HOUSTON — Fifty years ago, on July 20, 1969, the world stopped to watch in awe as Apollo 11 astronauts walked on the moon. The semi-centennial has rekindled NASA’s interplanetary ambitions. Tapping into a vibrant U.S. space industry, it’s eyeing the moon as a stepping stone to Mars.

After launching from the Kennedy Space Center in Florida on July 16, 1969, the Apollo 11spacecraft, propelled by a series of three rockets, traveled at 25 times the speed of sound, and covered the 238,900 miles to the moon in about three days.

Neil Armstrong and Buzz Aldrin were the first of only 12 people, all NASA astronauts, ever to walk on the moon’s dusty, cratered surface, just over 2% of the 550 people who have reached space since Russian cosmonaut Yuri Gagarin first did so in 1961.

Armstrong’s famous radio message back to Mission Control at NASA’s Johnson Space Center in Houston: “That’s one small step for a man, one giant leap for mankind,” culminated eight years of work by more than 300,000 technicians.

The feat cost $25 billion and fulfilled the goal of getting a man to the moon within the decade, which President John F. Kennedy laid out in 1961, prompted by Cold War fears that the Soviet Union would surpass America in space.

NASA’s lunar missions ended in the early 1970s as federal funding fell off amid a move by Congress away from big government projects, to a more fiscally conservative approach that favored partnerships with the private sector.

But U.S. space ambitions have revved up in recent years, fueled by tech billionaires Elon Musk’s and Jeff Bezos’ rival rocket companies, Space Exploration Technologies Corp. and Blue Origin LLC.

President Donald Trump signed a directive in December 2017 calling for NASA to send astronauts back to the moon by 2024 and establish a base there.

Though Trump dedicated $1.6 billion to NASA in May this year for its new Artemis moon missions, and the agency is set to receive $21 billion in federal funding for 2020, it has contracted with a private company to build a centerpiece.

NASA accepted a $375 million bid from Maxar Technologies of Colorado to build a power and propulsion component of a spacecraft NASA has dubbed Gateway, which will take shape like a giant floating Lego set.

“Imagine the Power Propulsion Element as the engine of a car,” Mike Gold, a Maxar vice president, said in an email to Courthouse News. “It will provide power, maneuvering to get the astronauts closer to the surface of the moon, and communications to Earth and other systems in lunar orbit or on the surface of the moon.”

NASA plans to dock a small astronaut quarters to it by 2024. The living space will be built by other countries’ space programs and private companies adding modules and hardware, just as Russia, Canada, Japan and the United States constructed the International Space Station.

The propulsion element and Gateway will be powered by a solar electric system, a system Gold said took decades and 100,000 work hours to perfect and is essential for any mission to Mars.

Maxar is to test launch in late 2022 and NASA has the option of buying it or not. It’s designed to operate for at least 15 years, Gold said.

Maxar’s history with NASA goes back to Apollo’s roots. It built the agency’s Mission Control Center and supplied instruments Aldrin installed on the moon, Gold said.

While few companies can boast of such a track record, the semi-centennial finds the U.S. space exploration industry in full bloom. Dozens of startups are competing to help NASA construct a lunar human habitat and to build a launch platform for deep-space missions.

With some describing the moon as the “Eighth Continent,” they are building robots and 3D printers to construct lunar buildings, designing lasers to melt moon dust into building materials and landers to explore its south pole, where NASA plans to land astronauts, including the first woman on the moon, for its Artemis mission.

The United States is not the only world power vying for lunar real estate.

China has a rival program. Named for the Chinese moon goddess Chang’e, its missions started in 2007.

China in January became the first country to land a spacecraft on the moon’s dark side. It was loaded with radiation and water-detecting devices built by Swedish, Dutch, German and Saudi Arabian scientists.

The moon is a magnet for multinational collaboration.

A 2008 spacecraft launch by India’s space agency collected data that led to the discovery of ice packed in shadowed craters on the moon’s southern pole, which never get warmer than -250 degrees Fahrenheit.

NASA hopes to extract the ice and convert it into oxygen for humans and hydrogen fuel for a rocket launch to Mars. Commercial space firms are researching how to do this.

China also aims to build a lunar outpost on the south pole for exploration missions.

Vice President Mike Pence sees China as a threat to U.S. space supremacy. Some experts believe China will beat NASA back to the moon, and the next message from its surface will be spoken in Mandarin.

“Make no mistake about it, we’re in a space race today, just as we were in the 1960s, and the stakes are even higher,” Pence said in March.

With its headquarters 2 miles from the Johnson Space Center, Intuitive Machines is one of

It plans to transport its first lander, capable of carrying 330 pounds, on a SpaceX rocket, its vice president of aerospace services Trent Martin said in an email.

“Our first mission includes five NASA payloads, one commercial payload, and one academic payload. Each payload is performing specific scientific or engineering technology demonstration missions,” Martin said.

Though the company has many former NASA employees on its payroll, none of them worked on the Apollo missions. But Martin said they all have collaborated with Apollo-era NASA technicians and astronauts.

“It was their pioneering spirit that allows us to even attempt to perform a feat previously relegated only to governments of superpowers,” he said.

— By Cameron Langford and James Palmer