Questions tagged [propulsion]
The propulsion tag has no usage guidance.
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Where does Energy get lost in the Rocket Ship propulsion vs "direct acceleration" scenario? [closed]
The scenario is as follows. In a hypothetical future drive I spend energy E to accelerate a mass of propellant m to velocity v (e.g., plasma state propellant in the very powerful circular accelerator),...
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Frame of reference for work done against air resistance by ground vehicle
An online cycling calculator shows power required to overcome air resistance for given wind speed and groundspeed. To cycle at 30mph in still air requires twice the power of cycling at 15mph with a ...
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Propulsion of a spacecraft [closed]
If a craft is positioned at the strongest point of the earth's electromagnetic field being either positive or negative and the craft activates the same field it would repel each other would it create ...
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If photons can be used to accelerate solar sails, why can't they be ejected from a spacecraft and be used as an "engine?"
I'm not really sure why or how, but photons apparently have momentum. This goes against my very limited sense of physics, as they have no mass at all. How is this possible?
At any rate, I came to ...
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Can one build a nuclear jet engine based on alpha emitter for small space satellite?
Let assume a metal tube open on one side having alpha emitter material on the other blocked side. Since alpha particles are blocked by the metal they will be emitted only through the open side and ...
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Are all conservation of momentum scenarios simply particles bouncing on walls? [duplicate]
All explanations of jet propulsion that I've seen are formulated as "due to conservation of momentum, air with momentum coming out of one end means the rocket must gain momentum in the opposing ...
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Rocket propulsion energy efficiency
What ratio of final to initial mass of a rocket to achieves the highest energy efficiency - the highest ratio of final mass kinetic energy to chemical energy expended? And more generally the relation ...
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How is the specific impulse of a gridded ion thruster derived?
How is the specific impulse of a gridded ion thruster derived?
I've searched and got a variety of answers and Bard gives a different answer each time I ask it.
Too the best that I can reckon it's:
1/9....
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What are the light emissions from an ion engine?
Consider an ion thruster like a DS4G (Dual-Stage 4 Grid) thruster. Gas is released, ionized, and accelerated. Assume it's in a vacuum, be it a chamber or space. Also assume the propellant is Xenon.
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Can an ion thruster work without applied voltage?
In this image, power is used to apply voltage to the charged grids.
But if no voltage is applied, would ions still be accelerated by Coulomb forces to create thrust? If not, why?
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Why is hydrogen considered the most efficient rocket fuel and how it relates to the concept of specific impulse (ISP)?
Why is hydrogen considered the most efficient fuel? I mean I know it is very light and can be accelerated very fast, but can’t you use a denser fuel but throw it at a slower speed bunch, and it’ll ...
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Do EM waves carry momentum and if they do can it be used to generate thrust? [duplicate]
I read EM waves carry momentum and can exert pressure, if this is the case can ejecting them be used to generate thrust? Radiation pressure is cited as a real thing but I read about the EM drive and ...
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Propeller design comparison [closed]
Why does boat/airplane propellers are designed so differently then of a turbine/pump propellers? (blade spacing, pitch, blade shape and width, etc) although both just push fluids backwards
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Relationship between fuel consumption and kinetic energy increase
The spacecraft with the same physical properties is moving in space. Let's assume that there are no resistance in space.
A stationary observer observes a spacecraft whose speed varies from 100 m/s to ...
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Double the speed, four times the fuel, yet again [closed]
This question has been asked several times already but it usually involves pushing against the Earth or a rocket carrying the fuel within itself. Let's simplify the problem to a projectile pushed by ...
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The formula of the net external force and rocket propulsion [duplicate]
The mathematical representation of the net external force on a system is $\vec F_{net} = \frac {d\vec P}{dt}$, which is the rate of change of linear momentum of the system. If we substitute $\vec P = ...
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Unclear negative sign in rocket propulsion equation
The usual proof of Rocket propulsion goes something like this (University of Central Florida, Rocket propulsion)
$mv = (m-dm_g)(v+dv) + dm_g(v-v_{rel})$
where:
m - initial weight of rocket
v - ...
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Could Zapata’s Flying airboard be used on Space missions [closed]
The following Zapata’s flying air board (FAB) can fly on Earth for 10 minutes up to 3km ceiling, carrying 100kg person at a speed of 150km/hr. I was wondering if it could fly on Moon or Mars, or ...
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Does a box of Pendulum's weigh more if they are swinging?
The question is more specifically to explain why the box doesn't weigh more, because if it did then I could revolutionize space travel.
Consider a rigid box suspending two counter oscillating ...
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Regarding Speed of launched rocket inside the atmosphere
I am a 15 yr old, so please forgive my mistakes as I have not entirely read rocket mechanics.
I have been wondering why rockets accelerate to mind-boggling speeds, (mach7-8 or even more)when that must ...
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How would one go about writing the momentum equilibrium for a rocket whose thrust is equal to the force of gravity? (The rocket's "hanging" in the sky
My question specifically is where do we look for the "missing" momentum. If I understand the situation correctly we have some momentum from the exhaust of the rocket. Where do we get the &...
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The relationship of yaw and roll on a spacecraft using Trust Vector Control
I’ve previously asked the question how does applying rudder (yaw) on aircraft also cause roll. Turns out it’s caused by both the rudder usually being above or below the center of mass and the ...
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Optimization of using a speaker membrane as a propulsion unit - best frequency and shape of the excitation curve
with optimized frequency and excitation curve pattern, a speaker membrane vibrates with a higher speed away from the speaker (representing frequency 1) and with a lower speed back to the speaker (...
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Based on Dyson's reasoning about speed for Orion spacecraft, have our nuclear tests sent macro debris at .1 c?
In the Wikipedia article about the atomic explosion-powered craft, his reasoning about top speed based on the Tsiolkovsky equation assumed very high-speed debris (although he was not sure), indeed, ...
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The Orion Project --- do the predicted speeds violate the Tsiolkovsky Equation?
I understand that a conventional rocket may move faster than its thrust but IIRC the equation developed in the 19th century the speed is limited to 4/3 the thrust speed.
Now, I understand that the ...
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Why are the blades of a pedestal fan so different from the blades on an aircraft propeller?
Both fans and propellers move a quantity of air. In the former, that is the end goal. In the latter, this movement of air creates a force in the direction opposite to the airflow. So, why are the ...
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Propellant less propulsion when there is nothing to push against
Is there a way for a vehicle to move without losing mass when there is nothing for the vehicle to push against? For example, a helicopter flying around in a vacuum.
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Can relativistic mass increase be used to increase propulsion momentum?
If the propellant used in a rockets is accelerated to near relativistic speed before being ejected from a space craft (accelerating the propellant molecules in a loop before releasing them), can the ...
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Resources for Rocket propulsion
I am a Mechanical Engineering student who is very much interested in Rocket propulsion. Lately I have been searching for good resources to learn concepts about rocket propulsion. I'd be glad to get ...
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Why does a rocket engine that produces a constant thrust over a set period of time have less energy if it has more mass? (Zero-$g$) [closed]
A rocket engine with the thrust of 1N working for 10 seconds will add more kinetic energy to the rocket if it is attached to a 10kg rocket and less if it is attached to a 20kg rocket. The rocket ...
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How does the thrust achieved in my model differ from a rocket engine?
I am experimenting with a design that looks this,
using both straight and 90 degree curved pipes:
I am supplying compressed air marked by yellow arrows and the pipe is producing a very small force in ...
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tGiven a propulsion system with constant power, how long does it take to travel a given distance in space? (non-rel. and relativistic)
Suppose a space ship of mass $m$ is travelling away from our solar system, starting with "starting speed" $v_{start} > v_{escape\ \odot}$, meaning it will escape sun and have some ...
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Would metallic hydrogen be powerful enough to fuel a 1g rocket?
I have read that the issue with a 1g rocket is that no fuel in existence is powerful enough to provide a constant acceleration of 9.8 meters per second for years on end, and it would take hundreds of ...
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Why flapping rudder produce net thrust if one half-stroke produce thrust and second half-stroke drag?
In small sailing boat like optimist is well know technique when there is no wind, rudder pupming which push boat forward.You just need push-pull rudder stick left to right with fast movement.
Rudder ...
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Are bacterial flagella the most efficient propulsion system at the microscopic scale?
Bacterial flagella can be regarded as microscopic propellers. The rotor is a long, helical protein filament powered by proton gradient. When protons pass through the gap between the rotor and stator, ...
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Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?
The JP Aerospace's Tandem airship achieved a record-breaking 28,982 meters for the highest airship flight.
After reaching this height, can the helium balloon be used as a propellant, the same way if ...
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Do you have to leave something behind to go forward? (ie a contained system)
By "behind" I mean a particle outside of the box.
( assume a 1d system)Imagine a closed box. And at the very center of that box, is a device that fires particles 1,2 in opposite direction.
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Is photon drive reaction less propulsion? [duplicate]
If photon dont have mass how can produce thrust, it seems that violate Newton 3. law?
If light dont have mass how can push solar sail?
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Linear acceleration, gravity, and flipping 180° to slow down
In The Expanse ships use linear acceleration for gravity with the decks placed perpendicular to the thrust vector, this creating a "floor."
When it comes time to decelerate a ship would need ...
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How can satellites change direction without any medium in space? [duplicate]
How can satellites change direction without any medium in space? How do spaceships move in space if there is no medium?
How does Newton's third law of motion work in space?
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Wouldn't a black-hole starship quickly lose its black hole?
There seem to be somewhat serious proposals to propel a starship using a black hole (after all it has its own Wikipedia page!). The idea is to use the Hawking radiation from a small black hole and a ...
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Einstein propulsion system
Will an extended body(cylinder) with asymmetric energy distribution across its H axis experience free-fall(geodesic)acceleration in free space(outside of any influences) in vacuum because of the time ...
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Would a relativistic rocket need more fuel if it were powered externally?
If a relativistic rocket is pushed by a laser sail, in the frame of reference from which the laser is being fired, the ship is gaining mass and needs more and more energy to accelerate it any further, ...
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Reaction wheel for linear motion
Reaction wheels can rotate a spacecraft only around its center of mass (see torque); they are not capable of moving the spacecraft from one place to another (see translational force) from wikipedia
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Why does the ion thruster trust not assume a simpler form?
Consider the thrust of an ion thruster in a vacuum as described by Dan M. Goebel and Ira Katz, Fundamentals of Electric
Propulsion: Ion and Hall Thrusters. From the conservation of momentum, the trust ...
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Theoretical rocket engine based on plasma shock waves particle acceleration
Credits for the article - https://www.quantamagazine.org/cosmic-map-of-ultrahigh-energy-particles-points-to-long-hidden-treasures-20210427
Can this mechanism be used to speed up gas particles to ...
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Origin of the thrust force in jet engine
I am reading a lot about the jet engine operation and I meet mostly explenation that the thrust is generated thanks to the exhaust nozzle that "accelerates" the air. However the nozzle ...
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Why cant there be a sonic velocity inside the convergent part of a nozzle? (ie upstream of the throat)
A convergent-divergent nozzle is typically used for accelerating or decelerating airflow to or from supersonic speeds. The typical configuration for such a nozzle is the de Laval nozzle that is ...
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Ion-propelled device ionization
Imagine we have an ion-propelled device:
Lower part is made of 1cm wide aluminum foil, upper part is separated from it with 3cm gap and made of 0.1mm copper wire. Parts are connected to high-voltage ...
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How do satellites accelerate in space with thrusters?
In my space exploration topic we are learning about satellites. We need to know a bit about thrusters and what they do. However I don’t know how the thrusters accelerate the satellite in space. It ...
