The chamber's internal metal liner and external jacket are bonded together under very high pressures and temperatures.

"The innovative bonding process has reduced the chamber cost and build time by around 50 percent each." said Mike Shadoan, the SLS combustion devices manager for liquid engines. "This series of nine tests allows us to test flight controllers for early missions and at the same time expose parts made with innovative techniques to the same conditions they will see during launch and flight."

The RS-25 was proven during the Space Shuttle Program and has been updated with new controllers and nozzle insulation for its job with SLS. Currently, the SLS Program has 16 engines in its inventory from the Space Shuttle Program, enough for four flights.

Engines for later flights are being built by the SLS core stage engine prime contractor, Aerojet Rocketdyne, at its factory in Canoga Park, California. NASA and Aerojet engineers are working to smartly incorporate today's modern manufacturing techniques not just in the chamber, but also on key components across the entire engine, leading to a host of benefits in cost, schedule and reduced complexity.

"Engine hot fire testing is the ultimate demonstration that new component designs and incorporation of modern manufacturing technologies are paying off big-time for the program," said Dan Adamski, RS-25 program director for Aerojet Rocketdyne. "Continued testing will integrate additional upgraded components into the engine design culminating with final certification testing in 2021."

During six tests, technicians and engineers tested the first 3D printed part on an RS-25 engine, the pogo accumulator. Aerojet Rocketdyne is under contract to manufacture an initial set of six new engines for future SLS missions. These new engines will be fabricated using the components and techniques that are being validated on development engines during engine tests at Stennis.

NASA is leading a return to the Moon through an innovative and sustainable program of exploration to expand human presence into the solar system. Beginning with Exploration Mission-1, SLS and Orion will demonstrate the critical backbone capabilities that will carry humans to the Moon and farther into space than ever before on a variety of missions with increasing complexity. SLS's unprecedented power and volume will also carry the large pieces of hardware needed to build the Gateway and other long-term infrastructure at the Moon and, later, for human missions to Mars.