Nominal, burn, SLS: words you might hear during the launch of Artemis 1


Look to CNN for live coverage from Kennedy Space Center in Florida, beginning Saturday morning through launch Monday morning. Space correspondents Kristin Fisher and Rachel Crane will bring us instant coverage of the launch, along with a team of experts.

But if you’re a casual observer, few things may be more confusing than hearing some of the lingo used by Mission Control.

Celebrities and spectators from around the world will gather at NASA’s Kennedy Space Center in Florida to watch the new Space Launch System rocket and uncrewed Orion spacecraft begin their journey to the moon.

For anyone who isn’t a NASA scientist or hobbyist astrophysicist, here are some of the terms you might hear during the historic launch – and what they mean.

Take-off jargon

NASA aims to launch Artemis I between 8:33 a.m. and 10:33 a.m. ET Monday – with backup windows September 2 and 5 in case of bad weather or any delay. If the launch is a “go”, that means things are on track. If it’s a “no”, the launch can be postponed.

As mission teams go through the countdown, they will use phrases and shortcuts that may be unfamiliar to them. Expect to hear “SLS” to indicate the rocket, rather than the Space Launch System, and “nominal” to mean things are normal or going as planned.

When the rocket is loaded with cryogenic (super cold) liquid oxygen and liquid hydrogen to fuel takeoff, the shortcut is “LO2” for oxygen and “LH2” for hydrogen.

Chances are the Artemis launch team will mention “ICPS”, which refers to the intermediate cryogenic propulsion stage. This upper segment of the rocket will give Orion the propulsion it needs in space after the two solid-fuel rocket boosters and the middle stage, or backbone, of the separate rocket from the spacecraft.

The core stage of the rocket includes the engines, propellant tanks, and avionics, or aviation electronics systems.

Snoopy, mannequins and Apollo 11 artifacts will swing across the moon aboard Artemis I

During the countdown, teams will refer to “L minus” and “T minus” times.

“L Minus” is used to indicate the time until takeoff in hours and minutes, while “T Minus” corresponds to the events included in the launch countdown.

If the launch team announces a “wait”, this is a natural pause in the countdown to allow for tasks or to wait for a specific launch window that does not disrupt the schedule. During a wait, expect the countdown and T minus time to stop, while L minus time will continue.

Post-launch shortcut

After launch, the team may refer to the solid rocket boosters as “SRB” and the launch abort system as “LAS”. Two of the three engines in the launch abort system can be used to return the Orion crew module safely to Earth in the event of a systems malfunction or failure during launch. The third engine is used to jettison the launch abort system, which occurs shortly after launch if everything goes well.

Several “burns”, which occur when the propulsion system fires, will probably be mentioned after takeoff.

The “perigee elevation maneuver” will take place approximately 12 minutes after launch. This is when the ICPS undergoes a burn to raise Orion’s altitude so that it does not re-enter Earth’s atmosphere.

Shortly after, it is the “trans-lunar injection burn”, when the ICPS increases Orion’s speed from 17,500 miles per hour (28,163 kilometers per hour) to 22,600 miles per hour (36,371 kilometers per hour) to escape the pull of Earth’s gravity and set off for the moon. After this burn, the ICPS will separate from Orion.

Around 4:30 p.m. Monday, Orion will perform its first “outbound course correction burn” using the European Service Module, which provides the spacecraft with power, propulsion and thermal control. This maneuver will put Orion on a path to the moon.

On its journey, Artemis I will venture further beyond the moon than any spacecraft intended to carry humans. It is expected to spend 42 days in space, entering a distant retrograde orbit around the moon before crashing into the Pacific Ocean off San Diego on October 10.

Check out our Mission Calendar for everything you need to know about the start the countdown and what happens during the six-week mission. This is just the start of the Artemis program, which aims to bring humans back to the Moon and eventually land crewed missions on Mars.

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