NASA built a new mega-rocket, the Space Launch System, to return astronauts to the moon.
SLS, which stands taller than the Statue of Liberty, is set to launch for the first time Tuesday.
See how SLS compares to other rockets past, present, and future in size and strength.
NASA built a new mega-rocket for the next lunar astronaut era, and it's about to launch for the first time as soon as Tuesday.
The Space Launch System (SLS) is 17 years and an estimated $50 billion in the making. It's designed to fly astronauts to the moon for the first time since 1972, when astronauts conducted the last moonwalk of the Apollo era.
Now NASA is kicking off a new program, called Artemis, to build a space station orbiting the moon and set up a permanent human presence on the surface of the lunar south pole. Eventually, the agency wants to mine resources there to send astronauts to Mars.
This first mission, called Artemis I, is a test flight that will carry no astronauts. The rocket is set to scream through the Florida skies and push its Orion spaceship into a path around the moon and back. If that goes well, NASA aims to land astronauts on the lunar surface again in 2025.
NASA needs a powerful rocket to carry out such a long-distance mission. The current iteration of SLS, called Block 1, stands taller than the Statue of Liberty at 322 feet, about 30 stories.
To understand just how large that is, and just how much power it takes to fly to the moon, let's compare it to other astronaut-flying rockets.
SLS is huge, but it's small for a moon rocket
Let's start small. The rocket that carried Jeff Bezos to the edge of space in July 2021, called New Shepard, stands about as tall as a five-story building. It doesn't pack big enough engines, or large enough quantities of fuel, to push itself into Earth's orbit.
Instead, New Shepard skims the edge of the atmosphere in the three minutes between when it stops climbing and when it starts falling. Then it descends back to Earth, for a total flight time of 11 minutes. That's why it's called a suborbital rocket.
Then there are orbital rockets, like Russia's Soyuz and SpaceX's Falcon 9, which generate enough thrust to push spaceships full of humans and cargo into orbit around the Earth, where they can dock at the International Space Station.
Clocking in anywhere from 150 to 250 feet, these workhorses are probably what you're picturing when you think of a standard rocket.
Lunar rockets like the Saturn V, which powered the Artemis program, are about another 100 feet taller. They need the extra thrust to push their spaceships past Earth's orbit toward the moon.
SLS has white rocket boosters installed on the sides of its core stage, which burn solid fuel for extra firepower.
Right now, SLS is smaller than its past and future lunar-grade counterparts. But future iterations of the rocket are expected to tower 365 feet.
If Artemis I goes well, the next SLS mission will send an Orion spaceship around the moon with astronauts on board. The following mission, according to NASA's plan, will see Orion dock to a SpaceX Starship in lunar orbit. Two astronauts will board the new vessel, and Starship will land them on the moon's south pole.
Starship and its Super Heavy booster are still in development and testing at SpaceX facilities in Boca Chica, Texas. It's unclear when they will launch to orbit for the first time - a critical test flight before the rocket can fly humans or land on the moon.
Starship-Super Heavy is slated to be the largest rocket ever built.