Spacecraft Solar Sail Attitude Control via Robotic Arm

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Solution Overview

Problem

Existing methods for spacecraft attitude control and momentum desaturation, such as using magnetorquers or thrusters, are either ineffective in the absence of a strong ambient magnetic field or require propellant, which is limited and costly to transport.

Innovation Solution

A solar sail attitude control module comprising a reflective surface for reflecting solar photons and a robotic arm with at least 4 degrees of freedom to position and orient the solar sail, generating a torque opposing excess momentum in the reaction wheels without propellant consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magnetorquers are used to unload momentum, then momentum desaturation is achieved, but the method is ineffective when a strong ambient magnetic field is not available

Engineering Contradiction:

Improvemomentum desaturation capabilityVSAvoidenvironmental adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a solar sail as an intermediary device that couples the spacecraft to the solar radiation field. The solar sail acts as a mediator that transfers momentum from the spacecraft's reaction wheels to the solar photons, enabling momentum desaturation without requiring direct interaction with ambient magnetic fields or consumption of propellant.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the electromagnetic interaction mechanism (magnetorquers interacting with magnetic fields) with a mechanical/optical interaction mechanism (solar sail reflecting solar photons). This substitution eliminates the dependency on ambient magnetic fields while maintaining the momentum desaturation function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If thrusters are used to generate torque for momentum unloading, then momentum desaturation is achieved, but propellant is consumed which is limited and costly to transport

Engineering Contradiction:

Improvemomentum desaturation capabilityVSAvoidpropellant consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The solar sail system is self-service in that it utilizes the abundant solar radiation field as its energy and momentum source. The spacecraft itself, through the solar sail, provides the mechanism for momentum exchange without requiring external propellant supply or consumable resources, thereby eliminating propellant loss.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the fundamental parameter of momentum exchange from chemical propulsion (thrusters consuming propellant) to radiative propulsion (solar sail reflecting photons). This parameter change transforms the system from one that depletes finite resources to one that harnesses continuous external energy.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If reaction wheels are used for attitude control, then precise attitude control is achieved, but excess momentum builds up over time requiring regular unloading

Engineering Contradiction:

Improveattitude control precisionVSAvoidoperational duration before desaturation needed

Core Design Contradiction:

Measurement precisionVSDuration of action of moving object

Solution Approach 1:

The solar sail enables continuous momentum desaturation operations, allowing the reaction wheels to maintain precise attitude control without interruption. By providing an ongoing mechanism for momentum unloading, the system ensures that the reaction wheels can continuously perform their useful function of precise attitude control without being limited by momentum saturation.

Inventive Principle:

Principle #20Continuity of useful action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solar sail system enables propellant-free attitude control and momentum desaturation, effectively managing excess momentum and maintaining spacecraft stability without the need for propellant, thereby reducing operational costs and extending spacecraft lifespan.

Implementation Method 1

at least one solar sail comprising a reflective surface for reflecting solar photons

Methodology Applied

Scientific EffectRadiation pressure: Radiation Pressure

Implementation Method 2

at least one solar sail comprising a reflective surface for reflecting solar photons

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12202629B2Apparatus and methods for spacecraft attitude control using a solar sail

Publication Date: 2025.01.21 CANADIAN SPACE AGENCY

AI summary

An attitude control module is described for providing propellant-free attitude control and momentum desaturation to a spacecraft. The attitude control module includes at least one solar sail comprising a reflective surface for reflecting solar photons; and at least one robotic arm coupled to the at least one solar sail, said at least one robotic arm comprising at least 4 degrees of freedom for positioning and orienting the at least one solar sail relative to the spacecraft. A corresponding method for operating the attitude control module to unload excess momentum from a spacecraft is also described.