Four rocket engines that once helped launch space shuttles are now bolted into the base of NASA's next Moon rocket. Technicians at Kennedy Space Center's Vehicle Assembly Building have completed installation of all four RS-25 engines into the core stage of the Space Launch System rocket assigned to Artemis III, following a milestone that began Aug. 24 when the first engine was mated to the stage. The installation marks the next phase of core stage integration, coming after the engine section was mated to the top four-fifths of the stage earlier in the summer.
Each RS-25 weighs about 7,700 pounds and produces close to 500,000 pounds of thrust. During ascent, the four engines fire continuously for more than eight minutes, together drawing propellant from the core stage's two tanks at a rate of roughly 1,500 gallons per second — a consumption rate that helps explain why the SLS core stage is one of the largest single rocket stages ever built, and why the four engines beneath it need to be so thoroughly tested and inspected before they are ever asked to fire together.
Why It Matters
None of these four engines are new. Identified by their engine numbers — E2054, E2057, E2048, and E2052 — they are refurbished veterans of the Space Shuttle program. E2048 in particular has flown before: it powered Space Shuttle Atlantis on STS-129 in 2009, and earlier flew aboard Discovery on STS-95 in 1998, the mission that carried Senator John Glenn back to orbit 36 years after his historic first American orbital flight. NASA's decision to fly out its remaining shuttle-era RS-25 inventory on the first several SLS missions — before transitioning to a cheaper, expendable version of the engine for later flights — means Artemis III's ascent will be powered, in part, by hardware with a genuine multi-decade flight history stretching back to the twentieth century.
The engine installation is one of several parallel workstreams converging on the Artemis III rocket inside the Vehicle Assembly Building. Solid rocket booster segments are being stacked onto the mobile launcher in the same facility; NASA says teams began stacking in early July and are now more than halfway through that process. Meanwhile, the Orion spacecraft that will carry the crew has had its crew and service modules integrated, with an umbilical connector recently installed to link electrical, data, and fluid systems between the two halves — followed by a power-on test to confirm the connections work correctly before final closeout.
The four astronauts assigned to Artemis III — NASA's Randy Bresnik, Andre Douglas, and Frank Rubio, along with ESA's Luca Parmitano — were named to the mission on June 9, 2026, and have been working through survival and emergency-procedure training in parallel with the hardware buildup happening hundreds of miles away in Florida. Recent sessions have included water survival and post-landing emergency drills, spacesuit egress practice in the Neutral Buoyancy Lab's giant training pool, and integrated flight control simulations that put the crew and mission control through simulated ascent and orbital operations together, well before either the rocket or the crew is anywhere near ready to fly.
Bresnik's own history adds a layer of continuity to E2048's reuse: as a NASA astronaut who has flown to orbit before, he now trains for a mission that will launch atop an engine with its own shuttle-era flight record. It is one small illustration of how Artemis, for all its new hardware, new destinations, and new international partners, is still built in part out of the program that came before it — down to the individual engines doing the lifting on launch day, engines that in some cases have already carried other astronauts into space and returned safely more than once.
