Can the nozzels shape be other a circle?

[RandomRyan]

Hi.

i was thinking about something and thought of this.

can a nozzle's shape can be other than a circle?

Example: a rectangular nozzle

(I am not a rocket scientist)

Thanks in advance:)

[linkxsc]

Structurally and mechanically, yes you can have nozzel shapes other than a circle.

Problems with efficiency come up though... so we use circles.

[RandomRyan]

How about Jet engines? can they have rectangular nozzles?

[linkxsc]

How about Jet engines? can they have rectangular nozzles?

Well look at a picture of the rear end of a F-22 Raptor. They bring thats engines out to an essentially rectangular nozzel. It again, isnt the most efficient way. But if Im not mistaken, the shape of those is partly for its thrust vectoring.

[JoCRaM]

The "nozzle" in an linear aerospike isn't circular.

https://upload.wikimedia.org/wikipedia/commons/8/8c/Twin_Linear_Aerospike_XRS-2200_Engine_PLW_edit.jpg

[Hcube]

Well look at a picture of the rear end of a F-22 Raptor. They bring thats engines out to an essentially rectangular nozzel. It again, isnt the most efficient way. But if Im not mistaken, the shape of those is partly for its thrust vectoring.

Thrust vectoring AND stealth !

[B787_300]

yes they can although efficiency is a HUGE issue. there are linear aerospikes that were tested as part of the NASP which were nominally rectangular but the issue becomes manufacturing cost and efficiency

[Camacha]

yes they can although efficiency is a HUGE issue. there are linear aerospikes that were tested as part of the NASP which were nominally rectangular but the issue becomes manufacturing cost and efficiency

Bell shaped nozzles are kind of hard-ish to make though, so a nice linear piece should be easier and cheaper to build.

[softweir]

The actual "nozzle" part, yes, that's not excessively difficult, though making it strong enough and light enough has proved tricky. A circular-section nozzle is self-reinforcing: if it starts to bend out of shape then the pressure within restores it, but the curves of an aerospike (linear or circular) are shaped in such a way that if they start to deform then the pressure on them exaggerates that.

Another problem is that the engines that create the flame that plays over the aerospike are very difficult to make. A conventional combustion chamber is simple by comparison - it just needs to be a heat-resistant, pressure-resistant approximately spherical chamber with opening for combustants coming in and for exhaust going out to the nozzle. Rearranging all that to create nearly flat jets of exhaust that the aerospikes need is very tricky. Some designs have had many tiny combustion chambers each leading to a small, flat nozzle that directs the exhaust over a segment of the aerospike, or they have required large, heavy, complex manifolds to do the job. Either way, the engines are large, heavy, expensive and inefficient.

[Camacha]

The actual "nozzle" part, yes, that's not excessively difficult, though making it strong enough and light enough has proved tricky. A circular-section nozzle is self-reinforcing: if it starts to bend out of shape then the pressure within restores it, but the curves of an aerospike (linear or circular) are shaped in such a way that if they start to deform then the pressure on them exaggerates that.

The problem with traditional rocket bells is that they are, even though effective, quite complicated and expensive to make. Modern versions tend to simplify things as much as possible, for instance by replacing the multitude of tubes by a double wall construction type of thing.

[pincushionman]

Cost, weight, performance! Pick two.