Wunderkind. It is the word that comes to mind when you think of Clarke Simmons. After all, how many 18-year-olds do you know who have just devised a laser system so revolutionary the Army wants to patent it?

Or whose resume is already 23 pages long, mainly to leave room for the more than 50 awards he has received from organizations such as Mobil Oil, Edison Electric, General Motors, the Army, the Navy and the Air Force?

Or who created a solar collection system, for which he has a patent pending, when he was just 15?

Or who will spend his summer studying laser physics, instead of joining his colleagues on the sunny Virginia beaches?

Wunderkind, indeed!

An apt word to describe this young physicist, engineer and inventor, who has spent the last four years traveling around the country picking up award after award for his scientific ingenuity.

The crowning achievement came last week in New York, when Simmons, who graduated from Fort Hunt High School in Fairfax County yesterday, won a four-year, $40,000 college scholarship for his invention, "A Polarizing Retroreflecting Prism." The award, from U.S. Steel and the National Energy Foundation, is the largest prize of its kind ever awarded. Simmons was one of two students, chosen from a nationwide field of 300, awarded the prize.

The technical description of Simmons' invention sounds like something from an Einstein journal: "It beams laser light through a prism and jump combines the principles of the Brewster Window, corner reflector and total internal reflection into a single device," says Simmons, gradually breaking into a smile as he loses the listener.

Dr. Harry Paxton, vice president of research for U.S. Steel and one of the judges of the competition, prefers laymen's terms. "Basically, it's a clever way to increase the versatility in the use of lasers," he says.

The beauty lies in its simplicity. By using a prism, instead of finely ground and specially coated mirrors, to redirect light, Simmons creates a laser system that is more durable, less sensitive and easier to operate than conventional ones. His innovation, if it catches on, will enable more people to take advantage of laser technology because it can be built for a fraction of the cost of standard lasers. The U.S. Army considers Simmons' invention potentially so important that it is preparing a patent application for the system.

"It is a very, very ingenious project for an 18-year-old young man," Paxton says.

Simmons is clearly uncomfortable with such lavish praise. He does not see himself as as a superhuman intellect (he says he had a B average at Fort Hunt), nor does he appreciate the image of himself--easily imaginable--as an egghead who wears horn-rimmed glasses and trips over his slide rule while lost in thoughts not of this world.

"He's not just a walking, talking brain," says his science teacher at Fort Hunt, Thomas Casey. "He does not walk around with his head in a cloud. I'm sure he thinks the $40,000 scholarship is nice, but I just talked to him and he's more interested in the date he has tonight."

Casey says Simmons' success is due not so much to a genius intellect as to "hard work, discipline and an insatiable curiosity."

In fact, Simmons insists, "Some people say I'm a blithering idiot. And the teacher of my introductory law class says that I can't explain my way out of a paper bag.

"My mother thinks I'm crazy because I can't keep my bedroom straight," he says with a sweeping gesture that invites closer observation. Tacked to the closet door is a five-foot computer printout of the colleges he applied to. In the margin to the right, the results are scribbled in bold red letters: "Tulane: yes; Virginia Polytech: yes; Harvard: no; Carnegie-Mellon: yes; Duke: no; Brown: wait-list," and then further to the right "yes!"

The room also supports his contention that he is a perfectly "normal" teen-ager.

There is a bowling trophy next to a radio that pumps out rock music. He takes pride in a series of color photographs he took while working at the U.S. Department of Energy's Solar Energy Research Institute in Golden, Colo., two summers ago. Other memorabilia--equestrian ribbons, riflery medals, high school track awards, a picture of his girlfriend--clutter the room and suggest a childhood spent like any other.

His early interests, Simmons feels, were not so much telltale signs of extraordinary aptitude as typical boyhood diversions. "I've always been interested in building things. I worked in my dad's workshop a lot when I was younger. And I was given a lot of Legos as a kid. I used to build all sorts of things--boats, cars, robots. . . .

" 'Popular Science' Magazine is what really got me into science," he explains, pulling out a copy from the dozens of scientific journals that crowd his bookshelves.

"But working with SOLCHEM," a solar energy research project at the Naval Research Laboratory in Washington, "when I was 14 was when my training in science really took off." His exposure to solar energy at that time spawned the development of "ISEPAC," a device he invented to collect solar power. A patent for the invention is pending.

That, in turn, led to his internship at the U.S. Army Night Vision and Electro-Optics Laboratory at Fort Belvoir, where he developed his award-winning laser system. Since he developed the system while working at the Army lab, the Army will hold the patent on it.

Simmons plans to study laser physics this summer on a scholarship at the Weizmann Institute of Science in Israel, after which he will use his $40,000 prize to work toward a degree in engineering or applied physics.

"But," he says, "I want a broad education in the traditional sense," and he hopes to take courses in the arts and humanities, which he has missed recently because of his obsession with science.

Nor does he visualize himself as a cloistered scientist, immune to the attractions of money or fame. He hopes to carve a niche in the lucrative fields of high technology or architecture and already is planning to earn a graduate degree in business administration.

He realizes his special calling, though, and says, "You have to make a choice. I just hope I can fulfill all the hopes that people have put into me and what I can do with my education."