The centerpiece of NASA's second Space Launch System rocket arrived this week at Kennedy Space Center in Florida. Agency officials plan to begin stacking the towering launch vehicle in the coming months for a mission late next year that will ferry a team of four astronauts around the moon.
The Artemis II mission, officially scheduled for September 2025, will be the first human trip to the lunar vicinity since the last Apollo moon landing mission in 1972. NASA astronauts Reid Wiseman, Victor Glover, Christina Koch and Canadian mission specialist Jeremy Hansen will blast off from Earth on the SLS rocket, then fly around the far side of the moon and return home in NASA's Orion spacecraft.
“The core is the backbone of SLS, and it's the backbone of the Artemis mission,” said Matthew Ramsey, NASA's mission manager for Artemis II. “We've been waiting for the core to be here because all the integrated testing and checkouts that we need to do have to be on the core stage. It has the flight avionics that run the whole system. The boosters are important, too, but the core is really the backbone of Artemis. So it's a big day.”
The core stage rolled off NASA's Pegasus The rocket arrived at Kennedy early Wednesday morning after a week-long sea voyage from New Orleans, where Boeing is building the rocket on behalf of NASA.
Ramsey told Ars that ground crews hope to begin stacking the two powerful solid rocket boosters on NASA's mobile launch platform in September. Each booster, supplied by Northrop Grumman, consists of five segments with pre-packaged solid fuel and a nose cone. All of the parts for the SLS boosters are at Kennedy and ready to be stacked, Ramsey said.
The SLS upper stage, built by United Launch Alliance, is also at the Florida launch site. The core stage is now at Kennedy. In August or September, NASA plans to bring the two remaining elements of the SLS rocket to Florida. These are the adapter structures that connect the core stage to the upper stage, and the upper stage to the Orion spacecraft.
A heavy-duty crane in the massive Vehicle Assembly Building (VAB) will hoist each segment of SLS boosters into place on the launch pad. Once the boosters are fully stacked, ground crews will lift the 212-foot (65-meter) vertical core stage into the transfer aisle that runs through the center of the VAB. A crane will then lower the core stage between the boosters. That could happen as early as December, Ramsey said.
This is followed by the launch vehicle stage adapter, the upper stage, the Orion stage adapter, and finally the Orion spacecraft itself.
On the way to the operation
NASA’s inspector general reported in 2022 that NASA’s first four Artemis missions will cost $4.1 billion each. Later documents, including a Government Accountability Office report last year, suggest that the replaceable SLS core stage accounts for at least a quarter of the cost of each Artemis flight.
The core stage for Artemis II is powered by four hydrogen-fueled RS-25 engines manufactured by Aerojet Rocketdyne. Two of the reusable engines for Artemis II flew on the Space Shuttle, and the other two RS-25s were built during the Shuttle era but never flew. Each SLS launch will deposit the core stage and engines in the Atlantic Ocean.
Steve Wofford, who manages the SLS program stage office at NASA's Marshall Space Flight Center, told Ars that there are “no major configuration differences” between the Artemis I and Artemis II core stages. The only minor differences involve the instrumentation NASA wanted on Artemis I to measure pressures, accelerations, vibrations, temperatures and other parameters during the Space Launch System's first flight.
“We're still working on some of the flight observations that we did on Artemis I, but there are no showstoppers,” Wofford said. “On the first article, the test flight, Artemis I, we really loaded it up. That's a golden opportunity to learn as much as we can about the vehicle and the flight regime, and cement all of your models. … As you go along, you need less and less of that. So Core Stage 2 will have less development flight instrumentation than Core Stage 1, and Core Stage 3 will have even less.”
