Nozzle Shapes - The Aerospike Nozzle
Aerospike nozzles are rather unique, in that they are somewhat of a reverse version of the standard bell nozzle. Instead of using a shroud to contain the exit flow, aerospikes direct the flow along the exterior of the nozzle. The interesting thing about the aerospike nozzle is that it overcomes problems with varying back-pressure by simply using the local atmospheric pressure to control the flow area.
Instead of using a physical shroud to contain the exhaust flow, the outer boundary is defined naturally by the local back-pressure. This results in a smoothly varying exit flow area which is always optimized as back-pressure changes.
Instead of using a physical shroud to contain the exhaust flow, the outer boundary is defined naturally by the local back-pressure. This results in a smoothly varying exit flow area which is always optimized as back-pressure changes.
There are two types of aerospike nozzles. The first of which is the toroidal aerospike. The characteristic spike gave the nozzle its name. Exhaust flow is directed from a toroidal shape around the exterior of the nozzle towards the spike, which results in a flow that expands to the optimal diameter as local pressure varies.
The second type is linear aerospike, seen here. This is a wedge-shaped nozzle, which has a linear exhaust profile. Linear aerospikes are exceptionally odd looking, but very effective. Exhaust is directed inward from a series of ports along each side of the wedge, and expands to an optimal flow area as local pressure varies.
Linear aerospikes provide an advantage over toroidal aerospikes, in that the turbomachinery and combustion chamber actually fit within the inner section of the nozzle, allowing for the entire assembly to be tilted from side to side for thrust vectoring purposes, which are discussed on the next page. Additionally, exhaust flow rates can be varied on each side to produce a twisting effect. Multiple linear aerospikes can be used on a single rocket to provide greater thrust and exceptional control.
Despite all of these advantages over the traditional bell nozzle, aerospike nozzles have never actually been used in production designs. A great deal of research and development has been conducted on the subject proving its effectiveness, yet the aerospike nozzle has not yet been utilized outside of an experimental capacity.
Linear aerospikes provide an advantage over toroidal aerospikes, in that the turbomachinery and combustion chamber actually fit within the inner section of the nozzle, allowing for the entire assembly to be tilted from side to side for thrust vectoring purposes, which are discussed on the next page. Additionally, exhaust flow rates can be varied on each side to produce a twisting effect. Multiple linear aerospikes can be used on a single rocket to provide greater thrust and exceptional control.
Despite all of these advantages over the traditional bell nozzle, aerospike nozzles have never actually been used in production designs. A great deal of research and development has been conducted on the subject proving its effectiveness, yet the aerospike nozzle has not yet been utilized outside of an experimental capacity.
JR