What is the Space Launch System (SLS)? NASA's Moon rocket, explained
By the WhyCosmos team · Last updated:
The Space Launch System (SLS) is NASA's super heavy-lift rocket, built to carry the Orion spacecraft and astronauts to the Moon under the Artemis programme. Its first flight, the uncrewed Artemis I in November 2022, produced more liftoff thrust than the Apollo-era Saturn V; its second flight, Artemis II in April 2026, carried four astronauts around the Moon and back — the first crewed lunar mission in over fifty years.
Children who love rockets eventually ask the size question: what is the biggest one? SLS is the heart of that conversation — alongside SpaceX’s Starship, the experimental rocket that has flown even more powerfully. This page keeps to what SLS is, why it exists, and how it compares to rockets a child in India already knows.
How to explain it to your child
Explain it to an 8-year-old
The Space Launch System is NASA’s giant Moon rocket — taller than a 30-floor building. Its job is to carry a spaceship called Orion, with astronauts inside, to the Moon and back. In 2026, it carried four astronauts around the Moon for the first time.
Explain it to a 13-year-old
SLS is NASA’s expendable super heavy-lift launcher for Artemis. The Block 1 version stands about 98 metres tall and produces roughly 39 meganewtons of liftoff thrust — about 15% more than Saturn V — using four RS-25 engines (from the Space Shuttle programme) plus two solid rocket boosters. Artemis I (November 2022) tested the rocket uncrewed; Artemis II (April 2026) carried a four-person crew around the Moon; Artemis III, planned for around 2027, aims to land astronauts near the Moon’s south pole.
Key facts
| Built by | NASA with industry partners (Boeing, Northrop Grumman, Aerojet Rocketdyne) |
|---|---|
| Purpose | Launching astronauts in the Orion spacecraft to the Moon — the Artemis programme |
| Height (Block 1) | About 98 metres — taller than the Statue of Liberty |
| Liftoff thrust | Roughly 39 meganewtons — about 15% more than the Apollo Saturn V |
| Engines | 4 RS-25 engines inherited from the Space Shuttle, plus 2 solid boosters |
| First flight | Artemis I — 16 November 2022, uncrewed Orion around the Moon |
| First crewed flight | Artemis II — 1 April 2026, four astronauts around the Moon and back |
| Next flight | Artemis III — planned crewed landing near the Moon’s south pole, around 2027 |
| Reusable? | No — SLS is expendable, unlike SpaceX's reusable rockets |
How big is SLS compared to other rockets?
| Rocket | Who | Approx. liftoff thrust | Claim to fame |
|---|---|---|---|
| Saturn V | NASA (1967–1973) | ~34.5 MN | Took Apollo astronauts to the Moon |
| SLS (Block 1) | NASA (2022– ) | ~39 MN | Most powerful rocket NASA has flown |
| Starship / Super Heavy | SpaceX (in testing) | ~74 MN | Most powerful rocket ever launched; fully reusable design |
| Falcon Heavy | SpaceX (2018– ) | ~23 MN | Most powerful operational commercial rocket for years |
| LVM3 | ISRO, India (2014– ) | ~10 MN class | Launched Chandrayaan-3 to the Moon |
Thrust figures are approximate liftoff values, rounded for comparison; consult agency sources for precise numbers.
Why does NASA need such a big rocket?
Going to the Moon is not about height, it is about speed and mass. Reaching the Moon means accelerating a heavy, crew-carrying spacecraft to roughly 40,000 km/h. Every kilogram of spacecraft needs many kilograms of fuel, and that fuel itself needs fuel to lift — which is why Moon rockets balloon into skyscrapers. SLS exists to throw the 26-tonne Orion, its service module and its crew far beyond Earth orbit in one go.
The question kids always ask: is SLS the most powerful rocket ever?
It is the most powerful rocket NASA has ever flown — but SpaceX’s Starship Super Heavy has produced roughly twice its thrust in test flights. Precision matters, and children enjoy the precision: Saturn V held the record for 50 years, SLS beat it in 2022, and Starship beat SLS within months. Rocketry’s record book is being rewritten in their lifetime.
Questions parents and kids ask
SLS is NASA’s giant Moon rocket. Its job is to launch the Orion spacecraft with astronauts on board toward the Moon as part of the Artemis programme. It first flew uncrewed in November 2022, and first carried astronauts in April 2026.
Yes — at liftoff SLS Block 1 produces about 15% more thrust than Saturn V. However, SpaceX's Starship Super Heavy has produced roughly double SLS's thrust in test flights.
Yes. Its first flight, Artemis I in 2022, was uncrewed by design — it sent an empty Orion around the Moon to prove the rocket was safe. Its second flight, Artemis II, launched on 1 April 2026 and carried four astronauts around the Moon and back. Its next flight, Artemis III, is planned to land a crew near the Moon’s south pole around 2027.
LVM3 is India’s most powerful operational rocket and launched Chandrayaan-3, but it is a medium-heavy lifter — SLS produces several times its thrust because it must send a heavy crewed spacecraft to the Moon directly.
Your child asks questions like this every week.WhyCosmos runs live online astronomy classes for ages 8–16, taught by real astrophysicists — where questions like these are the curriculum.
Related terms in this glossary
Sources and further reading