A U.S. scientist who paid $20 million to visit the international space station (ISS) is back on Earth, satisfied that the experience was worth the expense.

“I feel great,” said Gregory Olsen, the third space tourist to visit the ISS, as he finished an apple while recovery workers conducted medical checks. “I can’t wait to walk around and have some real food, and take a shower.”

The landing ended a 10-day spaceflight for Olsen and a six-month mission for ISS Expedition 11 commander Sergei Krikalev and flight engineer John Phillips. Krikalev and Phillips launched toward the ISS in mid-April and spent 179 days aboard the orbital outpost before turning it over to their replacements — Expedition 12 commander Bill McArthur and flight engineer Valery Tokarev — who chaperoned Olson on his way to the station.

The Oct. 11 landing concluded a dream come true for Olson, a New Jersey resident and co-founder of the optics firm Sensors Unlimited, Inc.

Olsen launched to the ISS with the Expedition 12 crew Sept. 30 under a commercial agreement with Russia’s Federal Space Agency, arriving at the orbital complex Oct. 3 for about eight days of weightlessness, Earth observation and medical experiments.

The U.S. scientist is the third spaceflight participant to visit the ISS under a deal brokered by the Arlington, V a.-based space tourism firm Space Adventures, which also arranged space station flights for South African Internet mogul Mark Shuttleworth in 2002 and American entrepreneur Dennis Tito in 2001.

Olsen overcame some hurdles to secure his multi-million dollar spaceflight, including an undisclosed medical condition that prevented him from completing his Russian cosmonaut training at Star City in 2004. But that condition was not a problem by May 2005 and he resumed his training in time to launch spaceward with the Expedition 11 crew.

With Olsen’s spaceflight completed, Russian space officials reportedly said that the next ISS-bound tourist would be either a Japanese businessman or an American.

“We now have the next, fourth candidate for space tourism, who has passed a medical test and will probably fly in a year,” Alexei Krasnov, chief of the Russian Federal Space Agency’s manned spaceflight programs, said in an interview for the Japanese Asahi newspaper.

According to Russia’s Interfax news agency, Krasnov said the Japanese businessman could face some competition from a U.S. space tourist. “The one who proves better prepared will fly,” Krasnov said, adding that any private space flyer would launch in fall 2006, since there are no vacant seats aboard the next Soyuz to liftoff in March.

A successful flight

The landing also capped a 179-day mission for Krikalev and Phillips, giving Krikalev a lifetime total of 803 days in space — the most any human has ever spent off the planet. Krikalev broke the record Aug. 16, when he surpassed 748 days in space and the previous record held by cosmonaut Sergei Avdeyev. Krikalev is the only cosmonaut to make six spaceflights and the first to serve two stints aboard the ISS.

“I think this is a big adventure,” Krikalev said in an interview conducted over the phone using a space-to-ground relay provided by NASA’s Johnson Space Center. Setting records, he added, was not his plan.

The Soyuz departure marked the end of Expedition 11’s months-long stay aboard the ISS, during which they maintained the space station, conducted one spacewalk and received the first visiting space shuttle crew since December 2002.

“I’m proud to say we’re leaving the station in excellent condition,” Phillips said during the same space-to-ground interview. “I’m very satisfied with the results of our mission.”

Despite the spaceflight’s success, there were some disappointments, including the delay of a second shuttle flight due to ongoing external tank debris issues, Phillips added.

“We were expecting to be here when the second shuttle flight came, and they were going to bring us a third crewmember, which would have been huge,” Phillips said. “We were disappointed … but the important thing is to make sure we fly safely.”

NASA is currently working to reduce foam shedding from external tanks during launch, a problem that doomed the Columbia shuttle in 2003 and cropped up again during the recent Discovery STS-114 flight to the ISS, before making its next orbiter flight in spring 2006.

Expedition 11 was Phillips’ first long-duration spaceflight and included the first spacewalk of his astronaut career.

“It was a wonderful adventure and a wonderful experience … it was basically everything I thought it would be,” Phillips said of working outside the ISS, adding that he was surprised that he didn’t have to steel himself against plunging into the blackness of space. “But it felt almost routine for me. It was time to go out, and I went out.”

Returning home

Phillips and Krikalev said they were looking forward to resuming their terrestrial lives and welcomed such small treasures as the aroma of fresh coffee, an open sky and weather.

“It’s kind of a sterile environment,” Phillips said of the ISS during a press conference last week. “I want to experience weather, the smell of trees, even the sound of cars going by, something that’s more like the real world that I live in at home.”

In the meantime, both Expedition 11 astronauts are confident that their time aboard the ISS helped prepare it for future crews. Last month, Krikalev restored the station’s finicky Elektron oxygen generator to operation, and Discovery’s STS-114 spacewalking crew replaced one of four vital gyroscopes required to orient the orbital platform.

“I don’t have any concerns about the future months for the next [station] crew of subsequent missions,” Krikalev told Space.com last week. “Everyday of our flight is preparation for future missions.”