She has played astrophysicist Samantha Carter on television for more than 10 years, but Amanda Tapping has never played her like this. Carter faces a real challenge in integrating herself with the established Atlantis team when she arrives in the Pegasus Galaxy, the actress said in a SCI FI Channel press event today.

“[Sam’s] discomfort comes from the fact that she’s completely out of her element,” Tapping said. “She’s not in her comfort zone. This is a woman who spent her entire career taking orders and being subordinate, to a degree, as per military protocol, and is now suddenly in a position where she influences lives by the decisions she makes. On that aspect she’s really struggling, too, to find that strength.”

Her new role as a series regular on the hit spin-off starts this Friday, September 28, when SCI FI airs the world premiere of “Adrift” at 10 p.m. Eastern/Pacific.

Carter takes command of the Atlantis expedition millions of light years from Earth when Elizabeth Weir is critically injured in the line of duty. (Actress Torri Higginson will appear in four episodes this season.)

That change weighs heavy on Carter, Tapping said. “She is aware that she is replacing a much-loved leader when she comes onto the show — or into the galaxy. And so she’s very aware of treading lightly. In a lot of ways for me, as the actor, it feels like playing a much different character. She’s almost not as confident, because she is out of her comfort zone.”

Taking on the role of a commanding officer will also bring out new aspects of Carter’s personality, aspects which even long-time fans have not seen. “She’s finding her strength, as the season goes on,” Tapping said. “She’s not letting any of the chinks in her armor show, obviously, but she is finding a quiet, inner strength as the season goes on.

“But I think what also Carter is struggling with in some ways as the season goes on is a certain amount of loneliness — sort of the ‘heavy is the head that wears the crown.’ She can’t fraternize in a relationship way with any of the people that she’s working with, and because she’s the leader she can’t become buddy-buddy. And she’s used to that. She’s used to the sense of camaraderie that she had on SG-1.

The collective IQ of the Pegasus Galaxy goes up a few points when Samantha Carter arrives in the fourth season of Stargate Atlantis.

“So it’s a little bit lonelier for her, I think. And I think what it will show — and as the season progresses you’ll see it come out — is the quieter strength of her character. As opposed to the kind of Carter bravado, ‘I know what I’m doing’ and ‘Here, let me explain the situation to you,’ as she was used to doing. Now it’s a little different.”

But the fish-out-of-water feeling won’t last forever, as Samantha Carter finds her place among the team and discovers her own inner strength. Likewise, the rest of the team will mesh with her.

“‘Quarantine’ probably brings everyone together, even though we spend the entire episode separated,” the actress said. “There’s a realization that we almost lost Atlantis. And there is a renewed sort of a vigor in terms of protecting it.”

Co-star (and fellow Atlantis newcomer) Jewel Staite added that “‘Quarantine’ puts the characters in a position where they absolutely have no choice but to bond.”

“I’m actually really happy with the way the character has been introduced,” Tapping said. “It could have been a very difficult transition, bringing Carter over from SG-1 to Atlantis. And I think it was handled really seamlessly. So in that sense I’m really happy with the way the transition went, with the way the character has developed this season.”

Watch the season premiere of Stargate Atlantis this Friday at 10 p.m. Eastern/Pacific on SCI FI! The season premiere also airs Monday, October 1 on Canada’s Movie Central, and Tuesday, October 9 on Sky One in the U.K.