Questions tagged [propulsion]

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Lighter car vs heavier car, energy efficiency

I typically assumed in vehicle energy efficiency debates, the importance always in propulsion- to reduce vehicle mass. This usually implies high energy mass density fuel, like hydrogen fuel cells, ...
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3answers
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Can sound be used for propulsion?

I'm no physicist so this might seem absurd. I Remember watching a cartoon as a kid where the character uses a powerful speaker to propel his cart and I was wondering if this was actually possible. ...
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3answers
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Given time dilation from traveling near light speed, would a spacecraft be able to reach any arbitrary distance including to another galaxy? [duplicate]

Not much more than in the title except that when I took an astronomy class the professor said, Andromeda is 2 million lightyears away so it is safe to say humans will never reach there. But with time ...
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1answer
38 views

Are there real-world devices similar to the thrust reversers in this scene in Star Wars? [closed]

In Star Wars 3 in the initial crash scene where a spaceship enters the atmosphere for an emergency landing the thrust engine is blocked by a part of the ship and absorbs a part of the thrust which ...
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1answer
27 views

How to calculate Mars and Lunar payload if I have LEO payload? [closed]

I am working on a project and i need the payload capabilities of different rockets to LEO, mars and lunar orbit. Usually the LEO payload along with all other relevant data is given for all rockets. is ...
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Spacecraft propulsion, thrust and delta V relation

For a spacecraft which has interplanetary mission(eg mars) After deciding the propellant ISP value and Delta V required, how to calculate the thrust required? F = m dot * Ve + (pe - p0) * Ae According ...
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1answer
48 views

How does a rocket travel in a vacuum space? [duplicate]

OK.. let us consider a rocket initially at rest in outer space. Space is considered as vacuum so there is hardly something that rocket can insert a force on. So if the rocket fires up its engines will ...
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1answer
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In the rocket equation, does lowering the acceleration due to gravity increase decrease exhaust velocity? [closed]

I'm doing work for an intro space flight class, and I have to calculate the amount of fuel I need to get sizable a space craft, around 200 thousand kg in dry mass, into a transfer orbit from the ...
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4answers
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Can we make a drone fly on the Moon by using cylinders with compressed air (or cold helium)? [closed]

Suppose we want to make a drone fly on the Moon (the gravity on the Moon is 1/6 of that on Earth), only by making use of its rotors and air. The drone is as light as possible ($m_{min}(kg)$, has ...
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1answer
48 views

Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust $F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
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1answer
50 views

How can I simulate a path for my model rocket?

I made a model rocket. Specifications: Total weight - 1.635 N (wet). It has a custom solid rocket motor with black powder producing 5 N for 15 sec. So how can I calculate how high will it travel? Some ...
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1answer
57 views

Invisible Coilgun Propagation

Forgive me in advance for not being 100% accurate in my explanation. I am not an electrical engineer, nor have I academically studied physics, algebra, or anything of the sort. So without further ado: ...
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1answer
32 views

Deriving Tsiolkovsky Rocket Equation using Conservation of Momentum

I recently tried to derive the rocket equation using conservation of momentum, and did not get very far; was wondering what I am missing. Here's my attempt: Let's say that over some small time $dt$, ...
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1answer
34 views

Is this why a satellite ejects mass (decreasing its mass) into space so that its orbital radius decreases?

I was doing a Physics question and the question was: How does a satellite reduce their orbital radius. The answer was by ejecting mass (thus decreasing the mass) but it didn't explain more. This is my ...
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Relationship Between Specific Impulse and Expansion Ratio Equation

I am trying to find an equation with both Specific Impulse and Expansion Ratio (throat area is constant with exit area changing) of a rocket. This assumes the following constants (all of which I know):...
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12answers
6k views

Can rockets fly without burning any fuel with the help of gases under extreme pressure only?

Why is it necessary to burn the hydrogen fuel coming out of the engine for the lift of rockets? If it is done to create a greater reaction force on the rocket then why can't we get the same lift with ...
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1answer
4k views

If an astronaut got stuck in the middle of a space station, can he propel himself towards a wall by blowing air out of his mouth?

Consider the astronaut as floating in the middle of the "Kibo" (ISS module) without him having any initial motion. The module has a diameter of 4.2 m (inner), and the goal is to reach any of ...
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Can an engine provide constant thrust? [duplicate]

Today while I am driving my car this question came to my mind but I cannot figure it out. Sorry I am not in physics related major that this question is not expressed professionally. When you drive a ...
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1answer
35 views

Magnetic acceleration for a spacecraft [closed]

This is a naive question about a shower thought, but perhaps someone could indulge me since I don't understand the physics at a sufficient level to know why it would not work. Could the ...
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1answer
60 views

If the ion trail behind a spacecraft were not neutralized by its electron gun, what would happen?

In the Space Exploration SE question Is there any possible reason to direct the electron gun specifically towards the ion trail behind an ion thruster? there is somewhat of a consensus that there isn'...
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1answer
26 views

Variable mass, jet airplane thrust

Currently struggling with a momentum problem. I have searched other online answers to similar questions, and the solutions contradict the book answer. Problem: A jet airplane travelling $200\ m/s$ ...
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2answers
78 views

How does a rocket slow down in space?

I’ve been reading about the conservation of momentum and its applications in deriving the rocket equation. I’m curious whether how can a rocket slow down in space. As far as i can comprehend, a rocket’...
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1answer
41 views

Lift force on a rocket [closed]

How is the lift force is generated on a rocket? I've tried to find answer online but all efforts were in vain.
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3answers
101 views

Why aren't rockets launched in movement? [closed]

Rockets launched to reach orbit usually start from a stationary position, engines are started and the rocket slowly gain acceleration upwards, eventually reaching orbit. What I'm thinking is that the ...
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2answers
70 views

Derivation of Tsiolkovsky rocket equation

My textbook derives the rocket equation from conservation of momentum like so: $$\begin{align}p_i&=p_f \tag{1}\\ mv&={(m-dm_g)}{(v+dv)}+dm_g(v-u)\\ mv&=mv+m\,dv-dm_g\,v-dm_g\,dv+dm_g\,v-...
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What does the Lorentz force depends on? Is it the current or the voltage in case of Magnetohydrodynamic Propulsion?

I recently came across a paper named "Magnetohydrodynamic Propulsion for the Classroom" by Gabriel I. Font and Scott C. Dudley. In that they explain about an experiment in which they try to ...
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1answer
54 views

Physics of Project Orion

I was reading the book "Project Orion" by George Dyson. For those who are unaware, Project Orion was basically a plan to launch a spaceship by flinging bombs out the rear and detonating them. The ...
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1answer
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Magnetic ion drive

One of the problems of ion drives is that the electrode is corroded by impacts from the ions we are accelerating. Instead of an electric potential, could we use a magnetic field to accelerate the ions?...
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26 views

What causes the pattern around the jet of Soyuz rocket

What physical phenomenon is happening in a following image? Is it dispersion like in prism?Stay Safe.
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1answer
100 views

What are the theoretical limits of ion propulsion? [closed]

What is the theoretical limit in terms of thrust and energy efficiency a ion thruster can have? Will they ever be able to lift humans on earth? If so, what would the minimum required conditions to do ...
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2answers
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Travelling in outerspace

Firstly, is it correct that for travel in outer space, the distance that can be travelled with a given amount of fuel is determined by the energy required to overcome the following forces: gravity ...
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6answers
334 views

Is it in principle possible to store energy more efficiently (per kg) than as antimatter?

I'd like to understand if there's a theoretical bound on how efficiently you could, in principle, store energy to be used for propulsion. The important quantity to consider is energy stored per kg of ...
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Can the Tsiolkovsky rocket equation be translated directly into two dimensions with constant gravity?

By taking the Tsiolkovsky rocket equation $$ \Delta v=v_{\mathrm{e}} \ln \frac{m_{0}}{m_{f}}$$ where $ v_e $ is velocity at which mass is being dispersed, can the same be done with vectors such that $...
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Why are ion-electron collisions important in an ion thruster plasma?

I'm starting to study Ion thrusters, and I was told that for high electron temperature, the collisions between the ions and electrons inside its plasma become important. Why is this like that? I ...
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Confusion about energy conservation

Suppose a rocket at rest turns on its jet and is now moving with kinetic energy $\frac12 mv^2$ in the lab frame. Suppose the efficiency was maximum so that exactly $\frac12mv^2$ of chemical energy was ...
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1answer
82 views

Maximum Speed for Space Travels

Considering a hypothetical spaceship that has an unlimited amount of fuel, traveling within the solar system planetary plane, what would be considered a safe maximum speed for traveling around ...
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2answers
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What kind of propulsion would a Scrubbing Bubble use [closed]

The brand name bathroom cleaner Scrubbing Bubbles has a mascot, that is a bubble with a rotating bush on the bottom. Please view this video to see an example of the motion. I would like to know what ...
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2answers
107 views

Why doesn't NASA try using high-explosives to fuel rockets?

For a smoothly burning liquid-vapor mixture, I understand that burning hydrogen and oxygen is the best possible solution, not just for now but even theoretically. (?) But I read about ideas, that ...
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31 views

Method adapted by ISRO

Why does the ISRO change orbits of a satellite in many steps? I've seen them do this in the MANGALYAAN as well as CHANDRAYAAN II missions. From what I understand, changing the orbit of the ...
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1answer
30 views

High frequency ionic wind thruster

I’ve wanted to build an ionic wind thruster for some time now and thought about ways to increase the thrust density. One thing which came to mind is to use high frequency AC tuned in such a way that ...
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2answers
69 views

On two requirements in order for an equation describing the propulsion of a rocket to hold

A rocket moving with a velocity $v$ releases a mass $\Delta m$ (fuel exhaustion) at a speed $v_{0}$ in a time interval $t$ and $t+\Delta t$, and increases its velocity by $\Delta v$. If we apply ...
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2answers
135 views

Understanding the interaction between the oar and water

I don't think the propulsion of boats using oars results from the water "pushing" the oars. I understand that momentum is conserved, but in terms of forces, what happens exactly during the interaction ...
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51 views

Why can't we fly aeroplane or shuttle directly into the space (beyond 100 km height above Earth's surface)? [duplicate]

Without rockets can we go beyond Karmans line by shuttle or plane?
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1answer
68 views

Why Don’t We Use Radios for Propulsion?

We’ve all heard the idea of laser propulsion before, but why can’t a high powered RF source be used to propel a body? A simple high current coil with an AC signal applied to it to it could produce ...
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0answers
131 views

NASA's “Impossible” Space Engine, Take Two [closed]

This question seems to be a close parallel of this one, but it's about a different design by a different author. I read a news article about a "helical engine" design by NASA engineer David Burns. ...
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1answer
66 views

Black hole Travel [closed]

Asking out of curiousity. All answers appreciated. You have a machine that generates micro black holes on the outside of it which evaporate quickly and then are immediately generated again upon ...
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1answer
34 views

Can a Tokamak-Based Mainframe feed Plasma to larger pipe-structure in order to create plasma-based propulsion engines?

Can a Tokamak-Based Mainframe feed Plasma to larger pipe-like structures in order to create plasma-based propulsion engines? It is a rather naive question.
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1answer
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Feasibility of fin drive

For marine propulsion, propellers/screws are de rigeur. Unfortunately, they are also very hazardous to marine life. I understand that alternatives like water jets and even MHD drives exist, but I am ...
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Deriving the Tsiolkovsky Rocket Equation using the rate at which the fuel burns

I'm trying to understand the derivation of the Tsiolkovsky Rocket Equation. $$\Delta v= \int_{t_0}^{t_1} \dfrac{|T|}{m_0 - t\Delta m}dt$$ The Wikipedia page ...
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1answer
184 views

Would deuterium or tritium be a better rocket fuel? [closed]

Im not that scientifically literate but through my basics as hell understanding of chemistry is that denser=better wouldn't the denser forms of hydrogen be better for fuel since they would weigh ...

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