Questions tagged [propulsion]

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14 views

Freewheels to fix direct shaft drive

Is it a valid solution to install freewheels between axel and wheels in order to allow the exterior wheel to spin faster than the interior wheel when turning in a system where the shaft bring the ...
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27 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 ...
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1answer
26 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 ...
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16 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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1answer
49 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 ...
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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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1answer
85 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. ...
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2answers
91 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 ...
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1answer
96 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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40 views

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 ...
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38 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.
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3answers
465 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 ...
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1answer
102 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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2answers
127 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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1answer
82 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 ...
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1answer
80 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 ...
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1answer
423 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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2answers
55 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 ...
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2answers
123 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 ...
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2answers
85 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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1answer
25 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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2answers
3k 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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1answer
309 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 ...
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1answer
33 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. ...
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2answers
73 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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1answer
271 views

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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2answers
201 views

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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2answers
466 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 ...
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1answer
78 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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1answer
139 views

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 ...
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1answer
1k 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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1answer
217 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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2answers
603 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 ...
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5answers
6k 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 ...
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3answers
906 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 ...
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2answers
112 views

Traction mechanisms for a robot in confined spaces

I'd like to build an exploratory robot that can fit within confined spaces1. What traction mechanisms should I consider to propel a robot along the inside of a 4" pipe? The pipe to be traversed will ...
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1answer
225 views

Magnetic levitation [closed]

I am currently considering turning my fascination with magnets into a diy activity. How feasible is it for a hobbyist to construct a working model of a maglev device? I'm looking to build something ...