A nozzle extension is an extension of the

nozzle A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, a ...

of a

reaction Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law *Chain reaction (disambiguation). Biology and me ...

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

. The application of nozzle extensions improves the

efficiency Efficiency is the often measurable ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without ...

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

cooling Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/technical-resources/free-resources/as ...

. Nozzle extensions can be both stationary, for high-altitude engines, or sliding, for engines designed to operate at a range of altitudes.

Description

As of 2009, the search for various schemes to achieve higher area ratios for rocket nozzles remains an active field of research and patenting.Extractable nozzle for rocket engine - Russian Patent 2180405
''Russian patents''
''Russian patents'' Generally, modern application of these designs can be divided into "air-to-vacuum" engines, which start their work at sea level and finish it at vacuum conditions, and "vacuum" engines, which perform all their operations in a vacuum.

"Air-to-vacuum" engines

For first stage

engines, the

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 In fluid dynamics, flow separation or boundary layer separation is the detachment of a boundary layer from a surface into a wake. A boundary layer exists whenever there is relative movement between a fluid and a solid surface with viscous fo ...

at sea level and increases efficiency of the engine in vacuum.Work on modifying NK-33
''News of cosmonautics'', November 2002 For example, application of ''nozzle extension'' for

liquid rocket engine A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...

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. The NK designation is derived from the initials of chief designer Nikolay Kuznetsov. The NK-33 was among the most powerf ...

improves the value of

specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...

up to 15-20 sec for near-space conditions. Therefore, this scheme adjusts the system to ambient conditions along the trajectory or, in other words, allows altitude compensation.

"Vacuum" engines

Rocket engines of upper stages 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. This makes the nozzles a very sizable part of the engine, which must be completely enclosed below the

nose cone A nose cone is the conically shaped forwardmost section of a rocket, guided missile or aircraft, designed to modulate oncoming airflow behaviors and minimize aerodynamic drag. Nose cones are also designed for submerged watercraft such as ...

of a rocket. The

payload fairing A payload fairing is a nose cone used to protect a spacecraft payload against the impact of dynamic pressure and aerodynamic heating during launch through an atmosphere. An additional function on some flights is to maintain the cleanroom environm ...

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

to be minimized, which in turn decreases the total mass of the nose cone.RL10B-2 - NOZZLE EXTENSION ASSEMBLY IMPROVEMENTS FOR DELTA IV
/ref> For these reasons, ''nozzle extensions'' are used for

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...

RL-10 The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to of thrust per engine in vacuum. Three RL10 ve ...

and

RD-58 The RD-58 (manufacturer designation 11D58) is a rocket engine, developed in the 1960s by OKB-1, now RKK Energia. The project was managed by Mikhail Melnikov, and it was based on the previous S1.5400 which was the first staged combustion engine i ...

.Expandable and fixed nozzle extensions without regenerative cooling
Discussion thread at "''News of cosmonautics''" forum

References

External links

*
Surprises of "Engines-2000"
''News of cosmonautics'', April 2000 *
Patent of NPO Iskra
''Patent department'' *

''Magazine "Engine"'' * {{in lang, ru ttp://engine.aviaport.ru/issues/02/page08.html Casing for fire ''Magazine "Engine"''
Vulcain-2 Cryogenic Engine Passes First Test with New Nozzle Extension
''European Space Agency'' Nozzles Rocket propulsion Spacecraft propulsion

Description

"Air-to-vacuum" engines

"Vacuum" engines

See also

References

External links