New Delhi, Jun 6 (IANS): Billionaire Elon Musk's SpaceX on Thursday successfully launched its fourth test flight.

"Liftoff of Starship!" SpaceX wrote in a post on X.

The 400-feet-tall Starship rocket along with the Heavy booster lifted off after 6 p.m. IST from SpaceX's Starbase facility near Boca Chica Beach in South Texas on June 6.

The US Federal Aviation Administration (FAA) on Tuesday, gave the green signal for the flight after all safety and other licensing requirements for the test were met.

The huge Starship's raptor engines ignited during hot-staging separation.

Flight 4 used a similar trajectory as the previous test flights and the Starship splashdown in the Indian Ocean.

"Super Heavy has splashed down in the Gulf of Mexico," the company said.

The fourth flight test is aimed at inching "closer to the rapidly reusable future on the horizon", the company said.

While it has so far had three test flights, its reusability remains a concern, as the "shuttle's heat shield required over 6 months of refurbishment by a large team", Musk said earlier.

"Building upon what we achieved during Starship's third flight test, our primary goal today is to get through the extreme heat of reentry," the company said.

To enable this, SpaceX "intentionally placed one thin heatshield tile and removed two tiles completely from the Ship".

This will help measure how hot things get without tiles in those locations, while also testing some thermal protection options.

"If Starship manages to make it all the way to reentry, we'll collect valuable data on the vehicle at hypersonic speeds, or more than 5x the speed of sound," the company noted, prior to the launch.

The huge Starship vehicle is intended to land astronauts on the Moon during the crewed Artemis 3 mission in 2026, and later to Mars and beyond.