The pressure-fed engine is a class of

rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...

designs. A separate gas supply, usually

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure. Pressure fed engines have simple plumbing and have no need for complex and occasionally unreliable

turbopump A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...

s. A typical startup procedure begins with opening a valve, often a one-shot pyrotechnic device, to allow the pressurizing gas to flow through check valves into the propellant tanks. Then the propellant valves in the engine itself are opened. If the fuel and oxidizer are

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

, they burn on contact; non-hypergolic fuels require an igniter. Multiple burns can be conducted by merely opening and closing the propellant valves as needed. If the pressurization system also has activating valves, they can be operated electrically, or by gas pressure controlled by smaller electrically operated valves. Care must be taken, especially during long burns, to avoid excessive cooling of the pressurizing gas due to adiabatic expansion. Cold helium won't liquify, but it could freeze a propellant, decrease tank pressures, or damage components not designed for low temperatures. The

Apollo Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed sp ...

Descent Propulsion System was unusual in storing its helium in a supercritical but very cold state. It was warmed as it was withdrawn through a

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...

from the ambient temperature fuel. OMS Pod schematic

Spacecraft

attitude control Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...

and

orbital maneuver In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth, an orbital maneuver is called a ''deep-space maneuver (DSM)''. When a spacec ...

ing thrusters are almost universally pressure-fed designs. Examples include the Reaction Control (RCS) and the Orbital Maneuvering (OMS) engines of the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

orbiter; the RCS and Service Propulsion System (SPS) engines on the

Apollo Command/Service Module The Apollo command and service module (CSM) was one of two principal components of the United States Apollo (spacecraft), Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functi ...

; the SuperDraco (in-flight abort) and Draco (RCS) engines on the

SpaceX Dragon 2 Dragon 2 is a class of partially reusable spacecraft developed, manufactured, and operated by the American space company SpaceX for flights to the International Space Station (ISS) and private spaceflight missions. The spacecraft, which consi ...

; and the RCS, ascent and descent engines on the

. Some launcher

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

s also use pressure-fed engines. These include the Aerojet

AJ10 The AJ10 is a hypergolic rocket engine manufactured by Aerojet Rocketdyne (previously Aerojet). It has been used to propel the upper stages of several launch vehicles, including the Delta II and Titan III. Variants were and are used as the servic ...

and TRW

TR-201 The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta (rocket family), Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and dinitrogen tetrox ...

used in the second stage of

Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...

launch vehicle, and the

Kestrel The term kestrel (from , derivative from , i.e. ratchet) is the common name given to several species of predatory birds from the falcon genus ''Falco''. Kestrels are most easily distinguished by their typical hunting behaviour which is to hover ...

engine of the

Falcon 1 Falcon 1 was a two-stage small-lift launch vehicle that was operated from 2006 to 2009 by SpaceX, an American aerospace manufacturer. On September 28, 2008, Falcon 1 became the first privately developed fully liquid-fueled launch vehicle to s ...

by SpaceX. The 1960s Sea Dragon concept by

Robert Truax Captain Robert C. Truax ( USN) (September 3, 1917 – September 17, 2010) was an American rocket engineer in the United States Navy, and companies such as Aerojet and Truax Engineering, which he founded. Truax was a proponent of low-cost rocket ...

for a

big dumb booster Big Dumb Booster (BDB) is a general class of launch vehicle based on the premise that it is cheaper to operate large rockets of simple design than it is to operate smaller, more complex ones regardless of the lower payload efficiency.Schnitt, Arthu ...

would have used pressure-fed engines. Pressure-fed engines have practical limits on propellant pressure, which in turn limits combustion chamber pressure. High pressure propellant tanks require thicker walls and stronger materials which make the vehicle tanks heavier, thereby reducing performance and payload capacity. The lower stages of

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

s often use either

solid fuel Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fu ...

or pump-fed liquid fuel engines instead, where high pressure ratio nozzles are considered desirable. Other vehicles or companies using pressure-fed engine: * OTRAG (rocket) * Quad (rocket) of Armadillo Aerospace * XCOR EZ-Rocket of XCOR Aerospace *

Masten Space Systems Masten Space Systems was an aerospace manufacturer startup company in Mojave, California (formerly in Santa Clara, California) that was developing a line of vertical takeoff, vertical landing (VTVL) rockets, initially for uncrewed research s ...

* Aquarius Launch Vehicle *NASA's Project Morpheus prototype lander * NASA Mighty Eagle mini lunar lander *

CONAE The National Space Activities Commission (Spanish language , Spanish: ''Comisión Nacional de Actividades Espaciales'', CONAE) is the civilian agency of the government of Argentina in charge of the national space programme. History Sociedad ...

's Tronador II upper stage *

Copenhagen Suborbitals Copenhagen Suborbitals is a crowd-funded human space program. It has flown six home-built rockets and capsules since 2011. The organization successfully launched its Nexø II rocket in the summer of 2018. Its stated goal is to have one of its me ...

' Spica

References

External links

Rocket power cycles
{{DEFAULTSORT:Pressure-Fed Cycle (Rocket) Rocket propulsion Rocket engines Thermodynamics

See also

References

External links