Nozzle extension — nozzle

De Laval nozzle

A de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape...

 expander of reaction

Reaction engine

A reaction engine is an engine or motor which provides propulsion by expelling reaction mass, in accordance with Newton's third law of motion...

/rocket

Rocket engine

A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...

 engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

. The application of nozzle extensions improves efficiency

Specific impulse

Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

 of rocket engines in vacuum by increasing nozzle ratio. As a rule, their modern design assumes use of carbon-carbon materials without regenerative cooling

Regenerative cooling

Regenerative cooling in rockets is where some or all of the propellant is passed through tubes, channels or otherwise in a jacket around the combustion chamber or nozzle to cool the engine because the fuel in particular and sometimes the oxidizer are good coolants...

. Along with sliding expanders, stationary nozzle extensions have some applications too.

Description

At present 2009 year, the search for various schemes to achieve higher area ratios for rocket nozzles stays an active field of research and patenting. Generally, modern application of these designs can be divided on use for engines, which start their work at sea level and finish it at vacuum conditions, and on use for engines, which perform all their operations in vacuum.

"Air-to-vacuum" engines

For first stage rocket

Expendable launch system

An expendable launch system is a launch system that uses an expendable launch vehicle to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once , and their components are not recovered for re-use after launch...

 engines, the engine

Rocket engine

A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...

 works with nozzle extension in disposed position during the first minutes of flight and expands it at some predefined level of air pressure. This scheme assumes the outer skirt of the bell is extended while the engine is functioning and its installation to working position happens in the upper layers of the atmosphere. It excludes problems with flow separation

Flow separation

All solid objects travelling through a fluid acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface. Boundary layers can be either laminar or turbulent...

 at sea level and increases efficiency of the engine in vacuum. For example, application of nozzle extension for liquid rocket engine NK-33

NK-33

The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau. They were intended for the ill-fated Soviet N-1 rocket moon shot. The NK-33 engine achieves the highest thrust-to-weight ratio of any Earth-launchable rocket engine, whilst...

 improves the value of specific impulse

Specific impulse

Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

 up to 15-20 sec

Second

The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

 for near-space conditions. Therefore, this scheme adjusts the system to ambient conditions along the trajectory or, in other words, allows altitude compensation

Altitude compensating nozzle

An altitude compensating nozzle is a class of rocket engine nozzles that are designed to operate efficiently across a wide range of altitudes.- Conventional designs :...

.

"Vacuum" engines

Rocket engines of upper stages

Multistage rocket

A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...

 perform all their operations in space and therefore in a vacuum. In order to achieve maximum efficiency for this class of engines they need high area ratios

Expansion ratio

The expansion ratio of a liquefied and cryogenic substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at a given temperature and pressure....

. This makes the nozzles a very sizable part of engine, which must be completely enclosed below the nose cone

Nose cone

The term nose cone is used to refer to the forwardmost section of a rocket, guided missile or aircraft. The cone is shaped to offer minimum aerodynamic resistance...

 of rocket. The payload fairing

Payload fairing

Payload fairing is one of the main components of a launch vehicle. The fairing protects the payload during the ascent against the impact of the atmosphere . More recently, an additional function is to maintain the cleanroom environment for precision instruments.Outside the atmosphere the fairing is...

 and supporting constructions must endure all stresses and loads during launch and flight. Consequently, the use of outer expandable skirt in this case allows the size of upper stage and payload fairing

Payload fairing

Payload fairing is one of the main components of a launch vehicle. The fairing protects the payload during the ascent against the impact of the atmosphere . More recently, an additional function is to maintain the cleanroom environment for precision instruments.Outside the atmosphere the fairing is...

 to be minimized, which in turn decreases the total mass of the nose cone. For these reasons, nozzle extensions are used for rocket engine

Rocket engine

A rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...

s RL-10

RL-10

The RL10 was USA's first liquid hydrogen fueled rocket engine. An updated version is used in several current launch vehicles. Six RL10 engines were used in the S-IV second stage of the Saturn I rocket. One or two RL10 engines are used in the Centaur upper stages of Atlas and Titan rockets...

 and RD-58

RD-58

The RD-58 is a rocket engine, developed in the 1960s by OKB-1, now RKK Energia. The project was managed by Mikhail Melnikov The engine was initially created to power the Block D stage of the Soviet Union's abortive N-1 rocket. Derivatives of this stage are now used as upper stages on some Proton...

.

See also

• Rocket engine nozzle
• De Laval nozzle
  De Laval nozzle
  A de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape...
  
  
• Stepped nozzle
• F-1
  F-1 (rocket engine)
  The F-1 is a rocket engine developed by Rocketdyne and used in the Saturn V. Five F-1 engines were used in the S-IC first stage of each Saturn V, which served as the main launch vehicle in the Apollo program. The F-1 is still the most powerful single-chamber liquid-fueled rocket engine ever...
  
  
• NK-33
  NK-33
  The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau. They were intended for the ill-fated Soviet N-1 rocket moon shot. The NK-33 engine achieves the highest thrust-to-weight ratio of any Earth-launchable rocket engine, whilst...
  
  

External links

Surprises of "Engines-2000", News of cosmonautics, April 2000 Patent of NPO Iskra, Patent department The research of possible options for construction of liquid rocket engine with changeable nozzle ratio, Magazine "Engine" Casing for fire, Magazine "Engine"

• Vulcain-2 Cryogenic Engine Passes First Test with New Nozzle Extension, European Space Agency