I've signed three liability waivers and I'm feeling serious jitters as I board a Boeing 727 at Dallas's Love Field. But it's when a staff member hands me three Dramamine pills that I really start to get nervous. I'm about to take the plane trip like no other, soaring up thousands of feet, then plummeting to earth again, all to experience a few moments of weightlessness. The folks at Zero Gravity Corp. promise the public an out-of-this-world adventure straight out of NASA—at $2,950 for a two-hour trip—beginning this month. So when the chance to catch a preview flight came up, I couldn't resist.

Soon the white-knuckling begins. To achieve the zero-G effect, the pilot takes us on a steep 45-degree ascent at 397 mph. We're warned to stare straight ahead if we don't want to become nauseated and see what we had for lunch again. Hurtling even higher for 25 seconds, I feel twice my weight, as if an anchor is pulling all my muscles downward. I focus my stare at a spot on the wall. Brad Pitt could be taking his shirt off behind me, and I wouldn't look.

Then the fun starts. Finishing its climb, the plane abruptly goes into free fall straight down. At the start of our precipitous descent, we're at one-third gravity—the same as Mars—and I begin to float up. I'm doing somersaults in midair with other passengers. Wheee! I get a fit of the giggles.

The effect lasts about 30 seconds, then the cycle repeats: Hello, steep climb; goodbye, gravity. The second time, gravity is at one-sixth what you earthlings are used to. Hey! I can do one-handed pushups. The third time, all the passengers float up to the ceiling. We roll and bump around like a bunch of Macy's Thanksgiving Day Parade floats, no strings attached.

By the tenth cycle, I am keenly aware of the airsick bag in my pocket—no wonder they call it the Vomit Comet. I walk off the plane feeling wobbly, though with a big smile on my face. Days later, I still feel as light as a cloud. But I'm not rushing to do it again.