Granted Patent
Utility
US 4,838,021 · App. 07/131,978
Electrostatic ion thruster with improved thrust modulation
Inventor:
John R. Beattie
Patented Case
View Patent ↗
Granted: Jun 13, 1989
Filed: Dec 11, 1987
Inventor
John R. Beattie
Assignee (at issue)
Hughes Aircraft Company
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.