The pressure-fed engine is a class of

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 accorda ...

designs. A separate gas supply, usually

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

, 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 propellant 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 purpo ...

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. T ...

, 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 In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process ...

. 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 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 conta ...

from the ambient temperature fuel. Spacecraft

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

and orbital maneuvering 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 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. Its official program ...

orbiter; the RCS and Service Propulsion System (SPS) engines on the Apollo Command/Service Module; the

SuperDraco SuperDraco is a hypergolic propellant rocket engine designed and built by SpaceX. It is part of the SpaceX Draco family of rocket engines. A redundant array of eight SuperDraco engines provides fault-tolerant propulsion for use as a launch es ...

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

SpaceX Dragon 2 Dragon 2 is a class of partially reusable spacecraft developed and manufactured by American aerospace manufacturer SpaceX, primarily for flights to the International Space Station (ISS). SpaceX has also launched private missions such as Ins ...

; and the RCS, ascent and descent engines on the Apollo Lunar Module. 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 engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...

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 servi ...

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. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 ...

launch vehicle, and the

Kestrel The term kestrel (from french: crécerelle, 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 behaviou ...

engine of the

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

by SpaceX. The 1960s Sea Dragon concept by

Robert Truax Captain Robert C. Truax (United States Navy, USN) (September 3, 1917 – September 17, 2010) was an American Aerospace engineering, rocket engineer in the United States Navy, and companies such as Aerojet and Truax Engineering, which he founded. T ...

for a big dumb booster 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 alloys which make the vehicle tanks heavier, thereby reducing performance and payload capacity. The lower stages of

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and ...

s often use either solid fuel 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) In rocketry, the Armadillo Aerospace Quad vehicle called Pixel is a computer-controlled VTVL rocket that was used in 2006 to compete in the Lunar Lander Challenge. General description The quad vehicle design is a pressure fed in blow-down mode ...

Armadillo Aerospace Armadillo Aerospace was an aerospace startup company based in Mesquite, Texas. Its initial goal was to build a crewed suborbital spacecraft capable of space tourism, and it had also stated long-term ambitions of orbital spaceflight. The company ...

* XCOR EZ-Rocket of

XCOR Aerospace XCOR Aerospace was an American private spaceflight and rocket engine development company based at the Mojave Air and Space Port in Mojave, California, Midland International Air and Space Port, Midland International Air and Spaceport in Midland, T ...

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 sub- ...

* Aquarius Launch Vehicle *NASA's

Project Morpheus Project Morpheus was a NASA project that began in 2010 to develop a vertical takeoff and vertical landing (VTVL) test vehicle called the Morpheus Lander. It is intended to demonstrate a new nontoxic spacecraft propellant system (methane and ox ...

prototype lander * NASA Mighty Eagle mini lunar lander * CONAE's Tronador II upper stage *

Copenhagen Suborbitals Copenhagen Suborbitals is an amateur, crowd-funded, and open-source human space program. Since its beginning in 2008, Copenhagen Suborbitals has flown five home-built rockets and two mock-up space capsules. Their stated goal is to have one of th ...

' Spica

References

External links

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

See also

References

External links