A warning klaxon sounds. Slowly, the centrifuge begins to spin. It looks like a giant arm swinging a fist. Closed-circuit TV shows a picture of the volunteer strapped in the capsule. Little of his face is visible through the tangle of helmet and mask. As speed increases, sheer force snaps the eyes into slits, and skin seems to flatten and flutter with strain.
Then, just as orbit seems inevitable, power is cut and the machine coasts to a stop. ``He made it to about 8.9 G,'' says Carter Alexander, a crew technology chief here at the Air Force's Human Resources Division.
That means the hapless spinning subject felt almost nine times heavier than normal - all in the name of understanding the stresses of aerial combat.
With such experiments, Air Force scientists are rushing work on the growing problem of blacking out in flight. Modern fighters are so nimble they subject pilots to unprecedented strain, causing between 30 and 60 cases of G-induced lost consciousness every year.
``The planes are ahead of the crew in some senses,'' says Lt. Col. Mark Massen, director of Advanced Life Support Systems.
The F-16, for instance, can subject its pilot to a force of 9 Gs in a second and a half. It could produce even more - but a G-limiting mechanism prevents the plane from turning any tighter.
Of course, G-forces have long been a pilot problem. As early as World War II, pilots were taught to ease up on turns when centrifugal strain narrowed their vision.
G-suits have been a staple piece of flight clothing for decades. Basically inflatable tubes wrapped around the legs and stomach, they automatically fill with air in tight turns, squeezing the body to keep blood from rushing to a pilot's feet.
By wearing G-suits and clenching their stomach muscles, pilots today can withstand a few 9-G maneuvers with few ill effects. Beyond that is largely unexplored territory. This is a fact of fighter pilot life which glamorous movies and TV shows tend to neglect.
Tactical Air Command, the fighter division of the Air Force, has made extra G protection a top priority. So the Air Force's Human Resources Division here is in the middle of a crash program to develop a new protective tunic and mask. Called ``Combat Edge,'' the equipment should be ready for all F-15 and F-16 pilots by the end of 1991, officials here say. A normal pace of development would have postponed the advent of the new system until the mid-1990s at the earliest.
Combat Edge will be in essence an extension of today's G-suit. It consists of a pressurized tunic and helmet, both intended to aid pilot breathing in high-stress conditions. It won't enable pilots to withstand more than 9 Gs. But it will allow them to make many more 9-G manueuvers than they can withstand in current clothing.
Taking pilots beyond 9 Gs will require changes in such things as cockpit design, Dr. Alexander says. A pilot who is lying down can withstand much more force than one sitting up, for instance.
``The optimum cockpit would be a reclined seat,'' he says.
Such a seat may be part of the next-generation aircraft, the Advanced Tactical Fighter, now under development. In 10 years Air Force scientists also hope to have pilots outfitted in a sort of semi-space suit, a version of today's flight overalls that incorporates many new G-suit features.
There is one large problem with this work. Pilots are a style-conscious lot - and several admit that they want to make sure any new garment looks good when lounging around the operations center.