#rocket testing

When our Space Launch System (SLS) rocket launches the Artemis missions to the Moon, it can have a top speed of more than six miles per second. Rockets and racecars are designed with speed in mind to accomplish their missions—but there’s more to speed than just engines and fuel. Learn more about the physics of going fast:

Take a look under the hood, so to speak, of our SLS mega Moon rocket and you’ll find that each of its four RS-25 engines have high-pressure turbopumps that generate a combined 94,400 horsepower per engine. All that horsepower creates more than 2 million pounds of thrust to help launch our four Artemis astronauts inside the Orion spacecraft beyond Earth orbit and onward to the Moon. How does that horsepower compare to a racecar? World champion racecars can generate more than 1,000 horsepower as they speed around the track.

As these vehicles start their engines, a series of special machinery is moving and grooving inside those engines. Turbo engines in racecars work at up to 15,000 rotations per minute, aka rpm. The turbopumps on the RS-25 engines rotate at a staggering 37,000 rpm. SLS’s RS-25 engines will burn for approximately eight minutes, while racecar engines generally run for 1 ½-3 hours during a race.

To use that power effectively, both rockets and racecars are designed to slice through the air as efficiently as possible.

While rockets want to eliminate as much drag as possible, racecars carefully use the air they’re slicing through to keep them pinned to the track and speed around corners faster. This phenomenon is called downforce.

Steering these mighty machines is a delicate process that involves complex mechanics.

Most racecars use a rack-and-pinion system to convert the turn of a steering wheel to precisely point the front tires in the right direction. While SLS doesn’t have a steering wheel, its powerful engines and solid rocket boosters do have nozzles that gimbal, or move, to better direct the force of the thrust during launch and flight.

Racecar drivers and astronauts are laser focused, keeping their sights set on the destination. Pit crews and launch control teams both analyze data from numerous sensors and computers to guide them to the finish line. In the case of our mighty SLS rocket, its 212-foot-tall core stage has nearly 1,000 sensors to help fly, track, and guide the rocket on the right trajectory and at the right speed. That same data is relayed to launch teams on the ground in real time. Like SLS, world-champion racecars use hundreds of sensors to help drivers and teams manage the race and perform at peak levels.

Knowing how to best use, manage, and battle the physics of going fast, is critical in that final lap. You can learn more about rockets and racecars here.

We continue to make progress toward the first launch of our Space Launch System (SLS) rocket for the Artemis I mission around the Moon. Engineers at NASA’s Stennis Space Center near Bay St. Louis, Mississippi are preparing for the last two tests of the eight-part SLS core stage Green Run test series.

The test campaign is one of the final milestones before our SLS rocket launches America’s Orion spacecraft to the Moon with the Artemis program. The SLS Green Run test campaign is a series of eight different tests designed to bring the entire rocket stage to life for the first time.

As our engineers and technicians prepare for the wet dress rehearsal and the SLS Green Run hot fire, here are some numbers to keep in mind:

212 Feet

The SLS rocket’s core stage is the largest rocket stage we have ever produced. From top to bottom of its four RS-25 engines, the rocket stage measures 212 feet.

35 Stories

For each of the Green Run tests, the SLS core stage is installed in the historic B-2 Test Stand at Stennis. The test stand was updated to accommodate the SLS rocket stage and is 35 stories tall – or almost 350 feet!

4 RS-25 Engines

All four RS-25 engines will operate simultaneously during the final Green Run Hot Fire. Fueled by the two propellant tanks, the cluster of engines will gimbal, or pivot, and fire for up to eight minutes just as if it were an actual Artemis launch to the Moon.

18 Miles

Our brawny SLS core stage is outfitted with three flight computers and special avionics systems that act as the “brains” of the rocket. It has 18 miles of cabling and more than 500 sensors and systems to help feed fuel and direct the four RS-25 engines.

733,000 Gallons

The stage has two huge propellant tanks that collectively hold 733,000 gallons of super-cooled liquid hydrogen and liquid oxygen. The stage weighs more than 2.3 million pounds when its fully fueled.

114 Tanker Trucks

It’ll take 114 trucks – 54 trucks carrying liquid hydrogen and 60 trucks carrying liquid oxygen – to provide fuel to the SLS core stage.

6 Propellant Barges

A series of barges will deliver the propellant from the trucks to the rocket stage installed in the test stand. Altogether, six propellant barges will send fuel through a special feed system and lines. The propellant initially will be used to chill the feed system and lines to the correct cryogenic temperature. The propellant then will flow from the barges to the B-2 Test Stand and on into the stage’s tanks.

100 Terabytes

All eight of the Green Run tests and check outs will produce more than 100 terabytes of collected data that engineers will use to certify the core stage design and help verify the stage is ready for launch.

For comparison, just one terabyte is the equivalent to 500 hours of movies, 200,000 five-minute songs, or 310,000 pictures!

32,500 holes

The B-2 Test Stand has a flame deflector that will direct the fire produced from the rocket’s engines away from the stage. Nearly 33,000 tiny, handmade holes dot the flame deflector. Why? All those minuscule holes play a huge role by directing constant streams of pressurized water to cool the hot engine exhaust.

One Epic First

When NASA conducts the SLS Green Run Hot Fire test at Stennis, it’ll be the first time that the SLS core stage operates just as it would on the launch pad. This test is just a preview of what’s to come for Artemis I!

The Space Launch System is the only rocket that can send NASA astronauts aboard NASA’s Orion spacecraft and supplies to the Moon in a single mission. The SLS core stage is a key part of the rocket that will send the first woman and the next man to the Moon through NASA’s Artemis program.

The comprehensive test series called Green Run for our Space Launch System (SLS) rocket is underway at Stennis Space Center in Mississippi. 

During Green Run, the rocket’s massive, 212-foot-tall core stage — the same flight hardware that will help launch Artemis I to the Moon – will operate together for the first time. 

Here’s what you need to know about this top-to-bottom test series of our megarocket’s huge core:

The Meaning Behind the Name 

Why is it called Green Run? “Green” refers to the new, untested hardware (AKA the core stage), and “run” represents the succession of tests the core stage paces through. One by one, this series will bring together several “firsts” for the rocket stage as the flight hardware undergoes eight different tests. Each test is designed to gradually bring our rocket’s core stage and all its systems to life for the first time. 

So far, engineers have completed three of the series: the modal test, the avionics power-on, and the safety systems checkout. The safety systems are designed to end the test and shutdown systems automatically under undesirable conditions.

You can follow the progress of Green Run with this Green Run checklist infographic. Our team will be updating in real time as each Green Run test is completed.

Setting the Stage

The world’s tallest rocket stage is tested in an equally giant test stand.  We upgraded the B-2 Test Stand used for the Saturn V rocket stages during the Apollo Program and, later, for the Space Shuttle Program. Now, the B-2 Test Stand is customized for testing our SLS core stage. When all four core stage engines fire up, they can generate some serious heat. So, the B-2 Test Stand will use roughly 100,000 gallons of water every 18 seconds to protect the stand and the hardware.

Hot fire in 3, 2, 1…

Speaking of engines firing up, the core stage will really show what it is capable of during the grand finale of Green Run. The goal is for the entire core stage to operate as one for up to 8.5 minutes — and that includes an impressive firing of all four RS-25 engines simultaneously. Just like at launch, more than 733,000 gallons of liquid propellant will flow from the two propellant tanks through the fuel lines to feed the RS-25 engines.  When operating at sea level on the test stand, the cluster of four RS-25 engines will produce just over 1.6 million pounds of thrust – the same amount it will produce during the early phase of launch. During ascent, the core stage will produce a maximum thrust of over 2 million pounds.

Data, data, data

All the Green Run tests, check outs and the 100 terabytes of collected data certify the core stage design and help verify the stage is ready for launch. To put the sheer amount of data collected during Green Run into perspective, just one terabyte is the equivalent of roughly 500 hours of movies. Even the Library of Congress’s collection only amounts to a total of 15 terabytes!

Next stop: Kennedy

The next time our SLS rocket’s core stage fires up will be on the launch pad at Kennedy Space Center for the debut of the Artemis program. This inaugural SLS flight will be just the beginning of increasingly complex missions that will enable human exploration to the Moon and, ultimately, Mars.