Space Launch System

The Space Launch System (SLS) is NASA's super-heavy-lift rocket and the launch vehicle of the Artemis program. Built around hardware and suppliers inherited from the Space Shuttle, it is the only rocket currently rated to send a crewed spacecraft, the Orion capsule, directly toward the Moon. It has flown twice: the uncrewed Artemis I mission in November 2022 and the crewed Artemis II lunar flyby in April 2026.^[1][2]

SLS produces about 8.8 million pounds of thrust at liftoff, more than the Saturn V, though it carries less payload. The program is also among the most criticized in NASA's portfolio: each launch costs billions of dollars, the vehicle is fully expendable, and in February 2026 NASA cancelled its planned Block 1B and Block 2 upgrades to contain cost and schedule risk.^[1][3]

Development#

Congress directed NASA to build SLS in the 2010 NASA Authorization Act after the cancellation of the Constellation program, requiring reuse of Space Shuttle and Ares project contracts and hardware. Boeing builds the 8.4-meter core stage, Northrop Grumman the five-segment solid rocket boosters, and Aerojet Rocketdyne (now part of L3Harris) supplies the RS-25 main engines, the same engine that powered the shuttle. The first four flights use refurbished engines that flew shuttle missions; new-production RS-25E engines follow.^[1]

First flight was originally targeted for late 2016. Delays in core stage manufacturing and the Green Run test campaign pushed the debut to November 2022, and development spending through the first launch totaled roughly 24 billion dollars.^[1][3]

Design and specifications#

Block 1 pairs the core stage with the Interim Cryogenic Propulsion Stage (ICPS), a single-engine upper stage derived from the Delta IV. The cancelled Block 1B would have replaced ICPS with the four-engine Exploration Upper Stage, raising trans-lunar payload to about 38-42 metric tons; a Block 2 with new boosters was to follow. Under the plan announced on February 26, 2026, NASA will instead standardize on Block 1 and, beginning with Artemis V, fly a version of the Centaur V upper stage developed for ULA's Vulcan Centaur.^[1][3][4]

Artemis I#

SLS first flew on November 16, 2022, from Launch Complex 39B at Kennedy Space Center after two scrubbed attempts and two hurricane delays. The rocket performed almost exactly to prediction, sending an uncrewed Orion into a distant retrograde orbit of the Moon. Orion spent 25.5 days in space, traveled farther from Earth than any spacecraft built for humans had before, and splashed down in the Pacific on December 11, 2022.^[1]

Artemis II#

The second SLS launched the first crewed Orion on April 1, 2026, carrying NASA astronauts Reid Wiseman (commander), Victor Glover (pilot), and Christina Koch, along with Canadian Space Agency astronaut Jeremy Hansen. The 10-day free-return mission looped around the far side of the Moon, taking the crew farther from Earth than any humans before them and breaking the distance record held by Apollo 13 since 1970. Across the flight the crew covered 695,081 miles, photographed far-side terrain never before seen directly by human eyes, and observed a total solar eclipse. Orion splashed down off the California coast at 5:07 p.m. PDT on April 10, 2026.^[2][5]

Artemis II verified Orion's life support, manual piloting modes, and communications on a lunar trajectory. It was the first crewed flight beyond low Earth orbit since Apollo 17 in December 1972.^[2][5]

Cost criticism#

NASA's Office of Inspector General has estimated the cost of a single Artemis launch (SLS, Orion, and ground systems together) at more than 4 billion dollars for the early missions, with the SLS rocket itself accounting for over 2 billion dollars per flight. Because every stage is expended, none of that hardware is recovered. The White House's fiscal year 2026 budget proposal, released in May 2025, called SLS "grossly expensive," put its per-launch cost at about 4 billion dollars, described the program as 140 percent over budget, and proposed ending SLS and Orion after Artemis III in favor of commercial rockets.^[3][6]

Congress pushed back. A reconciliation law signed in July 2025 appropriated 4.1 billion dollars specifically to keep building SLS vehicles for Artemis IV and Artemis V, ensuring the rocket's production line continues into the late 2020s regardless of the budget request.^[1][3]

Cost pressure has already moved payloads off the rocket: the Europa Clipper mission, once assigned to SLS by law, launched on a Falcon Heavy in 2024 at a fraction of the price.^[1]

Program future#

NASA's February 2026 restructuring reshaped the manifest. Artemis III, planned for 2027, is now an Earth-orbit mission in which an Orion crew will rendezvous and dock with lunar lander test vehicles, including a Starship pathfinder, rather than attempt a landing. Artemis IV in 2028 is planned as the first crewed landing at the lunar south pole. Both fly on Block 1 vehicles, and NASA cited schedule stability and risk reduction, arguing that launching such a complex rocket only once every few years was unsustainable.^[3][4][7]

Beyond Artemis V the rocket's future is unsettled. The cancellation of the Exploration Upper Stage ended Boeing's largest planned SLS upgrade, and the administration continues to press for a transition to commercial launch for lunar logistics. For now, SLS remains the only human-rated vehicle capable of dispatching Orion to the Moon in a single launch, and hardware for the next two missions is in production at Michoud Assembly Facility and Kennedy Space Center.^[1][3]

References#

1. Space Launch System - Wikipedia.
2. NASA Welcomes Record-Setting Artemis II Moonfarers Back to Earth - NASA.
3. NASA revises plans for future Artemis missions, cancels upgrades to SLS - SpaceNews.
4. Exploration Upper Stage - Wikipedia.
5. Artemis II - NASA.
6. Proposed 24 percent cut to NASA budget eliminates key Artemis architecture, climate research - Spaceflight Now.
7. NASA Marches Toward Artemis III Mission in 2027, Names Crew Members - NASA.