Watch: Elon Musk explains how SpaceX's Mechazilla can catch Super Heavy booster

The SpaceX on Sunday flew a 233-foot rocket booster back to its launch site and then caught it out of the air with two giant mechanical arms -- in a major step forward for SpaceX and Elon Musk. A video of Musk explaining how SpaceX's Mechazilla will catch the Super Heavy Boosters surfaced.

"This is a custom-built tower with arms that are designed to catch the largest flying and heaviest flying object ever made and pluck it outta the air. It'll weigh about 250 tons. We'll make that lighter over time," Elon explained.

"So you got a couple hundred tons plummeting at more than half the speed of sound. So this thing is still coming in really fast."

Another person on the video said Elon asked the experts to delete the legs of the tower and only to work with the arms.

"When the engines land... it's gonna drop the velocity to basically zero and come in between the arms. The arms will be wide, and as it's coming in, the arms will, will close, go flush against the side of the vehicle, and the vehicle will be descending through the arms. The probability is uncertain, but it is above zero," Elon explained.

Congratulatory messages poured in after SpaceX starship made a spectacular belly flop splash-down in the Indian Ocean following the successful test flight. Bill Nelson, the NASA administrator, congratulated SpaceX as he wrote, "As we prepare to go back to the Moon under Artemis, continued testing will prepare us for the bold missions that lie ahead -- including to the South Pole region of the moon and then on to Mars."

At 8:25 a.m. Eastern time, the Starship successfully launched and then separated from its Falcon Super Heavy rocket booster. The booster was then brought back to Earth by the Mechazilla arms.