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 ta ...

, 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. 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 ...

Descent Propulsion System The descent propulsion system (DPS - pronounced 'dips') or lunar module descent engine (LMDE), internal designation VTR-10, is a variable- throttle hypergolic rocket engine invented by Gerard W. Elverum Jr. and developed by Space Technology La ...

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 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 (for example those in orbits around the Sun) an orbital maneuver is called a ' ...

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 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 n ...

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, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother sh ...

; the SuperDraco (in-flight abort) and

Draco Draco is the Latin word for serpent or dragon. Draco or Drako may also refer to: People * Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived * ...

(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

. 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 s ...

and TRW TR-201 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 va ...

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 Sea Dragon or seadragon may refer to: Fish * Leafy seadragon (''Phycodurus eques'') * ''Phyllopteryx'' genus ** Common seadragon or weedy seadragon (''Phyllopteryx taeniolatus'') ** Ruby seadragon (''Phyllopteryx dewysea'') Military * Operation ...

concept by Robert Truax 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 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 sys ...

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 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) of Armadillo Aerospace *

XCOR EZ-Rocket The XCOR EZ-Rocket was a test platform for the XCOR XR-4A3 rocket propulsion system. The airplane was a modified Rutan Long-EZ, with the propeller replaced by first one, then later a pair of pressure-fed regeneratively cooled liquid-fueled rock ...

of XCOR Aerospace * Masten Space Systems *

Aquarius Launch Vehicle Aquarius is a launch vehicle concept designed for low-cost by Space Systems/Loral to carry small, inexpensive payloads into LEO. Concept The vehicle was primarily intended for launching bulk products, like water, fuel, and other consumables, tha ...

*NASA's Project Morpheus prototype lander *

NASA Mighty Eagle The Mighty Eagle (also known as the Warm Gas Test Article) is a Prototype Robotic Lander developed by NASA at the Marshall Space Flight Center in Huntsville, Alabama. The vehicle is an autonomous flying testbed that is used for testing hardw ...

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