NASA just hauled its massive heavy-lift rocket to a launchpad at Kennedy Space Center for some crucial testing ahead of its first moon mission.

It has been a long time since the U.S. space agency had a rocket of this size. One day, the Space Launch System, or SLS, is expected to put millions of miles on the odometer during the first crewed flight to Mars. It could be in the future that robotic scientific journeys are made to Jupiter and Saturn.

The Artemis I mission to lunar orbit, which could come as soon as May 2022, is one of the key facts about the megarocket.

1. It's the only rocket that can send the Orion spacecraft to the moon

the Orion spacecraft atop NASA's SLS rocket stack

NASA's SLS is the only rocket that can send the Orion capsule directly to the moon. Credit: NASA / Aubrey Gemignani

SLS is the only rocket that can send the capsule to the moon and beyond. Think of the capsule as an RV of the sky, with a habitat for up to four astronauts. People will need to be able to eat, sleep, and work for a long time in order to travel into deep space.

An uncrewed Orion will fly thousands of miles past and around the moon for Artemis I. The capsule will splash down in the ocean three weeks after liftoff. The purpose of the Artemis mission is to test its ability to safely reenter Earth's atmosphere and drop into the correct spot for the Navy to recover.

2. It's not the size, but the thrust, that counts

the SLS rocket's four main engines firing in a thrust test

In a NASA test, the four main rocket engines fired for eight minutes in March 2021 and generated 1.6 million pounds of thrust. Credit: NASA / Robert Markowitz

The Statue of Liberty and Big Ben are taller than the megarocket. The Space Shuttle rocket blasted astronauts to the space station.

The last rocket NASA used to take people into deep space was the shorter SLS. The rocket was 41 feet tall.

The new rocket is more powerful than the old one. During liftoff and ascent, SLS will produce 8.8 million pounds of thrust. That is 15 percent more than the other. Future configurations of the new rocket will pack more punch.

The four main SLS engines will produce a thrust powerful enough to keep eight Boeing 747s aloft.

3. The megarocket is state-of-the-art 1980s technology

NASA building the SLS moon rocket

Engineers and technicians at NASA’s Michoud Assembly Facility in New Orleans attaching the first of four RS-25 engines to the core stage of NASA’s Space Launch System (SLS) rocket. Credit: NASA / Jude Guidry

The Space Shuttle legacy is what built SLS. Major components of the shuttle were incorporated into the new rocket.

Engineers replaced the space plane with a cargo or crew spaceship. The shuttle external fuel tank is powered by four engines. NASA will ditch those engines in the ocean. 75 percent of the initial skyward push will be provided by the twin shuttle solid rocket boosters.

It is not all old tech. New tooling and manufacturing techniques were used by NASA to get the job done. Congress didn't allow the space agency to start from scratch to design the latest megarocket, but some parts have been modernized to meet the needs of deep-space travel.

4. Sorry, environment. It's not reusable.

the Orion spacecraft traveling for three weeks on the Artemis I mission

During Artemis I, the uncrewed Orion spacecraft will launch on the most powerful rocket in the world and travel farther than any spacecraft built for humans has ever flown. Credit: NASA

The new moon rocket is made with shuttle parts. The shuttle was designed to carry astronauts and supplies to the space station, which is 250 miles from Earth.

Engineers needed to lighten the load in order to modify the rocket so that it could travel deeper into space. The moon is around 1,000 times the distance of the space station.

The system that allowed the agency to use it again was gutted by engineers. The extra weight capacity for lunar trips was given back by this. The speed needed to send it on a moon-bound trajectory is 24,500 mph.

SLS will need new rockets for each mission.

At least the engine exhaust is clean. The engines are powered by liquid hydrogen and liquid oxygen. The booster insulation was upgraded to rubber materials.

5. The megarocket has an all-American price tag

NASA's rocket soaring above the American flag

NASA's Artemis missions will cost about $4.1 billion per launch, according to an inspector general report. Credit: NASA

It is considered a national asset by many people at NASA and in Congress.

It is thought to be the most expensive rocket ever built. Affordability was never a priority for SLS, as the burgeoning commercial spaceflight sector may prove it can build a more cost-efficient space transportation system.

Congress directed the space agency to build the rocket even though it didn't specify what parts to use, which companies to contract, or what kind of business arrangement to leverage. Lawmakers sought to support thousands of jobs in their districts during the Great Recession. Artemis is a jobs program.

The deputy associate administrator for common exploration systems said that 3,800 suppliers in all 50 states contributed to the rocket and Orion projects.

"When you see this rocket, it's not just a piece of metal that's going to sit at the pad. It's a whole bunch of people, rocket scientists throughout this country, throughout our agencies, that have worked on this."

He said on a call with reporters in March that it was a symbol of our country and our communities. A lot of people, rocket scientists throughout this country, throughout our agency, have worked on this.

Inspector General Paul Martin, who is the space agency watchdog for the federal government, estimated at a congressional committee in March that each launch would cost $4.1 billion, with half of the tab attributed to SLS. That is about one-fifth of the entire NASA budget. NASA will have spent more than $90 billion on the Artemis program by the year 2025, according to Martin.

6. The rocket is the ultimate Transformer

NASA's rocket transforming for different missions

NASA designed the Space Launch System as the foundation for a generation of human exploration missions to deep space. Credit: NASA

As Artemis missions become more complex, engineers designed SLS to evolve into increasingly powerful configurations.

The first assembly will use a central orange core booster with four main engines. It can send over 59,500 pounds. Solid rocket boosters and liquid fuel-fed engines will provide most of the thrust. After leaving Earth, the final rocket booster sends the capsule to the moon. NASA plans to use this configuration for the first three Artemis missions.

The powerful Exploration Upper Stage will be included in later missions, which will carry astronauts. This rocket design can transport crew and large amounts of cargo up to 83,700 pounds.

The workhorse vehicle for sending cargo to the moon, Mars, and other deep-space destinations will be an eight percent increase over Artemis I, thanks to the next iteration of SLS.

NASA astronauts will need supplies in the harsh places.