ORLANDO, Fla., Dec. 31 (UPI) -- Launching people into orbit from U.S. soil again during two SpaceX launches topped the year's accomplishments in spaceflight. With that and other achievements, it was a strong year for Elon Musk's company.
The launch of the Dragon Endeavour at the end of May with two astronauts on board, followed by the Crew 1 mission's successful flight starting Nov. 15, stood out as historic achievements to spaceflight experts.
"In the end, it's about the commercialization of spaceflight and what a tremendous success that has been," said retired astronaut Mike Massimo, now a professor teaching spaceflight topics at Columbia University in New York.
"Commercialization has unleashed private companies -- entrepreneurs -- to operate a little different than the government and use creativity to solve problems."
SpaceX's ability to reuse rockets and capsules allowed the Hawthorne, Calif.-based company to grow rapidly and meet more challenges, Massimo said.
Perfecting the reuse of the first-stage Falcon 9 booster, flying them for seven times, also was a major accomplishment in 2020, he said.
"To see those boosters flying back regularly -- it's pretty amazing," Massimo said. "The Crew Dragon also is a marvel of new technology, with touch screens, updated cockpit design -- all of it."
SpaceX's successful high-altitude test flight of its new Starship rocket Dec. 9 also ranks as a significant achievement for the year, he said. The new spacecraft, which is intended to be a deep-space rocket for trips to the moon and Mars, made a flight of over seven miles high Dec. 9.
Six launches in 2020 by California-based Rocket Lab also registered as a top advance in spaceflight for 2020, Massimo said, including the firm's recovery of a first-stage booster on Nov. 20.
SpaceX's crewed flights and Starship tests also impressed Erik Seedhouse, assistant professor of commercial space operations at Embry-Riddle Aeronautical University in Daytona Beach, Fla.
"Everything Musk does is to get to Mars," Seedhouse said. "Building Starship is a big accomplishment, especially with the recent test flight. Starship is moving ahead so fast, any other company would be years behind."
For Seedhouse, having space travelers living aboard International Space Station almost continuously for 20 years was the biggest accomplishment of the year.
"We've proven humans can live in space for two decades, and that all these countries can work together, which is an incredible achievement in spaceflight," said Seedhouse, who has authored books on spaceflight and counts himself as a suborbital astronaut.
Reusability milestones reached by SpaceX and Blue Origin, and also Rocket Lab, also were highlights of the year, he said.
"Blue Origin also has reused their New Shepard suborbital rocket for the seventh time, and that's significant," Seedhouse said. "They haven't put a foot wrong, and that kind of track record is valuable in spaceflight."
New Shepard is Blue Origin's suborbital rocket, meaning it only reaches the edge of space. The company intends to launch passengers on it eventually, but so far the rocket only has carried science experiments or other cargo.
Seedhouse said 2020 also saw the first significant advances in spacesuit and flight suit design for space missions in decades.
NASA unveiled its new Artemis spacesuits in October, designed to allow for easier work in space and to fit a woman's body better. Those spacesuits haven't been used, but SpaceX employed the company's pressurized flight suits on both crewed missions.
SpaceX flight suits are mostly white with black trim and touchscreen-enabled gloves. They sport a sleek, smooth exterior in contrast to NASA's bulkier orange suits.
Launches with crews clad in those white suits marked a major transition from the shuttle era to the crew capsule, said Casey Dreier, chief advocate and senior space policy adviser for the nonprofit Planetary Society, a California-based non-profit that promotes space exploration.
"You can't emphasize it enough," Dreier said. "It was the return of human spaceflight to U.S. soil after nine long years" since the last space shuttle mission.
Dreier said other nations' accomplishments deserve recognition, particularly China's Chang'e-5 lunar sample mission, the launch of China's Tianwen-1 Mars probe and Japan's Hyabusa 2 asteroid sample return.
"The successful launch of three nations' Mars probes this summer -- the United States, the UAE and China -- has to be high on the list of accomplishments for 2020, but they still have to reach their target," Dreier said.
Closer to home, he said, Rocket Lab's recovery of a booster stage will be significant when the company reflies that booster for the first time.
And mega-constellations of satellites for SpaceX's Starlink and OneWeb are a more controversial accomplishment in 2020, he said.
"These huge satellite networks are technological advances, although they have come with problems regarding the interruption of sky-gazing and astronomy in some cases," Dreier said. "They are here to stay most likely, and China also wants to launch mega-constellations."