[2] He formed and led the team that designed and built the first geosynchronous communications satellite, Syncom, for Hughes Aircraft Company.
[4] Because at that time international telephony was very expensive and hard to arrange, and transoceanic television was impossible, he decided it should be some kind of communication satellite since these problems could be solved that way.
He gathered a small team of gifted colleagues (most notably, Don Williams, Tom Hudspeth and John Mendel) to convert the concept into a design for a practical geostationary communication satellite system.
[3] When his superiors initially refused to fund the project, Rosen began talking to his contacts at Raytheon; rather than lose him to his previous employer, Hughes' management agreed to support prototype development.
With communication satellites a commercial reality, Hughes formed a division to pursue this as a business, and Rosen became its technical director.
In these roles he was key in helping to build the world's largest communications satellite business at Hughes Aircraft Company.
They developed a gas turbine-powered series hybrid automotive powertrain using a 55,000 rpm flywheel energy storage subsystem to provide bursts of acceleration to augment the turbine's more steady power output.
The flywheel was composed of a titanium hub with a carbon fiber cylinder and was gimbal mounted to minimize adverse gyroscopic effects on vehicle handling.
[7] Rosen died at his home the Pacific Palisades neighborhood of Los Angeles on January 30, 2017, due to complications from a stroke, aged 90.