SLS Block 2
Cancelled highest-capacity SLS variant, ended February 2026.
Last refreshed: 2 April 2026
Was SLS Block 2 ever going to be built, or was it always aspirational?
Latest on SLS Block 2
- What was SLS Block 2?
- The most capable planned SLS variant, with advanced boosters for Mars and outer solar system missions; cancelled in 2026.Source: Lowdown briefing analysis
- What is the most powerful rocket NASA has now?
- SLS Block 1, following the cancellation of Block 1B and Block 2 upgrades in February 2026.Source: Lowdown briefing analysis
Background
SLS Block 2 was the most powerful planned variant of the Space Launch System, designed to add advanced boosters to the Block 1B stack and deliver the heaviest payloads to deep space. It was cancelled alongside Block 1B by NASA Administrator Jared Isaacman in February 2026 before entering active development.
Block 2 was conceived as the long-term successor for Mars and outer solar system missions, with a payload capacity exceeding 130 metric tonnes to low Earth orbit. Its cancellation means the SLS programme will never progress beyond the Block 1 configuration.
The dual cancellation of Block 1B and Block 2 effectively caps SLS at its current capability and signals that the architecture is in managed decline. Future NASA heavy-lift requirements are expected to migrate to commercial vehicles, primarily SpaceX Starship.
