NASA’s giant moon rocket will begin its slow voyage to its Florida launch pad early Saturday, marking a major milestone for Artemis II, the agency’s first crewed lunar mission in more than 50 years.
The launch of the Space Launch System and Orion spacecraft from the Cape Canaveral launch pad will kick off a final series of ground tests before NASA attempts to launch four astronauts – Reed Wiseman, Victor Glover, Christina Koch and Jeremy Hansen – into deep space on a 10-day flight.
The journey begins at 7 a.m. ET on January 17, and you can watch live below as the stacked rockets leave the Vehicle Assembly Building on a giant crawler transporter. They don’t call it “crawling” for nothing.
“Our cruise speed will be just under 1 mph,” launch director Charlie Blackwell-Thompson said at a press conference on Friday. “It will be slower on the turns and up the hills and it will take us about eight to 10 hours to get there.”
Once at the launch pad, the team will hook the rocket and capsule to the ground system and rotate the crew access arm into place. If refueling rehearsals go smoothly, NASA could target a launch opportunity as early as February.
Here’s what to know about NASA’s towering moon rocket.
1. SLS is powerful, but no longer most powerful
The SLS produces approximately 8.8 million pounds of thrust, roughly equivalent to the output of 160,000 Corvette engines. SpaceX’s Starship now exceeds that number, with expected production of 16 to 17 million pounds.
NASA’s rocket took the power crown when Artemis 1 debuted, but Starship has been tested numerous times in space since. That distinction comes with some caveats, though: SLS is already ready for astronauts to fly, while Starship isn’t even carrying cargo yet.
With Artemis 2, SLS could become the most powerful rocket ever to carry humans. Its four main engines burn approximately 700,000 gallons of super-cold fuel, generating enough power to keep eight Boeing 747 aircraft in the air. Future versions of the SLS could offer even more power if they come to fruition.
Dimensions tell a similar story. At 322 feet tall, the SLS is taller than the Statue of Liberty and Big Ben. It topped the Space Shuttle stack (a stack is a fully assembled, vertical version of a space rocket), but still trailed NASA’s Apollo-era moon rocket, the Saturn V. Starship once again appears the largest, towering over SLS by more than 80 feet.
Watch NASA’s livestream of the SLS launch starting at 7 a.m. ET on January 17 in the video above.
2. SLS is the only rocket built for Orion flights
Currently, SLS is the only vehicle capable of delivering Orion to the moon and beyond. Capsules, renamed upright Designed by the crew to serve as both a spacecraft and living quarters, it provides astronauts with comfortable space to work, eat and sleep during long-duration missions.
For Artemis 2, Orion will fly about 5,000 miles past the far side of the moon, potentially setting a new distance record for human spaceflight. When it returns, the spacecraft will splash down in the Pacific Ocean.
3. SLS is built with retro hardware
The giant moon rocket was actually built on the legacy of the space shuttle. NASA borrowed from flight plans from 1981 to 2011 and transplanted major space shuttle hardware into the new rocket.
Engineers replaced the winged orbiter with Orion, while extending the shuttle’s orange external fuel tanks into the rocket’s core stage. Four former shuttle main engines power the core.
Unlike before, these engines will not be reused. NASA plans to discard them after flight. Two shuttle-derived solid rocket boosters are located on either side of the core, providing about 75% of the thrust at liftoff. Despite congressional bans on entirely new designs, NASA modernized key systems and manufacturing methods.
On November 4, 2022, NASA’s crawler transport aircraft left behind debris while transporting the Space Launch System to the launch pad.
4. SLS sacrifices reusability to achieve its goals
Keep in mind that SLS relies on space shuttle hardware, so major changes will be required to reach the moon. After all, the space shuttle was originally designed for short trips to the International Space Station, which is about 250 miles above Earth. By comparison, the Moon is approximately 239,000 miles away.
To make this leap, engineers removed reusable features such as parachutes, reserve fuel and landing sensors. These changes freed up about 2,000 pounds of payload capacity, helping Orion reach about 24,500 mph, the speed required for lunar orbit. The price of this performance is disposability: the SLS uses new boosters and engines on every mission.
However, its exhaust is relatively clean. The engine burns liquid hydrogen and oxygen, producing superheated vapor. NASA also replaced asbestos insulation on the booster with rubber material.
5. SLS is often called the most expensive
Many at NASA and on Capitol Hill refer to the SLS as “America’s rocket,” viewing it as a national asset similar to an aircraft carrier custom-built for the military. Cost control has never been a top priority.
A 2010 spending law ordered NASA to build the rocket and detailed its design, contractors and business model. It was passed during the Great Recession in part to protect jobs. Today, approximately 3,800 vendors in all 50 states support SLS and Orion.
The SLS is generally considered the most expensive rocket ever built. In 2022, NASA’s inspector general estimates that each Artemis launch will cost $4.1 billion, about half of which is related to SLS alone.