Questions tagged [nozzle]

Questions regarding the rocket engine nozzles, semi-open compartments of various shapes and sizes into which propellant components are injected by their own pressure or with a help of a turbine, often preheated and ignited to start a thermochemical reaction in the nozzle's combustion chamber, producing thrust with expansion into gases and ejecting them through the nozzle's exhaust as plumes, accelerating the rocket to high-mach velocities.

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1answer
287 views

Contracting rocket engine nozzles

The efficiency of rocket engine nozzles depends greatly on their expansion ratio an how well the ambient pressure matches the rocket nozzles exit pressure. An optimal expansion ratio means that there ...
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82 views

At which pressure does a liquid fueled rocket start producing supersonic flow?

In a compressed-tank LOX+ethanol (or similar liquid fuel) rocket: How much should the tank or combustion chamber pressure (which should be the same) be to have a significant exhaust velocity increase ...
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116 views

Can exit pressure of nozzle be less than atmospheric pressure?

This is kinda dumb question .I got 5psi pressure at outlet of the nozzle from open motor software. Is that possible because its less than atmospheric pressure 14.7 psi? Am i missing out something?
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101 views

Why nozzle extensions for ULA's Vulcan; why not make them this long in the first place?

This answer to What is the difference between the Vulcan 562 configuration and the Vulcan 5H2 ("Heavy") configuration? explains that the 2nd stage nozzles were modified by extending them, ...
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Need help finding a clean expression for exit velocity [duplicate]

I'm trying to calculate a engine burning LOX and ethanol (96%) and for that I am using both CEAgui, a GUI for NASA's CEA (Chemical Equilibrium with Applications) code Sutton's Rocket Propulsion ...
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1answer
79 views

Efficiency of rocket stages and converging/diverging nozzle

It is a fact (to the best of my knowledge) that for optimum thrust from a rocket engine, one of the most important factor is the design of its converging/diverging Nozzle - the diverging cone to be ...
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1answer
148 views

Do converging-diverging engine nozzles need to be bell-shaped?

Many rockets designed after the V2 but prior to Saturn V, do not show the typical "Bell" shaped diverging nozzle. Why is it so? Do they achieve supersonic speeds for the exhaust gases in any other way?...
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66 views

Supersonic flow of non-compressible fluids

Will the non-compressible fluids, travelling at Mach 1, at the throat of a CD nozzle, accelerate after they leave the throat?
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2answers
140 views

Nozzle throat velocity

I have the following question regarding nozzles; It is known that in a CD nozzle there can be only one of the following outcomes; a flow fully subsonic in the convergent, subsonic at the throat and ...
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1answer
120 views

Nozzle Exit Pressure Too High?

I've been doing some simple rocket science for fun, and I wanted to calculate the specifications of the Lunar Module Descent Engine (LMDE). The LMDE uses Aerozine-50 (UDMH) and Dinitrogen Tetroxide($...
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1answer
170 views

What is the thickness of a rocket nozzle?

For a university project, I'm working on optimisation of a Falcon-9-like launch vehicle, and one element of that is varying expansion ratios of the engines. This will impact on the engine mass, but to ...
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1answer
223 views

What was the first rocket with de Laval (convergent-divergent) nozzle to fly?

Rocket engine Wikipedia article states that Goddard was the first to use a De Laval nozzle on a solid-propellant (gunpowder) rocket engine, doubling the thrust and increasing the efficiency by a ...
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Why do many ablative nozzles use phenolic resin and not some other resin?

I am currently looking into ablatively cooled nozzles. Most of the nozzles made out of composite material that I have found use phenol as resin (Space Shuttle Solid Rocket Booster, ARCA Excecutor). ...
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184 views

What is a typical sea-level engine nozzle/expansion ratio? What about vacuum engines?

On a sea-Level engine, what is the average nozzle ratio? What about an upper-stage vacuum engine?
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Deep throttling in sea level engines

In this excellent answer, asked for merlin engines deep throttling in first stage and produced here. To help you understand where the cross over point is, here is some math for understanding the ...
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1answer
109 views

Grossly overexpanded nozzle?

How do we classify a nozzle to be grossly overexpanded in the design phase? For example, looking at the dimensions and operating at sea level, can we determine if it will be overexpanded or grossly ...
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1answer
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Why should be velocity through the nozzle throat be sonic?

I have read (even on this site), that exhaust gas velocity is (normally?) sonic (exactly Mach 1) through the choke point of a De Laval, or convergent-divergent, nozzle: At the "throat", where the ...
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2answers
215 views

What factors determine the altitude at which rocket exhaust plumes start blooming hugely?

The images below are from a much larger set of photos in Spaceflight Now's August 8, 2019 article Photos: Atlas 5 paints the sky with spectacular sunrise launch. They show several effects related to ...
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1answer
147 views

Do the pipes used for RS-25 nozzle cooling channel have a constant section?

If I understand correctly from this question, The SSME's nozzle is made of pipes into which cool propellant circulate. The nozzle is larger at the end than near the combustion chamber. Thus, it must ...
9
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1answer
569 views

Sea level static test of an upper stage possible?

As we know that for the upper stages of the rocket, we need high propulsion efficiency thereby high specific impulse. For that we employ a nozzle with higher expansion ratios. Now, if we conduct the ...
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2answers
121 views

Does adding a nozzle increase peak pressure in a rocket?

If I had two charges of the same solid propellant both in the same geometry and casing, and added a de laval nozzle to one, while the other would have just a simple hole for an exhaust, upon firing, ...
2
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1answer
288 views

Under-expanded nozzle at sea level - is it a problem?

I'm designing a solid rocket motor with a fixed pressure in the combustion chamber $p_{cc} = 70~bar$. When it comes to the choice of the right nozzle, I have to consider the proper expansion ratio, in ...
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Why does the Superdraco exhaust seem so under-expanded in this photo?

The Ars Technica articles From zero to 100mph in 1.2 seconds, the SuperDraco thruster delivers Dragon was destroyed just before the firing of its SuperDraco thrusters both include this "file photo" ...
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What are these big shiny metallic “lumps” on the bottom edge of each Falcon Heavy nozzle?

What are these big shiny metallic "lumps" on the bottom edge of each nozzle of each core of this Falcon Heavy image from the Teslarati article SpaceX reveals Falcon Heavy Block 5 in first official ...
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1answer
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What is the white spray-pattern residue inside these Falcon Heavy nozzles?

What is the white residue in a spray pattern seen on the inside of each nozzle of each side core of this Falcon Heavy image from the Teslarati article SpaceX reveals Falcon Heavy Block 5 in first ...
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Issue with units for a rocket nozzle throat area problem

I'm working through How to Design, Build, and Test Small Liquid-Fuel Rocket Engines. The guide explains calculating a rocket nozzle throat area using Eq. (7): $$A_t = \frac{w_t}{P_t} \sqrt{\frac{R ...
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1answer
242 views

Weight Flow Rate

I read in the book INTRODUCTION TO ROCKET SCIENCE AND ENGINEERING by T.S.T that Rocket Engineers design how big the throat of the nozzle should be based on the Weight Flow Rate. So my question is HOW?
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Rao contour nozzle: Calculate throat and exit angle?

The Rao nozzle formula is an empiric formula for a parabolic nozzle used in pretty much all nozzles today. The problem is it depends on the throat and exit-angle of the nozzle, which varies with ...
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1answer
186 views

How is the exit velocity of the flow in a sounding rocket nozzle?

How is the exit velocity of the flow in a sounding rocket nozzle? Is it subsonic or supersonic? Is a de Laval nozzle required for sounding rockets? Bonus Question: What about Model Rockets?
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Could ablative material sublimation slow down a spacecraft?

Thought experiment illustrated below: Suppose a weird spacecraft entering Earth's atmosphere from low Earth orbit, payload first. Behind it there is an inverted nozzle shaped structure, attached with ...
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413 views

Why are exhaust nozzles in space shaped the way they are? [duplicate]

Why are nozzles in space shaped like a cone and not like a tube ensuring all the exhaust is directed strait?
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0answers
45 views

What are some common exit pressures for liquid propellant engines?

Most engines are overexpanded at launch so that they reach peak efficiency at altitude. It’s easy to find values for thrust, specific impulse, expansion ratio, chamber pressure, etc, but I’m trying to ...
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152 views

What modifications constituted the ‘reorificing’ of F-1 engines on later Saturn V flights?

The topic of uprating the Saturn V’s first stage engines appears to have been widely discussed, and yet there is little agreement as to how it was done. Early Rocketdyne F-1 engines quote lower ...
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2answers
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What causes those curtain-like hot and cool spots in the 2nd stage nozzle of this Electron ELaNa 19 launch?

Here is a GIF that I made of the recent Electron Launch from frame grabs in the Rocket Lab video ELaNa 19 Launch - 12/16/2018 It is about 4M, so it won't fit in SE's normal image import. Frames are ...
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Why doesn't a regeneratively cooled engine crack due to differential expansion induced by thermal gradients?

A liquid rocket engine with regeneratively cooled chamber walls and nozzles would definitely be one among those components experiencing the steepest thermal gradients (Chamber wall inner - $3000 K$ ...
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1answer
291 views

Are there rocket nozzles that use non-elliptical shapes?

I was reading this question: Why the non-symmetric design of rocket nozzles? Which got me thinking, have there been any nozzles that don't end in an ellipse? Even the one in that question ends in a ...
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235 views

Why is SpaceShipTwo's nozzle scarfed? [duplicate]

As seen in this photo (from here) there appears to be a significant scarf to the nozzle. I'm familiar with scarfing reaction control jet nozzles to fit fuselage contours, but this one is completely ...
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1answer
346 views

Analytical approximations for the shapes of these plots of ISP vs nozzle diameter? (Raptor engine)

A comment on the currently unanswered question Is there an authoritative catalog for rocket launch identifiers? led me to this Github page which links to r/spacexlounge on which currently appears a ...
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198 views

Nozzle skirt in the second stage of Rocketlab's Electron [duplicate]

As we can see, in the first stage of Rocketlab's Electron the nozzles have small nozzle exit area. Source (all) But for second stage why are they using nozzle skirt/ extension with huge exit area?
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1answer
225 views

F1 engine specification?

I am collecting the engine specification data of different engines. I want to know the nozzle length and combustion chamber length and diameter of the F1 engine of Saturn-5. Please give some ...
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1answer
875 views

Red color in the nozzles of Soyuz-2 rocket engines RD-107 and RD-108, is it only a decoration?

Many pictures of the Soyuz-2 show the inside of the nozzles painted with a brilliant red. Is there any function of the paint during ignition and operation of the rocket engines, or is it just a ...
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1answer
281 views

new nozzle design, is it a fail?

So I'm an amature rocket scientist. while having a conversation with a friend on a nozzles we though of a new nozzle: Its a double nozzle where it expands a lot and then compress. I want to put this ...
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1answer
292 views

How might an internal combustion engine generate substantial external thrust?

This answer mentions the proposed use of an internal combustion engine (ICE) in ULA's ACES upper stage to extract energy from LH2/LOX in multiple forms for multiple uses, which is described further in ...
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Where does the thrust act in a rocket engine and how is it transferred to rocket structure?

A rocket engine is basically a device that generates a high pressure inside the chamber and the pressure difference creates a force. A nozzle helps in effectively accelerating the flow and increases ...
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1answer
691 views

Why is the Merlin 1D Vacuum nozzle bigger than the Merlin 1D nozzle?

I know that the Merlin 1D is used in the Falcon first stage and the Merlin 1D Vac in the second stage but i can't find any information as to why the nozzle has to be bigger in vaccuum. I guess that a ...
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1answer
3k views

How to design a bell nozzle from scratch [closed]

I need help creating my own custom model rocket nozzle. I'm making a model rocket, it will have many intricate parts, but the most intricate maybe the nozzle. My question is where do I start if I want ...
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1answer
700 views

Cooling a hydrolox rocket with Water

Would it be efficient to use water as a coolant in a hydrolox rocket, then feed the steam after the water has boiled (due to heat transfer from the engine nozzle) into the combustion chamber, so as to ...
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1answer
288 views

Did I see the Formosat-5 F9 2nd stage nozzle vibrate at about 2Hz at SECO-1?

Did I see the F9 2nd stage nozzle vibrate at about 2Hz at SECO-1? It looked like the bottom of the bell vibrated in an elliptical shape. Did I imagine that? Has this happened before? $\hskip 3.4 cm$...
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1answer
290 views

TR-106 under-expansion in sea-level test?

I was looking at pictures of a test fire of a TR-106 engine, and it appears to be fairly under-expanded. What's the reason for this? Does this somehow increase efficiency with this specific engine?
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1answer
389 views

Why are exhaust flames “jumping around” the bases of the Falcon-9 engine nozzles; NROL-76? [duplicate]

I see something interesting the webcast of the NROL-76 launch. At around T+00:00:55 it looks like flames from the exhaust start jumping around the bases of the ring ...