Hughes System Makes Giant, Improved Satellites Possible—Hughes News November 3, 1967

AIAA Attendees View “Gyrostat Model in Action

Giant satellites with capabilities never before considered possible are on the near horizon, as demonstrated on a model satellite featuring HAC’s new “gyrostat” stabilization system on operation for the first time.

Anthony J. Iorillo, spacecraft dynamics specialist in Space Systems Division, conducted the demonstration during the annual meeting of the American Institute of Aeronautics and Astronautics at the Anaheim Convention Center last week.  He explained how his studies apparently have rendered obsolete a fundamental theory of satellite design.

Like Hatboxes

The theory holds that any spinning satellite would have to be built short and squat and spun—for stabilization—about its major axis.  That is why Mr. Iorillo said, all today’s commercial satellites look like large hatboxes.

Future satellites using the gyrostat concept can be spun about their minor axes and may have some parts spinning while other parts remain stationary with never a wobble in the spacecraft.  This will allow the spacecraft to vary widely in appearance for many varieties of purposes.  It will also assure major performance advantages, among which Mr. Iorillo cited.

• Satellites can be much larger, more powerful, longer lasting, and more  efficient.

• While a portion is spinning for stabilization, important payloads such as antennas, lasers, or telescopes can remain stationary or be moved to point them precisely in any direction.

• Pointing accuracy could be so great that, for example, one antenna could be pointed at New York and another at Los Angeles to provide genuine point-to-point satellite communications for the first time.

• Such satellites could continuously track and relay signals from other satellites or manned space capsules, and carry lasers or telescopes above the earth’s atmosphere, where they would be more effective.

•The new satellites can have elongated configurations and virtually unlimited size.  Since they no longer have to be squat in shape they can use the full volume of a booster shroud for the first time.

The “major axis theorem,” followed by satellite scientists since 1958 until Mr. Iorillo declared himself an unbeliever, stated that any non-rigid free rotating body will end up—as Explorer I did—spinning about the axis of greatest moment of inertia.  In what Mr. Iorillo described as “an oversimplification” such a satellite, after spinning for a while as a top, eventually would start tumbling end over end like a drum major’s baton.

Refutes “Elders”

His studies, started two years ago when he was 27 and completed with his recent delivery of a scientific paper, refute the “elders,” to say the least.  The studies showed that satellites can be designed as multi-spin vehicles and stabilized about their axes of minimum moment of inertia, he reported.  He added that satellites can carry non-rigid payloads in both rotor and despun platforms.

Mr. Iorillo discovered the gyrostat concept during a company-funded analysis of the dynamics of non-rigid elements within nutating dual-spin systems.  He and his associates built a dynamic model 9 feet tall, mounted on a spherical air bearing to provide complete rotational freedom.   They said it verified the concept completely.

How It Works

Mr. Iorillo says “the conclusion is quite simple.”  This in essence is how simple:

“Stability can be assured if the energy dissipation in the rotor (mainly by whip antennas and by fuel sloshing in the tanks) can be compensated for by artificial dissipation introduced on the despun platform.  This is accomplished by an eddy-current nutation damper, a magnet swinging like a pendulum in an induced magnetic field.”

“Thus by making the platform energy dissipation more efficient tha dissipation in the rotor, stability can be preserved.”

Mr. Iorillo received his bachelor’s and master’s degrees, both in aeronautics, from California Institute of Technology.

 Salute to Patent Award Winners Hughes News April 3, 1970

Tony Iorillo

Mr. Iorillo’s invention of the gyrostat principle turned Hughes’ early lead in synchronous communications satellites into a commanding position.  The invention allows a large antenna mounted on a spinning satellite to be aimed and stabilized mechanically by means of a nutation damper.  The present generation of HAC communications satellites is based on this breakthrough, and it is likely that the technique will dominate satellite technology for many years to come.  In addition, it has directly generated several hundreds of dollars worth of business and has substantially enhanced HAC’s competitive position in space.