Liquid Monopropellant Injection for Solid Rocket Motor Control

Solution Overview

Problem

Solid rocket motors face challenges in maximizing specific impulse and controlling operational parameters due to the weight and cost associated with solid propellant cases that need to handle high pressure and temperature, while existing solutions do not effectively utilize monopropellants for efficient burn rate control and thrust management.

Innovation Solution

Incorporating a monopropellant source to enhance specific impulse, control burn rate, and manage operational parameters by using techniques such as dP/dt extinguishment, deluge extinguishment, and pulsed operation, which allows for throttling and dynamic control of thrust vector and roll, and regenerative cooling of the nozzle and throat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If solid propellant is used in the solid rocket motor, then the motor can generate thrust, but the case weight increases due to high pressure and temperature handling requirements

Engineering Contradiction:

ImprovethrustVSAvoidcase weight

Core Design Contradiction:

ForceVSWeight of moving object

Solution Approach 1:

The propellant system is segmented into two distinct components: solid propellant for thrust generation and liquid monopropellant for control functions. This segmentation allows each component to be optimized independently, with the solid propellant confined to a smaller grain structure and the monopropellant handling pressure/temperature control, thereby reducing overall case weight requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the physical state parameters by introducing liquid monopropellant that can be injected in controlled amounts to modify combustion chamber pressure and temperature dynamically. This parameter control allows the case to operate at lower peak pressures and temperatures compared to traditional solid-only motors, reducing the weight requirements for pressure containment

Inventive Principle:

Principle #35Parameter changes

2Force

If solid propellant is used in the solid rocket motor, then the motor can generate thrust, but the cost increases due to high pressure and temperature handling requirements

Engineering Contradiction:

ImprovethrustVSAvoidmanufacturing cost

Core Design Contradiction:

ForceVSEase of manufacture

Solution Approach 1:

The propellant system is segmented into two distinct components: solid propellant for thrust generation and liquid monopropellant for control functions. This segmentation allows each component to be optimized independently, with the solid propellant confined to a smaller grain structure and the monopropellant handling pressure/temperature control, thereby reducing overall case weight requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the physical state parameters by introducing liquid monopropellant that can be injected in controlled amounts to modify combustion chamber pressure and temperature dynamically. This parameter control allows the case to operate at lower peak pressures and temperatures compared to traditional solid-only motors, reducing the weight requirements for pressure containment

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If monopropellant is used to control burn rate and thrust, then operational control is improved, but the device complexity increases

Engineering Contradiction:

Improveoperational controlVSAvoiddevice complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The monopropellant system is designed to be self-contained with onboard storage tanks and injection valves that automatically control the flow of monopropellant to the combustion chamber. The system uses the exothermic decomposition of the monopropellant itself as both the control mechanism and the cooling medium, eliminating the need for external cooling systems or complex control infrastructure

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The liquid monopropellant serves multiple functions simultaneously: it acts as a burn rate controller by modulating combustion chamber pressure, provides regenerative cooling to the nozzle and combustion chamber, and enables thrust vector control through selective injection points. This multi-functionality reduces the need for separate systems for each function, thereby limiting the increase in overall device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Use of energy by moving object

If more monopropellant is used to maximize specific impulse, then propulsion efficiency is improved, but the tank design becomes more challenging

Engineering Contradiction:

Improvespecific impulseVSAvoidtank design

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The monopropellant storage tanks utilize flexible bladder designs that can be collapsed as propellant is consumed, maintaining structural integrity without requiring heavy rigid walls. These flexible membranes are reinforced at critical stress points and work in conjunction with the ambient pressure of the rocket vehicle to minimize tank wall thickness while maximizing propellant volume

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The monopropellant system is designed to be self-contained with onboard storage tanks and injection valves that automatically control the flow of monopropellant to the combustion chamber. The system uses the exothermic decomposition of the monopropellant itself as both the control mechanism and the cooling medium, eliminating the need for external cooling systems or complex control infrastructure

Inventive Principle:

Principle #25Self-service

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 use of monopropellants enables lightweight, cost-effective control of solid rocket motor operations, maximizing mass fraction and specific impulse, while reducing the weight and cost of the propellant case, and allowing for flexible thrust management and efficient cooling.

Implementation Method 1

the monopropellant gasifies in the chamber thus increasing chamber pressure

Methodology Applied

Scientific EffectGasification: Evaporation

Implementation Method 2

the monopropellant ignites/decomposes, leading to solid propellant ignition

Methodology Applied

Scientific EffectDecomposition: Decomposition (biological)

Implementation Method 3

The monopropellant receives the heat from the surface of the solid propellant

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Implementation Method 4

The warmed/hot monopropellant can then be injected into the combustion chamber of the solid propellant section

Methodology Applied

Scientific EffectRegenerative cooling: Heat Exchanger

Implementation Method 5

the monopropellant ignites/decomposes, leading to solid propellant ignition

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 6

exhausting combustion gas from the combustion chamber through the nozzle to generate thrust

Methodology Applied

Scientific EffectThrust generation: Rocket

Data Source

PatentUS11629669B1Liquid monopropellant controlled solid rocket motor with aft end injection deflector

Publication Date: 2023.04.18 EXQUADRUM

AI summary

A solid rocket motor is described that includes a solid propellant section, a nozzle, and a source of monopropellant, such as liquid monopropellant. The monopropellant is used to control various operational parameters of the solid rocket motor, such as thrust vector control, roll control, extinguishment of the motor, and cooling of the nozzle and/or nozzle throat. The nozzle and the nozzle throat can be an integrated, single piece assembly that facilitates re-use of the nozzle.