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Old 08-08-2017, 03:18 AM   #1 (permalink)
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rocket aerodynamics

Why aren't rockets more teardrop shaped, especially the flared out engine cones? Why are the cones necessary in the first place? I thought all that needed to exist was a high pressure in a combustion chamber, and an opening at the bottom where the pressure was relieved.

Does aerodynamics not matter at supersonic speeds since air does not have enough time to respond?

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Old 08-08-2017, 07:35 AM   #2 (permalink)
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Minimal frontal area for the work that is expected? And the large shock bubble at the front prevents reattachment of the air flow?
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Old 08-08-2017, 09:21 AM   #3 (permalink)
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The Trident I missile has a deployable aerospike that pops out after it is launched. It causes the supersonic shock wave to form at it's tip, rather than at the nose of the missile.

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Old 08-09-2017, 03:03 PM   #4 (permalink)
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Quote:
Why aren't rockets more teardrop shaped, especially the flared out engine cones? Why are the cones necessary in the first place?
The exhaust fills the wake?

Rockets perform over a wide range of conditions. The shape of the rocket bell is highly constrained. https://en.wikipedia.org/wiki/Rocket_engine_nozzle

Think bullet vs dirigible.
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Old 09-06-2017, 05:21 PM   #5 (permalink)
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Here, have a picture(or two):

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Old 09-06-2017, 10:58 PM   #6 (permalink)
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Very interesting. How are secant ogive, tangent ogive, and power series defined?
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Old 09-07-2017, 01:06 AM   #7 (permalink)
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The (approximately) cone-shaped engine nozzles are necessary for the exahust to expand properly and produce as much thrust as possible. And as already mentioned, the expanding gas more than fills the space behind the rocket, so a teardrop tail is pointless.

As far as aerodynamics for the rest of the rocket, it just doesn't spend that much time in the thicker parts of the atmosphere. For instance, a Saturn V was at 25 km just 90 seconds after launch: https://upload.wikimedia.org/wikiped...ectory.pdf.jpg

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