Thrust Modulation in Solid Propellant Engines via Fluid Injection
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Solution Overview
Problem
Solid propellant engines for spacecraft landers require continuous and adjustable thrust with high amplitude, rapid modulation, and low size, complexity, and cost, but existing technologies are complex and expensive due to the need for precise valve control in hot combustion gases, and hybrid propulsion systems suffer from low density and volume performance.
Innovation Solution
A method using a solid propellant with a high pressure exponent, where thrust is modulated by injecting a fluid into the combustion chamber, controlling combustion and thrust without valve means, using low molar mass components like hydrogen or helium, and oxidizing components like nitrous oxide, to adjust pressure and temperature, thereby controlling the flow rate and thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If valve means are used to control thrust in solid propellant engines, then thrust modulation is achieved, but device complexity and cost increase due to precise positioning requirements in hot combustion gases
Solution Approach 1:
The invention extracts and removes the valve means from the thrust control system. Instead of using valves to modulate thrust, the patent uses a solid propellant grain whose geometry is designed to automatically provide the desired thrust profile through its combustion surface evolution. This eliminates the complex valve positioning system required in conventional approaches.
Solution Approach 2:
The propellant grain is designed to be self-regulating through its geometry. The combustion surface area naturally evolves during burning to provide the required thrust modulation without external control. The grain shape is predetermined to achieve the desired thrust-time profile, making the system self-service and eliminating the need for active valve control.
2Measurement precision
If multiple gas valve means are used for thrust modulation, then precise thrust control is achieved, but cost increases proportionally with the number of nozzles
Solution Approach 1:
The single solid propellant grain performs multiple functions: it provides thrust generation and simultaneously provides thrust modulation through its geometric design. The grain geometry is universally designed to control the combustion surface area evolution, thereby controlling thrust for multiple nozzles or a single nozzle without requiring separate valve means for each.
Solution Approach 2:
The invention merges the thrust generation function and thrust modulation function into a single integrated system - the solid propellant grain. Instead of separate valves for each nozzle, the grain's combustion characteristics are designed to naturally modulate thrust across all nozzles simultaneously, reducing the number of control elements.
3Power
If solid propellant engines are used for spacecraft landers, then high thrust in small dimensions is achieved, but thrust modulation requires complex valve control in hot combustion gases
Solution Approach 1:
The invention extracts the valve control system from the solid propellant engine design. By removing the valves, the patent eliminates the complexity associated with positioning control in hot combustion gases while maintaining the high thrust density characteristic of solid propellant engines through optimized grain geometry.
Solution Approach 2:
The invention replaces the mechanical valve control system with a geometrically-designed propellant grain. Instead of using mechanical valves to modulate thrust in hot gases, the grain shape is predetermined to provide the desired thrust profile through its combustion surface evolution, substituting a passive geometric solution for an active mechanical control system.
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
This approach allows for continuous and adjustable thrust with high amplitude modulation, reducing complexity and cost, and achieving efficient thrust control suitable for braking and positioning of spacecraft landers, with a simple and modular device design.
Implementation Method 1
the self-combustion of a solid propellant charge in a combustion chamber of a propellant, and the ejection of the gases generated by this self-combustion
Implementation Method 2
it is necessary to modify the pressure in the combustion chamber to increase or decrease the propellant combustion rate
Implementation Method 3
the law of combustion speed of a propellant, known as the Paul Vieille law, can be written in the form: where Vc is the propellant combustion speed in mm/s P the combustion chamber pressure in MPa has the pressure coefficient n the pressure exponent
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to: - a continuous-thrust pyrotechnic propulsion method with thrust modulation, comprising: + the combustion of a solid propellant charge (11) in the combustion chamber (7) of a propellant (8), and + the ejection of the gases generated by said combustion, and further comprising the injection, on demand, of at least one fluid (G and/or L) into said combustion chamber (7); said injection ensuring, at least in part, advantageously on its own, the control of the combustion of said propellant charge and, consequently, said thrust modulation; - devices suitable for implementing said method; - a spacecraft including in its structure at least one such device.