Ullage (rocketry): Difference between revisions
Mark Foskey (talk | contribs) Created as part of merger of 'ullage motor' and 'ullage engine' |
Mark Foskey (talk | contribs) Put article together from pieces of 'ullage motor' and 'ullage engine'. |
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In a barrel or wine bottle, for example, ''ullage'' is the space within the container but above the liquid. |
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In [[rocketry]], ''ullage'' is the space within a fuel tank but above the liquid fuel. This term derives from the same term '[[ullage]]' in winemaking, where it referse to the space above the liquid in a container such as a barrel or wine bottle. |
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Liquid, [[cryogenic]]-fueled [[rocket]]s keep their fuel in big tanks. These tanks are never completely filled, to allow for the natural expansion of the cold liquid fuel. On the ground, the space between the top of the fuel load and the capacity of the tank is the known as "ullage space". |
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The reason these are necessary is that liquid, [[cryogenic]]-fueled [[rocket]]s keep their fuel in big tanks. These tanks are never completely filled, to allow for the natural expansion of the cold liquid fuel. On the ground, the space between the top of the fuel load and the capacity of the tank is the known as "ullage space". |
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'''Ullage motors''' are relatively small, independently-fueled rocket engines that may be fired to accelerate the rocket. By [[Newton's laws of motion]], this forces the main engine liquid fuel and [[oxidizer]] to the bottom of their tanks where they can be properly pumped. In this way the ullage space remains at the top. Such motors were first invented by Soviet engineers for the Molniia interplanetary launch vehicle in 1960. |
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The firing of the ullage motors may also assist in separation of rocket stages and/or stabilization of the rocket. |
The firing of the ullage motors may also assist in separation of rocket stages and/or stabilization of the rocket. |
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A '''ullage engine''' allows a liquid fuel rocket engine to start in space under weightless conditions. It provides a small pre-acceleration to settle fuel in the tanks before the main engine and fuel pumps start. The term "ullage" refers to the amount of empty space in a barrel of liquid. Ullage engines were first invented by Soviet engineers for the Molniia interplanetary launch vehicle in 1960. |
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The term ''ullage engine'' or ''ullage rocket'' is also used, although sometimes a distinction is made between a solid-fueled ullage motor that can thus only be used once, and a reusable ullage engine. |
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[[Category:Rocket engines]] |
[[Category:Rocket engines]] |
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Revision as of 16:19, 9 July 2006
In rocketry, ullage is the space within a fuel tank but above the liquid fuel. This term derives from the same term 'ullage' in winemaking, where it referse to the space above the liquid in a container such as a barrel or wine bottle.
The reason these are necessary is that liquid, cryogenic-fueled rockets keep their fuel in big tanks. These tanks are never completely filled, to allow for the natural expansion of the cold liquid fuel. On the ground, the space between the top of the fuel load and the capacity of the tank is the known as "ullage space".
Ullage motors are relatively small, independently-fueled rocket engines that may be fired to accelerate the rocket. By Newton's laws of motion, this forces the main engine liquid fuel and oxidizer to the bottom of their tanks where they can be properly pumped. In this way the ullage space remains at the top. Such motors were first invented by Soviet engineers for the Molniia interplanetary launch vehicle in 1960.
The firing of the ullage motors may also assist in separation of rocket stages and/or stabilization of the rocket.
The four ullage motors of the Saturn V rocket used in the American Apollo program were located on the second stage.
The term ullage engine or ullage rocket is also used, although sometimes a distinction is made between a solid-fueled ullage motor that can thus only be used once, and a reusable ullage engine.