Watch NASA’s Artemis Moon Rocket take off on the launchpad

What are the Space Launch System and Orion, and why are they important?

The Space Launch System and Orion are key components of NASA’s plans to return astronauts to the lunar surface in the coming years. Getting there would require a rocket powerful enough to propel a large spacecraft out of low-Earth orbit to the moon, some 240,000 miles away. Orion is a capsule designed to carry astronauts on spaceflights of up to a few weeks.

What problems occurred during the dress rehearsal?

NASA first rolled out an SLS rocket to the launch pad in mid-March. In early April, it attempted a “rehearsal” of countdown procedures, including loading more than 700,000 gallons of liquid hydrogen and liquid oxygen rocket thrusters. However, technical glitches, including a hydrogen leak during three exercise attempts, cut the countdown short.

NASA then returned the rocket to the Vehicle Assembly Building for repairs. In June, the rocket returned to the launch pad for another attempt at rehearsal. That attempt, on June 20, encountered a different hydrogen leak, in the fuel line connector to the rocket’s boost stage. However, for the first time the fuel tanks were fully filled, and the controllers were able to continue training until the countdown expired 29 seconds ago. Originally, the goal was to stop the countdown in less than 10 seconds, when the engines would start to actually launch.

Despite the leak, NASA officials determined that all critical systems had been adequately tested and declared the test a success. The missile returned to the vehicle assembly building again for final preparations, including the installation of a flight termination system, which would detonate the missile if something went wrong during launch and eliminate the possibility of a collision with a populated area.

The batteries for the flight termination system, which were installed on August 11, are usually rated to last only 20 days, but the part of the US Space Force that oversees launches from Florida has given NASA a waiver that extends to 25 days. This allows for a launch date of August 29 as well as backup opportunities on September 2 and 5.

NASA is hoping to fix the hydrogen leak, but it won’t know for sure until the countdown on August 29, when the fuel line will be cooled to frigid temperatures, something that cannot be tested in the Vehicle Assembly Building.