After retiring from the Navy in 1960 Stefan went to work for the University of Minnesota as technical director of their wind tunnel laboratories.
In 1963 he joined the Mechanical Division of General Mills and managed a team of engineers and technicians in the design, manufacture, and operation of stratospheric balloon systems and associated instrumentation.
In 1965 Stefan assumed responsibilities with the National Center for Atmospheric Research, Boulder, Colorado, for research and development programs involving advance ballooning concepts for scientific applications. His many activities included design and test of stratospheric balloon problems, thermal and aerodynamic analysis services for balloon borne packages, and supervision of major ballooning projects. These programs included Project Stratoscope, a joint effort of NASA, Princeton University, and the National Center for Atmospheric Research.
Both his post-graduate work and later employment at the University of Minnesota brought Stefan in contact with Don Piccard and other aeronauts interested in balloon flight. It would be these contacts that would result in his involvement in lighter-than-air flight and close connection to research and design of hot air balloons and gas airships.
In 1964 Stefan worked closely with Tracy Barnes on Barnes’ altitude record flight in an AA-3 gas balloon to 11,780 meters—a record that still stands.
In 1971 Stefan would establish his own altitude world record piloting a hot air balloon. He received the FAI’s highest honor, Montgolfier Diploma, in 1972 for the flight.
In 1973 Stefan with Tracy Barnes and Dodds Meddock formed The Balloon Works to manufacture and sell sport balloons. Stefan handled engineering and FAA certification. The Balloon Works entry into sport ballooning with low cost balloons helped to ignite the market for ballooning.
With growing interest in ballooning Stefan became an active member of the Balloon Federation of America. His interest in competition lead him to chair of the BFA Events Committee. In the late 1970s Stefan was elected by the Balloon Federation of America as the organization’s representative to the Committee Internationale Aerostation (the ballooning committee of the FAI).
In 1985 Stefan was elected President of the CIA, a position that he held for ten years. From this position he over saw much of the development and international rule making for the sport of ballooning.
In 1978 Stefan participated in the formation of U.S. Airships, Inc., and served as the technical director. He prepared designs for larger airships intended for advertising applications.
In 1980 Stefan joined ILC Dover where he contributed to conceptual and practical development of flexible structures, including balloons and airships and Shuttle space suits.
In 1987 Stefan moved to Colorado and established his consulting company, Stefan LTA, Inc. He has written more than 14 technical papers on lighter-than-air subjects.
Mr. Stefan holds licenses as instrument rated commercial pilot for single and multi- engine aircraft and rotorcraft, and for free balloons. He holds positions with the Federal Aviation Administration as a Designated Engineering Representative with engineering approval authority for balloons. He is an active member of the Balloon Federation of America and continues to serve as chair for the CIA’s Records Review subcommittee. He is currently a “President of Honor” of the CIA committee of the FAI.
Karl Stefan, for more than 50 years, has made contributions of significant value to aeronautics and has reflected credit upon America and himself.