The RD-701 (''russian: Раке́тный дви́гатель 701'', Rocket Engine 701) is a

liquid-fuel rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid rocket propellant, liquid propellants. Liquids are desirable because they have a reasonably high density and high Specific impulse, specific impulse (''I''sp). T ...

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 ...

developed by

Energomash The Energomash Corporation (Cyrillic: "Энергомаш") was a Russian power engineering company. Energomash manufactures small cogeneration Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to gene ...

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

(

USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

at that time). It was briefly proposed to propel the reusable

MAKS space plane The MAKS (Multipurpose aerospace system) (Russian: МАКС (Многоцелевая авиационно-космическая система)) is a Soviet air-launched orbiter reusable launch system project that was proposed in 1988, but canc ...

, but the project was cancelled shortly before the end of

. The ''RD-701'' is a tripropellant engine that uses a

staged combustion cycle The staged combustion cycle (sometimes known as topping cycle, preburner cycle, or closed cycle) is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thu ...

with afterburning of

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

-rich hot

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...

gas. The RD-701 has two modes. ''Mode 1'' uses three components:

LOX Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...

as an

and a

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

mixture of

RP-1 RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (LH2), but is cheaper, is st ...

LH2 Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully liq ...

which is used in the lower atmosphere. ''Mode 2'' also uses LOX, with

as fuel in vacuum where atmospheric influence is negligible. The use of less dense fuel components at maximum

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 ...

conditions allows minimizing the volume of fuel tanks and subsequently their mass down to 30%. The ''RD-701'' was developed into the RD-704 with one combustion chamber. The RD-701 is derived from the hydrogen fueled

RD-0120 The Soviet RD-0120 (also designated 11D122) was the Energia (rocket), Energia core rocket engine, fueled by LH2, LH/LOX, roughly equivalent to the Space Shuttle Main Engine (SSME). These were attached to the Energia core rather than the orbiter, ...

. It is essentially two engines with common hydraulic and pneumatic systems, and boost pumps. Until 2020, the engine held the record for the highest pressure successfully recorded in a

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...

with a pressure of . In August 2020, this record was surpassed surpassed by the

SpaceX Raptor Raptor is a family of full-flow staged-combustion-cycle rocket engines developed and manufactured by SpaceX for use on the in-development SpaceX Starship. The engine is powered by cryogenic liquid methane and liquid oxygen ("methalox") rather t ...

engine, which reached 33 MPa (330 bar) during a static fire test.

Specifications

The 'RD-701' is a two chamber engine. It can operate in two modes. In the first, it burns both kerosene and hydrogen, granting it greater thrust and impulse density, allowing for smaller, lighter tanks. In the second, it burns only hydrogen, allowing for greater specific impulse. The RD-701 has two preburners per combustion chamber, both of which run oxygen rich. One is used to pump kerosene and oxygen, the other is used to pump hydrogen and oxygen. In mode one, both burn kerosene. Liquid hydrogen is combined with kerosene and oxygen rich preburner exhaust in the combustion chamber. In this mode, it produces 4 MN of thrust, with a vacuum specific impulse of 415s, using 73.7 kg/s of kerosene, 29.5 kg/s of hydrogen, and 388.4 kg/s of oxygen. In mode two, the preburner used to pump kerosene is shut down, and the other is switched to burning hydrogen. A small amount of kerosene is still used to ensure oxygen is effectively atomised. Gases from the preburner combined with hydrogen in the combustion chamber. In this mode it burns 27.4 kg/s of hydrogen, and 148 kg/s of oxygen. Thrust reduces to 1.6 MN, and specific impulse increases to 460s. {{Cite web, url=http://www.buran.ru/htm/rd-701.htm, title=Двигатели МАКСа, website=www.buran.ru

References

External links

''Engines of MAKS: RD-701''
(in Russian) * ttps://web.archive.org/web/20160811033039/http://www.astronautix.com/r/rd-701.html ''Astronautix: RD-701''br>''Astronautix: RD-704''
''19 June 2007 year'' (in Russian) Rocket engines of Russia Rocket engines using hydrogen propellant Rocket engines of the Soviet Union

Specifications

See also

References

External links