System and method for managing momentum accumulation

Patent metadata

Field	Value
Publication number	US-9428285-B2
Application number	US-201414461415-A
Country	US
Kind code	B2
Filing date	Aug 17, 2014
Priority date	Aug 17, 2014
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A system for managing momentum accumulation of a spacecraft in orbit may include a reaction wheel assembly for controlling an attitude of a body of a spacecraft, the body defining at least one face, and absorbing momentum, a plurality of arcjet thrusters coupled to the face to generate thrust, and a control processor coupled to the plurality of arcjet thrusters for controlling the thrust, wherein actuation of each arcjet thruster of the plurality of arcjet thrusters is configured to produce a net momentum accumulation in the reaction wheel assembly that is below a momentum saturation point of the reaction wheel assembly.

First claim

What is claimed is:

1. A system for managing momentum accumulation of a spacecraft in orbit, said spacecraft comprising a body defining at least one face, said system comprising:
a reaction wheel assembly for controlling an attitude of said body and absorbing momentum;
a plurality of arcjet thrusters coupled to said face to generate thrust; and
a control processor coupled to said plurality of arcjet thrusters for controlling said thrust, wherein said control processor is configured to:
actuate at least one of said plurality of arcjet thrusters to generate a first thrust, said first thrust generating a first directional component of momentum about an axis of momentum; and
actuate at least two of said plurality of arcjet thrusters to generate a second thrust, said second thrust generating a second directional component of momentum about said axis of momentum opposite to said first directional component of momentum,

wherein a net momentum accumulated in said reaction wheel in response to said first thrust and said second thrust is maintained below a momentum saturation point of said reaction wheel assembly.

2. The system of claim 1 wherein said net momentum is zero.

3. The system of claim 1 further comprising a power conditioning unit coupled to said plurality of arcjets,
wherein said power conditioning unit is configured to control a discrete power level of said each arcjet thruster.

4. The system of claim 3 wherein said plurality of arcjet thrusters comprises:
a first arcjet thruster comprising a first discrete power level controllable by said power conditioning unit; and
a second arcjet thruster comprising a second discrete power level controllable by said power conditioning unit;
wherein said first arcjet thruster and said second arcjet are opposite one another and equidistant from an axis of momentum, and
wherein said first discrete power level and said second discrete power level are defined to balance said net momentum about said axis of momentum.

5. The system of claim 1 wherein said plurality of arcjet thrusters comprises:
a first arcjet thruster comprising a first timing of firing controllable by said control processor; and
a second arcjet thruster comprising a second timing of firing controllable by said control processor,
wherein said first arcjet thruster and said second arcjet are opposite one another and equidistant from an axis of momentum, and
wherein said first timing of firing and said second timing of firing are defined to balance said net momentum about said axis of momentum.

6. The system of claim 5 wherein said plurality of arcjet thrusters further comprises:
a third arcjet thruster comprising a third timing of firing controllable by said control processor; and
a fourth arcjet thruster comprising a fourth timing of firing controllable by said control processor,
wherein said axis of momentum is a first axis of momentum,
wherein said third arcjet thruster and said fourth arcjet thruster are opposite one another and equidistant from a second axis of momentum, and
wherein said third timing of firing and said fourth timing of firing are defined to balance said net momentum about said second axis of momentum.

7. The system of claim 6 wherein said first timing of firing, said second timing of firing, said third timing of firing, and said fourth timing of firing are defined to balance said net momentum about both said first axis of momentum and said second axis of momentum.

8. A method for managing momentum accumulation of a spacecraft in orbit, said method comprising:
actuating, by way of a control processor, at least one of a plurality of arcjet thrusters to generate a first thrust, said first thrust generating a first directional component of momentum about an axis of momentum;
actuating, by way of said control processor, at least two of said plurality of arcjet thrusters to generate a second thrust, said second thrust generating a second directional component of momentum about said axis of momentum opposite to said first directional component of momentum;
accumulating momentum in a reaction wheel assembly in response to said first thrust and said second thrust; and maintaining a net momentum accumulation in said reaction wheel assembly below a momentum saturation point of said reaction wheel assembly.

9. The method of claim 8 further comprising modulating a power level of said plurality of arcjet thrusters by changing said power level of at least one arcjet thruster of said at least two of said plurality of arcjet thrusters to balance said momentum accumulated in said reaction wheel assembly about at least one axis of momentum.

10. The method of claim 8 further comprising modulating a timing of firing of said plurality of arcjet thrusters by at least one of:
changing a firing start time of at least one arcjet thruster of said at least two of said plurality of arcjet thrusters to balance said momentum accumulated in said reaction wheel assembly about at least one axis of momentum;
changing a firing stop time of said at least one arcjet thruster of said at least two of said plurality of arcjet thrusters to balance said momentum accumulated in said reaction wheel assembly about at least one axis of momentum; and
changing a firing duration of said at least one arcjet thruster of said at least two of said plurality of arcjet thrusters to balance said momentum accumulated in said reaction wheel assembly about at least one axis of momentum.

11. The method of claim 8 further comprising:
generating a combined estimate torque resulting from actuation of said plurality of arcjet thrusters required to balance said net momentum accumulation in said reaction wheel assembly; and
determining at least one of a power level and a timing of firing of said plurality of arcjet thrusters to generate said combined torque estimate.

12. The method of claim 11 further comprising:
determining an error represented by a non-zero net momentum accumulation in said reaction wheel assembly; and
refining modulation of at least one of said power level and said timing of firing of said plurality of arcjet thrusters to balance said net momentum accumulation in said reaction wheel assembly.

13. A method for managing momentum accumulation of a spacecraft in orbit, said method comprising:
actuating, by way of a control processor, a first arcjet thruster to generate a first thrust;
increasing momentum accumulated in a reaction wheel assembly in response to a first directional component of momentum about an axis of momentum generated by said first thrust;
actuating, by way of said control processor, a second arcjet thruster to generate a second thrust; and
decreasing said momentum accumulated in said reaction wheel assembly in response to a second directional component of momentum about said axis of momentum generated by said second thrust,
wherein a net momentum accumulation in said reaction wheel assembly is below a momentum saturation point of said reaction wheel assembly.

14. The method of claim 13 further comprising:
operating said first arcjet thruster at a first discrete power level; and
operating said second arcjet thruster at a second discrete power level,
wherein said first discrete power level and said second discrete power level are defined by at least one of a maximum momentum threshold and a minimum momentum threshold about said axis of momentum to balance said net momentum accumulation about said axis of momentum.

15. The method of claim 14 further comprising setting said second discrete power level to be higher than said first discrete power level when a first

Assignees

• Boeing Co

Inventors

• Mansour Sadek W
• Haskell John D
• Mactavish Andrew I

Classifications

• B64G1/26 Primary

  using jets · CPC title

• B64G1/2425

  Geosynchronous orbits · CPC title

• B64G1/2429

  Station keeping · CPC title

• B64G2001/245

  Operations & Transport · mapped topic

• B64G1/283

  using reaction wheels · CPC title