NASA’s space-exploration ambitions gained a much-needed boost with Orion’s almost flawless debut flight Friday, an initial step in the quest to carry humans to Mars in the 2030s.

The Apollo-like capsule, the first U.S. craft built to transport humans to space since the shuttle in 1981, orbited Earth twice to test critical functions. Then, tethered to three orange-and-white parachutes, Orion splashed down in the Pacific Ocean, capping a 4 1/2 hour-trip.

The voyage, less than two months after a pair of disasters stunned the commercial space industry, helps bolster NASA’s political case for its biggest-ever expedition with costs over 20 years that will probably dwarf those of the $100-billion International Space Station, the most-expensive structure ever built.

“It’s going to be a long time, unfortunately, before the capsule is ready to carry people, but it’s a first step and as such I think a significant one and hopefully a successful one,” said Jeff Hoffman, professor of aeronautics and astronautics at Massachusetts Institute of Technology.

The flight showed that the capsule’s thermal protection system worked, an essential part of sending a mission safely to and from somewhere as far as the moon or Mars, Hoffman said by telephone from Cambridge. “If it had not survived then the whole program would have been set back tremendously.”

The capsule is a small component in a massive undertaking, its flight hearkening to the Apollo era in the 1960s as NASA and its partners redevelop deep-space capabilities not used in four decades.

Orion is the National Aeronautics and Space Administration’s first spaceship developed to carry humans beyond the moon, on long-range missions to asteroids next decade and to Mars in the 2030s.

“Today we showed ourselves and the rest of the world that as a space team, we’re ready to leave our Earth neighborhood and go farther,” said Cady Coleman, an astronaut who spent six months on the space station.

Friday’s journey bodes well for the space industry after two recent explosions, said Henry Hertzfeld, research professor of space policy and international affairs at George Washington University.

An unmanned Orbital Sciences Corp. rocket burst into a fireball in October as it took off from Virginia on a cargo- carrying mission to the space station. Three days later, a Virgin Galactic spacecraft crashed during a test flight in California, killing the co-pilot and injuring the pilot.

“Any time you have a success like that on something new it’s great,” Hertzfeld said. “Good for the agency, good for the country and for all the rest, particularly coming after the couple of setbacks two different companies had a few weeks ago.”

Built by Lockheed Martin, Orion is named after one of the largest constellations in the night sky. It was carried aloft by a Delta IV Heavy rocket that rose atop a pillar of flame from Kennedy Space Center in Cape Canaveral, Florida, a day after an initial launch was postponed.

“There were a few moments when I held my breath, but today’s flight couldn’t have gone better,” said Mike Hawes, Lockheed Martin vice president and Orion program manager.

The weather worn buildings at the Space Center, left from the Apollo and space shuttle eras, evoke NASA’s storied past.

Signs identifying buildings’ news affiliations – CBS News, Reuters, Orlando Sentinel, Florida Today – have faded over the years, a reminder that interest in space flights diminished after the U.S. won the race to the moon in the 1960s and as shuttle flights later became routine.

A brass historical plaque on the side of one cinder block structure close to the press building commemorates the glory days. The marker, placed by the Society of Professional Journalists in 1975, reminds visitors that “The largest corps of newsmen in history gathered to watch and report fully and freely to the largest audience in history” during the space program’s heyday.

Whether Orion, with its goal of sending travelers to Mars, kindles a fresh interest in space is still unknown in an age of social media, budget cuts and even shorter attention spans. Friday’s launch was among the top trending topics worldwide on Twitter.com.

As Orion’s camera sent images of the curved blue planet far below, several journalists in the Kennedy Space Center pressroom applauded. The images recalled iconic photos of a distant Earth sent decades ago.

The craft reached its apogee more than three hours into the flight — an altitude of 3,600 miles (5,800 kilometers). That’s the greatest distance from Earth traveled by a vehicle designed for humans since lunar voyages ended in 1972. NASA is targeting a trip with astronauts by 2021.

While similar in appearance to the Apollo capsules that first flew in the 1960s, Orion was built with 21st-century manufacturing techniques and materials, Bill Hill, NASA’s deputy associate administrator for exploration systems development, said in an interview before the launch.

The pod can hold as many as four people, one more than the Apollo vehicles. The habitable space has been expanded to more than 300 cubic feet (8.5 cubic meters) — a 45 percent boost in roominess over Apollo’s cabin.

The latest capsule has been in development since 2006, when it was commissioned for lunar travel under the Constellation program. The Obama administration canceled the return to the moon in 2010, over budget and years behind schedule, shifting focus to Orion and trips farther into the solar system.

NASA spent about $4.7 billion on Orion’s development and design as part of the Constellation project and expects to invest another $8.5 billion to $10.3 billion in craft through 2021, the Government Accountability Office said in a May 2014 report.

To help reduce costs for more-routine, near-Earth missions, NASA is turning to private industry, including the company led by billionaire Elon Musk, for tasks such as ferrying freight and astronauts to the space station. Jeff Bezos’s Blue Origin venture is working on an advanced engine that could power the large new rockets NASA plans to develop in the 2020s.

The agency doesn’t yet have a rocket powerful enough to blast it into space that is also deemed safe enough to transport people. The Delta IV rocket, built by the Lockheed-Boeing Co. venture United Launch Alliance, is serving as a temporary propulsion system until a next-generation rocket is developed.

Orion will be paired with the new rocket system in an unmanned test flight scheduled for 2018 that will travel 435,000 miles past the moon in an elliptical orbit.

Its next flight, slated for early next decade, will take astronauts to the same region in a 25-day test of humans’ ability to live and work independently of Earth, according to a NASA white paper published May 29.

While Mars’s distance from Earth varies because of the two planets’ orbits, the average is about 140 million miles, almost 600 times longer than the trips to the moon made by the Apollo astronauts.

Where the program goes from here is still to be determined, George Washington University’s Hertzfeld said by telephone from Washington, D.C. While the success of the flight can’t hurt budget allocations, “we have a new congress in January, let’s see what happens,” he said.