Space Launch System (SLS)

📷 Joel Kowsky / Wikimedia Commons (Public domain)

The Space Launch System is NASA’s rocket for the Artemis program, built to send astronauts in the Orion capsule back to the Moon. Boeing builds the core stage, Northrop Grumman the boosters and Aerojet Rocketdyne the engines. In its Block 1 form it stands 98 m tall, lifts off on 39,100 kN of thrust — about 15 percent more than a Saturn V — and can send roughly 27,000 kg toward the Moon or 95,000 kg to low Earth orbit.

SLS flew for the first time on 16 November 2022, launching the uncrewed Artemis I mission. It is the most powerful rocket NASA has ever operated, and the only vehicle flying today designed from the start to launch humans into deep space.

Development History

Congress ordered SLS into existence in 2010 after the cancellation of the Constellation program, directing NASA to reuse Space Shuttle technology. The core stage is essentially a stretched Shuttle external tank fitted with four RS-25 engines — the same engines that powered the orbiters, many literally pulled from Shuttle inventory with flight histories stretching back decades.

Development ran long and expensive. First flight slipped from 2017 to 2022, and government auditors put the cost of a single launch above two billion dollars, drawing constant criticism as commercial rockets grew cheaper. After hurricanes and stubborn hydrogen leaks through the autumn of 2022, Artemis I finally lifted off in the middle of the night and performed almost flawlessly.

That mission sent Orion looping around the Moon on a 25.5-day flight, traveling farther from Earth than any spacecraft built for humans had ever gone, and ended with a successful high-speed reentry test over the Pacific.

Design & Capabilities

Block 1 pairs the orange 8.4 m hydrogen-oxygen core with two five-segment solid rocket boosters — stretched versions of the Shuttle’s four-segment motors — which together supply about 75 percent of liftoff thrust. Everything is expended: the RS-25s, once carefully refurbished between Shuttle flights, now get one final mission each before falling into the Atlantic.

Block 1 uses the Interim Cryogenic Propulsion Stage, powered by one RL10 engine, to send Orion toward the Moon. Earlier plans proposed the larger Exploration Upper Stage for Block 1B. NASA’s February 2026 architecture instead prioritizes a more standardized SLS configuration for the near-term mission sequence; older growth plans should not be read as a committed flight schedule. NASA architecture update.

Notable Missions

Artemis I, launched 16 November 2022, was the vehicle’s only flight through 2025 — and a thorough one. The rocket delivered Orion with unusual precision, the capsule spent nearly a month in space including about six days in a distant orbit around the Moon, and it survived reentry at close to 40,000 km/h, the fastest return of a human-rated capsule since Apollo.

Artemis II launched on April 1, 2026 and splashed down on April 10, completing a crewed lunar flyby with four astronauts. It did not land on the Moon. NASA’s February 2026 architecture targets Artemis III for a low-Earth-orbit systems and docking test in 2027, followed by an Artemis IV lunar landing targeted for 2028. These later dates are plans, subject to testing and readiness. NASA: Artemis II; NASA architecture update.

Frequently Asked Questions

Why does SLS use old Space Shuttle engines?

Congress required Shuttle heritage to reuse proven, human-rated hardware and preserve the industrial base. The RS-25 is among the most efficient large rocket engines ever built, and NASA inherited sixteen of them when the Shuttle retired. The twist is that SLS expends them: engines that once flew dozens of missions now fly exactly once more.

Is SLS more powerful than the Saturn V?

By liftoff thrust, SLS Block 1 is more powerful: about 39,100 kN against Saturn V’s 34,500 kN. Thrust is not payload capacity; the two rockets have different mission and stage configurations.

How much does an SLS launch cost?

NASA’s inspector general estimated about 2.2 billion dollars per SLS launch, and more than four billion per Artemis mission once the Orion spacecraft and ground systems are counted. That price — far beyond any commercial rocket — is the program’s biggest controversy and the main argument its critics raise against it.

Has SLS carried astronauts?

Yes. Artemis II launched on April 1, 2026 and splashed down on April 10, completing a crewed lunar flyby with four astronauts. It did not land on the Moon. NASA’s February 2026 architecture targets Artemis III for a low-Earth-orbit systems and docking test in 2027, followed by an Artemis IV lunar landing targeted for 2028. These later dates are plans, subject to testing and readiness.