Jonny Kim, a former Navy SEAL, Harvard Medical School graduate and now a NASA astronaut, blasted off with two cosmonaut crewmates aboard a Russian Soyuz rocket early Tuesday, chased down the International Space Station and moved in for a picture-perfect docking three hours after liftoff.

With veteran commander Sergey Ryzhikov, 50, at the controls, flanked on the left by rookie cosmonaut Alexey Zubritsky, 32, and on the right by Kim, 41, the Soyuz MS-27/73S ferry ship rocketed away from the Baikonur Cosmodrome in Kazakhstan at 1:47 a.m. EDT (10:47 a.m. local time).

“The crew is feeling good, everything is nominal,” Ryzhikov periodically assured Russian flight controllers as the rocket climbed toward orbit.

Eight minutes and 46 seconds later, the third stage engine of the Soyuz 2.1a rocket shut down and the crew ship was released to fly on its own, followed moments later by deployment of its two solar panels and navigation antennas.

The ferry ship then carried out an automated rendezvous with the space station, moving in for docking at the multiport Prichal module at 4:57 a.m. as the two spacecraft sailed 260 miles above western Russia.

“Congratulations, Sergey, congratulations on your arrival at the International Space Station,” Russian mission control radioed. After extensive leak checks to verify an airtight structural seal, hatches were opened at 7:28 a.m., allowing Ryzhikov, Zubritsky and Kim to float into the station.

Welcoming them aboard were Soyuz MS-26/72S crewmates Alexey Ovchinin, Ivan Vagner and NASA astronaut Donald Pettit, along with SpaceX Crew 10 commander Anne McClain, NASA astronaut Nichole Ayers, Japanese astronaut Takuya Onishi and cosmonaut Kirill Peskov.

“It was the trip of a lifetime and an honor to be here,” Kim told flight controllers during a traditional postdocking video conference.

Ryzhikov, Zubritsky and Kim are replacing Ovchinin, Vagner and Pettit, who were launched to the ISS on Sept. 11 and who plan to return to Earth aboard their own Soyuz on April 19 to wrap up a 219-day stay in space.

The Crew 10 fliers, launched on March 14, replaced their Crew 9 predecessors — Nick Hague, cosmonaut Alexander Gorbunov and Starliner astronauts Butch Wilmore and Sunita Williams — who returned to Earth on March 18.

Rotating space station crews have typically carried out, on average, six-month tours of duty aboard the lab complex. But starting with Kim’s flight, the Russians are increasing Soyuz durations to eight months to gather more data on the effects of long-term stays in space.

As such, Ryzhikov, Zubritsky and Kim are expected to return to Earth around Dec. 9.

In a pre-flight interview with CBS News, Jonathan Yong “Jonny” Kim, the son of South Korean immigrants and a father of three, said he first heard of the Navy’s SEALs when he was 16 years old. He eventually joined the elite corps and went on to participate in more than 100 combat operations as a member of SEAL Team Three in support of Operation Iraqi Freedom.

“To me, it is the strongest calling I’ve ever had in my life, even to this day,” he said. “I’ve had additional callings in life. But it was really that first calling I had to be a SEAL that I will remember for the rest of my life. Because it was the first time that I felt I had a purpose, and I had a dream.”

That dream was to serve as a warrior.

“Back then, I used to have a really narrow focus on that,” he said. “But to me, a warrior is someone that is in continued pursuit of excellence in their craft. It doesn’t have to be combat. It can be in medicine. It can be as a NASA astronaut. It can be in politics. It can be anything.

“But it’s someone who’s passionate and in pursuit of continued excellence. And the reason why it just resonated so well with me is because it was everything I wasn’t at the time, but I wanted to be.”

Kim said he had “some terrible moments” in combat and ended up “just really burnt out. I was very burnt out from the combat, from the war and the loss. … I needed a way to continue serving, and it seemed logical that medicine would be that vehicle.”

Already a veteran combat medic, Kim was accepted in Harvard Medical School. Along the way, he said, he “probably went a little too extreme in ensuring that previous successes did not set myself up for the future.”

“I ensured that the people I worked with in the hospital didn’t know I was previously a SEAL, because I wanted my patients, I wanted my colleagues to think of me as dependable and proficient and a good physician. Not because I used to be a SEAL, but because that’s who I was.”

Then, as he was wrapping up medical school and preparing for his residency, Kim watched the initial test flight of NASA’s Orion moonship in 2014 on YouTube and became a self-described “space nerd.” He met physician and former astronaut Scott Parazynski, who encouraged him to apply to NASA for astronaut training.

Out of 18,000 applications for the class of 2017, NASA chose 12, including Kim.

He said learning Russian was the most challenging aspect of training to fly aboard a Soyuz, but added that his crewmates spoke excellent English and had gone out of their way to welcome him aboard.

“We are friends. I mean, we’re very, very professional,” Kim said. “We work well together. … I’ve had Alexey and Sergey over for dinner and they’ve done the same thing for me. So our relationships are personal and there’s a lot of trust and friendship there.

As for being assigned to a Soyuz flight, riding a vehicle that’s been around for decades as opposed to the roomier touchscreen-equipped SpaceX Crew Dragon, Kim said he was more than happy to fly with the Russians.

“I just love technology (but) there’s also something to be said about reliability, or as the saying goes, ‘If it’s not broke, don’t fix it,'” he said. “The amount of testing and the reliability the Soyuz has shown over decades is unsurpassed and is absolutely admirable.”

During the course of his stay aboard the station, Kim said, he hopes to venture outside the lab for a spacewalk at some point, but added he would be more that happy to serve in any capacity.

“The modern day astronaut is a jack of all trades,” he told CBS News. “You know, we train to do spacewalks. We train to support space walks, train to do research. One day we might be plumbers or mechanics, we might be technicians repairing a radio or we might be pipetting various fluids into other fluids for research.

“So it’s kind of all of the above, whatever the demands that the space station need at a time.”

Don Pettit, NASA’s oldest active-duty astronaut, celebrated his 70th birthday with two cosmonaut crewmates overnight Saturday, undocking from the International Space Station and plunging back to Earth in a blaze of re-entry heat to close out a 220-day expedition.

Pettit, Soyuz MS-26/72S commander Alexey Ovchinin and flight engineer Ivan Vagner undocked from the Russian Rassvet module at 5:57 p.m. EDT, setting up a parachute-assisted landing on the steppe of Kazakhstan near the town of Dzhezkazgan at 9:20 p.m. EDT — 6:20 a.m. local time Sunday, Pettit’s birthday, at the landing site.

Russian recovery crews and NASA personnel rushed to the spacecraft, opened the top hatch and helped carry the returning crew members to nearby recliners where flight surgeons carried out initial health checks.

Ovchinin and Vagner appeared to be in good spirits, smiling, chatting with support crews and enjoying drinks and snacks. Pettit, however, looked disoriented as he was carried from the descent module, letting his head fall back and closing his eyes as he was moved to his recliner. He was not seen again on the landing site video.

But there were no indications of any sort of major problem, medical or otherwise. From Kazakhstan, Ovchinin and Vagner will head back to Star City near Moscow, while Pettit will be flown to Houston and the Johnson Space Center for more detailed tests and the start of physical re-habilitation.

In an April 16 interview with KOIN-TV in Portland, Oregon, Pettit said he had more difficulty than most when returning to gravity after a long stay in space.

“The very first thing I’m going to do when I get to Earth will probably be to empty the contents of my stomach,” he said, prompting laughter. “It’s a physiological thing, it affects different people different ways. Some people can land and go out and eat pizza and dance. When I land, it takes me about 24 hours to feel like I’m a human being again.”

With the on-time landing, mission duration stood at 220 days and nearly nine hours, spanning 3,520 orbits and 93.3 million miles since launch last Sept. 11 from the Baikonur Cosmodrome in Kazakhstan.

Ovchinin has now logged 595 days in space over four flights, followed closely by Pettit, whose total stands at 590 days over four flights of his own. Vagner’s total after two station visits stands at 416 days.

The world record for most cumulative time in space is held by cosmonaut Oleg Kononenko, who spent nearly 1,111 days in orbit over five missions. The U.S. record is held by astronaut Peggy Whitson. She spent 675 days in space over four flights.

As for Pettit’s age, John Glenn, the first American in orbit, was 77 when he flew aboard the space shuttle in 1998 as a NASA spaceflight participant. He holds the record as the oldest person to fly in orbit.

The Soyuz crew’s return to Earth marked the final chapter in an extended crew rotation that began with launch of SpaceX Crew 10 commander Anne McClain, Nichole Ayers, Japanese astronaut Takuya Onishi and cosmonaut Kirill Peskov on March 14.

Crew 10’s arrival at the station cleared the way for Crew 9 commander Nick Hague, cosmonaut Alexander Gorbunov, Starliner commander Barry “Butch” Wilmore and pilot Sunita Williams to return to Earth four days later.

The Russians then launched replacements for Pettit’s crew — Soyuz commander Sergey Ryzhikov, Alexey Zubritsky and NASA’s Jonny Kim — on April 8, clearing the way for Ovchinin, Vagner and Pettit to return to Earth Saturday.

In a brief ceremony Friday, Ovchinin turned command of the station over to Onishi.

“It’s a great honor for me to accept the command of the ISS,” Onishi said. “I feel so special that I am taking over the command from you because it’s been almost nine years since we met here in 2016 during Expedition 48. At that time, both of us were rookies and here we are two veterans who are ISS commanders.”

“Human space flight is not easy. Only continuous dedication from generation to generation made it possible for human beings to get here. Now today, we have four rookies (on board). I’m sure one day they will come back and become commanders … that’s how we will continue to develop human space flight,” Onishi said.

The ISS has been continuously staffed by rotating crews since Nov. 2, 2000. Scheduled for retirement in five years, the lab is facing problems on multiple fronts, ranging from air leaks in the Russian segment to uncertain funding, spare parts shortages and resupply delays.

“Spaceflight is difficult and very risky,” Rich Williams, a member of NASA’s independent Aerospace Safety Advisory Panel, told the group in a public meeting Thursday. “The ISS has entered the riskiest period of its existence.”

“The ISS management, crew and support personnel always make spaceflight look easy. Spaceflight is anything but easy, and the increasing risks attending the ISS program are making it harder,” Williams said.

The air leaks in the Zvezda module’s aft docking compartment are presumably the results of metal fatigue and repeated pressure cycles as visiting Soyuz crew ships and Progress cargo freighters come and go.

“Primary risk mitigation activities at this point include application and patching materials to known cracks and limiting … pressurization cycles to try to limit stress and fatigue,” Williams said. “The ISS program is monitoring this closely, and the panel considers this one of our highest concerns.”

NASA has hired SpaceX to build a U.S. deorbit vehicle, or USDV, to drive the million-pound space station back into the atmosphere in 2030 to ensure it breaks up over the southern Pacific Ocean, far from shipping lanes and populated areas. The USDV is expected to arrive at the lab in 2029.

“Delivering and utilizing this USDV capability is critical to ensuring that the deorbit debris risk meets the established government public safety standards,” Williams said. “If there is a deorbit of the ISS before the USDV is delivered, the risk to the public from ISS breakup debris will increase by orders of magnitude.”

He said NASA and Russian space officials are working “to address the challenges associated with achieving a safe deorbit capability, both for end-of-life as well as a risk-managed deorbit for contingencies.”

The major problem facing the ISS is what Williams called “a large ISS budget shortfall.” NASA’s fiscal 2024 budget included nearly $1 billion for station operations and maintenance with another $1.6 billion earmarked for crew launches and resupply missions.

“It is critical to maintain adequate budget and resources until the vehicle has safely re-entered, not only to assure safety of day-to-day operations in a high-risk environment, but also to ensure controlled, safe deorbit within debris footprint requirements for the sake of public safety,” Williams said.

In summary, he said, “the panel appreciates the demonstrated operational excellence of the ISS program, but remains deeply concerned about the increasing and cascading risks attending the program over the next several years.”