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.

Up top sits the Interim Cryogenic Propulsion Stage, a single RL10-powered stage borrowed from the Delta IV rocket, which performs the trans-lunar injection burn that pushes Orion to nearly 39,000 km/h. The future Block 1B swaps in the much larger Exploration Upper Stage to send roughly 40 percent more mass toward the Moon, and a later Block 2 with upgraded boosters is planned beyond that.

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, scheduled as of early 2026, is to carry astronauts Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen on a flyby around the Moon — the first humans beyond low Earth orbit since 1972. Artemis III is planned to follow with a crewed landing near the lunar south pole, using SpaceX’s Starship as the lander.

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, yes — 39,100 kN against 34,500 kN, roughly 15 percent more. But thrust is not payload: Saturn V could send about 48,600 kg toward the Moon, while SLS Block 1 manages about 27,000 kg. Later versions with the Exploration Upper Stage are designed to close much of that gap.

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.

When will SLS carry astronauts?

Artemis II is the first crewed flight, scheduled as of early 2026 to send four astronauts around the Moon on a free-return trajectory, without landing. Artemis III, planned for later in the decade, would have SLS and Orion meet a Starship lander in lunar orbit for the first crewed Moon landing since Apollo 17.