What Happened to Space Launch System (SLS)?
The Space Launch System (SLS) is NASA's super heavy-lift expendable launch vehicle, serving as the backbone for the Artemis program to return humans to the Moon. After its uncrewed maiden flight with Artemis I in 2022, SLS successfully launched its first crewed mission, Artemis II, in April 2026, sending astronauts on a lunar flyby. In a significant programmatic shift in early 2026, NASA cancelled future upgrades (Block 1B/2) to standardize on the Block 1 configuration and redefined Artemis III as a low Earth orbit docking test in 2027, aiming to accelerate subsequent lunar landings.
Quick Answer
The Space Launch System (SLS) is NASA's powerful rocket for the Artemis program, which successfully completed its first crewed mission, Artemis II, on April 1, 2026, sending four astronauts on a lunar flyby. As of August 2026, NASA has decided to standardize the SLS on its Block 1 configuration, canceling the previously planned Block 1B and Block 2 upgrades to streamline operations and increase launch cadence. The next mission, Artemis III, is now scheduled for mid-to-late 2027 as a low Earth orbit test of docking with commercial lunar landers, with crewed lunar landings now targeted for Artemis IV and V in 2028.
📊Key Facts
📅Complete Timeline12 events
NASA announces initial plans for SLS
NASA officially announced the Space Launch System (SLS) as the agency's new heavy-lift rocket to replace the Ares V, leveraging Space Shuttle-derived hardware.
Vertical Assembly Center opens for SLS fuel tank production
The Vertical Assembly Center at Michoud Assembly Facility, used to weld SLS fuel tanks, opened. However, a tower misalignment was soon discovered, contributing to early launch date slips.
Artemis Program formally established
The Artemis program, with SLS as its primary launch vehicle, was formally established via Space Policy Directive-1 by President Donald Trump, aiming to return humans to the Moon.
Artemis I successfully launches
The uncrewed Artemis I mission, the first integrated flight test of the SLS rocket and Orion spacecraft, successfully launched, sending Orion on a 25-day journey around the Moon.
Orion spacecraft splashes down, concluding Artemis I
The Orion spacecraft successfully splashed down in the Pacific Ocean, concluding the Artemis I mission and validating the SLS and Orion for future crewed flights.
Artemis II SLS/Orion rolls out to launch pad
NASA began rolling out the SLS rocket and Orion spacecraft for the Artemis II mission to Launch Pad 39B at Kennedy Space Center, preparing for the first crewed flight around the Moon.
NASA announces major Artemis program restructuring
NASA Administrator Jared Isaacman announced the cancellation of SLS Block 1B/2 upgrades and redefined Artemis III as a low Earth orbit docking test, aiming to standardize Block 1 and increase launch cadence.
SLS returns to launch pad after repairs for Artemis II
After being rolled back to the Vehicle Assembly Building for repairs to a helium flow issue and other prelaunch work, the SLS rocket for Artemis II returned to Launch Pad 39B.
Artemis II successfully launches with crew
The Artemis II mission, carrying four astronauts (Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen), successfully launched on SLS for a lunar flyby, marking the first crewed flight of the program.
Final RS-25 engine delivered for Artemis III
The final RS-25 engine for the Artemis III mission's SLS core stage was delivered to Kennedy Space Center, with integration work planned for the summer.
Artemis III Orion crew and service modules joined
Engineers successfully joined the Orion crew and service modules for the Artemis III mission inside the Neil A. Armstrong Operations and Checkout Building at Kennedy Space Center.
SLS solid rocket booster stacking begins for Artemis III
Teams began stacking the twin SLS solid rocket booster segments inside Kennedy's Vehicle Assembly Building for the Artemis III mission, starting with the left-hand aft assembly.
Follow this story
Get an email when this timeline gets a major update.
🔍Deep Dive Analysis
The Space Launch System (SLS) is NASA's cornerstone for deep space exploration, specifically designed to launch the Orion spacecraft and cargo for the Artemis program, aiming to return humans to the Moon. Conceived as a successor to the Space Shuttle and building on elements from the canceled Constellation program, SLS development has been marked by significant technical challenges, cost overruns, and schedule delays since its inception.
Its maiden flight, the uncrewed Artemis I mission, successfully launched on November 16, 2022, sending an Orion capsule on a journey around the Moon and back, validating the rocket's performance and Orion's heat shield. This critical test paved the way for crewed missions, though the program continued to face scrutiny over its high cost per launch, estimated at least $2.5 billion (excluding Orion), partly due to a low launch cadence.
A key turning point occurred in early 2026. After multiple delays, the Artemis II mission, the first crewed flight of SLS and Orion, successfully launched on April 1, 2026, carrying four astronauts on a lunar flyby. This mission, named 'Integrity' by its crew, marked the first time humans traveled beyond low Earth orbit since Apollo 17 in 1972. However, prior to its launch, the mission experienced issues such as hydrogen leaks, leading to postponements from its initial 2024 and 2025 targets.
Following the Artemis II success, NASA announced a major reorganization of the Artemis campaign on February 27, 2026. Administrator Jared Isaacman confirmed the cancellation of the planned Block 1B and Block 2 upgrades for the SLS, which included the more powerful Exploration Upper Stage (EUS). This decision was made to standardize the SLS on its current Block 1 architecture, aiming to reduce multi-year development delays and massive infrastructure costs associated with the upgrades. The goal is to increase the launch cadence to approximately one mission every 10 months, fostering more operational experience.
Consequently, the Artemis III mission, originally intended as the first crewed lunar landing, was redefined. It is now scheduled for mid-to-late 2027 as a low Earth orbit (LEO) docking and systems validation flight. This mission will test rendezvous and docking operations between the Orion spacecraft and commercial Human Landing Systems (HLS) from providers like SpaceX and Blue Origin. Crewed lunar landings are now targeted for Artemis IV in early 2028 and Artemis V in late 2028, leveraging the standardized Block 1 SLS and the validated HLS systems. As of August 2026, hardware for Artemis III is actively being assembled at Kennedy Space Center, with the Orion crew and service modules joined in late July.
What If...?
Explore alternate histories. What if Space Launch System (SLS) made different choices?