Richard P Hofer

US Patent:

8143788, Mar 27, 2012

Filed:

Aug 30, 2008

Appl. No.:

12/202252

Inventors:

Richard R. Hofer - Monrovia CA, US
Dan M. Goebel - Tarzana CA, US
Ronnie M. Watkins - Oro Valley AZ, US

Assignee:

California Institute of Technology - Pasadena CA

International Classification:

H01J 17/06

US Classification:

313618, 31511181

Abstract:

An apparatus and method for achieving an efficient central cathode in a Hall effect thruster is disclosed. A hollow insert disposed inside the end of a hollow conductive cathode comprises a rare-earth element and energized to emit electrons from an inner surface. The cathode employs an end opening having an area at least as large as the internal cross sectional area of the rare earth insert to enhance throughput from the cathode end. In addition, the cathode employs a high aspect ratio geometry based on the cathode length to width which mitigates heat transfer from the end. A gas flow through the cathode and insert may be impinged by the emitted electrons to yield a plasma. One or more optional auxiliary gas feeds may also be employed between the cathode and keeper wall and external to the keeper near the outlet.

US Patent:

8407979, Apr 2, 2013

Filed:

Oct 29, 2007

Appl. No.:

11/926279

Inventors:

Richard R. Hofer - Monrovia CA, US

Assignee:

The United States of America as Represented by the Administrator of the National Aeronautics and Space Administration - Washington DC

International Classification:

F03H 3/00

US Classification:

60202

Abstract:

The invention is a Hall thruster that incorporates a discharge chamber having a variable area channel including an ionization zone, a transition region, and an acceleration zone. The variable area channel is wider through the acceleration zone than through the ionization zone. An anode is located in a vicinity of the ionization zone and a cathode is located in a vicinity of the acceleration zone. The Hall thruster includes a magnetic circuit which is capable of forming a local magnetic field having a curvature within the transition region of the variable area channel whereby the transition region conforms to the curvature of the local magnetic field. The Hall thruster optimizes the ionization and acceleration efficiencies by the combined effects of the variable area channel and magnetic conformity.

US Patent:

20140053531, Feb 27, 2014

Filed:

Feb 15, 2013

Appl. No.:

13/768788

Inventors:

Dan Michael Goebel - Tarzana CA, US
Richard Robert Hofer - Monrovia CA, US
Ioannis G. Mikellides - Valencia CA, US

Assignee:

California Institute of Technology - Pasadena CA

International Classification:

F03H 1/00

US Classification:

60202

Abstract:

A Hall thruster apparatus having walls constructed from a conductive material, such as graphite, and having magnetic shielding of the walls from the ionized plasma has been demonstrated to operate with nearly the same efficiency as a conventional non-magnetically shielded design using insulators as wall components. The new design is believed to provide the potential of higher power and uniform operation over the operating life of a thruster device.

US Patent:

20160333866, Nov 17, 2016

Filed:

Jul 25, 2016

Appl. No.:

15/218682

Inventors:

- PASADENA CA, US
Richard Robert HOFER - Monrovia CA, US
Ioannis G. MIKELLIDES - Valencia CA, US

International Classification:

F03H 1/00
B64G 1/40

Abstract:

A Hall thruster apparatus having walls constructed from a conductive material, such as graphite, and having magnetic shielding of the walls from the ionized plasma has been demonstrated to operate with nearly the same efficiency as a conventional nonmagnetically shielded design using insulators as wall components. The new design is believed to provide the potential of higher power and uniform operation over the operating life of a thruster device.