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.
118
questions
2
votes
0
answers
36
views
Nozzle contour estimation (Merlin 1D Vacuum)
I would like to run a fluid simulation of the diverging section of a Merlin 1D Vacuum engine. While most relevant parameters (such as expansion ratio, flow rate, and nozzle area) are readily available,...
- 149
1
vote
0
answers
108
views
Does an overexpanded nozzle behave like a suction cup?
It is generally said that, to obtain optimal specific impulse, a nozzle should be just the right size that the exhaust pressure is equal to the ambient pressure. Quoting this answer, a relevant ...
- 482
2
votes
0
answers
97
views
Help with designing nozzle geometry for compressed air thruster
I am designing a compressed air thruster with a conical nozzle geometry. The general design consists of a compressed air tank, pneumatic tubing, and then the actual chamber with the nozzle. The ...
- 21
5
votes
1
answer
479
views
Why is the expansion ratio of the nozzle of the 2nd stage larger than the expansion ratio of the nozzle of the 1st stage of a rocket?
As an answer I have two statements, which statement is correct? If one or both are wrong, can you please provide me an explanation?
Statement 1:
The goal is to achieve maximum efficiency in thrust. ...
1
vote
0
answers
122
views
How to find the correct size and angle for a conical nozzle on a rocket engine? [closed]
So I need to know the equations for finding the size and angle for a conical nozzle. I am making a rocket engine and I decided the conical nozzle would be the easiest to build. The rocket is going to ...
- 221
2
votes
1
answer
154
views
Is specific impulse and thrust maximum in vacuum or for exit pressure equals atmospheric pressure?
According to the thrust formulation of a rocket one can show, that maximum thrust is not delivered for pambient= 0 but for pambient=pnozzle_exit since then the momentum term is maximized.
But then I ...
- 29
3
votes
0
answers
108
views
How do ablatively cooled rocket engines compare to regeneratively cooled ones, in terms of mass?
Assuming equivalent thrust and single continuous burn duration, is there a figure that roughly tells the difference in mass between these two engines cooling methods? This question focuses on first ...
- 4,218
4
votes
1
answer
134
views
Would it make sense to compress air around a bell nozzle during booster ascent?
Regarding boosters having one single liquid fuel engine, such as Delta 4 for example.
Would some sort of annular aerodynamic device, attached to the skirt and placed around the bell nozzle, help ...
- 4,218
0
votes
1
answer
68
views
Higher nozzle exit velocity generally means higher thrust right?
Higher nozzle exit velocity generally means higher thrust right? If that is the case, then a higher heat capacity could potentially lead to a higher exit velocity, thus higher thrust?
- 403
0
votes
1
answer
132
views
Calculate Thrust of Rocket Nozzle - Off Design
I have designed a nozzle for the following input parameters
$p_{combustion}=p_c=200*10e5 Pa$
$T_{combustion}=T_c=2800 K$
$F=70 kN$
$\kappa=1,2$
$R = 330 J/kgK$
I assume that all my gas properties ...
- 29
0
votes
0
answers
123
views
How to avoid big nozzle lengths in high altitude?
I am currently designing a serial staged rocket with 3 stages. The first stage brings me up to 10 km. When I do my calculations for the required expansion ratio and nozzle length (Rao Nozzle) for the ...
- 37
2
votes
1
answer
143
views
Difference between Optimum Expansion Ratio and Maximum Thrust
when I look at the equation for thrust of a rocket:
$$
F=\dot{m}*v_{exit}+(p_{exit}-p_{amb})*A_{exit}
$$
In the book "Rocket Propulsion" from Sutton it says on page 33:
In the vacuum of ...
- 37
0
votes
1
answer
61
views
Choked Flow: Throat Radius should not change any more below critical pressure ratio?
I am trying to understand some calculations of a student colleague:
The pressure inside the combustion chamber is 200 bar. This means, the critical pressure ratio should be p*/p0 with p0=101325 ...
- 37
1
vote
1
answer
189
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
339
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
597
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
172
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 ...
- 527
6
votes
1
answer
710
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 ...
- 135
1
vote
1
answer
183
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
177
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 ...
- 183
0
votes
0
answers
53
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 ...
- 33
5
votes
2
answers
2k
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 ...
- 3,095
4
votes
1
answer
202
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 ...
- 527
3
votes
1
answer
226
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 (...
- 3,758
3
votes
0
answers
105
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 ...
- 31
1
vote
1
answer
173
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 ...
- 3,758
0
votes
1
answer
136
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 ...
- 18k
0
votes
1
answer
4k
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 $T_t$ ...
- 117
3
votes
1
answer
190
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) ...
- 31
2
votes
1
answer
213
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 ...
- 41
3
votes
1
answer
500
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 ...
- 69
3
votes
1
answer
374
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 ...
- 133
5
votes
0
answers
146
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 ...
- 461
4
votes
1
answer
748
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 ...
- 148k
1
vote
1
answer
314
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
591
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 ...
- 148k
17
votes
3
answers
2k
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 ...
- 4,297
0
votes
0
answers
73
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
1k
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 ...
- 1,633
3
votes
1
answer
201
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 ...
- 2,223
1
vote
0
answers
113
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....
- 2,590
16
votes
2
answers
4k
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 ...
- 11.5k
0
votes
1
answer
223
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 ...
- 229
1
vote
1
answer
113
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 ...
- 11
5
votes
1
answer
743
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 ...
- 1,232
3
votes
1
answer
144
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
976
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?
- 1,496
3
votes
0
answers
204
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, ...
- 148k
1
vote
0
answers
86
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 ...
- 185
0
votes
1
answer
124
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 ...
- 3,758