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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1 answer
138 views

How to find the average ambient pressure during rocket ascent?

I am trying to find the average ambient pressure that my rocket will flight through during its ascent to then determine the most optimum conditions in my combustion chamber and nozzle. I have ...
3 votes
1 answer
295 views

What am I missing about rocket nozzle isentropic flow?

Playing a bit with Cpropep-Web, something looked wrong to me about how it models isentropic flow through a CD nozzle. I'm taking the RS-25 characteristics as an example. I ask for a frozen equilibrium ...
9 votes
1 answer
544 views

What is the area of the SSME nozzle knowing only thrust at sea level and in vacuum?

Looking at the SSME Wikipedia RS-25 Space Shuttle Engines, the data shown that the thrust at sea level ($F_{sl}$) is 1.816*10$^6$ N, while the thrust in vacuum ($F_{vac}$) is 2.278*10$^6$ N. Knowing ...
2 votes
1 answer
76 views

Discrepancies in thrust chamber dimensions for RL10

I've recently been developing some automated scripts in Python for the purpose of calculating engine parameters. I've been using the RocketCEA interface library, which links to NASA's Chemical ...
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6 votes
1 answer
547 views

What happens if the mass flow rate is increased continuously in a converging nozzle?

I recently studied about nozzles where I came to know that the maximum velocity one could attain using a converging nozzle is the sonic velocity at the exit of the converging nozzle. An further ...
1 vote
1 answer
126 views

Does thrust vectoring by a gimballed nozzle in rockets affect thrust/efficiency?

I was wondering if thrust vectoring via a maneuvering gimballed nozzle affected the thrust of a rocket. I've read a couple times that a gimballed rocket engine's thrust doesn't change while exhaust ...
2 votes
2 answers
128 views

Restartable Solid Rocket Motors Through Expanding Throats?

I recall seeing diagrams on a solid rocket motor that could "blow" itself out through suddenly expanding its nozzle, leading to the propellant no long burning or producing any thrust. First ...
0 votes
0 answers
52 views

Analytical representations for thrust in underexpanded flow (P_e>P_a) [duplicate]

I am familiar with the ideal thrust equation: $F=\dot{m}U_e +(P_e-P_a)A_e$ When $P_a$ is greater than $P_e$, you have thrust losses, and the equation accounts for that. When $P_a=P_e$, you achieve ...
5 votes
2 answers
1k views

Are nozzle plugs taken out before launch or are they ejected upon ignition?

Inspired by this question. For most orbital launch vehicles, do their engines have nozzle plugs installed and what happen to them at launch? Are they manually removed during the prelaunch/rollout or ...
4 votes
1 answer
126 views

Discrepancy in local Mach behavior between CEA and other sources

I'm exploring some designs using the NASA CEA (Chemical Equilibrium with Applications) code and I ran into a discrepancy between CEA predicted values for local Mach number at the exit plane and values ...
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3 votes
1 answer
158 views

Specific impulse of a rocket engine

Keeping other things (fuel, oxidizer, their ratio, mass flow rates, throat diameter, other hardware like pump, injector nozzles & impinging pattern etc.) same, if I changed only the geometry (...
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3 votes
0 answers
90 views

Using a laval nozzle as supersonic inlet - what happens at throat? [closed]

I am wondering what will happen, if I use the laval-nozzle , which normaly accelerates a fluid the other way round: So what happens if I fly with my aircraft at Mach 2 and I collect all the air in my ...
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1 vote
1 answer
129 views

Designing of CD nozzle with respect to Mass flow rate of propellants

How do I calculate the flow rate of exhaust gases required at the throat of a CD nozzle, with given throat diameter of "D", so as to achieve a "Choked flow condition" (velocity of ...
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0 votes
1 answer
128 views

Can Vacuum nozzles be used as cooling radiators in LEO?

Radiators are used for thermoregulation of spacecraft. https://www.academia.edu/934756/Thermal_Control_Handbook . Their effectiveness requires their surface be exposed to deep space, not an IR ...
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0 votes
1 answer
2k views

Calculating rocket nozzle throat area

I'm trying to calculate a rocket nozzle throat area, $A_t$. My propellant is KNDX. I am trying to do this according to the following equations, taken from this reference: where $P_t$ is and $T_t$ ...
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3 votes
1 answer
162 views

What happens with thrust if I decrease the convergent divergent nozzle exit area?

I am new to rocket design and I have a couple of questions. If I have a convergent - divergent nozzle and I have a choked flow condition for the throat, what will happen a) with my exit pressure b) ...
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2 votes
1 answer
179 views

What expansion ratio is the best for mars surface level engines?

What expansion ratio is the best for mars surface level engines? For launches from Earth, first stage nozzles are much shorter than second stage nozzles because of Earth's high sea-level pressure. For ...
3 votes
1 answer
471 views

Conversion of heat into electricity in rocket nozzles

Can we use advanced thermoelectric materials to reduce the temperature of nozzles by converting heat energy to electric energy and reducing the strain on the nozzle material and the coolant while ...
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3 votes
1 answer
231 views

Sea-level nozzles

I understand that there are sea level-optimised and vacuum-optimised nozzles, but why optimise for sea level when the rocket doesn't spend much time there? I would expect the first stage nozzles to be ...
5 votes
0 answers
117 views

Aerospike calculator software doesn't seem to altitude-compensate - am I misunderstanding aerospikes?

I'm using mvernacc's Aerospike Nozzle Design GUI, which is supposed to be able to design and predict the performance of aerospike rocket engines. The workings of the software are apparently based on ...
4 votes
1 answer
579 views

What were/are the stingiest and most generous vacuum nozzle? (records for the smallest and largest expansion ratios)

Vacuum nozzles are huge compared to their sea-level or atmospheric counterparts, as can be seen by comparing the first stage engines on an Electron or Falcon-9 to their second stages, where a big ...
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1 vote
1 answer
187 views

nozzle throat area calculation for choked flow

I am quite confused for my sugar propellant rocket nozzle. I have designed a CD nozzle by hit and trial method. It worked but produced so less amount of thrust .I have used 2.3 kg propellant which ...
10 votes
1 answer
526 views

How can firing a Space Shuttle OMS engine below 21 km cause its nozzle to "collapse"?

This answer to Can the space shuttle use OMS engines during landing? says: No and quotes Section 3.7 of the Orbital Maneuvering System Workbook; OMS 21002 October 10, 2006, Final version, USA006500 ...
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17 votes
3 answers
1k views

Is it always one nozzle per combustion chamber and one combustion chamber per nozzle?

When I read about engines like the RD-170 they might have a single turbopump feeding multiple combustion chambers, and each combustion chamber has its own nozzle. Is there, or would it be reasonable ...
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0 votes
0 answers
52 views

Design a cold gas ACS nozzle

I have the total thrust required to be F=16.9 KN. I am using nitrogen gas, and the stored temperature in the nitrogen gas cylinder is 155 bars with a temperature of 325k. How would I design the nozzle ...
6 votes
3 answers
894 views

Aerospike with solid fuel

I was scrolling in youtube and I saw this awesome video and I think, if we put an aerospike nozzle in a sounding rocket,or even a small orbital rocket, as a first stage solid booster, this type of ...
3 votes
1 answer
151 views

Do pulse detonation rocket engines require any type of nozzle?

Rocket nozzles are used to convert slow moving gas under high pressure and temperature into hypersonic gas under approximately ambient pressure. From many videos of experimental Pulse Detonation ...
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1 vote
0 answers
106 views

Which engine has the highest nozzle wall temperature? [closed]

From all the rocket engines that were used in flight, which one has the highest nozzle wall temperature? The nozzle wall is not heated uniformly. But there are regions where they reach max temperature....
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15 votes
2 answers
3k views

How hot do rocket engine nozzles get?

What temperatures are encountered by the nozzles of rocket engines like those in SpaceX's Merlin series? Radiative or regenerative cooling, atmosphere or vacuum. There's plenty of info about exhaust ...
0 votes
1 answer
186 views

What if we have a DC nozzle instead of a CD nozzle?

My understanding is that the exhaust gas gains velocity as its heat converts to kinetic energy, regardless of the geometry of the nozzle, and the reason we have a convergent-divergent (CD) nozzle is ...
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1 vote
1 answer
99 views

I'm having a problem with the Throat Area formula derivation

I came upon this when reading "Introduction to Rocket Science and Engineering, he said "by differentiating" , my question is: differentiate with respect to what? and how do you get such ...
5 votes
1 answer
554 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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3 votes
1 answer
120 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 ...
5 votes
1 answer
696 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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3 votes
0 answers
183 views

Why use 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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1 vote
0 answers
84 views

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 ...
0 votes
1 answer
110 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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4 votes
1 answer
240 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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0 votes
0 answers
76 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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6 votes
2 answers
395 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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2 votes
1 answer
641 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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6 votes
1 answer
986 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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7 votes
2 answers
490 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 ...
6 votes
1 answer
522 views

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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1 vote
1 answer
874 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?
user avatar
2 votes
0 answers
109 views

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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2 votes
1 answer
245 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 ...
11 votes
2 answers
5k views

Why should the 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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5 votes
2 answers
555 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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2 votes
1 answer
403 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 ...
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