# Questions tagged [propulsion]

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29 views

### When something undergoes angular acceleration (like a bar) how does the distribution of forces look along the bar?

This is something kind of explained with propellers and turbine blades but I'd love some good explanations. Thank you!
18 views

### How to estimate air velocity at turbine in turbojet?

I am designing a small turbojet. I wanted to know how to calculate the air volume expansion to predict the outlet velocity of air towards the turbine. Theoretically, I wouldn't know the flame ...
89 views

### Would a conical-shaped solenoid be propelled by its interaction with the Earth's magnetic field?

I am wondering if the interaction between the magnetic field created by a conical-shaped solenoid and the Earth's magnetic field will result in this conical-shaped solenoid being propelled through the ...
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77 views

### Is a centrifuge force-based levitation system operable in the real world?

In the sci-fi comic Betelgeuse, the artist Leo presents a flying car with an unusual system for levitation and propulsion. The interesting point is that at the end of the comic, there is a page on ...
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1 vote
159 views

### Benefits of twin-in/single-out propulsion

I've seen, in some marine engine project guides, arrangements where you have two medium-speed engines coupled to one propeller through a gearbox instead of one larger engine running that propeller. I'...
62 views

### Could a downwind cart, or “push-me, pull-me” boat of a substantially heavier size be propelled with the use of a CVT, or continuous gear?

As broadly proven now before the academia, a vehicle including a boat or cart (probably a glider too) can move faster than the speed of wind up to about 2.5-2.8 times with a propeller generating lift ...
122 views

### Angle of attack on variable pitch propeller?

For a variable pitch propeller where the angle of attack can be adjusted during flight, are the individual blades similar in design to standard propellers, with a low angle of attack at the edge of ...
3k views

### How to calculate the moment of inertia of a propeller

I am trying to design a VTOL system that uses a servo to rotate a propeller and the attached motor so that it can provide thrust when it is at 0 degree and lift when it is at 90 degree. However, I ...
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144 views

### Predicting thrust of a Motor

I want to be able to predict the load a single motor and propeller can carry, so I can choose an appropriately sized propeller and powerful enough motor. I say predict because I'm first going to ...
158 views

### Multiple vs single rocket engine nozzles [closed]

I am an aeronautical engineering student and at university with a group of friends we are are working on building a rocket aimed at getting past the Karman Line (boundary to space). We will be ...
165 views

### How does Kia charge the high-voltage battery in EV mode?

I recently bought a Kia Ceed 2020 PHEV (Plug-in Hybrid Electric Vehicle). Its specs mention a 6-gear Dual-Clutch Transmission (DCT), a 105 kW Internal Combustion Engine (ICE) and a 44 kW Motor-...
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### How to do Blade Element Momentum Theory Analysis for NACA airfoils?

I wanna perform BEMT analysis on blades of different geometry and not just symmetric thin airfoil. How to do this?
74 views

### Sizing electric motor

I've been looking for a way to size an electric motor for a vehicle that could be assumed as a box-shaped load with a mass of 60 kg, up a 10° incline, at 1.6 m/s, using continuous tracks with 1 motor ...
264 views

### Time-rate of change of P and T in a pressurized rigid volume with a hole in it

I am trying to model the time-rate of change of pressure and temperature of a gas being held within a pressurized rigid volume as it escapes: an unsteady, open system with no heat transfer. Most ...
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1 vote
44 views

### Ducted fan thrust in confined space

I would greatly appreciate any insight into this. I'd like to place a ducted fan inside of a box with the bottom cut out. The fan is attached to the sides of the box by support rods. The ducted fan ...
218 views

### Stagnation,static and dynamic pressures

Please can someone help out with the actual concept of stagnation,static and dynamic pressures . I have learnt all that stagnation pressure is when velocity of flow is 0 when isentropically stopped ...
1 vote
25 views

### Air flow at the outlet of a reactor

I wish to calculate the air flow in cubic meters per second of a system that is not exactly a jet engine, but seems close to it, mathematically speaking. The data available to me is the following : ...
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1 vote
220 views

### Why do trains use the same wheels for staying on track and propulsion?

Trains where originally designed to keep the train on track. At the time trains where pulled by horses and used to transport coal (and such) out of mines. The two functions have very different ...
• 121
1 vote
174 views

### Basic dimension relationships in a valveless pulsejet engine

I'm willing to take my own shot at the construction of a blast supercharged valveless pulsejet, a holy grail among DIY jet enthusiasts. However, since my idea is not very compatible with the geometry ...
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187 views

### Could boiling water inside a semi-enclosed pipe be a low-cost method for a silent marine propulsion system? (redesigned)

I am wondering if boiling water that is trapped inside of a semi-enclosed pipe would be a low-cost method of creating an underwater thruster that would function as a silent marine propulsion system. ...
• 271
266 views

### Amount of thrust needed to Hover on the moon?

I am interested in knowing how many newton's of force is needed to keep 1 kg of mass hovering above the moon's surface. And whether the current most powerful ion thrusters would be up to the task? I ...
669 views

### What's the minimum area ratio required to achieve choking in Converging nozzle?

Is there any equation for minimum area ratio (Throat area (At)/ Combustion Chamber area (Ac) ) required for choked flow in convergent nozzle (just like equations for minimum Pressure ratio and ...
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### Method of Characteristics nozzle - outputs area ratio?

I am designing a rocket engine as my final project at college, and I tried using a MatLab code developed by youtuber JoshTheEngineer. However, after running the code, it seems that the output points ...
40 views

### Is it possible to protect electronics on a cubesat from 100-1000g of acceleration

I am currently researching the feasibility of setting up a coilgun that launches Cubesats for a paper.
552 views

### Will this water jet propulsion system design produce any forward thrust?

I am interested in building a very basic water jet propulsion system for a toy boat. Before I build it, I would like to know from a conceptual standpoint if this design of a water jet propulsion ...
187 views

### Why there are no jets (missile or aircraft) faster than Mach 3.3?

Fastest plane ever built: SR-71 ,Max Speed: 3.3 Mach , Development - 1950s Fastest drone ever built: Lockheed-D21 ,Max Speed: 3.3 Mach, Development -1960s Fastest cruise missile ever built: Brahmos ,...
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433 views

### Is there an ideal propeller shape?

Are there theories that assert about the ideal shape (i.e., ignoring structural constraints) of a propeller? Just looking at the shapes that emerge in practice, it appears that both the fluid speed ...
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141 views

### Why don't propeller designers use multiple profiles?

I'm designing a ducted fan, and I'm deciding on the airfoil profile. NACA 16-series profiles are well-suited to M > .5 or .6, but they're not particularly efficient at lower Mach numbers. On the other ...
127 views

### RC drone rotor air access

I am attempting to design a "flying saucer." The saucer is an ellipsoidal-ish body with a RC drone inside. I plan to allow for air access to the rotors as shown in the rudimentary diagram below: I am ...
780 views

### Thrust distribution of engine

I am studying the thrust distribution of jet engines. But I'm now a bit confused. In Rolls-Royce's "The Jet Engine" book, http://aeromodelbasic.blogspot.com/2012/05/thrust-distribution-distribution-...
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77 views

### Heating the air inside a turbojet instead of combusting it

Would an aircraft that uses propellers for movement but with a turbo jet like structure where the ignition chamber only heats the air a bit, similar to a hair dryer instead of releasing fuel and ...
371 views

### Compressing the air thrusted by an aircraft's propeller through a cone like tube

If I had an aircraft that used propellers for movement and took the air from the front running it through a tube that gets very small towards the end, would it have any impact on the speed? Would the ...
115 views

### Is it possible to extract mechanical energy using Turbines behind PulseJet engine?

Pulsejet expels pulse of hot gas (unlike turbojet engine) which create some thrust(Not good enough for ). These gases are hot, fast and pulsed. Is it possible to convert kinetic energy of these gases ...
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35 views

### What is the fraction of power transmitted to the generator in full-hybrid cars?

In full-hybrid cars like the Toyota Prius, usually both internal combustion engine (ICE) and electric motor produces mechanical power to the wheels at cruise. But some of the mechanical power produced ...
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8k views

### What is the difference between shaft power and brake power?

I know little about internal combustion engines and I feel a little confused about brake and shaft powers. I read a book that only talks about shaft power, and other that only talks about brake power, ...
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636 views

### Increase thrust of ion thruster?

Ion thruster has very low thrust due to its low mass flow rate. However is it possible to increase the mass flow rate? Together with its high exhaust velocity, won't the ion thruster be able to reach ...
47 views

### Development of an interstellar mission: should I design the propulsion system or the main hull of the ship first?

I am currently developing an interstellar mission for a school project. I am thinking whether to design the propulsion system (Bussard scoop) or the main hull and structure of the spaceship first. ...
109 views

### Bearings for a contra rotating tubes

Consider a mechanical setup, in which there are two concentric tubes, both to rotate counter to each other ie in a contra rotating fashion. Inner tube runs clockwise, and outer tube runs counter ...
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### Calculating Thrust for Contra-Rotating Propellers

How do I calculate the thrust of ducted contrarotating propellers? Is there any formula or website calculator or would it have to be done through experimenting with scale replicas?
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### Propane rocket nozzle material

As far as I know, propane with oxygen will burn at 2800 °C and steel will melt at ~1500 °C. Brass is even less. What I am trying to do is a rocket nozzle. Is there a way I can built this with steel ...
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1k views

### Why is high stagnation pressure important for propulsion?

In my propulsion notes I always see mention of the importance of minimizing stagnation pressure loss across the inlet shock of a ramjet/turbojet/turbofan. Could anyone explain further why this is the ...
108 views

### turbojet axial compressor: blades of HP compressor

I noticed that blades of HP compressor are shorter in axial dimension next to its LP counterpart. Why? I understand why it is smaller in radial dimension (this is because compressed air has smaller ...
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1 vote
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### In what order turbojet engine parameters are calculated?

As I see it, if you're going to calculate a twin-spool turbojet engine, you Determine expected max aircraft speed, and engine thrust at that speed and when stationary. Calculate peak mass of air flow ...
• 115
2k views

### Valve for mini CO2 gas canister?

I am in the process of helping my son design a sort of model of the Bloodhound SSC car for his school project, using balsa wood, model aircraft wheels, etc... It doesn't have to a like of like, but ...
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1 vote
279 views

### How to calculate propulsive force of gas ejection

How can I calculate the propulsive force produced by ejection of a gas? I suppose it depends on the gas, the velocity with which it ejects, the amount of gas, and some other parameters, like the ...
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640 views

### Why My Mini Boat Does Not Move Forward?

I am currently building a mini boat-like robot to clean the water from floating trash. I used two servo motors to move the loader that I have installed in front of the boat, and two 3 V DC motors ...
9k views

### Purpose of spheres and fins on submarine propeller

On a recently launched Russian diesel-electric submarine, the rear propeller has two distinct features. You can see spheres at the base of every propeller blade: Also, the trailing edge of the shaft ...
1k views

### Could air-launched space planes reach escape velocities?

Rockets like the Ariane 5 weigh hundreds of tons, but with about 85% of that weight being fuel, the payload fraction is only about 3% (~10-20 tons). Virgin Galactic is building suborbital space ...