Questions tagged [propulsion]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
3 answers
88 views

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, ...
user avatar
  • 365
15 votes
9 answers
9k views

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 ...
user avatar
  • 1,889
-1 votes
2 answers
54 views

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. ...
user avatar
  • 4,243
-1 votes
1 answer
32 views

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?
user avatar
  • 199
0 votes
4 answers
56 views

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 ...
user avatar
  • 3
4 votes
3 answers
894 views

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?
user avatar
  • 41
0 votes
0 answers
10 views

Variations in using the General Thrust Equation for a Jet Engine, which to use when?

I've been studying The General Thrust Equation form J. Anderson. The author left the subject at T=(m_air + m_fuel)V_e-m_airV_infinity+A_e(P_e-P_infinity) But while illustrating solved examples he ...
user avatar
2 votes
0 answers
61 views

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 ...
user avatar
  • 1,120
0 votes
1 answer
115 views

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 ...
user avatar
  • 11
1 vote
1 answer
65 views

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, ...
user avatar
0 votes
1 answer
41 views

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 ...
user avatar
  • 1
0 votes
1 answer
55 views

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 ...
user avatar
  • 725
2 votes
2 answers
83 views

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 ...
user avatar
4 votes
6 answers
221 views

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 ...
user avatar
1 vote
1 answer
48 views

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 ...
user avatar
0 votes
0 answers
33 views

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 ...
user avatar
1 vote
3 answers
58 views

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 ...
user avatar
1 vote
1 answer
42 views

Would light sails be a practical means of travel in the center of Andromeda? [closed]

I've read that at Andromeda's center, stars are only 0.008 lightyears apart from each other. Is this a short enough distance for light sails to be a practical means of space travel, or is this still ...
user avatar
0 votes
0 answers
29 views

What is the maximum speed a Blackbird (wind-powered vehicle) can achieve? [duplicate]

Can someone drive/calculate the maximum speed which can be achieved by a Blackbird (wind-powered vehicle, link below) when going downwind? Suppose mass of the vehicle is $m$, wind speed relative to ...
user avatar
  • 881
0 votes
1 answer
37 views

Significance of a close system propulsion [closed]

I have an idea of a close system propulsion powered by electricity. It can move mass in space without expelling anything. If this shall be proven to work, is this significant to the space flight ...
user avatar
  • 105
0 votes
3 answers
74 views

More confusion about the faster-than-wind Blackbird

There's been plenty of discussion on here about the Blackbird as featured in this video. I get that it harvests energy from the relative velocity of air to ground. But I still can't wrap my head ...
user avatar
  • 1,468
0 votes
0 answers
33 views

Why the magnet in a Hall-effect thruster?

I am reading explanations of how a Hall-effect thruster works. I keep reading that the cathode emits electrons, which are trapped by the B field to form an electron cloud which accelerates the ...
user avatar
  • 416
1 vote
1 answer
39 views

What is the nature behind the periodicity of the Mach diamonds?

I've heard very interesting and sometimes contradictory hypothesis about why the Mach Diamonds have well defined spatial periodicities. I am not sure I understand most of them, and I cannot exclude ...
user avatar
  • 14k
1 vote
1 answer
177 views

What is stopping a Electromagnetic rail gun to propel a body in space? [duplicate]

Why are railguns not used to for propulsion is it due to the air resistance? IMP-If we were to provide some propellant to the body inside the rail gun to be used after leaving the nozzle of the rail ...
user avatar
  • 11
1 vote
1 answer
84 views

Does the speed in which a gas through a medium matter?

There are two thrusters. They both expel the same volume of gas. The difference is, one has a fine stream of propellant at a higher velocity, and the other a wider stream at a lower velocity. Would ...
user avatar
1 vote
0 answers
83 views

Would helium-3 be a better lifting gas than normal helium?

Buoyant force is proportional to the mass of the fluid displaced minus the mass of the volume doing the displacing. Thus the best choices of lifting gas are nothing(vacuum), hydrogen, and then helium ...
user avatar
0 votes
1 answer
287 views

Why don't we use rocket engines in cars?

If rocket engines can reach 70% efficiency, why don't we use them in cars? Internal combustion engines get less and less efficient with higher speed just due to the kinetic energy equation (a unit of ...
user avatar
  • 416
5 votes
3 answers
1k views

Converting heat to mechanical energy

Could an object convert heat in the air around it to mechanical energy in order to accelerate itself? In other words, the craft would take in surrounding air composed of random-velocity molecules and ...
user avatar
1 vote
2 answers
84 views

Why the path of a balloon left untied is unpredictable but of a rocket is predictable? [duplicate]

When a water rocket is projected, it goes in a specific trajectory. But when a balloon is inflated and left untied, it does not follow a definite path. It goes in a random way. I do not see any ...
user avatar
  • 1
0 votes
2 answers
90 views

Can a boat move by using an onboard fan to blow its sail? [closed]

Consider a boat with one sail and a fan fixed on the boat's deck. The fan is blowing air into the sail. If the fan is strong enough, will the boat move?
user avatar
  • 103
1 vote
1 answer
79 views

How is NASA expecting this nuclear propulsion technology to become feasible? [closed]

This NASA announcement provides some hope of nuclear-powered rockets for long trips. I understand that, unlike chemical rockets that would be high thrust for shorter periods of time, a nuclear-powered ...
user avatar
0 votes
0 answers
69 views

Calculating total burn time for a rocket under constant acceleration with two propellant consumption rates

I'm trying to create a simplified model of hypothetical fusion-powered thrusters for a sci-fi setting (on excel), such that upon entering ship mass and operating parameters, all the common performance ...
user avatar
  • 1
0 votes
2 answers
42 views

Would an inertia electric motor propel a spacecraft in zero gravity?

There's an interesting mechanic that is used by self balancing proof of concept robots where they have a wheel on two axis and when the stock robot starts to pivot and fall over, it spins the wheel ...
user avatar
0 votes
2 answers
105 views

How do rockets create thrust in a vacuum? [duplicate]

I understand that rockets create a lot of gas which is pushed out of the back and because of equal and opposite reactions the rocket is propelled forwards. What I don’t quite understand is this: The ...
user avatar
  • 330
1 vote
1 answer
30 views

Electron/Ion beam propulsion

Similar to the concept of how a spacecraft with a light sail and a ground station laser would be used to accelerate a craft, could a similar approach be taken using ions or electrons? If it is ...
user avatar
  • 461
0 votes
0 answers
16 views

"Reactionless" propulsion in heterogenous gravitational field - term

If orbiting planet in heterogenuous gravitational field (common case), it is possible to propulse (change orbit) "recationless" by changing position of massive parts of the spacecraft during ...
user avatar
  • 1,606
-1 votes
1 answer
50 views

Magnetic sunspot propulsion [closed]

Could a solar sail use the sun, its sunspots, or solar flares, in close proximity, use opposing magnetic fields, to add significant acceleration? https://www.mae.ucla.edu/nasa-selects-artur-davoyans-...
user avatar
1 vote
1 answer
47 views

About rocket propusion

As a rocket expels burned fuel the location of the center of the mass of the rocket (in a frame attached to the rocket) changes. Must one take this into account in an exact solution of the rocket ...
user avatar
0 votes
0 answers
59 views

Tsiolkovsky rocket equation with external force

I think I understand how the equation arises when there is no external force. I'm following the Wikipedia article on this, there is a nice sketch: At time $t$, the total momentum of the system is $...
user avatar
  • 222
0 votes
2 answers
98 views

Would shooting an atom out the back of a rocket at the speed of light propel the rocket forward at the speed of light? [closed]

Although impossible as far as we know, if we were to somehow shoot even an atom out the back of a rocket at the speed of light, would that propel the rocket forward at the speed of light? If I ...
user avatar
  • 213
3 votes
2 answers
234 views

Rocket's momentum

It is well known that to give a liftoff a rocket, we use the momentum principle: The momentum of the gases emitted by a rocket and the rocket's momentum is equal to zero. So why is it not enough to ...
user avatar
1 vote
0 answers
27 views

Earth to space without using confessional engines [closed]

Let's say we had a source of almost unlimited electric energy comparable to the volume and weight of today's orbital rockets. Is there a known propulsion engine that can take such vehicle from the ...
user avatar
  • 11
0 votes
0 answers
57 views

Why is the propulsive force related Coriolis term ignored in flight dynamics (rocket equation)?

Consider a variable mass vehicle body $B$ with it's center of mass $B$ stationary with respect to the body fixed referenced frame $B$. We obtain the translational dynamics of the variable mass body as ...
user avatar
  • 2,338
0 votes
4 answers
94 views

How do chemical propulsion systems not break the law of conservation of energy?

Lets say that hypothetically we have a rocket with constant mass, and an engine providing a constant force. I understand that it is unrealistic to have a rocket of constant mass with a rocket engine ...
user avatar
0 votes
1 answer
125 views

Are chemical rockets really beyond 60% efficient?

Are chemical rockets really beyond 60% efficient? https://en.wikipedia.org/wiki/Rocket_engine “Rocket engine nozzles are surprisingly efficient heat engines for generating a high speed jet, as a ...
user avatar
  • 157
0 votes
2 answers
45 views

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, ...
user avatar
4 votes
3 answers
704 views

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. ...
user avatar
0 votes
3 answers
160 views

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 ...
user avatar
  • 1,946
0 votes
1 answer
41 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 ...
user avatar
1 vote
1 answer
41 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 ...
user avatar

1
2 3 4 5 6