To calibrate the senses when politics and technology converge to rev up support for multibillion-dollar schemes, it is useful to contemplate an episode from the go-go days of the Cold War: the little-remembered, but very serious, 15-year-long attempt to build a nuclear-powered airplane.

A look back is pertinent at this time because technological monumentalism has special charms in times of crisis -- witness John F. Kennedy's moon-landing goal as an immediate diversion from the Bay of Pigs fiasco and Richard Nixon's sudden declaration of a "War on Cancer" to preempt Sen. Edward Kennedy's becoming the champion of that disease. Today, some of the spiritual adherents of technology as a national tranquilizer are off and running with pitches that range from an ill-conceived crash program for synthetic-fuel plants to revival of the B1 bomber. There are those who want to build vast mirrors in space to beam solar energy to earth and, beyond that, there's high-technology's "destiny" cult, rattling the cup for a few billions to get moving on the establishment of human space colonies.

These self-proclaimed new-era missionaries find it useful to dredge up long-ago cases of otherwise sage non-prophets who proclaimed the impossibility of powered flight, nuclear weapons and intercontinental missiles. But the present dilemma in choosing among big technologies that are soundly based on scientific knowledge isn't whether something can be done. Engineering has become so sophisticated and inventive that doability is not often the issue, even in the realm of some crackpot proposals. Rather, the issue is desirablility and, from that perspective, the nuclear-plane project of 1946-1961 provides a swell case study of technological intoxication long triumphing over common sense.

Conceived by the Air Force and quickly embraced by the newly established Joint Congressional Committee on Atomic Energy, the nuclear airplane characteristically commenced as one of those modest "let's-just-take-a-look" research projects. Five years later, however, it got sanctified as a research and development project, which is important in the growth patterns of these things, because research is relatively cheap, while development means big and expensive engineering work.

The Joint Chiefs certified a military "requirement" for the plane; the Air Force followed by assigning the project a high priority for talent and money, and General Electric was awarded a contract for designing and building the airborne nuclear engines. All of this came under the direction of an Office for Aircraft Nuclear Propulsion, with $150 million a year at its disposal in the mid-1950s. This sum, incidentally, was about seven times the amount the U.S. government then spent on cancer research.

Thus, within a few years after its founding, the nuclear-airplane project possessed the essentials of political success -- powerful congressional patrons, an executive branch bureaucracy of its own and industrial constituents.

What it lacked -- given the fact that the tonnage of its lead-shielded reactor would never permit it to go high, fast or near populated areas -- was any sensible purpose, as was observed by then-defense secretary Charles E. Wilson: "The atomic-powered airplane reminds me of a shite-poke -- a great big bird that flies over the marshes, that doesn't have too much body or speed to it, or anything, but can fly."

Support was being displaced first by puzzlement over the indisputable lunacy of seeking to power an airplane in this fashion, and then by outright disfavor. But the proponents knew how to respond. Congressional supporters hurried over to Russia and returned with reports -- never substantiated -- that a Soviet nuclear airplane would soon make its maiden flight. Meanwhile, the Navy got behind the Air Force, for the price of being cut into the show with a project for a nuclear seaplane. And so the program went on, even with Dwight Eisenhower complaining that "the whole program would be to get a plane a few hundred feet off the ground."

When Kennedy came to office, the nucelar-powered airplane project was no more airworthy than a battleship, despite expenditures totaling about $1.5 billion. Advocates of the project confidently asserted that, with another $1.5 billion, they'd be ready to go aloft in 10 years. Whereupon the new administration turned off the money, and the bizarre enterprise to achieve nuclear-powered flight was abruptly terminated.

The lesson of this is not to shun grand undertakings; the United States, with its continental scale and diversity of scientific and engineering institutions, is very good at doing big things. Rather, the task in the new decade is to pick and choose carefully among many possibilities -- a task that calls for navigating between penny-pinching technological timidity and technological megalomania, as typified by the nuclear airplane.