The pressure-fed engine is a class of
rocket engine designs. A separate gas supply, usually
helium, 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
turbopumps. 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, 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 Labo ...
was unusual in storing its helium in a
supercritical but very cold state. It was warmed as it was withdrawn through a
heat exchanger from the ambient temperature fuel.
Spacecraft
attitude control 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 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 ship ...
; 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
* D ...
(RCS) engines on the
SpaceX Dragon 2; and the RCS, ascent and descent engines on 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 ...
.
Some launcher
upper stages also use pressure-fed engines. These include the Aerojet
AJ10 and TRW
TR-201 used in the second stage of
Delta II launch vehicle,
and the
Kestrel engine of the
Falcon 1 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
* Operat ...
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 vehicles 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 fuels ...
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)
The OTRAG rocket was a modular satellite-delivery rocket developed by the OTRAG company in the 1970s and 80s. The OTRAG rocket was to become a rocket built up from several mass-produced units, intended to carry satellites with a weight of 1-10 to ...
*
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 hardwa ...
mini lunar lander
*
CONAE's
Tronador II
Tronador (Spanish for Thunderer) is a series of Argentine rockets, including the Tronador I and Tronador II vehicles, to develop a liquid-propellant rocket expendable launch system called ISCUL (''Inyector Satelital de Cargas Utiles Ligeras'', ...
upper stage
*
Copenhagen Suborbitals' Spica
See also
*
Gas-generator cycle
*
Combustion tap-off cycle
*
Expander cycle
*
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 ...
References
External links
Rocket power cycles
{{DEFAULTSORT:Pressure-Fed Cycle (Rocket)
Rocket propulsion
Rocket engines
Thermodynamics