Liquid-propellant rocket engines are capable of on-command variable thrust or thrust modulation, an operability advantage that has been studied intermittently since the late 1930s. Throttleable liquid-propellant rocket engines can be used for planetary entry and descent, space rendezvous, orbital maneuvering including orientation and stabilization in space, and hovering and hazard avoidance during planetary landing. Other applications have included control of aircraft rocket engines, limiting of vehicle acceleration or velocity using retrograde rockets, and ballistic missile defense trajectory control. Throttleable liquid-propellant rocket engines can also continuously follow the most economical thrust curve in a given situation, as opposed to making discrete throttling changes over a few select operating points. The effects of variable thrust on the mechanics and dynamics of an liquid-propellant rocket engine as well as difficulties and issues surrounding the throttling process are important aspects of throttling behavior. This review provides a detailed survey of liquid-propellant rocket engine throttling centered around engines from the United States. Several liquid-propellant rocket engine throttling methods are discussed, including high-pressure-drop systems, dual-injector manifolds, gas injection, multiple chambers, pulse modulation, throat throttling, movable injector components, and hydrodynamically dissipative injectors. Concerns and issues surrounding each method are examined, and the advantages and shortcomings compared.

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Liquid-propellant rocket engine throttling: A comprehensive review

Liquid-Propellant Rocket Engines (LREs) are capable of on-command variable thrust or thrust modulation, an operability advantage that has been studied intermittently since the late 1930s. Throttleable LREs can be used for planetary entry and descent, space rendezvous, orbital maneuvering including orientation and stabilization in space, and hovering and hazard avoidance during planetary landing. Other applications have included control of aircraft rocket engines, limiting of vehicle acceleration or velocity using retrograde rockets, and ballistic missile defense trajectory control. Throttleable LREs can also continuously follow the most economical thrust curve in a given situation, compared to discrete throttling changes over a few select operating points. The effects of variable thrust on the mechanics and dynamics of an LRE as well as difficulties and issues surrounding the throttling process are important aspects of throttling behavior. This review provides a detailed survey of LRE throttling centered around engines from the United States. Several LRE throttling methods are discussed, including high-pressure-drop systems, dual-injector manifolds, gas injection, multiple chambers, pulse modulation, throat throttling, movable injector components, and hydrodynamically dissipative injectors. Concerns and issues surrounding each method are examined, and the advantages and shortcomings compared.

/pdf/liquid-propellant-rocket-engine-throttling-a-comprehensive-1uq0n39qtw.pdf

Liquid-Propellant Rocket Engine Throttling: A Comprehensive Review

Exhaust nozzle recombination of hydrogen fuel in subsonic ramjet engines at hypersonic speeds

Effects of exhaust nozzle recombination on hypersonic ramjet performance. ii - analytical investigation of the effects of exhaust nozzle recombination on hydrogen-fueled hypersonic ramjet performance

Flow measurement and instrumentation flow control characteristics of throttling venturi valve with adjustable area

The gas-deployed skirt (CDS) is a metal nozzle extension that is folded radially inward and packaged entirely within the cavity of a rocket motor nozzle. The skirt is deployed by low-pressure motor ignition gases and then stabilized in the open position by the internal pressure of fully developed nozzle exhaust gas flow. The conception, design, and analysis are discussed in the context of seven successful CDS tests on 100-lb liquid rocket rocket motors and 5000-lb solid rocket motors. Typical applications and the resulting performance improvements are also discussed.

Lee Carey

Papers

Dual-mode, 100-1 thrust modulation rocket engine.

Convoluted Nozzle Extension

Extendible Exit Cone Development for the C4 Third-Stage Motor

Pressure-fed liquid rocket payload potential

Extendible exit cone development for the C4 third stage motor