In rocketry, a SERN, which stands for single expansion ramp nozzle, is a type of physical linear expansion
nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe (material), pipe.
A nozzle is often a pipe or tube of varying cross ...
where the gas pressure transfers work only on one side. Traditional nozzles are axially symmetric, and therefore surround the expanding gas. Linear nozzles are not axially symmetric, but consist of a 2D configuration of two expansion ramps. A SERN could also be seen as a single sided
aerospike engine
The aerospike engine is a type of rocket engine that maintains its aerodynamic efficiency across a wide range of altitudes. It belongs to the class of altitude compensating nozzle engines. Aerospike engines were proposed for many single-stage- ...
.
Many designs for
space planes with
scramjet
A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully b ...
engines make use of SERNs because of the weight reduction at large expansion ratios, or the additional lift at under-expansion. The
X-43, a test vehicle in
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's Hyper-X programme, is a flying example.
One of the practical problems with the use of SERNs is the fact that they produce a pitching moment depending on the throttling of the engine, thereby requiring more control authority of the
elevator
An elevator (American English) or lift (Commonwealth English) is a machine that vertically transports people or freight between levels. They are typically powered by electric motors that drive traction cables and counterweight systems suc ...
s, more complex control systems, etc.
References
Nozzles
Rocket engines
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