Green Run gets a green light
The test of the Space Launch System core stage, where all four RS-25
engines and systems will be fired to simulate a launch is scheduled to take
place in November.
The final test of NASA’s Space Launch System rocket is set to happen at Stennis
Space Center in early November, the first time the vehicle, its engines and its
electrical and mechanical systems will be put together to operate as one unit.
The SLS is the world’s most powerful and tallest rocket and the tallest ever built by
NASA. It will kick of a new series of exploration beyond earth’s orbit, that will
culminate in a 2024 mission that will once again send astronauts to the moon 55
years after the original lunar landing.
“I am excited to see the flight systems come to life that will control the rocket as it
sends the first Artemis mission to the moon,” said Lisa Espy, the core stage avionics
lead at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
It is fitting that the SLS is being put through its paces at Stennis, because the facility
was built to test the Saturn rocket stages that sent Americans to the moon in the late
60s and early 70s.
The hot fire test, which is set to last for about eight minutes, is the last hurdle before
the rocket can power the Artemis I mission. The mission is currently set to launch in
November 2021 and will be one of the first steps in the process of getting men and
women on the moon.
NASA started the Green Run test in January, when it installed the 212 foot core
stage in a test stand at Stennis. The test gets its name because it involves making
sure new or “green” hardware works.
There are eight separate tests that make up the battery of Green Run tests, which
include such tasks as making sure the main propulsion system components work,
simulating a launch countdown and checking out the hydraulic systems.
The hot fire test will replicate the launch by loading in the liquid hydrogen and liquid
oxygen propellants and allowing them to flow throughout the system as the four RS-
25 engines are fired. This will demonstrate all parts of the rocket can work together,
just as they must do for a successful launch.
“It is the ultimate proof that the vehicle works as advertised,” said Maury Vander,
chief of test operations at Stennis.
The Green Run test has seen some delays. Stennis was closed from March to late
May because of the coronavirus pandemic, with only personnel handling essential
safety and security functions allowed inside.
When workers were allowed back after more than two months, they had to
reactivate systems and check out the test stand and test control center, while
following guidelines set by the Centers for Disease Control to reduce the spread of
The final test was then set to happen October 24, but Vander said there was a
slight delay because of the threats Hurricanes Marco and Laura posed to the Gulf
Coast in late August. While Marco fizzled out, Laura did heavy damage to a swath of
The core stage is the backbone of the rocket, containing the fuel and all of the
systems needed to feed the four engines, along with flight computers and avionics
needed to make the flight happen. It was built at NASA’s Michoud Assembly Facility in
New Orleans with contributions from suppliers across the country. The advanced
manufacturing facility at Michoud has been used by NASA for decades to build
components, such as Saturn launch vehicles and the external fuel tanks on the
space shuttle. Boeing is the lead contractor for the core stage, with the RS-25
engines built by Aerojet Rocketdyne, and the test is being conducted by engineers
from Stennis, Marshall and SLS contractors. Vander said hundreds of people are
involved in staging the test.
If everything goes well with the test in early November, Vander said the SLS core
stage will remain at Stennis for a few more weeks, then preparations will begin to
transport it to Kennedy Space Center in Florida. “If it all goes according to plan, this
should occur late this year/early next year,” he said. Once at Kennedy, the core
stage will be assembled with the other parts of the SLS rocket and the Orion
The SLS is the only rocket that can send the Orion craft, astronauts and cargo to
the moon in a single mission. By reducing the number of trips to the moon, the risk of
the journey is reduced. Eventually, the SLS will be capable of sending a payload of
more than 45 metric tons to the moon, or just under 100,000 pounds.
The SLS Program was formed in the fall of 2011, said Tracy McMahan, a Marshall
spokeswoman. The rocket completed its critical design review in 2015, where the
design was set and work started on building the hardware that will fly. Most parts of
the rocket are new, McMahan said, but 16 engines came from the Space Shuttle
program. Those engines had to be upgraded to fly on SLS and they were tested at
The first flight of the SLS will be powering the Artemis I mission, set to launch in
November 2021. It will be an unmanned mission, in which the Orion spacecraft will
travel 280,000 miles from Earth, well past the moon. Orion will fly miles above the
moon, then use the gravitational force of the body to propel it in a new orbit about
40,000 miles away. The craft will spend six days collecting data, pass the moon
again, and use the gravity to propel it on a quick trip back to earth. Orion will make a
splash landing in the Pacific Ocean, off the coast of Baja California. Artemis II will be
a similar mission, set to launch in 2023, but astronauts will be onboard.
- Timothy Boone