By Joey Roulette

(Reuters) - Elon Musk's SpaceX is set on Tuesday to launch the sixth test of its giant Starship rocket from Texas, eyeing improvements in its hypersonic reentry into Earth's atmosphere and a novel technique for landing its booster, as U.S. President-elect Donald Trump watches in person.

Trump is expected to be joined by his son Donald Jr. and Republican U.S. Senator Ted Cruz at the launch of Starship scheduled for 4 p.m. CT (2200 GMT) from SpaceX's sprawling rocket development site in Boca Chica, Texas, according to two people familiar with the president-elect's plans.

The roughly 400-foot (122-meter) tall rocket system is designed to land astronauts on the moon and ferry crews to Mars. The first stage, called Super Heavy, on Tuesday is due to boost Starship into space before returning to land, while Starship travels around Earth for a planned daytime splashdown in the Indian Ocean some 90 minutes later.

In a launch last month, Starship's first stage booster returned to land for the first time by falling into giant mechanical arms at the launch site, a key step in its reusable design that the company will repeat on Tuesday, but "faster/harder," Musk wrote on social media.

Musk, the world's wealthiest person, was a prominent supporter of Trump's presidential election campaign, appearing with him at rallies and backing him with at least $119 million in political support. Musk stands to benefit from Trump's victory, with the billionaire entrepreneur expected to wield extraordinary influence to help his companies and secure favorable government treatment.

"I’m heading to the Great State of Texas to watch the launch of the largest object ever to be elevated, not only to Space, but simply by lifting off the ground," Trump wrote on social media, wishing Musk luck on the launch.

Trump on Nov. 13 appointed Musk as co-leader of a new government efficiency project that the SpaceX founder and Tesla CEO has said will rid the federal government of wasteful spending and regulations he has called burdensome.

The U.S. Federal Aviation Administration's regulation of commercial rocket launches has been a source of frustration for Musk, who has complained that the agency impedes his company's progress in getting to Mars.

Musk on Tuesday listed four core objectives for the test flight - restarting Starship's space-tailored engine during flight - key for its in-space maneuverability - and making a more visible ocean landing during the daytime, while past attempts have been at night.