It’s been a long time coming. NASA and its main contractor, Boeing, have been working on the Space Launch System (SLS) since the early 2010s. There have been a lot of delays and cost overruns along the way. The SLS rocket finally came out of NASA’s Vehicle Assembly Building on March 17. It was fully stacked, and it took a long time to get to its main launch pad at Kennedy Space Center in Florida. Called LC-39B, the launchpad used for Apollo and Shuttle launches was called that. It was also used for many Shuttle launches.
5pm ET is when the launch team will arrive and things will start to happen! When the flight controllers start up both SLS and Orion soon after, they will be able to use them. That’s when the team decides if they can start filling the car with gas on Sunday, April 3rd. The excitement doesn’t really start until then. The SLS’s tanks will be filled with cryogenic liquid oxygen and liquid hydrogen if they say “yes.” Over the course of the day, as the propellant boils away, they’ll have to add more to the tanks.
The flight controllers will count down to a predetermined “launch” time after the rocket has been filled up. They will eventually reach “terminal count.” When the support teams switch Orion to internal power just six minutes before zero, the rocket will do the same thing. The countdown will keep going until it’s T-minus 33 seconds, at which point the teams will stop the launch. Recycle: Then they’ll try again to go through the last part of the countdown again. This will show how well the team can try again if the launch is delayed. Terminal count will be done again, and they’ll get to T-minus 10 seconds before they cut things off for the second time.
