Alexander Kossiakoff, 91, who helped develop the Navy's first guided missiles and who directed Johns Hopkins University's Applied Physics Laboratory, died of congestive heart failure Aug. 6 at Montgomery General Hospital. He lived in Brookeville.

Dr. Kossiakoff spent nearly 60 years as a scientist, director and academic innovator at the Applied Physics Laboratory, one of the country's leading centers of research on military technology, space science and engineering.

His first project at the laboratory, undertaken early in 1946, was to manage the laboratory's Bumblebee program to develop missiles for the Navy to guard against airborne attacks on ships. The project -- so named because, aerodynamically, a bumblebee should not be able to fly -- resulted in the development of the Terrier, Tartar and Talos radar-guided supersonic missiles.

Dr. Kossiakoff helped devise the technology for the solid rocket fuel that enabled the missiles to launch. In later years, he guided the laboratory's research in radar, air defense systems, communications, submarines, space science and spacecraft.

"Dr. Kossiakoff was curious about the nature of the universe and the world around him, and he also cared a great deal about people," said Sam Seymour, an Applied Physics Laboratory administrator who worked with Dr. Kossiakoff for more than 30 years. "He was a brilliant problem-solver who loved to take on some of the most difficult problems and apply systems engineering principles to their solution."

From 1969 to 1980, Dr. Kossiakoff was director of the laboratory, which was founded in Silver Spring in 1942 and is based on 360 acres in Laurel.

"His greatest achievement was to build a lab that evolves with the times and has scientific integrity," said his son, Anthony Kossiakoff, chairman of the biochemistry department at the University of Chicago. Among his other scientific achievements, Dr. Kossiakoff developed the engineering concept of sectionalization, in which the various functions of a larger system or machine were isolated within a series of smaller subsystems. If one element failed, it would not shut the entire system and could be repaired more easily.

After stepping down as the laboratory's director in 1980, Dr. Kossiakoff stayed on as the laboratory's chief scientist for 25 more years, devoting much of his time to expanding its educational offerings. He instigated and designed the curriculums for master's degree programs in technical management and systems engineering that now enroll more than 700 students. He published two books, the first in 1938 and the second -- a 400-page graduate-level textbook on systems engineering -- last year, when he was 90.

"He was active every day in the laboratory, and in particular in education," Seymour said. "He came to work every day until the last few weeks."

Dr. Kossiakoff was born June 26, 1914, in St. Petersburg, Russia. His father was an officer in the czar's White Russian army and was forced to flee his homeland after the communist revolution of 1917. The family escaped on the next-to-last train to leave Siberia, said Dr. Kossiakoff's son, and lived for six years in Hankou, China, before settling in Seattle in 1923.

Dr. Kossiakoff graduated in 1936 from the California Institute of Technology and received a doctorate in chemistry from Johns Hopkins in 1938. He then returned to Caltech for a year of postdoctoral study under future Nobel laureate Linus Pauling.

From 1939 to 1942, Dr. Kossiakoff taught at Catholic University before joining the National Defense Research Committee, a presidential panel studying military preparedness. From 1944 to 1946, he worked at the Allegheny Ballistics Laboratory at George Washington University, where he developed his first solid-propellant rockets, an advance that led to his later designs for Navy missiles.

At the Applied Physics Laboratory, Dr. Kossiakoff was assistant director for technical operations from 1948 to 1961, then was associate and deputy director before taking the top position. Throughout his tenure, he served on various government panels and scientific advisory councils.

He had two patents on radar systems and received many awards for his scientific work. In 1981, the Department of Defense awarded him its highest civilian honor, the Medal for Distinguished Public Service. He also received the Navy's Distinguished Public Service Award and the Presidential Certificate of Merit. The laboratory's conference and education center is named in his honor, and in 2004 Dr. Kossiakoff was awarded the President's Medal from Johns Hopkins.

Besides his son, of Chicago, survivors include his wife of 66 years, Arabelle Kossiakoff of Brookeville; a daughter, Tanya Schmieler of White Oak; and five granddaughters.

"Probably the country will never again see the quality of genius and dedication that scientists like Dr. Kossiakoff had," Seymour said, adding that his colleague possessed the same qualities as great scientific thinkers of the past: "deep technical knowledge, immense curiosity, tremendous breadth of experience and, finally, inordinate dedication to the problem at hand."

Alexander Kossiakoff was director of Johns Hopkins University's Applied Physics Laboratory.