BOCA CHICA, Texas, Nov 18 (Reuters) - SpaceX's highly anticipated test flight of its Starship spacecraft ended in failure for the second time as the rocket exploded over the Gulf of Mexico shortly after detaching from its Super Heavy first stage booster on Saturday.

The uncrewed spacecraft, designed to carry astronauts to the moon and beyond, took off from SpaceX's Starbase launch site near Boca Chica, Texas. It reached an altitude of approximately 55 miles (90 km) above ground before encountering the catastrophic event.

Although the rocket's Super Heavy booster appeared to successfully separate from the core Starship stage, it exploded shortly after detachment, as shown on a SpaceX webcast.

Meanwhile, the core Starship booster continued its ascent into space. However, a few minutes later, SpaceX mission control lost contact with the vehicle, leaving uncertainties about the fate of the booster. The rocket had reached an altitude of 91 miles (148 km) before the incident occurred.

The test mission aimed to propel the Starship into space just shy of reaching orbit and then execute a splashdown off the coast of Hawaii. Initially scheduled for Friday, the launch was delayed by a day due to a last-minute swap of flight-control hardware.

The U.S. Federal Aviation Administration (FAA), responsible for overseeing commercial launch sites, confirmed a mishap resulting in the loss of the vehicle. Fortunately, no injuries or property damage were reported. The FAA will oversee a SpaceX-led investigation into the failure and will need to approve measures to prevent similar incidents in the future.

SpaceX, in a social media post, acknowledged that the core Starship stage's engines had fired for several minutes during its journey to space. The company stated that despite the test's failure, valuable insights would be gained to enhance Starship's reliability as SpaceX envisions a future of multiplanetary existence.

The success of the Starship's test flight is significant to SpaceX's long-term ambitions. The company aims to develop a versatile spacecraft capable of sending both people and cargo to the moon in collaboration with NASA's Artemis program, which aims to return humans to the lunar surface later this decade. SpaceX's founder and CEO, Elon Musk, also sees Starship as a potential replacement for the Falcon 9 rocket, currently used for most of the company's satellite and commercial payload launches.

It is important to note that this was the second failed attempt for the Starship test flight, following an explosion during the first attempt in April. The previous failure was attributed to engine issues at lift-off, with a subsequent stage separation failure caused by an internal fire.

The latest setback underscores the challenges and complexities of developing advanced space technology, and SpaceX's ongoing pursuit to refine its rockets and expand humanity's reach beyond Earth.

Reporting by Joe Skipper in Boca Chica, Texas, Joey Roulette in Washington, and Steve Gorman in Los Angeles; Editing by Will Dunham and Ros Russell