Movable Thermal Choke Rocket Nozzle for Altitude Thrust
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Solution Overview
Problem
Rocket propulsion systems face a conflict between achieving high thrust at sea level and high specific impulse at high altitude due to the need for a nozzle with a high area ratio, which results in reverse pressure differential and reduced thrust at low altitudes, and existing solutions complicate engine construction and performance.
Innovation Solution
A rocket engine with a single chamber and fixed geometry featuring a thermal choke point that moves along the engine axis, created by injectors on the internal wall, allowing the thermal choke area ratio to vary as the vehicle ascends, maintaining exit static pressure near ambient pressure and optimizing thrust and specific impulse across environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a nozzle with high area ratio is used to achieve high specific impulse at high altitude, then specific impulse is improved, but thrust at sea level deteriorates due to reverse pressure differential
Solution Approach 1:
The patent implements a movable thermal choke that dynamically adjusts the effective throat area of the nozzle during flight. At sea level, the thermal choke is positioned to reduce the throat area, preventing excessive expansion and reverse pressure differential. As the vehicle ascends to high altitude, the thermal choke moves to increase the throat area, enabling high specific impulse. This dynamic adjustment resolves the contradiction between sea level thrust and high altitude specific impulse.
Solution Approach 2:
The patent changes the thermal parameters (temperature and pressure distribution) within the nozzle by introducing coolant flow that creates a thermal choke. This thermal choke effectively changes the throat area parameter without mechanical movement of solid parts. By controlling the thermal field, the nozzle adapts its effective geometry to match ambient pressure conditions, simultaneously achieving high thrust at sea level and high specific impulse at altitude.
2Adaptability or versatility
If variable exit area nozzle is used to adapt to different altitudes, then performance across environments is improved, but device complexity and weight increase
Solution Approach 1:
The patent replaces complex mechanical variable geometry mechanisms (such as movable nozzle flaps or telescoping sections) with a thermal field-based solution. The thermal choke is created by injecting coolant that forms a low-pressure region, effectively creating a virtual throat boundary through thermal and pressure gradients rather than mechanical structures. This substitution dramatically reduces device complexity and weight while maintaining adaptability across different altitude environments.
Solution Approach 2:
The patent introduces coolant flow as an intermediary substance that mediates between the combustion chamber and the nozzle expansion section. This coolant creates the thermal choke boundary without requiring direct mechanical interaction or complex moving parts. The intermediary coolant flow enables smooth, continuous adjustment of the effective throat area, simplifying the overall engine construction compared to discrete mechanical adjustment mechanisms.
3Ease of operation
If multiple pintle injectors are used to control combustion process, then throttling capability is improved, but device complexity and weight increase
Solution Approach 1:
The patent makes the single thermal choke mechanism serve multiple functions: it controls both the thrust magnitude and the effective nozzle area ratio simultaneously. Instead of requiring separate control systems (multiple injectors for throttling, separate mechanisms for area ratio adjustment), the thermal choke position and intensity are controlled by a single coolant flow parameter, providing universal control over engine performance across different flight conditions.
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 engine achieves significantly higher sea-level thrust and improved specific impulse at altitude, with thrust at sea level being three times higher and specific impulse 3.5% higher than conventional designs, while maintaining performance in vacuum environments.
Implementation Method 1
a thermal choke point that moves along the engine axis in the direction of the forward end of the engine as the vehicle climbs and progresses from a high-pressure environment to a low-pressure environment. The thermal choke point is created by injectors in the internal wall of the engine
Implementation Method 2
The plane in which the thermal choke point resides acts as a thermal throat
Implementation Method 3
maintaining exit static pressure near ambient pressure and optimizing thrust and specific impulse across environments
Implementation Method 4
the expansion caused by a high area ratio produces an internal pressure at the nozzle wall near the nozzle exit that is below the external (atmospheric) pressure
Data Source
AI summary
High thrust at sea level and high Isp at high altitudes with low ambient pressure are obtained in a vehicle with an engine of fixed geometry including an exit of non-changing cross section, by incorporating a series of propellant injectors in a divergent section of the engine, spaced apart along the engine axis at points of different engine cross section. At takeoff, the injectors at sites with a large cross section are used, and as the vehicle climbs, these injectors are successively closed leaving injectors activated at sites of successively smaller cross sections. The injectors establish thermal choke points, and the area ratio of the cross section at the exit to the cross section at the thermal choke point thus increases as the vehicle climbs from low to high altitudes.