As space exploration advances, both NASA’s Space Launch System (SLS) and SpaceX’s Starship are leading the way in large-scale space launch capabilities. While both rockets boast impressive capabilities, they differ in design goals, power, and intended mission scope. Here’s a closer look at how SLS and Starship compare in terms of power, payload capacity, and long-term objectives.
Thrust Comparison
- SLS: NASA’s SLS Block 1 rocket generates 8.8 million pounds of thrust at liftoff, making it the most powerful rocket ever developed by NASA. This thrust surpasses that of the Apollo-era Saturn V rocket, which had 7.5 million pounds of thrust.
- Starship: When fully assembled with its Super Heavy booster, SpaceX’s Starship rocket is designed to produce a maximum thrust of 17 million pounds at liftoff. This immense thrust is nearly double that of the SLS Block 1, positioning Starship as the most powerful rocket ever constructed in terms of raw power.
Payload Capacity
- SLS: In its current configuration (Block 1), the SLS can carry approximately 27 metric tons to lunar orbit. Future configurations, Block 1B and Block 2, are expected to increase this capacity to 37 metric tons and 45 metric tons to lunar orbit, respectively. SLS is tailored to support NASA’s Artemis program by delivering heavy payloads to the Moon for extended lunar exploration.
- Starship: Starship is designed to carry up to 100 metric tons to low Earth orbit (LEO) in its reusable configuration and up to 150 metric tons in an expendable configuration. For missions beyond Earth, such as to the Moon or Mars, payload capacity would be slightly reduced due to in-space refueling needs, yet Starship’s design offers significantly more potential payload capacity compared to SLS. This capacity, combined with Starship’s in-orbit refueling capability, extends its mission versatility.
Reusability
- SLS: The SLS is an expendable rocket, meaning it is not designed for reuse. NASA prioritized reliability, maximum payload capacity, and deep space capability over reusability in SLS’s design, aiming for single powerful launches that can support lunar exploration missions within the Artemis program.
- Starship: Starship, on the other hand, is designed as a fully reusable rocket system. The Super Heavy booster and the Starship upper stage are intended to be reusable, with the booster returning to Earth for refurbishment and relaunch. This reusability is central to SpaceX’s goal of making space travel more cost-effective and increasing launch frequency, supporting long-term goals of establishing a human presence on Mars.
Mission Goals and Focus
- SLS: SLS was developed with a specific focus on NASA’s Artemis program, aimed at enabling human exploration of the Moon and, eventually, Mars. It is optimized to carry the Orion spacecraft, astronauts, and essential cargo to lunar orbit, where lunar exploration will take place. The SLS provides the high reliability needed for crewed space missions beyond low Earth orbit.
- Starship: Starship’s design is versatile and broader in scope, supporting a range of missions from Mars colonization and lunar exploration to satellite deployment, space tourism, and even point-to-point travel on Earth. Its capability to carry large payloads, coupled with its reusability, allows Starship to serve both scientific and commercial space missions.
Current Status and Development Timeline
- SLS: NASA’s SLS completed its first uncrewed mission, Artemis I, in 2022, successfully sending the Orion spacecraft around the Moon and back to Earth. This mission proved the SLS’s capabilities in deep space missions, and as of 2024, NASA is preparing for Artemis II, the first crewed mission using the SLS, expected to launch in the near future.
- Starship: Starship is still undergoing rigorous testing. SpaceX has conducted multiple test flights of the Starship upper stage, and further testing of the fully stacked Starship with its Super Heavy booster is expected as SpaceX refines the rocket system. When operational, Starship will be capable of supporting a range of missions, including NASA’s Artemis program through a contract with SpaceX to use Starship as a lunar lander for Artemis III.
Summary
In terms of raw power and payload capacity, Starship outmatches SLS with nearly double the thrust and significantly greater payload capacity. However, the SLS currently remains the only certified rocket for human space missions to the Moon under NASA’s Artemis program, prioritizing reliability and mission-specific design over reusability. Starship, with its reusability and scalability, offers potential cost savings and a broader mission range, making it a key player in future space exploration. While SLS leads in crewed lunar missions, Starship’s ambitious design may enable more frequent and diverse space missions, particularly as it advances toward full operational readiness.
