While the secrecy involved in Air Force flights has protected the service from the kind of notoriety dogging the National Aeronautics and Space Administration over the shuttle's assorted difficulties, the service has also had problems launching satellites.

Last August, for example, a secret KH11 photo-intelligence satellite, said to be worth nearly $800 million, was lost in the explosion of an Air Force Titan 34D booster rocket carrying it into orbit from Vandenberg Air Force Base, Calif., according to congressional and military sources.

A four-month Air Force accident investigation, according to sources, failed to pinpoint the cause of the explosion. As a result, all the remaining Titan 34D missiles were reexamined, but remained certified for use.

"The rocket business is an imperfect one," a top former Pentagon scientist said recently. "Some satellites are going to be lost."

The Atlas and Titan 34D launchers, according to this source, have been running at about 85 percent reliability. The National Aeronautics and Space Administration's Delta rocket, which has a record of 94 percent reliability, is considered exceptional.

The KH11 satellite is able to maneuver over the Soviet Union and take clear pictures of small objects on Earth. It orbits as high as 300 miles above the surface and beams back high-quality television pictures, as well as other data.

The first in a series of KH11s was launched in late 1976. At present there is one in space, sources said. The KH11 that was destroyed on launch last year was supposed to be the last of the system, but one source said a spare is being modified into an operational satellite to replace the one that was destroyed.