For 10 years Ken Dychtwald has been, by his own description, "the Mr. Happy Age Wave guy."

As a psychologist (blessed with telegenically good looks), he pushed a reassuring message to baby boomers that their autumn years could be exciting, rewarding, productive. And as a business consultant turned best-selling author (his book, like his company, is called Age Wave), he rose to marketing guru with his vision of a new oldhood, one that foresaw countless opportunities for corporate America.

On the eve of his 50th birthday, Dychtwald's still riding a crest. Only he's not so cheery anymore. In fact, he seems depressingly worried.

Right there, on Page 78 of his new book, "Age Power," are the words Train Wreck. They're on Page 79, too, and Pages 80 and 81, bold italics listing five looming disasters that could derail much of the next century:

Wreck #1: "Using 65 as a marker of old age--and the onset of old-age entitlements--is meaningless, unfair and even dangerous."

Wreck #2: "Without a dramatic shift in health care skills and priorities, our society will face epidemics of chronic disease."

Wreck #3: "A care-giving crunch could become the social and economic sinkhole of the 21st century."

Wreck #4: "Tens of millions of boomers are heading toward a poverty-stricken old age."

Wreck #5: "Without envisioning a new purpose for old age, we are creating an elder wasteland."

No more sugarcoating, no more trying to make difficult issues appetizing and winning, he says. "I've grown up," Dychtwald explained this week during a visit in Washington, his third stop on a month-long coast-to-coast tour for "Age Power," the book he regards as his "wake-up call" to America. "I can see the challenges that are going to confront this generation and we're not dealing with them."

It's hardly a surprise prediction that the huge bulge of women and men born between 1946 and 1964 will fundamentally change this country as they move into the traditional retirement years. For virtually all of their lives, these 76 million boomers have been the tail wagging the dog, and their future collective impact on institutions such as Social Security and attitudes about longevity is debated endlessly these days.

But Dychtwald says much of the debate is ill-focused--Medicare, for example, is less a funding issue than a health issue, he argues--and he believes he could be the person to get the discussion back on track. In another train reference, he calls himself the switchman who sees the massive locomotive hurtling down the track, the wrong track, straight toward catastrophe, and manages to pull the control that redirects the cars and saves the day. He could be the Ralph Nader or Rachel Carson of his time, he suggests.

While the smooth, packaged delivery and self-promotion draws detractors, who fault Dychtwald for a simplistic, even glib approach that leans toward business solutions, he is an undeniably charismatic speaker and packs them in at conferences.

At the 1997 annual meeting of the American Society on Aging--a professional group that had given Dychtwald one of its top awards the previous year--more than 600 people crowded in to hear him preview the material that is now his new book. C-SPAN aired his speech.

Larry J. Polivka, for one, was not wowed. The director of the University of South Florida's Policy Center on Aging later wrote a harsh response for the organization's newspaper. Among other points, he hit Dychtwald for characterizing many of today's elders as self-centered and greedy.

"It's an invidious comparison," Polivka echoed Tuesday, in advance of a review he soon will do on "Age Power." The academic gerontologist remains critical of the popular gerontologist, including his suggestion that boomers will distinguish themselves more than their parents by the time they reach their seventies and eighties. "I'm not sure they're as spiritually fit, as socially focused or as generous," Polivka says.

Still, Dychtwald has some big-name fans. His latest book jacket sports encomiums from Jimmy Carter, Coca-Cola CEO M. Douglas Ivester and financial pop guru Suze Orman. Carter labels him "today's most innovative and original thinker on this important subject."

This thinker-author offers 50 product/service/business ideas for the burgeoning ranks of aging boomer consumers, including:

* On the anti-aging front: bio-implants to "continually monitor biomarkers and deliver anti-aging nutrients and hormones on an as-needed basis."

* On the technology front: adult androids, a la Furby, "that would be programmed to talk, remember and react to their owner's thoughts and concerns, even play bridge or discuss current events."

* And on the housing front, among the half-dozen-plus retirement housing concepts for the "needs and fancies" of the new mature adults, how about "hedonism complexes" for elder swingers? Dychtwald acknowledges its improbability with a grin. That idea, he says, was slipped in for the fun of it.

Other thoughts have far greater heft, although he explores several too superficially. Many are already part of the ongoing public dialogue about the graying of America--about the significant health, financial and social implications of having more than 70 million people age 65 and older. Should projections hold, by 2030 more than one in five Americans would be part of that group.

Like the AARP (that seniors-advocacy leviathan with which he so frequently parts company), Dychtwald fears too many boomers are saving far too little for a retirement that could last several decades. He calls his generation financially illiterate: "Our naivete and ignorance are dangerous." A major public education campaign should be launched, he says. Pensions should be made more portable. Government entitlements should be targeted through "affluence testing." But as long as the issue is framed simply in terms of shoring up Social Security, he warns, no lasting solution will be found.

Similarly, like the Washington-based Alliance for Aging Research, Dychtwald wants a huge infusion in medical research funding for chronic diseases such as Alzheimer's. Barring a scientific breakthrough, more than 14 million men and women could be living with Alzheimer's and related dementias midway through the next century, at a staggering financial and emotional cost. "Let's take a billion dollars and invest it in the neurosciences," he suggests.

It's absolutely "shameful," Dychtwald continues, hands gesturing, voice rising, that today's seniors haven't taken the lead on this issue. Especially since so many are suffering day-to-day with these "horrors of old age." He wonders why they're not marching on Capitol Hill, if not for themselves, then for their children. "Shame on AARP," he says.

For all his soothsaying, Dychtwald does strike out. His Emeryville, Calif., company, Age Wave LLC, has evolved from a research and consulting firm to start its own ventures in publishing and home-delivered foods "nutritionally tailored to the dietary needs of mature adults." Yet two weeks ago, Age Wave Communications filed for Chapter 11 bankruptcy and ceased publication of its monthly Get Up and GO! magazine for the 50-plus set.

"It was a bit of a heartbreak for me," the company chairman concedes. Not that he thinks the magazine was a bad idea, mind you, only a little ahead of its time.

That's the way an optimist spins, and in the end, for all his darker prognostications, Dychtwald is nothing if not an optimist. He's particularly hopeful about the way today's seniors--the true "age pioneers"--are pushing through that once immovable 65 barrier. John Glenn, 78, is the most recent example, of course, but he notes in his book that there are many others. Lena Horne, 82, for one. Alan Greenspan, 73, for another. Or Sean Connery, at 69 named one of the world's sexiest men.

"It will become increasingly in" to be productive when you're old, he enthuses, to be pursuing either a second or third or even fourth career, crusading for causes in the community or serving as elder mentor well into a ninth decade of life.

Indeed, the boomers already are warming up, coming around to the idea of a century's second-half potential, Dychtwald says. He's certainly sold on the possibilities. To his way of thinking, he won't really be old until he's at least 75. "And I hope that by the time I get there it will be 85."

CAPTION: "I can see the challenges that are going to confront this generation and we're not dealing with them," says author Ken Dychtwald.