Ripple Effect: Satirical musical comedy. By Michael Gene Sullivan, Eugenie Chan, Tanya Shaffer. Music and lyrics by Ira Marlowe. Directed by Hugo E. Carbajal and Wilma Bonet. San Francisco Mime Troupe. Free. In Bay Area and Northern California parks through Sept. 1. 85 minutes. (415) 285-1717. www.sfmt.org

If you're fighting the power, raising a fist for labor and working on your tan, you must be at a San Francisco Mime Troupe show. Now in its 55th season of offering free revolutionary musical comedy in parks, the Mime Troupe - "loud mimes," as they describe themselves - has hit some rough economic times in recent years but seems to have come out on the other side.

This year's offering, "Ripple Effect," which opened, as tradition dictates, in Dolores Park on the Fourth of July, could be full of rage, disgust and an overwhelming sense of injustice. And it is, to a degree. But it's wrapped in a brightly written, laugh-laden, altogether chipper package that makes it one of the most enjoyable Mime Troupe outings in recent memory.

As written by Michael Gene Sullivan, Eugenie Chan and Tanya Shaffer, "Ripple Effect" takes its time working the audience into a fit of San Francisco outrage (about life in San Francisco no less), but by the end, fists are pumping and everyone's chanting, "Justice rules and the Earth comes first!"

Though tech companies, outrageous rents and the displacement of San Francisco's working class are the obvious fuel for this year's show, the focus is personal. The conceit here is that three women are sailing the bay on a vessel called the Distant Horizon. Deborah (Velina Brown), the captain and tour guide, doesn't trust anything invented after 1988, the year of cell phones and Prozac.

She has two passengers. Jeanine (Lisa Hori-Garcia) is a Nebraska transplant and app developer who works for tech giant Octopus and is prone to overstimulation when outside the safe confines of her work cubicle. And there's Sunny (Keiko Shimosato Carreiro), a Vietnamese immigrant raising a daughter and running a beauty salon in Bayview.

The bulk of the mostly plotless show involves lengthy flashbacks addressing each woman's history and relationship with San Francisco. Sunny is up first, and her recollection of life in Vietnam is enlivened by puppets and scenes of murder, refugee camps and abandonment.

Jeanine tells of her grandmother's struggle with dementia and how that inspired the creation of an app that - if used properly - can track movements and keep people safe.

And Deborah takes us back to 1977, a groovy year of afros and jumpsuits, to detail the end of '60s-style activism and the triumph of exploitative capitalism.

All of this backstory is punctuated by amiable songs with music and lyrics by Ira Marlowe performed by the energetic cast, which also includes Sullivan in a variety of roles, the most memorable involving a googly-eyed octopus costume.

Directors Wilma Bonet and Hugo E. Carbajal contend with some lulls in the script, but once the flashbacks end, the energy picks up, and a villainous tech giant elicits boos from the audience with observations like, "Altruism is a trap set by some hippie visionary" or "You can't buy a Maserati with justice!"

"Ripple Effect" really hits its stride in its final scenes when Jeanine whines, "I'm a software engineer. I'm not political!" To which the more seasoned Deborah responds, much to the crowd's delight, "There is no such thing as not political!"

Chad Jones is a freelance writer in San Francisco who blogs at www.theaterdogs.net. E-mail: datebook@sfchronicle.com Twitter:@theaterdogs