Spacecraft Tether Reaction Control System
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Solution Overview
Problem
Conventional reaction control systems (RCS) for spacecraft are limited by fuel capacity, are expensive, and toxic, making them inadequate for sustained attitude control during atmospheric re-entry, which requires precise control of angle of attack and deceleration to avoid damage.
Innovation Solution
A tether-based RCS system that generates torque by creating friction at a distance from the axis of rotation, allowing for attitude control through a tether extending from the spacecraft, which can be offset to alter pitch, yaw, and roll, and also serves as a hypersonic parachute to decelerate the vehicle, with a propellant-based system as a backup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reaction control systems (RCS) are used for spacecraft attitude control, then attitude control capability is provided, but the system is limited by fuel capacity, high cost, and toxicity
Solution Approach 1:
The patent replaces the conventional propellant-based mechanical RCS system with an aerodynamic tether system. The tether, when deployed during atmospheric entry, uses aerodynamic drag forces acting at a distance from the spacecraft center of mass to generate torque for attitude control, eliminating the need for carried propellant and associated fuel storage systems.
Solution Approach 2:
The patent introduces the atmosphere as an intermediary medium to provide the reaction force needed for attitude control. Instead of using onboard propellant, the tether interacts with atmospheric molecules to generate drag forces that produce the necessary torques, converting the atmosphere from a harmful factor into a useful resource for control.
2Reliability
If conventional RCS systems are used, then attitude control is achieved, but the system becomes expensive and toxic
Solution Approach 1:
The patent employs a disposable tether system that is deployed only when needed during atmospheric entry. The tether is a simple, inexpensive structure compared to complex propellant systems, and its temporary use eliminates the need for expensive, toxic propellants while providing the necessary attitude control capability.
Solution Approach 2:
The patent converts the harmful effect of atmospheric drag, which normally acts as a source of heating and deceleration, into a useful resource for attitude control. By positioning the tether to experience aerodynamic drag at an offset from the center of mass, the previously harmful drag force becomes the mechanism for generating control torques.
3Speed
If spacecraft re-enters atmosphere at high velocity, then orbital velocity is maintained, but kinetic energy causes vaporization and extreme heating
Solution Approach 1:
The patent applies preliminary aerodynamic braking action during the early phases of atmospheric entry. The tether is deployed to create drag forces that gradually reduce velocity before the spacecraft encounters the denser, hotter regions of the atmosphere, preventing excessive heating and vaporization while maintaining control.
Solution Approach 2:
The patent uses a dynamic tether deployment strategy where the tether length and deployment timing are adjusted during entry. This allows the system to optimize the balance between maintaining orbital velocity for mission requirements and applying sufficient drag to prevent excessive heating, adapting the drag force in real-time during atmospheric passage.
4Reliability
If atmospheric transit occurs over longer period, then flight control improves and aeroheating reduces, but deceleration time increases
Solution Approach 1:
The patent employs dynamic adjustment of tether deployment and retraction to optimize the entry trajectory. By controlling when and how the tether is deployed, the system extends the atmospheric transit time just enough to improve flight control and reduce peak heating, while minimizing the overall deceleration time to meet mission requirements.
Solution Approach 2:
The patent uses periodic deployment and retraction of the tether during atmospheric entry to maintain optimal control authority. This periodic action allows the spacecraft to alternate between phases of tether-based drag control and phases of ballistics, extending control capability while managing the overall deceleration timeline.
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
Enables continuous radio communication and controlled re-entry by avoiding plasma interference and provides a backup for attitude control, reducing thermal and mechanical loads, allowing for a safer and more precise re-entry.
Implementation Method 1
A tether-based RCS system that generates torque by creating friction at a distance from the axis of rotation
Implementation Method 2
generates torque by creating friction at a distance from the axis of rotation
Implementation Method 3
serves as a hypersonic parachute to decelerate the vehicle
Implementation Method 4
This heating causes the plasma 'fireball' that surrounds a reentering spacecraft
Data Source
AI summary
A spacecraft reaction control system comprising: a spacecraft having a center of mass; a length of tether extending from said spacecraft and offset from said spacecraft's center of mass and means for controllably changing said extension of said offset such that a variable force is exerted upon said spacecraft by said tether, said force being offset from said center of mass.