Ullage

Ullage is a term used in various fields, including winemaking, brewing, and spacecraft propulsion. It refers to the unfilled space in a container, such as a bottle or tank. The word originates from the Old French ouillage, derived from ouil, meaning eye or hole, and is related to the verb ouiller, to fill up to the top.

Winemaking and Brewing

In winemaking and brewing, ullage refers to the space between the liquid and the top of its container. This space is necessary to allow for the expansion and contraction of the liquid due to changes in temperature. However, excessive ullage can lead to oxidation of the wine or beer, which can negatively affect its taste and quality.

Spacecraft Propulsion

In the context of spacecraft propulsion, ullage refers to the empty space within a fuel tank. In a zero-gravity environment, the fuel within a tank can float away from the outlet pipe, making it impossible for the fuel to be used. To solve this problem, small rocket engines known as ullage motors are used to settle the fuel at the bottom of the tank before the main engine is ignited.

Measurement

The measurement of ullage is important in various industries. In the wine industry, for example, it can be used to determine the quality of a bottle of wine. In the shipping industry, it is used to calculate the volume of liquid in a tank.

See Also

• Winemaking
• Brewing
• Spacecraft propulsion
• Oxidation (wine)