Paul Kantner, a founding member of the seminal San Francisco group Jefferson Airplane, has seen it all: Haight-Ashbury at the height of its psychedelic benevolence; headlining the Fillmore West's opening night; and playing at Woodstock to half a million groggy tripsters.

He longed for, loved and lost Airplane singer Grace Slick, cracked his head against a tree in a motorcycle accident, and in 1980 had a brain hemorrhage that might have killed him had it not been for the faultline in his skull that released the pressure.

Beyond his musical interests, Kantner is a fervent advocate of space exploration and has had a near-lifelong interest in science fiction.

So it's not surprising that this year's model of Jefferson Starship, which is what became of the Airplane in the 1970s, goes beyond hits such as "Someone to Love" and "Volunteers" and continues to seek new musical frontiers.

"Oddly enough (fans) come back to us with ideas after hearing our songs that are totally different than the ideas we had when we created a song," he said. "And sometimes I've even gotten new songs out of it."

Kantner celebrated his 70th birthday in March by jamming with old friends at Mill Valley's 142 Throckmorton theater and has no intention of playing a staid revue of greatest hits Saturday at Napa's Uptown Theatre.

"We mix it up a lot from show to show," he said. "We could never do the same show (every night). That would get tediously boring.

"One of the great things about music is the expansionism of it. Even if we play some of the same songs, we play them differently every time. That's part of the joy of doing it the way we do. You never know quite what's going to happen."

Jefferson Starship has a repertoire of about 100 songs and chooses 15 to 20 each night, a mix of classic Airplane songs and newer additions, such as covers from the most recent album, 2008's "Tree of Liberty."

That disc lends the Starship's sound to folk and protest songs from bands such as The Weavers.

Kantner, who grew up listening to Pete Seeger singing with The Weavers, calls "Tree of Liberty" a "tribute to our beginnings, or my beginnings. Before we were rock-and-roll people, we were folkies.

"The reason I wanted to sing with a woman was because of the Weavers," he said, adding that the Airplane admired the "type of songs they do, the chord changes and the connection with social responsibility."

Jefferson Airplane and Starship have gone through myriad incarnations since the original band's formation 46 years ago. Kantner is the only constant.

His supporting cast for this show includes David Freiberg on guitar and vocals, and Cathy Richardson, who sings Slick's parts as well as Marty Balin songs such as "Miracles."

Kantner says he's writing a science fiction book and working on a "half-autobiographical" book called "Tales from the Mothership" that is "not just about me but about our band and where we started all the way up till now."

The Napa show will be a tribute to space exploration, he said, and will note the anniversary of the alleged UFO recovery in Roswell, N.M., on July 8, 1947. (U.S. government scientists said the object was a weather balloon that had fallen to Earth.)

Asked if he believes in extra-terrestrial life, Kantner said, "I have no idea. Just like with religion, I'm an agnostic on both levels. I don't know about it, I haven't met anybody who appears to know about it, and I don't think I ever will."

As he embarks on his eighth decade on this planet, Kantner remains entranced by the power of music and its effect on human emotions.

"A song can make you cry or think of an old girlfriend," he said. How it creates an emotional response "in the brain is fascinating to me. It's a very alive kind of thing that happens there."

It's always a surprise when it works, Kantner added. "It was then and it is now, and I enjoy being surprised that way and probably will continue to be for a good long time to come."

Michael Shapiro writes about entertainment for The Press Democrat. Contact him at michael.shapiro@pressdemocrat.com.